core.c

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/*
 * Performance events core code:
 *
 *  Copyright (C) 2008 Thomas Gleixner <[email protected]>
 *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <[email protected]>
 *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <[email protected]>
 *
 * For licensing details see kernel-base/COPYING
 */

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/reboot.h>
#include <linux/vmstat.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/hardirq.h>
#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/anon_inodes.h>
#include <linux/kernel_stat.h>
#include <linux/perf_event.h>
#include <linux/ftrace_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>

#include "internal.h"

#include <asm/irq_regs.h>

struct remote_function_call {
    struct task_struct  *p;
    int         (*func)(void *info);
    void            *info;
    int         ret;
};

static void remote_function(void *data)
{
    struct remote_function_call *tfc = data;
    struct task_struct *p = tfc->p;

    if (p) {
        tfc->ret = -EAGAIN;
        if (task_cpu(p) != smp_processor_id() || !task_curr(p))
            return;
    }

    tfc->ret = tfc->func(tfc->info);
}

static int
task_function_call(struct task_struct *p, int (*func) (void *info), void *info)
{
    struct remote_function_call data = {
        .p  = p,
        .func   = func,
        .info   = info,
        .ret    = -ESRCH, /* No such (running) process */
    };

    if (task_curr(p))
        smp_call_function_single(task_cpu(p), remote_function, &data, 1);

    return data.ret;
}

static int cpu_function_call(int cpu, int (*func) (void *info), void *info)
{
    struct remote_function_call data = {
        .p  = NULL,
        .func   = func,
        .info   = info,
        .ret    = -ENXIO, /* No such CPU */
    };

    smp_call_function_single(cpu, remote_function, &data, 1);

    return data.ret;
}

#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
               PERF_FLAG_FD_OUTPUT  |\
               PERF_FLAG_PID_CGROUP)

/*
 * branch priv levels that need permission checks
 */
#define PERF_SAMPLE_BRANCH_PERM_PLM \
    (PERF_SAMPLE_BRANCH_KERNEL |\
     PERF_SAMPLE_BRANCH_HV)

enum event_type_t {
    EVENT_FLEXIBLE = 0x1,
    EVENT_PINNED = 0x2,
    EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};

/*
 * perf_sched_events : >0 events exist
 * perf_cgroup_events: >0 per-cpu cgroup events exist on this cpu
 */
struct static_key_deferred perf_sched_events __read_mostly;
static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
static DEFINE_PER_CPU(atomic_t, perf_branch_stack_events);

static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_task_events __read_mostly;

static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;

/*
 * perf event paranoia level:
 *  -1 - not paranoid at all
 *   0 - disallow raw tracepoint access for unpriv
 *   1 - disallow cpu events for unpriv
 *   2 - disallow kernel profiling for unpriv
 */
int sysctl_perf_event_paranoid __read_mostly = 1;

/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */

/*
 * max perf event sample rate
 */
#define DEFAULT_MAX_SAMPLE_RATE 100000
int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE;
static int max_samples_per_tick __read_mostly =
    DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);

int perf_proc_update_handler(struct ctl_table *table, int write,
        void __user *buffer, size_t *lenp,
        loff_t *ppos)
{
    int ret = proc_dointvec(table, write, buffer, lenp, ppos);

    if (ret || !write)
        return ret;

    max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);

    return 0;
}

static atomic64_t perf_event_id;

static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                  enum event_type_t event_type);

static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                 enum event_type_t event_type,
                 struct task_struct *task);

static void update_context_time(struct perf_event_context *ctx);
static u64 perf_event_time(struct perf_event *event);

static void ring_buffer_attach(struct perf_event *event,
                   struct ring_buffer *rb);

void __weak perf_event_print_debug(void)    { }

extern __weak const char *perf_pmu_name(void)
{
    return "pmu";
}

static inline u64 perf_clock(void)
{
    return local_clock();
}

static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
    return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
}

static void perf_ctx_lock(struct perf_cpu_context *cpuctx,
              struct perf_event_context *ctx)
{
    raw_spin_lock(&cpuctx->ctx.lock);
    if (ctx)
        raw_spin_lock(&ctx->lock);
}

static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
                struct perf_event_context *ctx)
{
    if (ctx)
        raw_spin_unlock(&ctx->lock);
    raw_spin_unlock(&cpuctx->ctx.lock);
}

#ifdef CONFIG_CGROUP_PERF

/*
 * Must ensure cgroup is pinned (css_get) before calling
 * this function. In other words, we cannot call this function
 * if there is no cgroup event for the current CPU context.
 */
static inline struct perf_cgroup *
perf_cgroup_from_task(struct task_struct *task)
{
    return container_of(task_subsys_state(task, perf_subsys_id),
            struct perf_cgroup, css);
}

static inline bool
perf_cgroup_match(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

    return !event->cgrp || event->cgrp == cpuctx->cgrp;
}

static inline bool perf_tryget_cgroup(struct perf_event *event)
{
    return css_tryget(&event->cgrp->css);
}

static inline void perf_put_cgroup(struct perf_event *event)
{
    css_put(&event->cgrp->css);
}

static inline void perf_detach_cgroup(struct perf_event *event)
{
    perf_put_cgroup(event);
    event->cgrp = NULL;
}

static inline int is_cgroup_event(struct perf_event *event)
{
    return event->cgrp != NULL;
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
    struct perf_cgroup_info *t;

    t = per_cpu_ptr(event->cgrp->info, event->cpu);
    return t->time;
}

static inline void __update_cgrp_time(struct perf_cgroup *cgrp)
{
    struct perf_cgroup_info *info;
    u64 now;

    now = perf_clock();

    info = this_cpu_ptr(cgrp->info);

    info->time += now - info->timestamp;
    info->timestamp = now;
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
    struct perf_cgroup *cgrp_out = cpuctx->cgrp;
    if (cgrp_out)
        __update_cgrp_time(cgrp_out);
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
    struct perf_cgroup *cgrp;

    /*
     * ensure we access cgroup data only when needed and
     * when we know the cgroup is pinned (css_get)
     */
    if (!is_cgroup_event(event))
        return;

    cgrp = perf_cgroup_from_task(current);
    /*
     * Do not update time when cgroup is not active
     */
    if (cgrp == event->cgrp)
        __update_cgrp_time(event->cgrp);
}

static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
              struct perf_event_context *ctx)
{
    struct perf_cgroup *cgrp;
    struct perf_cgroup_info *info;

    /*
     * ctx->lock held by caller
     * ensure we do not access cgroup data
     * unless we have the cgroup pinned (css_get)
     */
    if (!task || !ctx->nr_cgroups)
        return;

    cgrp = perf_cgroup_from_task(task);
    info = this_cpu_ptr(cgrp->info);
    info->timestamp = ctx->timestamp;
}

#define PERF_CGROUP_SWOUT   0x1 /* cgroup switch out every event */
#define PERF_CGROUP_SWIN    0x2 /* cgroup switch in events based on task */

/*
 * reschedule events based on the cgroup constraint of task.
 *
 * mode SWOUT : schedule out everything
 * mode SWIN : schedule in based on cgroup for next
 */
void perf_cgroup_switch(struct task_struct *task, int mode)
{
    struct perf_cpu_context *cpuctx;
    struct pmu *pmu;
    unsigned long flags;

    /*
     * disable interrupts to avoid geting nr_cgroup
     * changes via __perf_event_disable(). Also
     * avoids preemption.
     */
    local_irq_save(flags);

    /*
     * we reschedule only in the presence of cgroup
     * constrained events.
     */
    rcu_read_lock();

    list_for_each_entry_rcu(pmu, &pmus, entry) {
        cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
        if (cpuctx->unique_pmu != pmu)
            continue; /* ensure we process each cpuctx once */

        /*
         * perf_cgroup_events says at least one
         * context on this CPU has cgroup events.
         *
         * ctx->nr_cgroups reports the number of cgroup
         * events for a context.
         */
        if (cpuctx->ctx.nr_cgroups > 0) {
            perf_ctx_lock(cpuctx, cpuctx->task_ctx);
            perf_pmu_disable(cpuctx->ctx.pmu);

            if (mode & PERF_CGROUP_SWOUT) {
                cpu_ctx_sched_out(cpuctx, EVENT_ALL);
                /*
                 * must not be done before ctxswout due
                 * to event_filter_match() in event_sched_out()
                 */
                cpuctx->cgrp = NULL;
            }

            if (mode & PERF_CGROUP_SWIN) {
                WARN_ON_ONCE(cpuctx->cgrp);
                /*
                 * set cgrp before ctxsw in to allow
                 * event_filter_match() to not have to pass
                 * task around
                 */
                cpuctx->cgrp = perf_cgroup_from_task(task);
                cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
            }
            perf_pmu_enable(cpuctx->ctx.pmu);
            perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
        }
    }

    rcu_read_unlock();

    local_irq_restore(flags);
}

static inline void perf_cgroup_sched_out(struct task_struct *task,
                     struct task_struct *next)
{
    struct perf_cgroup *cgrp1;
    struct perf_cgroup *cgrp2 = NULL;

    /*
     * we come here when we know perf_cgroup_events > 0
     */
    cgrp1 = perf_cgroup_from_task(task);

    /*
     * next is NULL when called from perf_event_enable_on_exec()
     * that will systematically cause a cgroup_switch()
     */
    if (next)
        cgrp2 = perf_cgroup_from_task(next);

    /*
     * only schedule out current cgroup events if we know
     * that we are switching to a different cgroup. Otherwise,
     * do no touch the cgroup events.
     */
    if (cgrp1 != cgrp2)
        perf_cgroup_switch(task, PERF_CGROUP_SWOUT);
}

static inline void perf_cgroup_sched_in(struct task_struct *prev,
                    struct task_struct *task)
{
    struct perf_cgroup *cgrp1;
    struct perf_cgroup *cgrp2 = NULL;

    /*
     * we come here when we know perf_cgroup_events > 0
     */
    cgrp1 = perf_cgroup_from_task(task);

    /* prev can never be NULL */
    cgrp2 = perf_cgroup_from_task(prev);

    /*
     * only need to schedule in cgroup events if we are changing
     * cgroup during ctxsw. Cgroup events were not scheduled
     * out of ctxsw out if that was not the case.
     */
    if (cgrp1 != cgrp2)
        perf_cgroup_switch(task, PERF_CGROUP_SWIN);
}

static inline int perf_cgroup_connect(int fd, struct perf_event *event,
                      struct perf_event_attr *attr,
                      struct perf_event *group_leader)
{
    struct perf_cgroup *cgrp;
    struct cgroup_subsys_state *css;
    struct fd f = fdget(fd);
    int ret = 0;

    if (!f.file)
        return -EBADF;

    css = cgroup_css_from_dir(f.file, perf_subsys_id);
    if (IS_ERR(css)) {
        ret = PTR_ERR(css);
        goto out;
    }

    cgrp = container_of(css, struct perf_cgroup, css);
    event->cgrp = cgrp;

    /* must be done before we fput() the file */
    if (!perf_tryget_cgroup(event)) {
        event->cgrp = NULL;
        ret = -ENOENT;
        goto out;
    }

    /*
     * all events in a group must monitor
     * the same cgroup because a task belongs
     * to only one perf cgroup at a time
     */
    if (group_leader && group_leader->cgrp != cgrp) {
        perf_detach_cgroup(event);
        ret = -EINVAL;
    }
out:
    fdput(f);
    return ret;
}

static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
    struct perf_cgroup_info *t;
    t = per_cpu_ptr(event->cgrp->info, event->cpu);
    event->shadow_ctx_time = now - t->timestamp;
}

static inline void
perf_cgroup_defer_enabled(struct perf_event *event)
{
    /*
     * when the current task's perf cgroup does not match
     * the event's, we need to remember to call the
     * perf_mark_enable() function the first time a task with
     * a matching perf cgroup is scheduled in.
     */
    if (is_cgroup_event(event) && !perf_cgroup_match(event))
        event->cgrp_defer_enabled = 1;
}

static inline void
perf_cgroup_mark_enabled(struct perf_event *event,
             struct perf_event_context *ctx)
{
    struct perf_event *sub;
    u64 tstamp = perf_event_time(event);

    if (!event->cgrp_defer_enabled)
        return;

    event->cgrp_defer_enabled = 0;

    event->tstamp_enabled = tstamp - event->total_time_enabled;
    list_for_each_entry(sub, &event->sibling_list, group_entry) {
        if (sub->state >= PERF_EVENT_STATE_INACTIVE) {
            sub->tstamp_enabled = tstamp - sub->total_time_enabled;
            sub->cgrp_defer_enabled = 0;
        }
    }
}
#else /* !CONFIG_CGROUP_PERF */

static inline bool
perf_cgroup_match(struct perf_event *event)
{
    return true;
}

static inline void perf_detach_cgroup(struct perf_event *event)
{}

static inline int is_cgroup_event(struct perf_event *event)
{
    return 0;
}

static inline u64 perf_cgroup_event_cgrp_time(struct perf_event *event)
{
    return 0;
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
}

static inline void perf_cgroup_sched_out(struct task_struct *task,
                     struct task_struct *next)
{
}

static inline void perf_cgroup_sched_in(struct task_struct *prev,
                    struct task_struct *task)
{
}

static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
                      struct perf_event_attr *attr,
                      struct perf_event *group_leader)
{
    return -EINVAL;
}

static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
              struct perf_event_context *ctx)
{
}

void
perf_cgroup_switch(struct task_struct *task, struct task_struct *next)
{
}

static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
    return 0;
}

static inline void
perf_cgroup_defer_enabled(struct perf_event *event)
{
}

static inline void
perf_cgroup_mark_enabled(struct perf_event *event,
             struct perf_event_context *ctx)
{
}
#endif

void perf_pmu_disable(struct pmu *pmu)
{
    int *count = this_cpu_ptr(pmu->pmu_disable_count);
    if (!(*count)++)
        pmu->pmu_disable(pmu);
}

void perf_pmu_enable(struct pmu *pmu)
{
    int *count = this_cpu_ptr(pmu->pmu_disable_count);
    if (!--(*count))
        pmu->pmu_enable(pmu);
}

static DEFINE_PER_CPU(struct list_head, rotation_list);

/*
 * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
 * because they're strictly cpu affine and rotate_start is called with IRQs
 * disabled, while rotate_context is called from IRQ context.
 */
static void perf_pmu_rotate_start(struct pmu *pmu)
{
    struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
    struct list_head *head = &__get_cpu_var(rotation_list);

    WARN_ON(!irqs_disabled());

    if (list_empty(&cpuctx->rotation_list))
        list_add(&cpuctx->rotation_list, head);
}

static void get_ctx(struct perf_event_context *ctx)
{
    WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
}

static void put_ctx(struct perf_event_context *ctx)
{
    if (atomic_dec_and_test(&ctx->refcount)) {
        if (ctx->parent_ctx)
            put_ctx(ctx->parent_ctx);
        if (ctx->task)
            put_task_struct(ctx->task);
        kfree_rcu(ctx, rcu_head);
    }
}

static void unclone_ctx(struct perf_event_context *ctx)
{
    if (ctx->parent_ctx) {
        put_ctx(ctx->parent_ctx);
        ctx->parent_ctx = NULL;
    }
}

static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
{
    /*
     * only top level events have the pid namespace they were created in
     */
    if (event->parent)
        event = event->parent;

    return task_tgid_nr_ns(p, event->ns);
}

static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
{
    /*
     * only top level events have the pid namespace they were created in
     */
    if (event->parent)
        event = event->parent;

    return task_pid_nr_ns(p, event->ns);
}

/*
 * If we inherit events we want to return the parent event id
 * to userspace.
 */
static u64 primary_event_id(struct perf_event *event)
{
    u64 id = event->id;

    if (event->parent)
        id = event->parent->id;

    return id;
}

/*
 * Get the perf_event_context for a task and lock it.
 * This has to cope with with the fact that until it is locked,
 * the context could get moved to another task.
 */
static struct perf_event_context *
perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
{
    struct perf_event_context *ctx;

    rcu_read_lock();
retry:
    ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
    if (ctx) {
        /*
         * If this context is a clone of another, it might
         * get swapped for another underneath us by
         * perf_event_task_sched_out, though the
         * rcu_read_lock() protects us from any context
         * getting freed.  Lock the context and check if it
         * got swapped before we could get the lock, and retry
         * if so.  If we locked the right context, then it
         * can't get swapped on us any more.
         */
        raw_spin_lock_irqsave(&ctx->lock, *flags);
        if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
            raw_spin_unlock_irqrestore(&ctx->lock, *flags);
            goto retry;
        }

        if (!atomic_inc_not_zero(&ctx->refcount)) {
            raw_spin_unlock_irqrestore(&ctx->lock, *flags);
            ctx = NULL;
        }
    }
    rcu_read_unlock();
    return ctx;
}

/*
 * Get the context for a task and increment its pin_count so it
 * can't get swapped to another task.  This also increments its
 * reference count so that the context can't get freed.
 */
static struct perf_event_context *
perf_pin_task_context(struct task_struct *task, int ctxn)
{
    struct perf_event_context *ctx;
    unsigned long flags;

    ctx = perf_lock_task_context(task, ctxn, &flags);
    if (ctx) {
        ++ctx->pin_count;
        raw_spin_unlock_irqrestore(&ctx->lock, flags);
    }
    return ctx;
}

static void perf_unpin_context(struct perf_event_context *ctx)
{
    unsigned long flags;

    raw_spin_lock_irqsave(&ctx->lock, flags);
    --ctx->pin_count;
    raw_spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
 * Update the record of the current time in a context.
 */
static void update_context_time(struct perf_event_context *ctx)
{
    u64 now = perf_clock();

    ctx->time += now - ctx->timestamp;
    ctx->timestamp = now;
}

static u64 perf_event_time(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;

    if (is_cgroup_event(event))
        return perf_cgroup_event_time(event);

    return ctx ? ctx->time : 0;
}

/*
 * Update the total_time_enabled and total_time_running fields for a event.
 * The caller of this function needs to hold the ctx->lock.
 */
static void update_event_times(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;
    u64 run_end;

    if (event->state < PERF_EVENT_STATE_INACTIVE ||
        event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
        return;
    /*
     * in cgroup mode, time_enabled represents
     * the time the event was enabled AND active
     * tasks were in the monitored cgroup. This is
     * independent of the activity of the context as
     * there may be a mix of cgroup and non-cgroup events.
     *
     * That is why we treat cgroup events differently
     * here.
     */
    if (is_cgroup_event(event))
        run_end = perf_cgroup_event_time(event);
    else if (ctx->is_active)
        run_end = ctx->time;
    else
        run_end = event->tstamp_stopped;

    event->total_time_enabled = run_end - event->tstamp_enabled;

    if (event->state == PERF_EVENT_STATE_INACTIVE)
        run_end = event->tstamp_stopped;
    else
        run_end = perf_event_time(event);

    event->total_time_running = run_end - event->tstamp_running;

}

/*
 * Update total_time_enabled and total_time_running for all events in a group.
 */
static void update_group_times(struct perf_event *leader)
{
    struct perf_event *event;

    update_event_times(leader);
    list_for_each_entry(event, &leader->sibling_list, group_entry)
        update_event_times(event);
}

static struct list_head *
ctx_group_list(struct perf_event *event, struct perf_event_context *ctx)
{
    if (event->attr.pinned)
        return &ctx->pinned_groups;
    else
        return &ctx->flexible_groups;
}

/*
 * Add a event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_add_event(struct perf_event *event, struct perf_event_context *ctx)
{
    WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
    event->attach_state |= PERF_ATTACH_CONTEXT;

    /*
     * If we're a stand alone event or group leader, we go to the context
     * list, group events are kept attached to the group so that
     * perf_group_detach can, at all times, locate all siblings.
     */
    if (event->group_leader == event) {
        struct list_head *list;

        if (is_software_event(event))
            event->group_flags |= PERF_GROUP_SOFTWARE;

        list = ctx_group_list(event, ctx);
        list_add_tail(&event->group_entry, list);
    }

    if (is_cgroup_event(event))
        ctx->nr_cgroups++;

    if (has_branch_stack(event))
        ctx->nr_branch_stack++;

    list_add_rcu(&event->event_entry, &ctx->event_list);
    if (!ctx->nr_events)
        perf_pmu_rotate_start(ctx->pmu);
    ctx->nr_events++;
    if (event->attr.inherit_stat)
        ctx->nr_stat++;
}

/*
 * Called at perf_event creation and when events are attached/detached from a
 * group.
 */
static void perf_event__read_size(struct perf_event *event)
{
    int entry = sizeof(u64); /* value */
    int size = 0;
    int nr = 1;

    if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
        size += sizeof(u64);

    if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
        size += sizeof(u64);

    if (event->attr.read_format & PERF_FORMAT_ID)
        entry += sizeof(u64);

    if (event->attr.read_format & PERF_FORMAT_GROUP) {
        nr += event->group_leader->nr_siblings;
        size += sizeof(u64);
    }

    size += entry * nr;
    event->read_size = size;
}

static void perf_event__header_size(struct perf_event *event)
{
    struct perf_sample_data *data;
    u64 sample_type = event->attr.sample_type;
    u16 size = 0;

    perf_event__read_size(event);

    if (sample_type & PERF_SAMPLE_IP)
        size += sizeof(data->ip);

    if (sample_type & PERF_SAMPLE_ADDR)
        size += sizeof(data->addr);

    if (sample_type & PERF_SAMPLE_PERIOD)
        size += sizeof(data->period);

    if (sample_type & PERF_SAMPLE_READ)
        size += event->read_size;

    event->header_size = size;
}

static void perf_event__id_header_size(struct perf_event *event)
{
    struct perf_sample_data *data;
    u64 sample_type = event->attr.sample_type;
    u16 size = 0;

    if (sample_type & PERF_SAMPLE_TID)
        size += sizeof(data->tid_entry);

    if (sample_type & PERF_SAMPLE_TIME)
        size += sizeof(data->time);

    if (sample_type & PERF_SAMPLE_ID)
        size += sizeof(data->id);

    if (sample_type & PERF_SAMPLE_STREAM_ID)
        size += sizeof(data->stream_id);

    if (sample_type & PERF_SAMPLE_CPU)
        size += sizeof(data->cpu_entry);

    event->id_header_size = size;
}

static void perf_group_attach(struct perf_event *event)
{
    struct perf_event *group_leader = event->group_leader, *pos;

    /*
     * We can have double attach due to group movement in perf_event_open.
     */
    if (event->attach_state & PERF_ATTACH_GROUP)
        return;

    event->attach_state |= PERF_ATTACH_GROUP;

    if (group_leader == event)
        return;

    if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
            !is_software_event(event))
        group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;

    list_add_tail(&event->group_entry, &group_leader->sibling_list);
    group_leader->nr_siblings++;

    perf_event__header_size(group_leader);

    list_for_each_entry(pos, &group_leader->sibling_list, group_entry)
        perf_event__header_size(pos);
}

/*
 * Remove a event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_del_event(struct perf_event *event, struct perf_event_context *ctx)
{
    struct perf_cpu_context *cpuctx;
    /*
     * We can have double detach due to exit/hot-unplug + close.
     */
    if (!(event->attach_state & PERF_ATTACH_CONTEXT))
        return;

    event->attach_state &= ~PERF_ATTACH_CONTEXT;

    if (is_cgroup_event(event)) {
        ctx->nr_cgroups--;
        cpuctx = __get_cpu_context(ctx);
        /*
         * if there are no more cgroup events
         * then cler cgrp to avoid stale pointer
         * in update_cgrp_time_from_cpuctx()
         */
        if (!ctx->nr_cgroups)
            cpuctx->cgrp = NULL;
    }

    if (has_branch_stack(event))
        ctx->nr_branch_stack--;

    ctx->nr_events--;
    if (event->attr.inherit_stat)
        ctx->nr_stat--;

    list_del_rcu(&event->event_entry);

    if (event->group_leader == event)
        list_del_init(&event->group_entry);

    update_group_times(event);

    /*
     * If event was in error state, then keep it
     * that way, otherwise bogus counts will be
     * returned on read(). The only way to get out
     * of error state is by explicit re-enabling
     * of the event
     */
    if (event->state > PERF_EVENT_STATE_OFF)
        event->state = PERF_EVENT_STATE_OFF;
}

static void perf_group_detach(struct perf_event *event)
{
    struct perf_event *sibling, *tmp;
    struct list_head *list = NULL;

    /*
     * We can have double detach due to exit/hot-unplug + close.
     */
    if (!(event->attach_state & PERF_ATTACH_GROUP))
        return;

    event->attach_state &= ~PERF_ATTACH_GROUP;

    /*
     * If this is a sibling, remove it from its group.
     */
    if (event->group_leader != event) {
        list_del_init(&event->group_entry);
        event->group_leader->nr_siblings--;
        goto out;
    }

    if (!list_empty(&event->group_entry))
        list = &event->group_entry;

    /*
     * If this was a group event with sibling events then
     * upgrade the siblings to singleton events by adding them
     * to whatever list we are on.
     */
    list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
        if (list)
            list_move_tail(&sibling->group_entry, list);
        sibling->group_leader = sibling;

        /* Inherit group flags from the previous leader */
        sibling->group_flags = event->group_flags;
    }

out:
    perf_event__header_size(event->group_leader);

    list_for_each_entry(tmp, &event->group_leader->sibling_list, group_entry)
        perf_event__header_size(tmp);
}

static inline int
event_filter_match(struct perf_event *event)
{
    return (event->cpu == -1 || event->cpu == smp_processor_id())
        && perf_cgroup_match(event);
}

static void
event_sched_out(struct perf_event *event,
          struct perf_cpu_context *cpuctx,
          struct perf_event_context *ctx)
{
    u64 tstamp = perf_event_time(event);
    u64 delta;
    /*
     * An event which could not be activated because of
     * filter mismatch still needs to have its timings
     * maintained, otherwise bogus information is return
     * via read() for time_enabled, time_running:
     */
    if (event->state == PERF_EVENT_STATE_INACTIVE
        && !event_filter_match(event)) {
        delta = tstamp - event->tstamp_stopped;
        event->tstamp_running += delta;
        event->tstamp_stopped = tstamp;
    }

    if (event->state != PERF_EVENT_STATE_ACTIVE)
        return;

    event->state = PERF_EVENT_STATE_INACTIVE;
    if (event->pending_disable) {
        event->pending_disable = 0;
        event->state = PERF_EVENT_STATE_OFF;
    }
    event->tstamp_stopped = tstamp;
    event->pmu->del(event, 0);
    event->oncpu = -1;

    if (!is_software_event(event))
        cpuctx->active_oncpu--;
    ctx->nr_active--;
    if (event->attr.freq && event->attr.sample_freq)
        ctx->nr_freq--;
    if (event->attr.exclusive || !cpuctx->active_oncpu)
        cpuctx->exclusive = 0;
}

static void
group_sched_out(struct perf_event *group_event,
        struct perf_cpu_context *cpuctx,
        struct perf_event_context *ctx)
{
    struct perf_event *event;
    int state = group_event->state;

    event_sched_out(group_event, cpuctx, ctx);

    /*
     * Schedule out siblings (if any):
     */
    list_for_each_entry(event, &group_event->sibling_list, group_entry)
        event_sched_out(event, cpuctx, ctx);

    if (state == PERF_EVENT_STATE_ACTIVE && group_event->attr.exclusive)
        cpuctx->exclusive = 0;
}

/*
 * Cross CPU call to remove a performance event
 *
 * We disable the event on the hardware level first. After that we
 * remove it from the context list.
 */
static int __perf_remove_from_context(void *info)
{
    struct perf_event *event = info;
    struct perf_event_context *ctx = event->ctx;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

    raw_spin_lock(&ctx->lock);
    event_sched_out(event, cpuctx, ctx);
    list_del_event(event, ctx);
    if (!ctx->nr_events && cpuctx->task_ctx == ctx) {
        ctx->is_active = 0;
        cpuctx->task_ctx = NULL;
    }
    raw_spin_unlock(&ctx->lock);

    return 0;
}


/*
 * Remove the event from a task's (or a CPU's) list of events.
 *
 * CPU events are removed with a smp call. For task events we only
 * call when the task is on a CPU.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This is OK when called from perf_release since
 * that only calls us on the top-level context, which can't be a clone.
 * When called from perf_event_exit_task, it's OK because the
 * context has been detached from its task.
 */
static void perf_remove_from_context(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;
    struct task_struct *task = ctx->task;

    lockdep_assert_held(&ctx->mutex);

    if (!task) {
        /*
         * Per cpu events are removed via an smp call and
         * the removal is always successful.
         */
        cpu_function_call(event->cpu, __perf_remove_from_context, event);
        return;
    }

retry:
    if (!task_function_call(task, __perf_remove_from_context, event))
        return;

    raw_spin_lock_irq(&ctx->lock);
    /*
     * If we failed to find a running task, but find the context active now
     * that we've acquired the ctx->lock, retry.
     */
    if (ctx->is_active) {
        raw_spin_unlock_irq(&ctx->lock);
        goto retry;
    }

    /*
     * Since the task isn't running, its safe to remove the event, us
     * holding the ctx->lock ensures the task won't get scheduled in.
     */
    list_del_event(event, ctx);
    raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Cross CPU call to disable a performance event
 */
int __perf_event_disable(void *info)
{
    struct perf_event *event = info;
    struct perf_event_context *ctx = event->ctx;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

    /*
     * If this is a per-task event, need to check whether this
     * event's task is the current task on this cpu.
     *
     * Can trigger due to concurrent perf_event_context_sched_out()
     * flipping contexts around.
     */
    if (ctx->task && cpuctx->task_ctx != ctx)
        return -EINVAL;

    raw_spin_lock(&ctx->lock);

    /*
     * If the event is on, turn it off.
     * If it is in error state, leave it in error state.
     */
    if (event->state >= PERF_EVENT_STATE_INACTIVE) {
        update_context_time(ctx);
        update_cgrp_time_from_event(event);
        update_group_times(event);
        if (event == event->group_leader)
            group_sched_out(event, cpuctx, ctx);
        else
            event_sched_out(event, cpuctx, ctx);
        event->state = PERF_EVENT_STATE_OFF;
    }

    raw_spin_unlock(&ctx->lock);

    return 0;
}

/*
 * Disable a event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisifed when called through
 * perf_event_for_each_child or perf_event_for_each because they
 * hold the top-level event's child_mutex, so any descendant that
 * goes to exit will block in sync_child_event.
 * When called from perf_pending_event it's OK because event->ctx
 * is the current context on this CPU and preemption is disabled,
 * hence we can't get into perf_event_task_sched_out for this context.
 */
void perf_event_disable(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;
    struct task_struct *task = ctx->task;

    if (!task) {
        /*
         * Disable the event on the cpu that it's on
         */
        cpu_function_call(event->cpu, __perf_event_disable, event);
        return;
    }

retry:
    if (!task_function_call(task, __perf_event_disable, event))
        return;

    raw_spin_lock_irq(&ctx->lock);
    /*
     * If the event is still active, we need to retry the cross-call.
     */
    if (event->state == PERF_EVENT_STATE_ACTIVE) {
        raw_spin_unlock_irq(&ctx->lock);
        /*
         * Reload the task pointer, it might have been changed by
         * a concurrent perf_event_context_sched_out().
         */
        task = ctx->task;
        goto retry;
    }

    /*
     * Since we have the lock this context can't be scheduled
     * in, so we can change the state safely.
     */
    if (event->state == PERF_EVENT_STATE_INACTIVE) {
        update_group_times(event);
        event->state = PERF_EVENT_STATE_OFF;
    }
    raw_spin_unlock_irq(&ctx->lock);
}
EXPORT_SYMBOL_GPL(perf_event_disable);

static void perf_set_shadow_time(struct perf_event *event,
                 struct perf_event_context *ctx,
                 u64 tstamp)
{
    /*
     * use the correct time source for the time snapshot
     *
     * We could get by without this by leveraging the
     * fact that to get to this function, the caller
     * has most likely already called update_context_time()
     * and update_cgrp_time_xx() and thus both timestamp
     * are identical (or very close). Given that tstamp is,
     * already adjusted for cgroup, we could say that:
     *    tstamp - ctx->timestamp
     * is equivalent to
     *    tstamp - cgrp->timestamp.
     *
     * Then, in perf_output_read(), the calculation would
     * work with no changes because:
     * - event is guaranteed scheduled in
     * - no scheduled out in between
     * - thus the timestamp would be the same
     *
     * But this is a bit hairy.
     *
     * So instead, we have an explicit cgroup call to remain
     * within the time time source all along. We believe it
     * is cleaner and simpler to understand.
     */
    if (is_cgroup_event(event))
        perf_cgroup_set_shadow_time(event, tstamp);
    else
        event->shadow_ctx_time = tstamp - ctx->timestamp;
}

#define MAX_INTERRUPTS (~0ULL)

static void perf_log_throttle(struct perf_event *event, int enable);

static int
event_sched_in(struct perf_event *event,
         struct perf_cpu_context *cpuctx,
         struct perf_event_context *ctx)
{
    u64 tstamp = perf_event_time(event);

    if (event->state <= PERF_EVENT_STATE_OFF)
        return 0;

    event->state = PERF_EVENT_STATE_ACTIVE;
    event->oncpu = smp_processor_id();

    /*
     * Unthrottle events, since we scheduled we might have missed several
     * ticks already, also for a heavily scheduling task there is little
     * guarantee it'll get a tick in a timely manner.
     */
    if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
        perf_log_throttle(event, 1);
        event->hw.interrupts = 0;
    }

    /*
     * The new state must be visible before we turn it on in the hardware:
     */
    smp_wmb();

    if (event->pmu->add(event, PERF_EF_START)) {
        event->state = PERF_EVENT_STATE_INACTIVE;
        event->oncpu = -1;
        return -EAGAIN;
    }

    event->tstamp_running += tstamp - event->tstamp_stopped;

    perf_set_shadow_time(event, ctx, tstamp);

    if (!is_software_event(event))
        cpuctx->active_oncpu++;
    ctx->nr_active++;
    if (event->attr.freq && event->attr.sample_freq)
        ctx->nr_freq++;

    if (event->attr.exclusive)
        cpuctx->exclusive = 1;

    return 0;
}

static int
group_sched_in(struct perf_event *group_event,
           struct perf_cpu_context *cpuctx,
           struct perf_event_context *ctx)
{
    struct perf_event *event, *partial_group = NULL;
    struct pmu *pmu = group_event->pmu;
    u64 now = ctx->time;
    bool simulate = false;

    if (group_event->state == PERF_EVENT_STATE_OFF)
        return 0;

    pmu->start_txn(pmu);

    if (event_sched_in(group_event, cpuctx, ctx)) {
        pmu->cancel_txn(pmu);
        return -EAGAIN;
    }

    /*
     * Schedule in siblings as one group (if any):
     */
    list_for_each_entry(event, &group_event->sibling_list, group_entry) {
        if (event_sched_in(event, cpuctx, ctx)) {
            partial_group = event;
            goto group_error;
        }
    }

    if (!pmu->commit_txn(pmu))
        return 0;

group_error:
    /*
     * Groups can be scheduled in as one unit only, so undo any
     * partial group before returning:
     * The events up to the failed event are scheduled out normally,
     * tstamp_stopped will be updated.
     *
     * The failed events and the remaining siblings need to have
     * their timings updated as if they had gone thru event_sched_in()
     * and event_sched_out(). This is required to get consistent timings
     * across the group. This also takes care of the case where the group
     * could never be scheduled by ensuring tstamp_stopped is set to mark
     * the time the event was actually stopped, such that time delta
     * calculation in update_event_times() is correct.
     */
    list_for_each_entry(event, &group_event->sibling_list, group_entry) {
        if (event == partial_group)
            simulate = true;

        if (simulate) {
            event->tstamp_running += now - event->tstamp_stopped;
            event->tstamp_stopped = now;
        } else {
            event_sched_out(event, cpuctx, ctx);
        }
    }
    event_sched_out(group_event, cpuctx, ctx);

    pmu->cancel_txn(pmu);

    return -EAGAIN;
}

/*
 * Work out whether we can put this event group on the CPU now.
 */
static int group_can_go_on(struct perf_event *event,
               struct perf_cpu_context *cpuctx,
               int can_add_hw)
{
    /*
     * Groups consisting entirely of software events can always go on.
     */
    if (event->group_flags & PERF_GROUP_SOFTWARE)
        return 1;
    /*
     * If an exclusive group is already on, no other hardware
     * events can go on.
     */
    if (cpuctx->exclusive)
        return 0;
    /*
     * If this group is exclusive and there are already
     * events on the CPU, it can't go on.
     */
    if (event->attr.exclusive && cpuctx->active_oncpu)
        return 0;
    /*
     * Otherwise, try to add it if all previous groups were able
     * to go on.
     */
    return can_add_hw;
}

static void add_event_to_ctx(struct perf_event *event,
                   struct perf_event_context *ctx)
{
    u64 tstamp = perf_event_time(event);

    list_add_event(event, ctx);
    perf_group_attach(event);
    event->tstamp_enabled = tstamp;
    event->tstamp_running = tstamp;
    event->tstamp_stopped = tstamp;
}

static void task_ctx_sched_out(struct perf_event_context *ctx);
static void
ctx_sched_in(struct perf_event_context *ctx,
         struct perf_cpu_context *cpuctx,
         enum event_type_t event_type,
         struct task_struct *task);

static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
                struct perf_event_context *ctx,
                struct task_struct *task)
{
    cpu_ctx_sched_in(cpuctx, EVENT_PINNED, task);
    if (ctx)
        ctx_sched_in(ctx, cpuctx, EVENT_PINNED, task);
    cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE, task);
    if (ctx)
        ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task);
}

/*
 * Cross CPU call to install and enable a performance event
 *
 * Must be called with ctx->mutex held
 */
static int  __perf_install_in_context(void *info)
{
    struct perf_event *event = info;
    struct perf_event_context *ctx = event->ctx;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
    struct perf_event_context *task_ctx = cpuctx->task_ctx;
    struct task_struct *task = current;

    perf_ctx_lock(cpuctx, task_ctx);
    perf_pmu_disable(cpuctx->ctx.pmu);

    /*
     * If there was an active task_ctx schedule it out.
     */
    if (task_ctx)
        task_ctx_sched_out(task_ctx);

    /*
     * If the context we're installing events in is not the
     * active task_ctx, flip them.
     */
    if (ctx->task && task_ctx != ctx) {
        if (task_ctx)
            raw_spin_unlock(&task_ctx->lock);
        raw_spin_lock(&ctx->lock);
        task_ctx = ctx;
    }

    if (task_ctx) {
        cpuctx->task_ctx = task_ctx;
        task = task_ctx->task;
    }

    cpu_ctx_sched_out(cpuctx, EVENT_ALL);

    update_context_time(ctx);
    /*
     * update cgrp time only if current cgrp
     * matches event->cgrp. Must be done before
     * calling add_event_to_ctx()
     */
    update_cgrp_time_from_event(event);

    add_event_to_ctx(event, ctx);

    /*
     * Schedule everything back in
     */
    perf_event_sched_in(cpuctx, task_ctx, task);

    perf_pmu_enable(cpuctx->ctx.pmu);
    perf_ctx_unlock(cpuctx, task_ctx);

    return 0;
}

/*
 * Attach a performance event to a context
 *
 * First we add the event to the list with the hardware enable bit
 * in event->hw_config cleared.
 *
 * If the event is attached to a task which is on a CPU we use a smp
 * call to enable it in the task context. The task might have been
 * scheduled away, but we check this in the smp call again.
 */
static void
perf_install_in_context(struct perf_event_context *ctx,
            struct perf_event *event,
            int cpu)
{
    struct task_struct *task = ctx->task;

    lockdep_assert_held(&ctx->mutex);

    event->ctx = ctx;
    if (event->cpu != -1)
        event->cpu = cpu;

    if (!task) {
        /*
         * Per cpu events are installed via an smp call and
         * the install is always successful.
         */
        cpu_function_call(cpu, __perf_install_in_context, event);
        return;
    }

retry:
    if (!task_function_call(task, __perf_install_in_context, event))
        return;

    raw_spin_lock_irq(&ctx->lock);
    /*
     * If we failed to find a running task, but find the context active now
     * that we've acquired the ctx->lock, retry.
     */
    if (ctx->is_active) {
        raw_spin_unlock_irq(&ctx->lock);
        goto retry;
    }

    /*
     * Since the task isn't running, its safe to add the event, us holding
     * the ctx->lock ensures the task won't get scheduled in.
     */
    add_event_to_ctx(event, ctx);
    raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Put a event into inactive state and update time fields.
 * Enabling the leader of a group effectively enables all
 * the group members that aren't explicitly disabled, so we
 * have to update their ->tstamp_enabled also.
 * Note: this works for group members as well as group leaders
 * since the non-leader members' sibling_lists will be empty.
 */
static void __perf_event_mark_enabled(struct perf_event *event)
{
    struct perf_event *sub;
    u64 tstamp = perf_event_time(event);

    event->state = PERF_EVENT_STATE_INACTIVE;
    event->tstamp_enabled = tstamp - event->total_time_enabled;
    list_for_each_entry(sub, &event->sibling_list, group_entry) {
        if (sub->state >= PERF_EVENT_STATE_INACTIVE)
            sub->tstamp_enabled = tstamp - sub->total_time_enabled;
    }
}

/*
 * Cross CPU call to enable a performance event
 */
static int __perf_event_enable(void *info)
{
    struct perf_event *event = info;
    struct perf_event_context *ctx = event->ctx;
    struct perf_event *leader = event->group_leader;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
    int err;

    if (WARN_ON_ONCE(!ctx->is_active))
        return -EINVAL;

    raw_spin_lock(&ctx->lock);
    update_context_time(ctx);

    if (event->state >= PERF_EVENT_STATE_INACTIVE)
        goto unlock;

    /*
     * set current task's cgroup time reference point
     */
    perf_cgroup_set_timestamp(current, ctx);

    __perf_event_mark_enabled(event);

    if (!event_filter_match(event)) {
        if (is_cgroup_event(event))
            perf_cgroup_defer_enabled(event);
        goto unlock;
    }

    /*
     * If the event is in a group and isn't the group leader,
     * then don't put it on unless the group is on.
     */
    if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
        goto unlock;

    if (!group_can_go_on(event, cpuctx, 1)) {
        err = -EEXIST;
    } else {
        if (event == leader)
            err = group_sched_in(event, cpuctx, ctx);
        else
            err = event_sched_in(event, cpuctx, ctx);
    }

    if (err) {
        /*
         * If this event can't go on and it's part of a
         * group, then the whole group has to come off.
         */
        if (leader != event)
            group_sched_out(leader, cpuctx, ctx);
        if (leader->attr.pinned) {
            update_group_times(leader);
            leader->state = PERF_EVENT_STATE_ERROR;
        }
    }

unlock:
    raw_spin_unlock(&ctx->lock);

    return 0;
}

/*
 * Enable a event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisfied when called through
 * perf_event_for_each_child or perf_event_for_each as described
 * for perf_event_disable.
 */
void perf_event_enable(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;
    struct task_struct *task = ctx->task;

    if (!task) {
        /*
         * Enable the event on the cpu that it's on
         */
        cpu_function_call(event->cpu, __perf_event_enable, event);
        return;
    }

    raw_spin_lock_irq(&ctx->lock);
    if (event->state >= PERF_EVENT_STATE_INACTIVE)
        goto out;

    /*
     * If the event is in error state, clear that first.
     * That way, if we see the event in error state below, we
     * know that it has gone back into error state, as distinct
     * from the task having been scheduled away before the
     * cross-call arrived.
     */
    if (event->state == PERF_EVENT_STATE_ERROR)
        event->state = PERF_EVENT_STATE_OFF;

retry:
    if (!ctx->is_active) {
        __perf_event_mark_enabled(event);
        goto out;
    }

    raw_spin_unlock_irq(&ctx->lock);

    if (!task_function_call(task, __perf_event_enable, event))
        return;

    raw_spin_lock_irq(&ctx->lock);

    /*
     * If the context is active and the event is still off,
     * we need to retry the cross-call.
     */
    if (ctx->is_active && event->state == PERF_EVENT_STATE_OFF) {
        /*
         * task could have been flipped by a concurrent
         * perf_event_context_sched_out()
         */
        task = ctx->task;
        goto retry;
    }

out:
    raw_spin_unlock_irq(&ctx->lock);
}
EXPORT_SYMBOL_GPL(perf_event_enable);

int perf_event_refresh(struct perf_event *event, int refresh)
{
    /*
     * not supported on inherited events
     */
    if (event->attr.inherit || !is_sampling_event(event))
        return -EINVAL;

    atomic_add(refresh, &event->event_limit);
    perf_event_enable(event);

    return 0;
}
EXPORT_SYMBOL_GPL(perf_event_refresh);

static void ctx_sched_out(struct perf_event_context *ctx,
              struct perf_cpu_context *cpuctx,
              enum event_type_t event_type)
{
    struct perf_event *event;
    int is_active = ctx->is_active;

    ctx->is_active &= ~event_type;
    if (likely(!ctx->nr_events))
        return;

    update_context_time(ctx);
    update_cgrp_time_from_cpuctx(cpuctx);
    if (!ctx->nr_active)
        return;

    perf_pmu_disable(ctx->pmu);
    if ((is_active & EVENT_PINNED) && (event_type & EVENT_PINNED)) {
        list_for_each_entry(event, &ctx->pinned_groups, group_entry)
            group_sched_out(event, cpuctx, ctx);
    }

    if ((is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE)) {
        list_for_each_entry(event, &ctx->flexible_groups, group_entry)
            group_sched_out(event, cpuctx, ctx);
    }
    perf_pmu_enable(ctx->pmu);
}

/*
 * Test whether two contexts are equivalent, i.e. whether they
 * have both been cloned from the same version of the same context
 * and they both have the same number of enabled events.
 * If the number of enabled events is the same, then the set
 * of enabled events should be the same, because these are both
 * inherited contexts, therefore we can't access individual events
 * in them directly with an fd; we can only enable/disable all
 * events via prctl, or enable/disable all events in a family
 * via ioctl, which will have the same effect on both contexts.
 */
static int context_equiv(struct perf_event_context *ctx1,
             struct perf_event_context *ctx2)
{
    return ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx
        && ctx1->parent_gen == ctx2->parent_gen
        && !ctx1->pin_count && !ctx2->pin_count;
}

static void __perf_event_sync_stat(struct perf_event *event,
                     struct perf_event *next_event)
{
    u64 value;

    if (!event->attr.inherit_stat)
        return;

    /*
     * Update the event value, we cannot use perf_event_read()
     * because we're in the middle of a context switch and have IRQs
     * disabled, which upsets smp_call_function_single(), however
     * we know the event must be on the current CPU, therefore we
     * don't need to use it.
     */
    switch (event->state) {
    case PERF_EVENT_STATE_ACTIVE:
        event->pmu->read(event);
        /* fall-through */

    case PERF_EVENT_STATE_INACTIVE:
        update_event_times(event);
        break;

    default:
        break;
    }

    /*
     * In order to keep per-task stats reliable we need to flip the event
     * values when we flip the contexts.
     */
    value = local64_read(&next_event->count);
    value = local64_xchg(&event->count, value);
    local64_set(&next_event->count, value);

    swap(event->total_time_enabled, next_event->total_time_enabled);
    swap(event->total_time_running, next_event->total_time_running);

    /*
     * Since we swizzled the values, update the user visible data too.
     */
    perf_event_update_userpage(event);
    perf_event_update_userpage(next_event);
}

#define list_next_entry(pos, member) \
    list_entry(pos->member.next, typeof(*pos), member)

static void perf_event_sync_stat(struct perf_event_context *ctx,
                   struct perf_event_context *next_ctx)
{
    struct perf_event *event, *next_event;

    if (!ctx->nr_stat)
        return;

    update_context_time(ctx);

    event = list_first_entry(&ctx->event_list,
                   struct perf_event, event_entry);

    next_event = list_first_entry(&next_ctx->event_list,
                    struct perf_event, event_entry);

    while (&event->event_entry != &ctx->event_list &&
           &next_event->event_entry != &next_ctx->event_list) {

        __perf_event_sync_stat(event, next_event);

        event = list_next_entry(event, event_entry);
        next_event = list_next_entry(next_event, event_entry);
    }
}

static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
                     struct task_struct *next)
{
    struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
    struct perf_event_context *next_ctx;
    struct perf_event_context *parent;
    struct perf_cpu_context *cpuctx;
    int do_switch = 1;

    if (likely(!ctx))
        return;

    cpuctx = __get_cpu_context(ctx);
    if (!cpuctx->task_ctx)
        return;

    rcu_read_lock();
    parent = rcu_dereference(ctx->parent_ctx);
    next_ctx = next->perf_event_ctxp[ctxn];
    if (parent && next_ctx &&
        rcu_dereference(next_ctx->parent_ctx) == parent) {
        /*
         * Looks like the two contexts are clones, so we might be
         * able to optimize the context switch.  We lock both
         * contexts and check that they are clones under the
         * lock (including re-checking that neither has been
         * uncloned in the meantime).  It doesn't matter which
         * order we take the locks because no other cpu could
         * be trying to lock both of these tasks.
         */
        raw_spin_lock(&ctx->lock);
        raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
        if (context_equiv(ctx, next_ctx)) {
            /*
             * XXX do we need a memory barrier of sorts
             * wrt to rcu_dereference() of perf_event_ctxp
             */
            task->perf_event_ctxp[ctxn] = next_ctx;
            next->perf_event_ctxp[ctxn] = ctx;
            ctx->task = next;
            next_ctx->task = task;
            do_switch = 0;

            perf_event_sync_stat(ctx, next_ctx);
        }
        raw_spin_unlock(&next_ctx->lock);
        raw_spin_unlock(&ctx->lock);
    }
    rcu_read_unlock();

    if (do_switch) {
        raw_spin_lock(&ctx->lock);
        ctx_sched_out(ctx, cpuctx, EVENT_ALL);
        cpuctx->task_ctx = NULL;
        raw_spin_unlock(&ctx->lock);
    }
}

#define for_each_task_context_nr(ctxn)                  \
    for ((ctxn) = 0; (ctxn) < perf_nr_task_contexts; (ctxn)++)

/*
 * Called from scheduler to remove the events of the current task,
 * with interrupts disabled.
 *
 * We stop each event and update the event value in event->count.
 *
 * This does not protect us against NMI, but disable()
 * sets the disabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * not restart the event.
 */
void __perf_event_task_sched_out(struct task_struct *task,
                 struct task_struct *next)
{
    int ctxn;

    for_each_task_context_nr(ctxn)
        perf_event_context_sched_out(task, ctxn, next);

    /*
     * if cgroup events exist on this CPU, then we need
     * to check if we have to switch out PMU state.
     * cgroup event are system-wide mode only
     */
    if (atomic_read(&__get_cpu_var(perf_cgroup_events)))
        perf_cgroup_sched_out(task, next);
}

static void task_ctx_sched_out(struct perf_event_context *ctx)
{
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

    if (!cpuctx->task_ctx)
        return;

    if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
        return;

    ctx_sched_out(ctx, cpuctx, EVENT_ALL);
    cpuctx->task_ctx = NULL;
}

/*
 * Called with IRQs disabled
 */
static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                  enum event_type_t event_type)
{
    ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
}

static void
ctx_pinned_sched_in(struct perf_event_context *ctx,
            struct perf_cpu_context *cpuctx)
{
    struct perf_event *event;

    list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
        if (event->state <= PERF_EVENT_STATE_OFF)
            continue;
        if (!event_filter_match(event))
            continue;

        /* may need to reset tstamp_enabled */
        if (is_cgroup_event(event))
            perf_cgroup_mark_enabled(event, ctx);

        if (group_can_go_on(event, cpuctx, 1))
            group_sched_in(event, cpuctx, ctx);

        /*
         * If this pinned group hasn't been scheduled,
         * put it in error state.
         */
        if (event->state == PERF_EVENT_STATE_INACTIVE) {
            update_group_times(event);
            event->state = PERF_EVENT_STATE_ERROR;
        }
    }
}

static void
ctx_flexible_sched_in(struct perf_event_context *ctx,
              struct perf_cpu_context *cpuctx)
{
    struct perf_event *event;
    int can_add_hw = 1;

    list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
        /* Ignore events in OFF or ERROR state */
        if (event->state <= PERF_EVENT_STATE_OFF)
            continue;
        /*
         * Listen to the 'cpu' scheduling filter constraint
         * of events:
         */
        if (!event_filter_match(event))
            continue;

        /* may need to reset tstamp_enabled */
        if (is_cgroup_event(event))
            perf_cgroup_mark_enabled(event, ctx);

        if (group_can_go_on(event, cpuctx, can_add_hw)) {
            if (group_sched_in(event, cpuctx, ctx))
                can_add_hw = 0;
        }
    }
}

static void
ctx_sched_in(struct perf_event_context *ctx,
         struct perf_cpu_context *cpuctx,
         enum event_type_t event_type,
         struct task_struct *task)
{
    u64 now;
    int is_active = ctx->is_active;

    ctx->is_active |= event_type;
    if (likely(!ctx->nr_events))
        return;

    now = perf_clock();
    ctx->timestamp = now;
    perf_cgroup_set_timestamp(task, ctx);
    /*
     * First go through the list and put on any pinned groups
     * in order to give them the best chance of going on.
     */
    if (!(is_active & EVENT_PINNED) && (event_type & EVENT_PINNED))
        ctx_pinned_sched_in(ctx, cpuctx);

    /* Then walk through the lower prio flexible groups */
    if (!(is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE))
        ctx_flexible_sched_in(ctx, cpuctx);
}

static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                 enum event_type_t event_type,
                 struct task_struct *task)
{
    struct perf_event_context *ctx = &cpuctx->ctx;

    ctx_sched_in(ctx, cpuctx, event_type, task);
}

static void perf_event_context_sched_in(struct perf_event_context *ctx,
                    struct task_struct *task)
{
    struct perf_cpu_context *cpuctx;

    cpuctx = __get_cpu_context(ctx);
    if (cpuctx->task_ctx == ctx)
        return;

    perf_ctx_lock(cpuctx, ctx);
    perf_pmu_disable(ctx->pmu);
    /*
     * We want to keep the following priority order:
     * cpu pinned (that don't need to move), task pinned,
     * cpu flexible, task flexible.
     */
    cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

    if (ctx->nr_events)
        cpuctx->task_ctx = ctx;

    perf_event_sched_in(cpuctx, cpuctx->task_ctx, task);

    perf_pmu_enable(ctx->pmu);
    perf_ctx_unlock(cpuctx, ctx);

    /*
     * Since these rotations are per-cpu, we need to ensure the
     * cpu-context we got scheduled on is actually rotating.
     */
    perf_pmu_rotate_start(ctx->pmu);
}

/*
 * When sampling the branck stack in system-wide, it may be necessary
 * to flush the stack on context switch. This happens when the branch
 * stack does not tag its entries with the pid of the current task.
 * Otherwise it becomes impossible to associate a branch entry with a
 * task. This ambiguity is more likely to appear when the branch stack
 * supports priv level filtering and the user sets it to monitor only
 * at the user level (which could be a useful measurement in system-wide
 * mode). In that case, the risk is high of having a branch stack with
 * branch from multiple tasks. Flushing may mean dropping the existing
 * entries or stashing them somewhere in the PMU specific code layer.
 *
 * This function provides the context switch callback to the lower code
 * layer. It is invoked ONLY when there is at least one system-wide context
 * with at least one active event using taken branch sampling.
 */
static void perf_branch_stack_sched_in(struct task_struct *prev,
                       struct task_struct *task)
{
    struct perf_cpu_context *cpuctx;
    struct pmu *pmu;
    unsigned long flags;

    /* no need to flush branch stack if not changing task */
    if (prev == task)
        return;

    local_irq_save(flags);

    rcu_read_lock();

    list_for_each_entry_rcu(pmu, &pmus, entry) {
        cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

        /*
         * check if the context has at least one
         * event using PERF_SAMPLE_BRANCH_STACK
         */
        if (cpuctx->ctx.nr_branch_stack > 0
            && pmu->flush_branch_stack) {

            pmu = cpuctx->ctx.pmu;

            perf_ctx_lock(cpuctx, cpuctx->task_ctx);

            perf_pmu_disable(pmu);

            pmu->flush_branch_stack();

            perf_pmu_enable(pmu);

            perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
        }
    }

    rcu_read_unlock();

    local_irq_restore(flags);
}

/*
 * Called from scheduler to add the events of the current task
 * with interrupts disabled.
 *
 * We restore the event value and then enable it.
 *
 * This does not protect us against NMI, but enable()
 * sets the enabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * keep the event running.
 */
void __perf_event_task_sched_in(struct task_struct *prev,
                struct task_struct *task)
{
    struct perf_event_context *ctx;
    int ctxn;

    for_each_task_context_nr(ctxn) {
        ctx = task->perf_event_ctxp[ctxn];
        if (likely(!ctx))
            continue;

        perf_event_context_sched_in(ctx, task);
    }
    /*
     * if cgroup events exist on this CPU, then we need
     * to check if we have to switch in PMU state.
     * cgroup event are system-wide mode only
     */
    if (atomic_read(&__get_cpu_var(perf_cgroup_events)))
        perf_cgroup_sched_in(prev, task);

    /* check for system-wide branch_stack events */
    if (atomic_read(&__get_cpu_var(perf_branch_stack_events)))
        perf_branch_stack_sched_in(prev, task);
}

static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
    u64 frequency = event->attr.sample_freq;
    u64 sec = NSEC_PER_SEC;
    u64 divisor, dividend;

    int count_fls, nsec_fls, frequency_fls, sec_fls;

    count_fls = fls64(count);
    nsec_fls = fls64(nsec);
    frequency_fls = fls64(frequency);
    sec_fls = 30;

    /*
     * We got @count in @nsec, with a target of sample_freq HZ
     * the target period becomes:
     *
     *             @count * 10^9
     * period = -------------------
     *          @nsec * sample_freq
     *
     */

    /*
     * Reduce accuracy by one bit such that @a and @b converge
     * to a similar magnitude.
     */
#define REDUCE_FLS(a, b)        \
do {                    \
    if (a##_fls > b##_fls) {    \
        a >>= 1;        \
        a##_fls--;      \
    } else {            \
        b >>= 1;        \
        b##_fls--;      \
    }               \
} while (0)

    /*
     * Reduce accuracy until either term fits in a u64, then proceed with
     * the other, so that finally we can do a u64/u64 division.
     */
    while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
        REDUCE_FLS(nsec, frequency);
        REDUCE_FLS(sec, count);
    }

    if (count_fls + sec_fls > 64) {
        divisor = nsec * frequency;

        while (count_fls + sec_fls > 64) {
            REDUCE_FLS(count, sec);
            divisor >>= 1;
        }

        dividend = count * sec;
    } else {
        dividend = count * sec;

        while (nsec_fls + frequency_fls > 64) {
            REDUCE_FLS(nsec, frequency);
            dividend >>= 1;
        }

        divisor = nsec * frequency;
    }

    if (!divisor)
        return dividend;

    return div64_u64(dividend, divisor);
}

static DEFINE_PER_CPU(int, perf_throttled_count);
static DEFINE_PER_CPU(u64, perf_throttled_seq);

static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bool disable)
{
    struct hw_perf_event *hwc = &event->hw;
    s64 period, sample_period;
    s64 delta;

    period = perf_calculate_period(event, nsec, count);

    delta = (s64)(period - hwc->sample_period);
    delta = (delta + 7) / 8; /* low pass filter */

    sample_period = hwc->sample_period + delta;

    if (!sample_period)
        sample_period = 1;

    hwc->sample_period = sample_period;

    if (local64_read(&hwc->period_left) > 8*sample_period) {
        if (disable)
            event->pmu->stop(event, PERF_EF_UPDATE);

        local64_set(&hwc->period_left, 0);

        if (disable)
            event->pmu->start(event, PERF_EF_RELOAD);
    }
}

/*
 * combine freq adjustment with unthrottling to avoid two passes over the
 * events. At the same time, make sure, having freq events does not change
 * the rate of unthrottling as that would introduce bias.
 */
static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
                       int needs_unthr)
{
    struct perf_event *event;
    struct hw_perf_event *hwc;
    u64 now, period = TICK_NSEC;
    s64 delta;

    /*
     * only need to iterate over all events iff:
     * - context have events in frequency mode (needs freq adjust)
     * - there are events to unthrottle on this cpu
     */
    if (!(ctx->nr_freq || needs_unthr))
        return;

    raw_spin_lock(&ctx->lock);
    perf_pmu_disable(ctx->pmu);

    list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
        if (event->state != PERF_EVENT_STATE_ACTIVE)
            continue;

        if (!event_filter_match(event))
            continue;

        hwc = &event->hw;

        if (needs_unthr && hwc->interrupts == MAX_INTERRUPTS) {
            hwc->interrupts = 0;
            perf_log_throttle(event, 1);
            event->pmu->start(event, 0);
        }

        if (!event->attr.freq || !event->attr.sample_freq)
            continue;

        /*
         * stop the event and update event->count
         */
        event->pmu->stop(event, PERF_EF_UPDATE);

        now = local64_read(&event->count);
        delta = now - hwc->freq_count_stamp;
        hwc->freq_count_stamp = now;

        /*
         * restart the event
         * reload only if value has changed
         * we have stopped the event so tell that
         * to perf_adjust_period() to avoid stopping it
         * twice.
         */
        if (delta > 0)
            perf_adjust_period(event, period, delta, false);

        event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
    }

    perf_pmu_enable(ctx->pmu);
    raw_spin_unlock(&ctx->lock);
}

/*
 * Round-robin a context's events:
 */
static void rotate_ctx(struct perf_event_context *ctx)
{
    /*
     * Rotate the first entry last of non-pinned groups. Rotation might be
     * disabled by the inheritance code.
     */
    if (!ctx->rotate_disable)
        list_rotate_left(&ctx->flexible_groups);
}

/*
 * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
 * because they're strictly cpu affine and rotate_start is called with IRQs
 * disabled, while rotate_context is called from IRQ context.
 */
static void perf_rotate_context(struct perf_cpu_context *cpuctx)
{
    struct perf_event_context *ctx = NULL;
    int rotate = 0, remove = 1;

    if (cpuctx->ctx.nr_events) {
        remove = 0;
        if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
            rotate = 1;
    }

    ctx = cpuctx->task_ctx;
    if (ctx && ctx->nr_events) {
        remove = 0;
        if (ctx->nr_events != ctx->nr_active)
            rotate = 1;
    }

    if (!rotate)
        goto done;

    perf_ctx_lock(cpuctx, cpuctx->task_ctx);
    perf_pmu_disable(cpuctx->ctx.pmu);

    cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
    if (ctx)
        ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);

    rotate_ctx(&cpuctx->ctx);
    if (ctx)
        rotate_ctx(ctx);

    perf_event_sched_in(cpuctx, ctx, current);

    perf_pmu_enable(cpuctx->ctx.pmu);
    perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
done:
    if (remove)
        list_del_init(&cpuctx->rotation_list);
}

void perf_event_task_tick(void)
{
    struct list_head *head = &__get_cpu_var(rotation_list);
    struct perf_cpu_context *cpuctx, *tmp;
    struct perf_event_context *ctx;
    int throttled;

    WARN_ON(!irqs_disabled());

    __this_cpu_inc(perf_throttled_seq);
    throttled = __this_cpu_xchg(perf_throttled_count, 0);

    list_for_each_entry_safe(cpuctx, tmp, head, rotation_list) {
        ctx = &cpuctx->ctx;
        perf_adjust_freq_unthr_context(ctx, throttled);

        ctx = cpuctx->task_ctx;
        if (ctx)
            perf_adjust_freq_unthr_context(ctx, throttled);

        if (cpuctx->jiffies_interval == 1 ||
                !(jiffies % cpuctx->jiffies_interval))
            perf_rotate_context(cpuctx);
    }
}

static int event_enable_on_exec(struct perf_event *event,
                struct perf_event_context *ctx)
{
    if (!event->attr.enable_on_exec)
        return 0;

    event->attr.enable_on_exec = 0;
    if (event->state >= PERF_EVENT_STATE_INACTIVE)
        return 0;

    __perf_event_mark_enabled(event);

    return 1;
}

/*
 * Enable all of a task's events that have been marked enable-on-exec.
 * This expects task == current.
 */
static void perf_event_enable_on_exec(struct perf_event_context *ctx)
{
    struct perf_event *event;
    unsigned long flags;
    int enabled = 0;
    int ret;

    local_irq_save(flags);
    if (!ctx || !ctx->nr_events)
        goto out;

    /*
     * We must ctxsw out cgroup events to avoid conflict
     * when invoking perf_task_event_sched_in() later on
     * in this function. Otherwise we end up trying to
     * ctxswin cgroup events which are already scheduled
     * in.
     */
    perf_cgroup_sched_out(current, NULL);

    raw_spin_lock(&ctx->lock);
    task_ctx_sched_out(ctx);

    list_for_each_entry(event, &ctx->event_list, event_entry) {
        ret = event_enable_on_exec(event, ctx);
        if (ret)
            enabled = 1;
    }

    /*
     * Unclone this context if we enabled any event.
     */
    if (enabled)
        unclone_ctx(ctx);

    raw_spin_unlock(&ctx->lock);

    /*
     * Also calls ctxswin for cgroup events, if any:
     */
    perf_event_context_sched_in(ctx, ctx->task);
out:
    local_irq_restore(flags);
}

/*
 * Cross CPU call to read the hardware event
 */
static void __perf_event_read(void *info)
{
    struct perf_event *event = info;
    struct perf_event_context *ctx = event->ctx;
    struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

    /*
     * If this is a task context, we need to check whether it is
     * the current task context of this cpu.  If not it has been
     * scheduled out before the smp call arrived.  In that case
     * event->count would have been updated to a recent sample
     * when the event was scheduled out.
     */
    if (ctx->task && cpuctx->task_ctx != ctx)
        return;

    raw_spin_lock(&ctx->lock);
    if (ctx->is_active) {
        update_context_time(ctx);
        update_cgrp_time_from_event(event);
    }
    update_event_times(event);
    if (event->state == PERF_EVENT_STATE_ACTIVE)
        event->pmu->read(event);
    raw_spin_unlock(&ctx->lock);
}

static inline u64 perf_event_count(struct perf_event *event)
{
    return local64_read(&event->count) + atomic64_read(&event->child_count);
}

static u64 perf_event_read(struct perf_event *event)
{
    /*
     * If event is enabled and currently active on a CPU, update the
     * value in the event structure:
     */
    if (event->state == PERF_EVENT_STATE_ACTIVE) {
        smp_call_function_single(event->oncpu,
                     __perf_event_read, event, 1);
    } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
        struct perf_event_context *ctx = event->ctx;
        unsigned long flags;

        raw_spin_lock_irqsave(&ctx->lock, flags);
        /*
         * may read while context is not active
         * (e.g., thread is blocked), in that case
         * we cannot update context time
         */
        if (ctx->is_active) {
            update_context_time(ctx);
            update_cgrp_time_from_event(event);
        }
        update_event_times(event);
        raw_spin_unlock_irqrestore(&ctx->lock, flags);
    }

    return perf_event_count(event);
}

/*
 * Initialize the perf_event context in a task_struct:
 */
static void __perf_event_init_context(struct perf_event_context *ctx)
{
    raw_spin_lock_init(&ctx->lock);
    mutex_init(&ctx->mutex);
    INIT_LIST_HEAD(&ctx->pinned_groups);
    INIT_LIST_HEAD(&ctx->flexible_groups);
    INIT_LIST_HEAD(&ctx->event_list);
    atomic_set(&ctx->refcount, 1);
}

static struct perf_event_context *
alloc_perf_context(struct pmu *pmu, struct task_struct *task)
{
    struct perf_event_context *ctx;

    ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);
    if (!ctx)
        return NULL;

    __perf_event_init_context(ctx);
    if (task) {
        ctx->task = task;
        get_task_struct(task);
    }
    ctx->pmu = pmu;

    return ctx;
}

static struct task_struct *
find_lively_task_by_vpid(pid_t vpid)
{
    struct task_struct *task;
    int err;

    rcu_read_lock();
    if (!vpid)
        task = current;
    else
        task = find_task_by_vpid(vpid);
    if (task)
        get_task_struct(task);
    rcu_read_unlock();

    if (!task)
        return ERR_PTR(-ESRCH);

    /* Reuse ptrace permission checks for now. */
    err = -EACCES;
    if (!ptrace_may_access(task, PTRACE_MODE_READ))
        goto errout;

    return task;
errout:
    put_task_struct(task);
    return ERR_PTR(err);

}

/*
 * Returns a matching context with refcount and pincount.
 */
static struct perf_event_context *
find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
{
    struct perf_event_context *ctx;
    struct perf_cpu_context *cpuctx;
    unsigned long flags;
    int ctxn, err;

    if (!task) {
        /* Must be root to operate on a CPU event: */
        if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
            return ERR_PTR(-EACCES);

        /*
         * We could be clever and allow to attach a event to an
         * offline CPU and activate it when the CPU comes up, but
         * that's for later.
         */
        if (!cpu_online(cpu))
            return ERR_PTR(-ENODEV);

        cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
        ctx = &cpuctx->ctx;
        get_ctx(ctx);
        ++ctx->pin_count;

        return ctx;
    }

    err = -EINVAL;
    ctxn = pmu->task_ctx_nr;
    if (ctxn < 0)
        goto errout;

retry:
    ctx = perf_lock_task_context(task, ctxn, &flags);
    if (ctx) {
        unclone_ctx(ctx);
        ++ctx->pin_count;
        raw_spin_unlock_irqrestore(&ctx->lock, flags);
    } else {
        ctx = alloc_perf_context(pmu, task);
        err = -ENOMEM;
        if (!ctx)
            goto errout;

        err = 0;
        mutex_lock(&task->perf_event_mutex);
        /*
         * If it has already passed perf_event_exit_task().
         * we must see PF_EXITING, it takes this mutex too.
         */
        if (task->flags & PF_EXITING)
            err = -ESRCH;
        else if (task->perf_event_ctxp[ctxn])
            err = -EAGAIN;
        else {
            get_ctx(ctx);
            ++ctx->pin_count;
            rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
        }
        mutex_unlock(&task->perf_event_mutex);

        if (unlikely(err)) {
            put_ctx(ctx);

            if (err == -EAGAIN)
                goto retry;
            goto errout;
        }
    }

    return ctx;

errout:
    return ERR_PTR(err);
}

static void perf_event_free_filter(struct perf_event *event);

static void free_event_rcu(struct rcu_head *head)
{
    struct perf_event *event;

    event = container_of(head, struct perf_event, rcu_head);
    if (event->ns)
        put_pid_ns(event->ns);
    perf_event_free_filter(event);
    kfree(event);
}

static void ring_buffer_put(struct ring_buffer *rb);

static void free_event(struct perf_event *event)
{
    irq_work_sync(&event->pending);

    if (!event->parent) {
        if (event->attach_state & PERF_ATTACH_TASK)
            static_key_slow_dec_deferred(&perf_sched_events);
        if (event->attr.mmap || event->attr.mmap_data)
            atomic_dec(&nr_mmap_events);
        if (event->attr.comm)
            atomic_dec(&nr_comm_events);
        if (event->attr.task)
            atomic_dec(&nr_task_events);
        if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
            put_callchain_buffers();
        if (is_cgroup_event(event)) {
            atomic_dec(&per_cpu(perf_cgroup_events, event->cpu));
            static_key_slow_dec_deferred(&perf_sched_events);
        }

        if (has_branch_stack(event)) {
            static_key_slow_dec_deferred(&perf_sched_events);
            /* is system-wide event */
            if (!(event->attach_state & PERF_ATTACH_TASK))
                atomic_dec(&per_cpu(perf_branch_stack_events,
                            event->cpu));
        }
    }

    if (event->rb) {
        ring_buffer_put(event->rb);
        event->rb = NULL;
    }

    if (is_cgroup_event(event))
        perf_detach_cgroup(event);

    if (event->destroy)
        event->destroy(event);

    if (event->ctx)
        put_ctx(event->ctx);

    call_rcu(&event->rcu_head, free_event_rcu);
}

int perf_event_release_kernel(struct perf_event *event)
{
    struct perf_event_context *ctx = event->ctx;

    WARN_ON_ONCE(ctx->parent_ctx);
    /*
     * There are two ways this annotation is useful:
     *
     *  1) there is a lock recursion from perf_event_exit_task
     *     see the comment there.
     *
     *  2) there is a lock-inversion with mmap_sem through
     *     perf_event_read_group(), which takes faults while
     *     holding ctx->mutex, however this is called after
     *     the last filedesc died, so there is no possibility
     *     to trigger the AB-BA case.
     */
    mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING);
    raw_spin_lock_irq(&ctx->lock);
    perf_group_detach(event);
    raw_spin_unlock_irq(&ctx->lock);
    perf_remove_from_context(event);
    mutex_unlock(&ctx->mutex);

    free_event(event);

    return 0;
}
EXPORT_SYMBOL_GPL(perf_event_release_kernel);

/*
 * Called when the last reference to the file is gone.
 */
static void put_event(struct perf_event *event)
{
    struct task_struct *owner;

    if (!atomic_long_dec_and_test(&event->refcount))
        return;

    rcu_read_lock();
    owner = ACCESS_ONCE(event->owner);
    /*
     * Matches the smp_wmb() in perf_event_exit_task(). If we observe
     * !owner it means the list deletion is complete and we can indeed
     * free this event, otherwise we need to serialize on
     * owner->perf_event_mutex.
     */
    smp_read_barrier_depends();
    if (owner) {
        /*
         * Since delayed_put_task_struct() also drops the last
         * task reference we can safely take a new reference
         * while holding the rcu_read_lock().
         */
        get_task_struct(owner);
    }
    rcu_read_unlock();

    if (owner) {
        mutex_lock(&owner->perf_event_mutex);
        /*
         * We have to re-check the event->owner field, if it is cleared
         * we raced with perf_event_exit_task(), acquiring the mutex
         * ensured they're done, and we can proceed with freeing the
         * event.
         */
        if (event->owner)
            list_del_init(&event->owner_entry);
        mutex_unlock(&owner->perf_event_mutex);
        put_task_struct(owner);
    }

    perf_event_release_kernel(event);
}

static int perf_release(struct inode *inode, struct file *file)
{
    put_event(file->private_data);
    return 0;
}

u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
    struct perf_event *child;
    u64 total = 0;

    *enabled = 0;
    *running = 0;

    mutex_lock(&event->child_mutex);
    total += perf_event_read(event);
    *enabled += event->total_time_enabled +
            atomic64_read(&event->child_total_time_enabled);
    *running += event->total_time_running +
            atomic64_read(&event->child_total_time_running);

    list_for_each_entry(child, &event->child_list, child_list) {
        total += perf_event_read(child);
        *enabled += child->total_time_enabled;
        *running += child->total_time_running;
    }
    mutex_unlock(&event->child_mutex);

    return total;
}
EXPORT_SYMBOL_GPL(perf_event_read_value);

static int perf_event_read_group(struct perf_event *event,
                   u64 read_format, char __user *buf)
{
    struct perf_event *leader = event->group_leader, *sub;
    int n = 0, size = 0, ret = -EFAULT;
    struct perf_event_context *ctx = leader->ctx;
    u64 values[5];
    u64 count, enabled, running;

    mutex_lock(&ctx->mutex);
    count = perf_event_read_value(leader, &enabled, &running);

    values[n++] = 1 + leader->nr_siblings;
    if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
        values[n++] = enabled;
    if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
        values[n++] = running;
    values[n++] = count;
    if (read_format & PERF_FORMAT_ID)
        values[n++] = primary_event_id(leader);

    size = n * sizeof(u64);

    if (copy_to_user(buf, values, size))
        goto unlock;

    ret = size;

    list_for_each_entry(sub, &leader->sibling_list, group_entry) {
        n = 0;

        values[n++] = perf_event_read_value(sub, &enabled, &running);
        if (read_format & PERF_FORMAT_ID)
            values[n++] = primary_event_id(sub);

        size = n * sizeof(u64);

        if (copy_to_user(buf + ret, values, size)) {
            ret = -EFAULT;
            goto unlock;
        }

        ret += size;
    }
unlock:
    mutex_unlock(&ctx->mutex);

    return ret;
}

static int perf_event_read_one(struct perf_event *event,
                 u64 read_format, char __user *buf)
{
    u64 enabled, running;
    u64 values[4];
    int n = 0;

    values[n++] = perf_event_read_value(event, &enabled, &running);
    if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
        values[n++] = enabled;
    if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
        values[n++] = running;
    if (read_format & PERF_FORMAT_ID)
        values[n++] = primary_event_id(event);

    if (copy_to_user(buf, values, n * sizeof(u64)))
        return -EFAULT;

    return n * sizeof(u64);
}

/*
 * Read the performance event - simple non blocking version for now
 */
static ssize_t
perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
{
    u64 read_format = event->attr.read_format;
    int ret;

    /*
     * Return end-of-file for a read on a event that is in
     * error state (i.e. because it was pinned but it couldn't be
     * scheduled on to the CPU at some point).
     */
    if (event->state == PERF_EVENT_STATE_ERROR)
        return 0;

    if (count < event->read_size)
        return -ENOSPC;

    WARN_ON_ONCE(event->ctx->parent_ctx);
    if (read_format & PERF_FORMAT_GROUP)
        ret = perf_event_read_group(event, read_format, buf);
    else
        ret = perf_event_read_one(event, read_format, buf);

    return ret;
}

static ssize_t
perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    struct perf_event *event = file->private_data;

    return perf_read_hw(event, buf, count);
}

static unsigned int perf_poll(struct file *file, poll_table *wait)
{
    struct perf_event *event = file->private_data;
    struct ring_buffer *rb;
    unsigned int events = POLL_HUP;

    /*
     * Race between perf_event_set_output() and perf_poll(): perf_poll()
     * grabs the rb reference but perf_event_set_output() overrides it.
     * Here is the timeline for two threads T1, T2:
     * t0: T1, rb = rcu_dereference(event->rb)
     * t1: T2, old_rb = event->rb
     * t2: T2, event->rb = new rb
     * t3: T2, ring_buffer_detach(old_rb)
     * t4: T1, ring_buffer_attach(rb1)
     * t5: T1, poll_wait(event->waitq)
     *
     * To avoid this problem, we grab mmap_mutex in perf_poll()
     * thereby ensuring that the assignment of the new ring buffer
     * and the detachment of the old buffer appear atomic to perf_poll()
     */
    mutex_lock(&event->mmap_mutex);

    rcu_read_lock();
    rb = rcu_dereference(event->rb);
    if (rb) {
        ring_buffer_attach(event, rb);
        events = atomic_xchg(&rb->poll, 0);
    }
    rcu_read_unlock();

    mutex_unlock(&event->mmap_mutex);

    poll_wait(file, &event->waitq, wait);

    return events;
}

static void perf_event_reset(struct perf_event *event)
{
    (void)perf_event_read(event);
    local64_set(&event->count, 0);
    perf_event_update_userpage(event);
}

/*
 * Holding the top-level event's child_mutex means that any
 * descendant process that has inherited this event will block
 * in sync_child_event if it goes to exit, thus satisfying the
 * task existence requirements of perf_event_enable/disable.
 */
static void perf_event_for_each_child(struct perf_event *event,
                    void (*func)(struct perf_event *))
{
    struct perf_event *child;

    WARN_ON_ONCE(event->ctx->parent_ctx);
    mutex_lock(&event->child_mutex);
    func(event);
    list_for_each_entry(child, &event->child_list, child_list)
        func(child);
    mutex_unlock(&event->child_mutex);
}

static void perf_event_for_each(struct perf_event *event,
                  void (*func)(struct perf_event *))
{
    struct perf_event_context *ctx = event->ctx;
    struct perf_event *sibling;

    WARN_ON_ONCE(ctx->parent_ctx);
    mutex_lock(&ctx->mutex);
    event = event->group_leader;

    perf_event_for_each_child(event, func);
    list_for_each_entry(sibling, &event->sibling_list, group_entry)
        perf_event_for_each_child(sibling, func);
    mutex_unlock(&ctx->mutex);
}

static int perf_event_period(struct perf_event *event, u64 __user *arg)
{
    struct perf_event_context *ctx = event->ctx;
    int ret = 0;
    u64 value;

    if (!is_sampling_event(event))
        return -EINVAL;

    if (copy_from_user(&value, arg, sizeof(value)))
        return -EFAULT;

    if (!value)
        return -EINVAL;

    raw_spin_lock_irq(&ctx->lock);
    if (event->attr.freq) {
        if (value > sysctl_perf_event_sample_rate) {
            ret = -EINVAL;
            goto unlock;
        }

        event->attr.sample_freq = value;
    } else {
        event->attr.sample_period = value;
        event->hw.sample_period = value;
    }
unlock:
    raw_spin_unlock_irq(&ctx->lock);

    return ret;
}

static const struct file_operations perf_fops;

static inline int perf_fget_light(int fd, struct fd *p)
{
    struct fd f = fdget(fd);
    if (!f.file)
        return -EBADF;

    if (f.file->f_op != &perf_fops) {
        fdput(f);
        return -EBADF;
    }
    *p = f;
    return 0;
}

static int perf_event_set_output(struct perf_event *event,
                 struct perf_event *output_event);
static int perf_event_set_filter(struct perf_event *event, void __user *arg);

static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct perf_event *event = file->private_data;
    void (*func)(struct perf_event *);
    u32 flags = arg;

    switch (cmd) {
    case PERF_EVENT_IOC_ENABLE:
        func = perf_event_enable;
        break;
    case PERF_EVENT_IOC_DISABLE:
        func = perf_event_disable;
        break;
    case PERF_EVENT_IOC_RESET:
        func = perf_event_reset;
        break;

    case PERF_EVENT_IOC_REFRESH:
        return perf_event_refresh(event, arg);

    case PERF_EVENT_IOC_PERIOD:
        return perf_event_period(event, (u64 __user *)arg);

    case PERF_EVENT_IOC_SET_OUTPUT:
    {
        int ret;
        if (arg != -1) {
            struct perf_event *output_event;
            struct fd output;
            ret = perf_fget_light(arg, &output);
            if (ret)
                return ret;
            output_event = output.file->private_data;
            ret = perf_event_set_output(event, output_event);
            fdput(output);
        } else {
            ret = perf_event_set_output(event, NULL);
        }
        return ret;
    }

    case PERF_EVENT_IOC_SET_FILTER:
        return perf_event_set_filter(event, (void __user *)arg);

    default:
        return -ENOTTY;
    }

    if (flags & PERF_IOC_FLAG_GROUP)
        perf_event_for_each(event, func);
    else
        perf_event_for_each_child(event, func);

    return 0;
}

int perf_event_task_enable(void)
{
    struct perf_event *event;

    mutex_lock(&current->perf_event_mutex);
    list_for_each_entry(event, &current->perf_event_list, owner_entry)
        perf_event_for_each_child(event, perf_event_enable);
    mutex_unlock(&current->perf_event_mutex);

    return 0;
}

int perf_event_task_disable(void)
{
    struct perf_event *event;

    mutex_lock(&current->perf_event_mutex);
    list_for_each_entry(event, &current->perf_event_list, owner_entry)
        perf_event_for_each_child(event, perf_event_disable);
    mutex_unlock(&current->perf_event_mutex);

    return 0;
}

static int perf_event_index(struct perf_event *event)
{
    if (event->hw.state & PERF_HES_STOPPED)
        return 0;

    if (event->state != PERF_EVENT_STATE_ACTIVE)
        return 0;

    return event->pmu->event_idx(event);
}

static void calc_timer_values(struct perf_event *event,
                u64 *now,
                u64 *enabled,
                u64 *running)
{
    u64 ctx_time;

    *now = perf_clock();
    ctx_time = event->shadow_ctx_time + *now;
    *enabled = ctx_time - event->tstamp_enabled;
    *running = ctx_time - event->tstamp_running;
}

void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
{
}

/*
 * Callers need to ensure there can be no nesting of this function, otherwise
 * the seqlock logic goes bad. We can not serialize this because the arch
 * code calls this from NMI context.
 */
void perf_event_update_userpage(struct perf_event *event)
{
    struct perf_event_mmap_page *userpg;
    struct ring_buffer *rb;
    u64 enabled, running, now;

    rcu_read_lock();
    /*
     * compute total_time_enabled, total_time_running
     * based on snapshot values taken when the event
     * was last scheduled in.
     *
     * we cannot simply called update_context_time()
     * because of locking issue as we can be called in
     * NMI context
     */
    calc_timer_values(event, &now, &enabled, &running);
    rb = rcu_dereference(event->rb);
    if (!rb)
        goto unlock;

    userpg = rb->user_page;

    /*
     * Disable preemption so as to not let the corresponding user-space
     * spin too long if we get preempted.
     */
    preempt_disable();
    ++userpg->lock;
    barrier();
    userpg->index = perf_event_index(event);
    userpg->offset = perf_event_count(event);
    if (userpg->index)
        userpg->offset -= local64_read(&event->hw.prev_count);

    userpg->time_enabled = enabled +
            atomic64_read(&event->child_total_time_enabled);

    userpg->time_running = running +
            atomic64_read(&event->child_total_time_running);

    arch_perf_update_userpage(userpg, now);

    barrier();
    ++userpg->lock;
    preempt_enable();
unlock:
    rcu_read_unlock();
}

static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
    struct perf_event *event = vma->vm_file->private_data;
    struct ring_buffer *rb;
    int ret = VM_FAULT_SIGBUS;

    if (vmf->flags & FAULT_FLAG_MKWRITE) {
        if (vmf->pgoff == 0)
            ret = 0;
        return ret;
    }

    rcu_read_lock();
    rb = rcu_dereference(event->rb);
    if (!rb)
        goto unlock;

    if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
        goto unlock;

    vmf->page = perf_mmap_to_page(rb, vmf->pgoff);
    if (!vmf->page)
        goto unlock;

    get_page(vmf->page);
    vmf->page->mapping = vma->vm_file->f_mapping;
    vmf->page->index   = vmf->pgoff;

    ret = 0;
unlock:
    rcu_read_unlock();

    return ret;
}

static void ring_buffer_attach(struct perf_event *event,
                   struct ring_buffer *rb)
{
    unsigned long flags;

    if (!list_empty(&event->rb_entry))
        return;

    spin_lock_irqsave(&rb->event_lock, flags);
    if (!list_empty(&event->rb_entry))
        goto unlock;

    list_add(&event->rb_entry, &rb->event_list);
unlock:
    spin_unlock_irqrestore(&rb->event_lock, flags);
}

static void ring_buffer_detach(struct perf_event *event,
                   struct ring_buffer *rb)
{
    unsigned long flags;

    if (list_empty(&event->rb_entry))
        return;

    spin_lock_irqsave(&rb->event_lock, flags);
    list_del_init(&event->rb_entry);
    wake_up_all(&event->waitq);
    spin_unlock_irqrestore(&rb->event_lock, flags);
}

static void ring_buffer_wakeup(struct perf_event *event)
{
    struct ring_buffer *rb;

    rcu_read_lock();
    rb = rcu_dereference(event->rb);
    if (!rb)
        goto unlock;

    list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
        wake_up_all(&event->waitq);

unlock:
    rcu_read_unlock();
}

static void rb_free_rcu(struct rcu_head *rcu_head)
{
    struct ring_buffer *rb;

    rb = container_of(rcu_head, struct ring_buffer, rcu_head);
    rb_free(rb);
}

static struct ring_buffer *ring_buffer_get(struct perf_event *event)
{
    struct ring_buffer *rb;

    rcu_read_lock();
    rb = rcu_dereference(event->rb);
    if (rb) {
        if (!atomic_inc_not_zero(&rb->refcount))
            rb = NULL;
    }
    rcu_read_unlock();

    return rb;
}

static void ring_buffer_put(struct ring_buffer *rb)
{
    struct perf_event *event, *n;
    unsigned long flags;

    if (!atomic_dec_and_test(&rb->refcount))
        return;

    spin_lock_irqsave(&rb->event_lock, flags);
    list_for_each_entry_safe(event, n, &rb->event_list, rb_entry) {
        list_del_init(&event->rb_entry);
        wake_up_all(&event->waitq);
    }
    spin_unlock_irqrestore(&rb->event_lock, flags);

    call_rcu(&rb->rcu_head, rb_free_rcu);
}

static void perf_mmap_open(struct vm_area_struct *vma)
{
    struct perf_event *event = vma->vm_file->private_data;

    atomic_inc(&event->mmap_count);
}

static void perf_mmap_close(struct vm_area_struct *vma)
{
    struct perf_event *event = vma->vm_file->private_data;

    if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
        unsigned long size = perf_data_size(event->rb);
        struct user_struct *user = event->mmap_user;
        struct ring_buffer *rb = event->rb;

        atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
        vma->vm_mm->pinned_vm -= event->mmap_locked;
        rcu_assign_pointer(event->rb, NULL);
        ring_buffer_detach(event, rb);
        mutex_unlock(&event->mmap_mutex);

        ring_buffer_put(rb);
        free_uid(user);
    }
}

static const struct vm_operations_struct perf_mmap_vmops = {
    .open       = perf_mmap_open,
    .close      = perf_mmap_close,
    .fault      = perf_mmap_fault,
    .page_mkwrite   = perf_mmap_fault,
};

static int perf_mmap(struct file *file, struct vm_area_struct *vma)
{
    struct perf_event *event = file->private_data;
    unsigned long user_locked, user_lock_limit;
    struct user_struct *user = current_user();
    unsigned long locked, lock_limit;
    struct ring_buffer *rb;
    unsigned long vma_size;
    unsigned long nr_pages;
    long user_extra, extra;
    int ret = 0, flags = 0;

    /*
     * Don't allow mmap() of inherited per-task counters. This would
     * create a performance issue due to all children writing to the
     * same rb.
     */
    if (event->cpu == -1 && event->attr.inherit)
        return -EINVAL;

    if (!(vma->vm_flags & VM_SHARED))
        return -EINVAL;

    vma_size = vma->vm_end - vma->vm_start;
    nr_pages = (vma_size / PAGE_SIZE) - 1;

    /*
     * If we have rb pages ensure they're a power-of-two number, so we
     * can do bitmasks instead of modulo.
     */
    if (nr_pages != 0 && !is_power_of_2(nr_pages))
        return -EINVAL;

    if (vma_size != PAGE_SIZE * (1 + nr_pages))
        return -EINVAL;

    if (vma->vm_pgoff != 0)
        return -EINVAL;

    WARN_ON_ONCE(event->ctx->parent_ctx);
    mutex_lock(&event->mmap_mutex);
    if (event->rb) {
        if (event->rb->nr_pages == nr_pages)
            atomic_inc(&event->rb->refcount);
        else
            ret = -EINVAL;
        goto unlock;
    }

    user_extra = nr_pages + 1;
    user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);

    /*
     * Increase the limit linearly with more CPUs:
     */
    user_lock_limit *= num_online_cpus();

    user_locked = atomic_long_read(&user->locked_vm) + user_extra;

    extra = 0;
    if (user_locked > user_lock_limit)
        extra = user_locked - user_lock_limit;

    lock_limit = rlimit(RLIMIT_MEMLOCK);
    lock_limit >>= PAGE_SHIFT;
    locked = vma->vm_mm->pinned_vm + extra;

    if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
        !capable(CAP_IPC_LOCK)) {
        ret = -EPERM;
        goto unlock;
    }

    WARN_ON(event->rb);

    if (vma->vm_flags & VM_WRITE)
        flags |= RING_BUFFER_WRITABLE;

    rb = rb_alloc(nr_pages, 
        event->attr.watermark ? event->attr.wakeup_watermark : 0,
        event->cpu, flags);

    if (!rb) {
        ret = -ENOMEM;
        goto unlock;
    }
    rcu_assign_pointer(event->rb, rb);

    atomic_long_add(user_extra, &user->locked_vm);
    event->mmap_locked = extra;
    event->mmap_user = get_current_user();
    vma->vm_mm->pinned_vm += event->mmap_locked;

    perf_event_update_userpage(event);

unlock:
    if (!ret)
        atomic_inc(&event->mmap_count);
    mutex_unlock(&event->mmap_mutex);

    vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
    vma->vm_ops = &perf_mmap_vmops;

    return ret;
}

static int perf_fasync(int fd, struct file *filp, int on)
{
    struct inode *inode = filp->f_path.dentry->d_inode;
    struct perf_event *event = filp->private_data;
    int retval;

    mutex_lock(&inode->i_mutex);
    retval = fasync_helper(fd, filp, on, &event->fasync);
    mutex_unlock(&inode->i_mutex);

    if (retval < 0)
        return retval;

    return 0;
}

static const struct file_operations perf_fops = {
    .llseek         = no_llseek,
    .release        = perf_release,
    .read           = perf_read,
    .poll           = perf_poll,
    .unlocked_ioctl     = perf_ioctl,
    .compat_ioctl       = perf_ioctl,
    .mmap           = perf_mmap,
    .fasync         = perf_fasync,
};

/*
 * Perf event wakeup
 *
 * If there's data, ensure we set the poll() state and publish everything
 * to user-space before waking everybody up.
 */

void perf_event_wakeup(struct perf_event *event)
{
    ring_buffer_wakeup(event);

    if (event->pending_kill) {
        kill_fasync(&event->fasync, SIGIO, event->pending_kill);
        event->pending_kill = 0;
    }
}

static void perf_pending_event(struct irq_work *entry)
{
    struct perf_event *event = container_of(entry,
            struct perf_event, pending);

    if (event->pending_disable) {
        event->pending_disable = 0;
        __perf_event_disable(event);
    }

    if (event->pending_wakeup) {
        event->pending_wakeup = 0;
        perf_event_wakeup(event);
    }
}

/*
 * We assume there is only KVM supporting the callbacks.
 * Later on, we might change it to a list if there is
 * another virtualization implementation supporting the callbacks.
 */
struct perf_guest_info_callbacks *perf_guest_cbs;

int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
{
    perf_guest_cbs = cbs;
    return 0;
}
EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);

int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
{
    perf_guest_cbs = NULL;
    return 0;
}
EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);

static void
perf_output_sample_regs(struct perf_output_handle *handle,
            struct pt_regs *regs, u64 mask)
{
    int bit;

    for_each_set_bit(bit, (const unsigned long *) &mask,
             sizeof(mask) * BITS_PER_BYTE) {
        u64 val;

        val = perf_reg_value(regs, bit);
        perf_output_put(handle, val);
    }
}

static void perf_sample_regs_user(struct perf_regs_user *regs_user,
                  struct pt_regs *regs)
{
    if (!user_mode(regs)) {
        if (current->mm)
            regs = task_pt_regs(current);
        else
            regs = NULL;
    }

    if (regs) {
        regs_user->regs = regs;
        regs_user->abi  = perf_reg_abi(current);
    }
}

/*
 * Get remaining task size from user stack pointer.
 *
 * It'd be better to take stack vma map and limit this more
 * precisly, but there's no way to get it safely under interrupt,
 * so using TASK_SIZE as limit.
 */
static u64 perf_ustack_task_size(struct pt_regs *regs)
{
    unsigned long addr = perf_user_stack_pointer(regs);

    if (!addr || addr >= TASK_SIZE)
        return 0;

    return TASK_SIZE - addr;
}

static u16
perf_sample_ustack_size(u16 stack_size, u16 header_size,
            struct pt_regs *regs)
{
    u64 task_size;

    /* No regs, no stack pointer, no dump. */
    if (!regs)
        return 0;

    /*
     * Check if we fit in with the requested stack size into the:
     * - TASK_SIZE
     *   If we don't, we limit the size to the TASK_SIZE.
     *
     * - remaining sample size
     *   If we don't, we customize the stack size to
     *   fit in to the remaining sample size.
     */

    task_size  = min((u64) USHRT_MAX, perf_ustack_task_size(regs));
    stack_size = min(stack_size, (u16) task_size);

    /* Current header size plus static size and dynamic size. */
    header_size += 2 * sizeof(u64);

    /* Do we fit in with the current stack dump size? */
    if ((u16) (header_size + stack_size) < header_size) {
        /*
         * If we overflow the maximum size for the sample,
         * we customize the stack dump size to fit in.
         */
        stack_size = USHRT_MAX - header_size - sizeof(u64);
        stack_size = round_up(stack_size, sizeof(u64));
    }

    return stack_size;
}

static void
perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
              struct pt_regs *regs)
{
    /* Case of a kernel thread, nothing to dump */
    if (!regs) {
        u64 size = 0;
        perf_output_put(handle, size);
    } else {
        unsigned long sp;
        unsigned int rem;
        u64 dyn_size;

        /*
         * We dump:
         * static size
         *   - the size requested by user or the best one we can fit
         *     in to the sample max size
         * data
         *   - user stack dump data
         * dynamic size
         *   - the actual dumped size
         */

        /* Static size. */
        perf_output_put(handle, dump_size);

        /* Data. */
        sp = perf_user_stack_pointer(regs);
        rem = __output_copy_user(handle, (void *) sp, dump_size);
        dyn_size = dump_size - rem;

        perf_output_skip(handle, rem);

        /* Dynamic size. */
        perf_output_put(handle, dyn_size);
    }
}

static void __perf_event_header__init_id(struct perf_event_header *header,
                     struct perf_sample_data *data,
                     struct perf_event *event)
{
    u64 sample_type = event->attr.sample_type;

    data->type = sample_type;
    header->size += event->id_header_size;

    if (sample_type & PERF_SAMPLE_TID) {
        /* namespace issues */
        data->tid_entry.pid = perf_event_pid(event, current);
        data->tid_entry.tid = perf_event_tid(event, current);
    }

    if (sample_type & PERF_SAMPLE_TIME)
        data->time = perf_clock();

    if (sample_type & PERF_SAMPLE_ID)
        data->id = primary_event_id(event);

    if (sample_type & PERF_SAMPLE_STREAM_ID)
        data->stream_id = event->id;

    if (sample_type & PERF_SAMPLE_CPU) {
        data->cpu_entry.cpu  = raw_smp_processor_id();
        data->cpu_entry.reserved = 0;
    }
}

void perf_event_header__init_id(struct perf_event_header *header,
                struct perf_sample_data *data,
                struct perf_event *event)
{
    if (event->attr.sample_id_all)
        __perf_event_header__init_id(header, data, event);
}

static void __perf_event__output_id_sample(struct perf_output_handle *handle,
                       struct perf_sample_data *data)
{
    u64 sample_type = data->type;

    if (sample_type & PERF_SAMPLE_TID)
        perf_output_put(handle, data->tid_entry);

    if (sample_type & PERF_SAMPLE_TIME)
        perf_output_put(handle, data->time);

    if (sample_type & PERF_SAMPLE_ID)
        perf_output_put(handle, data->id);

    if (sample_type & PERF_SAMPLE_STREAM_ID)
        perf_output_put(handle, data->stream_id);

    if (sample_type & PERF_SAMPLE_CPU)
        perf_output_put(handle, data->cpu_entry);
}

void perf_event__output_id_sample(struct perf_event *event,
                  struct perf_output_handle *handle,
                  struct perf_sample_data *sample)
{
    if (event->attr.sample_id_all)
        __perf_event__output_id_sample(handle, sample);
}

static void perf_output_read_one(struct perf_output_handle *handle,
                 struct perf_event *event,
                 u64 enabled, u64 running)
{
    u64 read_format = event->attr.read_format;
    u64 values[4];
    int n = 0;

    values[n++] = perf_event_count(event);
    if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
        values[n++] = enabled +
            atomic64_read(&event->child_total_time_enabled);
    }
    if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
        values[n++] = running +
            atomic64_read(&event->child_total_time_running);
    }
    if (read_format & PERF_FORMAT_ID)
        values[n++] = primary_event_id(event);

    __output_copy(handle, values, n * sizeof(u64));
}

/*
 * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
 */
static void perf_output_read_group(struct perf_output_handle *handle,
                struct perf_event *event,
                u64 enabled, u64 running)
{
    struct perf_event *leader = event->group_leader, *sub;
    u64 read_format = event->attr.read_format;
    u64 values[5];
    int n = 0;

    values[n++] = 1 + leader->nr_siblings;

    if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
        values[n++] = enabled;

    if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
        values[n++] = running;

    if (leader != event)
        leader->pmu->read(leader);

    values[n++] = perf_event_count(leader);
    if (read_format & PERF_FORMAT_ID)
        values[n++] = primary_event_id(leader);

    __output_copy(handle, values, n * sizeof(u64));

    list_for_each_entry(sub, &leader->sibling_list, group_entry) {
        n = 0;

        if (sub != event)
            sub->pmu->read(sub);

        values[n++] = perf_event_count(sub);
        if (read_format & PERF_FORMAT_ID)
            values[n++] = primary_event_id(sub);

        __output_copy(handle, values, n * sizeof(u64));
    }
}

#define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\
                 PERF_FORMAT_TOTAL_TIME_RUNNING)

static void perf_output_read(struct perf_output_handle *handle,
                 struct perf_event *event)
{
    u64 enabled = 0, running = 0, now;
    u64 read_format = event->attr.read_format;

    /*
     * compute total_time_enabled, total_time_running
     * based on snapshot values taken when the event
     * was last scheduled in.
     *
     * we cannot simply called update_context_time()
     * because of locking issue as we are called in
     * NMI context
     */
    if (read_format & PERF_FORMAT_TOTAL_TIMES)
        calc_timer_values(event, &now, &enabled, &running);

    if (event->attr.read_format & PERF_FORMAT_GROUP)
        perf_output_read_group(handle, event, enabled, running);
    else
        perf_output_read_one(handle, event, enabled, running);
}

void perf_output_sample(struct perf_output_handle *handle,
            struct perf_event_header *header,
            struct perf_sample_data *data,
            struct perf_event *event)
{
    u64 sample_type = data->type;

    perf_output_put(handle, *header);

    if (sample_type & PERF_SAMPLE_IP)
        perf_output_put(handle, data->ip);

    if (sample_type & PERF_SAMPLE_TID)
        perf_output_put(handle, data->tid_entry);

    if (sample_type & PERF_SAMPLE_TIME)
        perf_output_put(handle, data->time);

    if (sample_type & PERF_SAMPLE_ADDR)
        perf_output_put(handle, data->addr);

    if (sample_type & PERF_SAMPLE_ID)
        perf_output_put(handle, data->id);

    if (sample_type & PERF_SAMPLE_STREAM_ID)
        perf_output_put(handle, data->stream_id);

    if (sample_type & PERF_SAMPLE_CPU)
        perf_output_put(handle, data->cpu_entry);

    if (sample_type & PERF_SAMPLE_PERIOD)
        perf_output_put(handle, data->period);

    if (sample_type & PERF_SAMPLE_READ)
        perf_output_read(handle, event);

    if (sample_type & PERF_SAMPLE_CALLCHAIN) {
        if (data->callchain) {
            int size = 1;

            if (data->callchain)
                size += data->callchain->nr;

            size *= sizeof(u64);

            __output_copy(handle, data->callchain, size);
        } else {
            u64 nr = 0;
            perf_output_put(handle, nr);
        }
    }

    if (sample_type & PERF_SAMPLE_RAW) {
        if (data->raw) {
            perf_output_put(handle, data->raw->size);
            __output_copy(handle, data->raw->data,
                       data->raw->size);
        } else {
            struct {
                u32 size;
                u32 data;
            } raw = {
                .size = sizeof(u32),
                .data = 0,
            };
            perf_output_put(handle, raw);
        }
    }

    if (!event->attr.watermark) {
        int wakeup_events = event->attr.wakeup_events;

        if (wakeup_events) {
            struct ring_buffer *rb = handle->rb;
            int events = local_inc_return(&rb->events);

            if (events >= wakeup_events) {
                local_sub(wakeup_events, &rb->events);
                local_inc(&rb->wakeup);
            }
        }
    }

    if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
        if (data->br_stack) {
            size_t size;

            size = data->br_stack->nr
                 * sizeof(struct perf_branch_entry);

            perf_output_put(handle, data->br_stack->nr);
            perf_output_copy(handle, data->br_stack->entries, size);
        } else {
            /*
             * we always store at least the value of nr
             */
            u64 nr = 0;
            perf_output_put(handle, nr);
        }
    }

    if (sample_type & PERF_SAMPLE_REGS_USER) {
        u64 abi = data->regs_user.abi;

        /*
         * If there are no regs to dump, notice it through
         * first u64 being zero (PERF_SAMPLE_REGS_ABI_NONE).
         */
        perf_output_put(handle, abi);

        if (abi) {
            u64 mask = event->attr.sample_regs_user;
            perf_output_sample_regs(handle,
                        data->regs_user.regs,
                        mask);
        }
    }

    if (sample_type & PERF_SAMPLE_STACK_USER)
        perf_output_sample_ustack(handle,
                      data->stack_user_size,
                      data->regs_user.regs);
}

void perf_prepare_sample(struct perf_event_header *header,
             struct perf_sample_data *data,
             struct perf_event *event,
             struct pt_regs *regs)
{
    u64 sample_type = event->attr.sample_type;

    header->type = PERF_RECORD_SAMPLE;
    header->size = sizeof(*header) + event->header_size;

    header->misc = 0;
    header->misc |= perf_misc_flags(regs);

    __perf_event_header__init_id(header, data, event);

    if (sample_type & PERF_SAMPLE_IP)
        data->ip = perf_instruction_pointer(regs);

    if (sample_type & PERF_SAMPLE_CALLCHAIN) {
        int size = 1;

        data->callchain = perf_callchain(event, regs);

        if (data->callchain)
            size += data->callchain->nr;

        header->size += size * sizeof(u64);
    }

    if (sample_type & PERF_SAMPLE_RAW) {
        int size = sizeof(u32);

        if (data->raw)
            size += data->raw->size;
        else
            size += sizeof(u32);

        WARN_ON_ONCE(size & (sizeof(u64)-1));
        header->size += size;
    }

    if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
        int size = sizeof(u64); /* nr */
        if (data->br_stack) {
            size += data->br_stack->nr
                  * sizeof(struct perf_branch_entry);
        }
        header->size += size;
    }

    if (sample_type & PERF_SAMPLE_REGS_USER) {
        /* regs dump ABI info */
        int size = sizeof(u64);

        perf_sample_regs_user(&data->regs_user, regs);

        if (data->regs_user.regs) {
            u64 mask = event->attr.sample_regs_user;
            size += hweight64(mask) * sizeof(u64);
        }

        header->size += size;
    }

    if (sample_type & PERF_SAMPLE_STACK_USER) {
        /*
         * Either we need PERF_SAMPLE_STACK_USER bit to be allways
         * processed as the last one or have additional check added
         * in case new sample type is added, because we could eat
         * up the rest of the sample size.
         */
        struct perf_regs_user *uregs = &data->regs_user;
        u16 stack_size = event->attr.sample_stack_user;
        u16 size = sizeof(u64);

        if (!uregs->abi)
            perf_sample_regs_user(uregs, regs);

        stack_size = perf_sample_ustack_size(stack_size, header->size,
                             uregs->regs);

        /*
         * If there is something to dump, add space for the dump
         * itself and for the field that tells the dynamic size,
         * which is how many have been actually dumped.
         */
        if (stack_size)
            size += sizeof(u64) + stack_size;

        data->stack_user_size = stack_size;
        header->size += size;
    }
}

static void perf_event_output(struct perf_event *event,
                struct perf_sample_data *data,
                struct pt_regs *regs)
{
    struct perf_output_handle handle;
    struct perf_event_header header;

    /* protect the callchain buffers */
    rcu_read_lock();

    perf_prepare_sample(&header, data, event, regs);

    if (perf_output_begin(&handle, event, header.size))
        goto exit;

    perf_output_sample(&handle, &header, data, event);

    perf_output_end(&handle);

exit:
    rcu_read_unlock();
}

/*
 * read event_id
 */

struct perf_read_event {
    struct perf_event_header    header;

    u32             pid;
    u32             tid;
};

static void
perf_event_read_event(struct perf_event *event,
            struct task_struct *task)
{
    struct perf_output_handle handle;
    struct perf_sample_data sample;
    struct perf_read_event read_event = {
        .header = {
            .type = PERF_RECORD_READ,
            .misc = 0,
            .size = sizeof(read_event) + event->read_size,
        },
        .pid = perf_event_pid(event, task),
        .tid = perf_event_tid(event, task),
    };
    int ret;

    perf_event_header__init_id(&read_event.header, &sample, event);
    ret = perf_output_begin(&handle, event, read_event.header.size);
    if (ret)
        return;

    perf_output_put(&handle, read_event);
    perf_output_read(&handle, event);
    perf_event__output_id_sample(event, &handle, &sample);

    perf_output_end(&handle);
}

/*
 * task tracking -- fork/exit
 *
 * enabled by: attr.comm | attr.mmap | attr.mmap_data | attr.task
 */

struct perf_task_event {
    struct task_struct      *task;
    struct perf_event_context   *task_ctx;

    struct {
        struct perf_event_header    header;

        u32             pid;
        u32             ppid;
        u32             tid;
        u32             ptid;
        u64             time;
    } event_id;
};

static void perf_event_task_output(struct perf_event *event,
                     struct perf_task_event *task_event)
{
    struct perf_output_handle handle;
    struct perf_sample_data sample;
    struct task_struct *task = task_event->task;
    int ret, size = task_event->event_id.header.size;

    perf_event_header__init_id(&task_event->event_id.header, &sample, event);

    ret = perf_output_begin(&handle, event,
                task_event->event_id.header.size);
    if (ret)
        goto out;

    task_event->event_id.pid = perf_event_pid(event, task);
    task_event->event_id.ppid = perf_event_pid(event, current);

    task_event->event_id.tid = perf_event_tid(event, task);
    task_event->event_id.ptid = perf_event_tid(event, current);

    perf_output_put(&handle, task_event->event_id);

    perf_event__output_id_sample(event, &handle, &sample);

    perf_output_end(&handle);
out:
    task_event->event_id.header.size = size;
}

static int perf_event_task_match(struct perf_event *event)
{
    if (event->state < PERF_EVENT_STATE_INACTIVE)
        return 0;

    if (!event_filter_match(event))
        return 0;

    if (event->attr.comm || event->attr.mmap ||
        event->attr.mmap_data || event->attr.task)
        return 1;

    return 0;
}

static void perf_event_task_ctx(struct perf_event_context *ctx,
                  struct perf_task_event *task_event)
{
    struct perf_event *event;

    list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
        if (perf_event_task_match(event))
            perf_event_task_output(event, task_event);
    }
}

static void perf_event_task_event(struct perf_task_event *task_event)
{
    struct perf_cpu_context *cpuctx;
    struct perf_event_context *ctx;
    struct pmu *pmu;
    int ctxn;

    rcu_read_lock();
    list_for_each_entry_rcu(pmu, &pmus, entry) {
        cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
        if (cpuctx->unique_pmu != pmu)
            goto next;
        perf_event_task_ctx(&cpuctx->ctx, task_event);

        ctx = task_event->task_ctx;
        if (!ctx) {
            ctxn = pmu->task_ctx_nr;
            if (ctxn < 0)
                goto next;
            ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
        }
        if (ctx)
            perf_event_task_ctx(ctx, task_event);
next:
        put_cpu_ptr(pmu->pmu_cpu_context);
    }
    rcu_read_unlock();
}

static void perf_event_task(struct task_struct *task,
                  struct perf_event_context *task_ctx,
                  int new)
{
    struct perf_task_event task_event;

    if (!atomic_read(&nr_comm_events) &&
        !atomic_read(&nr_mmap_events) &&
        !atomic_read(&nr_task_events))
        return;

    task_event = (struct perf_task_event){
        .task     = task,
        .task_ctx = task_ctx,
        .event_id    = {
            .header = {
                .type = new ? PERF_RECORD_FORK : PERF_RECORD_EXIT,
                .misc = 0,
                .size = sizeof(task_event.event_id),
            },
            /* .pid  */
            /* .ppid */
            /* .tid  */
            /* .ptid */
            .time = perf_clock(),
        },
    };

    perf_event_task_event(&task_event);
}

void perf_event_fork(struct task_struct *task)
{
    perf_event_task(task, NULL, 1);
}

/*
 * comm tracking
 */

struct perf_comm_event {
    struct task_struct  *task;
    char            *comm;
    int         comm_size;

    struct {
        struct perf_event_header    header;

        u32             pid;
        u32             tid;
    } event_id;
};

static void perf_event_comm_output(struct perf_event *event,
                     struct perf_comm_event *comm_event)
{
    struct perf_output_handle handle;
    struct perf_sample_data sample;
    int size = comm_event->event_id.header.size;
    int ret;

    perf_event_header__init_id(&comm_event->event_id.header, &sample, event);
    ret = perf_output_begin(&handle, event,
                comm_event->event_id.header.size);

    if (ret)
        goto out;

    comm_event->event_id.pid = perf_event_pid(event, comm_event->task);
    comm_event->event_id.tid = perf_event_tid(event, comm_event->task);

    perf_output_put(&handle, comm_event->event_id);
    __output_copy(&handle, comm_event->comm,
                   comm_event->comm_size);

    perf_event__output_id_sample(event, &handle, &sample);

    perf_output_end(&handle);
out:
    comm_event->event_id.header.size = size;
}

static int perf_event_comm_match(struct perf_event *event)
{
    if (event->state < PERF_EVENT_STATE_INACTIVE)
        return 0;

    if (!event_filter_match(event))
        return 0;

    if (event->attr.comm)
        return 1;

    return 0;
}

static void perf_event_comm_ctx(struct perf_event_context *ctx,
                  struct perf_comm_event *comm_event)
{
    struct perf_event *event;

    list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
        if (perf_event_comm_match(event))
            perf_event_comm_output(event, comm_event);
    }
}

static void perf_event_comm_event(struct perf_comm_event *comm_event)
{
    struct perf_cpu_context *cpuctx;
    struct perf_event_context *ctx;
    char comm[TASK_COMM_LEN];
    unsigned int size;
    struct pmu *pmu;
    int ctxn;

    memset(comm, 0, sizeof(comm));
    strlcpy(comm, comm_event->task->comm, sizeof(comm));
    size = ALIGN(strlen(comm)+1, sizeof(u64));

    comm_event->comm = comm;
    comm_event->comm_size = size;

    comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
    rcu_read_lock();
    list_for_each_entry_rcu(pmu, &pmus, entry) {
        cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
        if (cpuctx->unique_pmu != pmu)
            goto next;
        perf_event_comm_ctx(&cpuctx->ctx, comm_event);

        ctxn = pmu->task_ctx_nr;
        if (ctxn < 0)
            goto next;

        ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
        if (ctx)
            perf_event_comm_ctx(ctx, comm_event);
next:
        put_cpu_ptr(pmu->pmu_cpu_context);
    }
    rcu_read_unlock();
}

void perf_event_comm(struct task_struct *task)
{
    struct perf_comm_event comm_event;
    struct perf_event_context *ctx;
    int ctxn;

    for_each_task_context_nr(ctxn) {
        ctx = task->perf_event_ctxp[ctxn];
        if (!ctx)
            continue;

        perf_event_enable_on_exec(ctx);
    }

    if (!atomic_read(&nr_comm_events))
        return;

    comm_event = (struct perf_comm_event){
        .task   = task,
        /* .comm      */
        /* .comm_size */
        .event_id  = {
            .header = {
                .type = PERF_RECORD_COMM,
                .misc = 0,
                /* .size */
            },
            /* .pid */
            /* .tid */
        },
    };

    perf_event_comm_event(&comm_event);
}

/*
 * mmap tracking
 */

struct perf_mmap_event {
    struct vm_area_struct   *vma;

    const char      *file_name;
    int         file_size;

    struct {
        struct perf_event_header    header;

        u32             pid;
        u32             tid;
        u64             start;
        u64             len;
        u64             pgoff;
    } event_id;
};

static void perf_event_mmap_output(struct perf_event *event,
                     struct perf_mmap_event *mmap_event)
{
    struct perf_output_handle handle;
    struct perf_sample_data sample;
    int size = mmap_event->event_id.header.size;
    int ret;

    perf_event_header__init_id(&mmap_event->event_id.header, &sample, event);
    ret = perf_output_begin(&handle, event,
                mmap_event->event_id.header.size);
    if (ret)
        goto out;

    mmap_event->event_id.pid = perf_event_pid(event, current);
    mmap_event->event_id.tid = perf_event_tid(event, current);

    perf_output_put(&handle, mmap_event->event_id);
    __output_copy(&handle, mmap_event->file_name,
                   mmap_event->file_size);

    perf_event__output_id_sample(event, &handle, &sample);

    perf_output_end(&handle);
out:
    mmap_event->event_id.header.size = size;
}

static int perf_event_mmap_match(struct perf_event *event,
                   struct perf_mmap_event *mmap_event,
                   int executable)
{
    if (event->state < PERF_EVENT_STATE_INACTIVE)
        return 0;

    if (!event_filter_match(event))
        return 0;

    if ((!executable && event->attr.mmap_data) ||
        (executable && event->attr.mmap))
        return 1;

    return 0;
}

static void perf_event_mmap_ctx(struct perf_event_context *ctx,
                  struct perf_mmap_event *mmap_event,
                  int executable)
{
    struct perf_event *event;

    list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
        if (perf_event_mmap_match(event, mmap_event, executable))
            perf_event_mmap_output(event, mmap_event);
    }
}

static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
{
    struct perf_cpu_context *cpuctx;
    struct perf_event_context *ctx;
    struct vm_area_struct *vma = mmap_event->vma;
    struct file *file = vma->vm_file;
    unsigned int size;
    char tmp[16];
    char *buf = NULL;
    const char *name;
    struct pmu *pmu;
    int ctxn;

    memset(tmp, 0, sizeof(tmp));

    if (file) {
        /*
         * d_path works from the end of the rb backwards, so we
         * need to add enough zero bytes after the string to handle
         * the 64bit alignment we do later.
         */
        buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);
        if (!buf) {
            name = strncpy(tmp, "//enomem", sizeof(tmp));
            goto got_name;
        }
        name = d_path(&file->f_path, buf, PATH_MAX);
        if (IS_ERR(name)) {
            name = strncpy(tmp, "//toolong", sizeof(tmp));
            goto got_name;
        }
    } else {
        if (arch_vma_name(mmap_event->vma)) {
            name = strncpy(tmp, arch_vma_name(mmap_event->vma),
                       sizeof(tmp));
            goto got_name;
        }

        if (!vma->vm_mm) {
            name = strncpy(tmp, "[vdso]", sizeof(tmp));
            goto got_name;
        } else if (vma->vm_start <= vma->vm_mm->start_brk &&
                vma->vm_end >= vma->vm_mm->brk) {
            name = strncpy(tmp, "[heap]", sizeof(tmp));
            goto got_name;
        } else if (vma->vm_start <= vma->vm_mm->start_stack &&
                vma->vm_end >= vma->vm_mm->start_stack) {
            name = strncpy(tmp, "[stack]", sizeof(tmp));
            goto got_name;
        }

        name = strncpy(tmp, "//anon", sizeof(tmp));
        goto got_name;
    }

got_name:
    size = ALIGN(strlen(name)+1, sizeof(u64));

    mmap_event->file_name = name;
    mmap_event->file_size = size;

    mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;

    rcu_read_lock();
    list_for_each_entry_rcu(pmu, &pmus, entry) {
        cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
        if (cpuctx->unique_pmu != pmu)
            goto next;
        perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
                    vma->vm_flags & VM_EXEC);

        ctxn = pmu->task_ctx_nr;
        if (ctxn < 0)
            goto next;

        ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
        if (ctx) {
            perf_event_mmap_ctx(ctx, mmap_event,
                    vma->vm_flags & VM_EXEC);
        }
next:
        put_cpu_ptr(pmu->pmu_cpu_context);
    }
    rcu_read_unlock();

    kfree(buf);
}

void perf_event_mmap(struct vm_area_struct *vma)
{
    struct perf_mmap_event mmap_event;

    if (!atomic_read(&nr_mmap_events))
        return;

    mmap_event = (struct perf_mmap_event){
        .vma    = vma,
        /* .file_name */
        /* .file_size */
        .event_id  = {
            .header = {
                .type = PERF_RECORD_MMAP,
                .misc = PERF_RECORD_MISC_USER,
                /* .size */
            },
            /* .pid */
            /* .tid */
            .start  = vma->vm_start,
            .len    = vma->vm_end - vma->vm_start,
            .pgoff  = (u64)vma->vm_pgoff << PAGE_SHIFT,
        },
    };

    perf_event_mmap_event(&mmap_event);
}

/*
 * IRQ throttle logging
 */

static void perf_log_throttle(struct perf_event *event, int enable)
{
    struct perf_output_handle handle;
    struct perf_sample_data sample;
    int ret;

    struct {
        struct perf_event_header    header;
        u64             time;
        u64             id;
        u64             stream_id;
    } throttle_event = {
        .header = {
            .type = PERF_RECORD_THROTTLE,
            .misc = 0,
            .size = sizeof(throttle_event),
        },
        .time       = perf_clock(),
        .id     = primary_event_id(event),
        .stream_id  = event->id,
    };

    if (enable)
        throttle_event.header.type = PERF_RECORD_UNTHROTTLE;

    perf_event_header__init_id(&throttle_event.header, &sample, event);

    ret = perf_output_begin(&handle, event,
                throttle_event.header.size);
    if (ret)
        return;

    perf_output_put(&handle, throttle_event);
    perf_event__output_id_sample(event, &handle, &sample);
    perf_output_end(&handle);
}

/*
 * Generic event overflow handling, sampling.
 */

static int __perf_event_overflow(struct perf_event *event,
                   int throttle, struct perf_sample_data *data,
                   struct pt_regs *regs)
{
    int events = atomic_read(&event->event_limit);
    struct hw_perf_event *hwc = &event->hw;
    u64 seq;
    int ret = 0;

    /*
     * Non-sampling counters might still use the PMI to fold short
     * hardware counters, ignore those.
     */
    if (unlikely(!is_sampling_event(event)))
        return 0;

    seq = __this_cpu_read(perf_throttled_seq);
    if (seq != hwc->interrupts_seq) {
        hwc->interrupts_seq = seq;
        hwc->interrupts = 1;
    } else {
        hwc->interrupts++;
        if (unlikely(throttle
                 && hwc->interrupts >= max_samples_per_tick)) {
            __this_cpu_inc(perf_throttled_count);
            hwc->interrupts = MAX_INTERRUPTS;
            perf_log_throttle(event, 0);
            ret = 1;
        }
    }

    if (event->attr.freq) {
        u64 now = perf_clock();
        s64 delta = now - hwc->freq_time_stamp;

        hwc->freq_time_stamp = now;

        if (delta > 0 && delta < 2*TICK_NSEC)
            perf_adjust_period(event, delta, hwc->last_period, true);
    }

    /*
     * XXX event_limit might not quite work as expected on inherited
     * events
     */

    event->pending_kill = POLL_IN;
    if (events && atomic_dec_and_test(&event->event_limit)) {
        ret = 1;
        event->pending_kill = POLL_HUP;
        event->pending_disable = 1;
        irq_work_queue(&event->pending);
    }

    if (event->overflow_handler)
        event->overflow_handler(event, data, regs);
    else
        perf_event_output(event, data, regs);

    if (event->fasync && event->pending_kill) {
        event->pending_wakeup = 1;
        irq_work_queue(&event->pending);
    }

    return ret;
}

int perf_event_overflow(struct perf_event *event,
              struct perf_sample_data *data,
              struct pt_regs *regs)
{
    return __perf_event_overflow(event, 1, data, regs);
}

/*
 * Generic software event infrastructure
 */

struct swevent_htable {
    struct swevent_hlist        *swevent_hlist;
    struct mutex            hlist_mutex;
    int             hlist_refcount;

    /* Recursion avoidance in each contexts */
    int             recursion[PERF_NR_CONTEXTS];
};

static DEFINE_PER_CPU(struct swevent_htable, swevent_htable);

/*
 * We directly increment event->count and keep a second value in
 * event->hw.period_left to count intervals. This period event
 * is kept in the range [-sample_period, 0] so that we can use the
 * sign as trigger.
 */

static u64 perf_swevent_set_period(struct perf_event *event)
{
    struct hw_perf_event *hwc = &event->hw;
    u64 period = hwc->last_period;
    u64 nr, offset;
    s64 old, val;

    hwc->last_period = hwc->sample_period;

again:
    old = val = local64_read(&hwc->period_left);
    if (val < 0)
        return 0;

    nr = div64_u64(period + val, period);
    offset = nr * period;
    val -= offset;
    if (local64_cmpxchg(&hwc->period_left, old, val) != old)
        goto again;

    return nr;
}

static void perf_swevent_overflow(struct perf_event *event, u64 overflow,
                    struct perf_sample_data *data,
                    struct pt_regs *regs)
{
    struct hw_perf_event *hwc = &event->hw;
    int throttle = 0;

    if (!overflow)
        overflow = perf_swevent_set_period(event);

    if (hwc->interrupts == MAX_INTERRUPTS)
        return;

    for (; overflow; overflow--) {
        if (__perf_event_overflow(event, throttle,
                        data, regs)) {
            /*
             * We inhibit the overflow from happening when
             * hwc->interrupts == MAX_INTERRUPTS.
             */
            break;
        }
        throttle = 1;
    }
}

static void perf_swevent_event(struct perf_event *event, u64 nr,
                   struct perf_sample_data *data,
                   struct pt_regs *regs)
{
    struct hw_perf_event *hwc = &event->hw;

    local64_add(nr, &event->count);

    if (!regs)
        return;

    if (!is_sampling_event(event))
        return;

    if ((event->attr.sample_type & PERF_SAMPLE_PERIOD) && !event->attr.freq) {
        data->period = nr;
        return perf_swevent_overflow(event, 1, data, regs);
    } else
        data->period = event->hw.last_period;

    if (nr == 1 && hwc->sample_period == 1 && !event->attr.freq)
        return perf_swevent_overflow(event, 1, data, regs);

    if (local64_add_negative(nr, &hwc->period_left))
        return;

    perf_swevent_overflow(event, 0, data, regs);
}

static int perf_exclude_event(struct perf_event *event,
                  struct pt_regs *regs)
{
    if (event->hw.state & PERF_HES_STOPPED)
        return 1;

    if (regs) {
        if (event->attr.exclude_user && user_mode(regs))
            return 1;

        if (event->attr.exclude_kernel && !user_mode(regs))
            return 1;
    }

    return 0;
}

static int perf_swevent_match(struct perf_event *event,
                enum perf_type_id type,
                u32 event_id,
                struct perf_sample_data *data,
                struct pt_regs *regs)
{
    if (event->attr.type != type)
        return 0;

    if (event->attr.config != event_id)
        return 0;

    if (perf_exclude_event(event, regs))
        return 0;

    return 1;
}

static inline u64 swevent_hash(u64 type, u32 event_id)
{
    u64 val = event_id | (type << 32);

    return hash_64(val, SWEVENT_HLIST_BITS);
}

static inline struct hlist_head *
__find_swevent_head(struct swevent_hlist *hlist, u64 type, u32 event_id)
{
    u64 hash = swevent_hash(type, event_id);

    return &hlist->heads[hash];
}

/* For the read side: events when they trigger */
static inline struct hlist_head *
find_swevent_head_rcu(struct swevent_htable *swhash, u64 type, u32 event_id)
{
    struct swevent_hlist *hlist;

    hlist = rcu_dereference(swhash->swevent_hlist);
    if (!hlist)
        return NULL;

    return __find_swevent_head(hlist, type, event_id);
}

/* For the event head insertion and removal in the hlist */
static inline struct hlist_head *
find_swevent_head(struct swevent_htable *swhash, struct perf_event *event)
{
    struct swevent_hlist *hlist;
    u32 event_id = event->attr.config;
    u64 type = event->attr.type;

    /*
     * Event scheduling is always serialized against hlist allocation
     * and release. Which makes the protected version suitable here.
     * The context lock guarantees that.
     */
    hlist = rcu_dereference_protected(swhash->swevent_hlist,
                      lockdep_is_held(&event->ctx->lock));
    if (!hlist)
        return NULL;

    return __find_swevent_head(hlist, type, event_id);
}

static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
                    u64 nr,
                    struct perf_sample_data *data,
                    struct pt_regs *regs)
{
    struct swevent_htable *swhash = &__get_cpu_var(swevent_htable);
    struct perf_event *event;
    struct hlist_node *node;
    struct hlist_head *head;

    rcu_read_lock();
    head = find_swevent_head_rcu(swhash, type, event_id);
    if (!head)
        goto end;

    hlist_for_each_entry_rcu(event, node, head, hlist_entry) {
        if (perf_swevent_match(event, type, event_id, data, regs))
            perf_swevent_event(event, nr, data, regs);
    }
end:
    rcu_read_unlock();
}

int perf_swevent_get_recursion_context(void)
{
    struct swevent_htable *swhash = &__get_cpu_var(swevent_htable);

    return get_recursion_context(swhash->recursion);
}
EXPORT_SYMBOL_GPL(perf_swevent_get_recursion_context);

inline void perf_swevent_put_recursion_context(int rctx)
{
    struct swevent_htable *swhash = &__get_cpu_var(swevent_htable);

    put_recursion_context(swhash->recursion, rctx);
}

void __perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
{
    struct perf_sample_data data;
    int rctx;

    preempt_disable_notrace();
    rctx = perf_swevent_get_recursion_context();
    if (rctx < 0)
        return;

    perf_sample_data_init(&data, addr, 0);

    do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, &data, regs);

    perf_swevent_put_recursion_context(rctx);
    preempt_enable_notrace();
}

static void perf_swevent_read(struct perf_event *event)
{
}

static int perf_swevent_add(struct perf_event *event, int flags)
{
    struct swevent_htable *swhash = &__get_cpu_var(swevent_htable);
    struct hw_perf_event *hwc = &event->hw;
    struct hlist_head *head;

    if (is_sampling_event(event)) {
        hwc->last_period = hwc->sample_period;
        perf_swevent_set_period(event);
    }

    hwc->state = !(flags & PERF_EF_START);

    head = find_swevent_head(swhash, event);
    if (WARN_ON_ONCE(!head))
        return -EINVAL;

    hlist_add_head_rcu(&event->hlist_entry, head);

    return 0;
}

static void perf_swevent_del(struct perf_event *event, int flags)
{
    hlist_del_rcu(&event->hlist_entry);
}

static void perf_swevent_start(struct perf_event *event, int flags)
{
    event->hw.state = 0;
}

static void perf_swevent_stop(struct perf_event *event, int flags)
{
    event->hw.state = PERF_HES_STOPPED;
}

/* Deref the hlist from the update side */
static inline struct swevent_hlist *
swevent_hlist_deref(struct swevent_htable *swhash)
{
    return rcu_dereference_protected(swhash->swevent_hlist,
                     lockdep_is_held(&swhash->hlist_mutex));
}

static void swevent_hlist_release(struct swevent_htable *swhash)
{
    struct swevent_hlist *hlist = swevent_hlist_deref(swhash);

    if (!hlist)
        return;

    rcu_assign_pointer(swhash->swevent_hlist, NULL);
    kfree_rcu(hlist, rcu_head);
}

static void swevent_hlist_put_cpu(struct perf_event *event, int cpu)
{
    struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);

    mutex_lock(&swhash->hlist_mutex);

    if (!--swhash->hlist_refcount)
        swevent_hlist_release(swhash);

    mutex_unlock(&swhash->hlist_mutex);
}

static void swevent_hlist_put(struct perf_event *event)
{
    int cpu;

    if (event->cpu != -1) {
        swevent_hlist_put_cpu(event, event->cpu);
        return;
    }

    for_each_possible_cpu(cpu)
        swevent_hlist_put_cpu(event, cpu);
}

static int swevent_hlist_get_cpu(struct perf_event *event, int cpu)
{
    struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
    int err = 0;

    mutex_lock(&swhash->hlist_mutex);

    if (!swevent_hlist_deref(swhash) && cpu_online(cpu)) {
        struct swevent_hlist *hlist;

        hlist = kzalloc(sizeof(*hlist), GFP_KERNEL);
        if (!hlist) {
            err = -ENOMEM;
            goto exit;
        }
        rcu_assign_pointer(swhash->swevent_hlist, hlist);
    }
    swhash->hlist_refcount++;
exit:
    mutex_unlock(&swhash->hlist_mutex);

    return err;
}

static int swevent_hlist_get(struct perf_event *event)
{
    int err;
    int cpu, failed_cpu;

    if (event->cpu != -1)
        return swevent_hlist_get_cpu(event, event->cpu);

    get_online_cpus();
    for_each_possible_cpu(cpu) {
        err = swevent_hlist_get_cpu(event, cpu);
        if (err) {
            failed_cpu = cpu;
            goto fail;
        }
    }
    put_online_cpus();

    return 0;
fail:
    for_each_possible_cpu(cpu) {
        if (cpu == failed_cpu)
            break;
        swevent_hlist_put_cpu(event, cpu);
    }

    put_online_cpus();
    return err;
}

struct static_key perf_swevent_enabled[PERF_COUNT_SW_MAX];

static void sw_perf_event_destroy(struct perf_event *event)
{
    u64 event_id = event->attr.config;

    WARN_ON(event->parent);

    static_key_slow_dec(&perf_swevent_enabled[event_id]);
    swevent_hlist_put(event);
}

static int perf_swevent_init(struct perf_event *event)
{
    int event_id = event->attr.config;

    if (event->attr.type != PERF_TYPE_SOFTWARE)
        return -ENOENT;

    /*
     * no branch sampling for software events
     */
    if (has_branch_stack(event))
        return -EOPNOTSUPP;

    switch (event_id) {
    case PERF_COUNT_SW_CPU_CLOCK:
    case PERF_COUNT_SW_TASK_CLOCK:
        return -ENOENT;

    default:
        break;
    }

    if (event_id >= PERF_COUNT_SW_MAX)
        return -ENOENT;

    if (!event->parent) {
        int err;

        err = swevent_hlist_get(event);
        if (err)
            return err;

        static_key_slow_inc(&perf_swevent_enabled[event_id]);
        event->destroy = sw_perf_event_destroy;
    }

    return 0;
}

static int perf_swevent_event_idx(struct perf_event *event)
{
    return 0;
}

static struct pmu perf_swevent = {
    .task_ctx_nr    = perf_sw_context,

    .event_init = perf_swevent_init,
    .add        = perf_swevent_add,
    .del        = perf_swevent_del,
    .start      = perf_swevent_start,
    .stop       = perf_swevent_stop,
    .read       = perf_swevent_read,

    .event_idx  = perf_swevent_event_idx,
};

#ifdef CONFIG_EVENT_TRACING

static int perf_tp_filter_match(struct perf_event *event,
                struct perf_sample_data *data)
{
    void *record = data->raw->data;

    if (likely(!event->filter) || filter_match_preds(event->filter, record))
        return 1;
    return 0;
}

static int perf_tp_event_match(struct perf_event *event,
                struct perf_sample_data *data,
                struct pt_regs *regs)
{
    if (event->hw.state & PERF_HES_STOPPED)
        return 0;
    /*
     * All tracepoints are from kernel-space.
     */
    if (event->attr.exclude_kernel)
        return 0;

    if (!perf_tp_filter_match(event, data))
        return 0;

    return 1;
}

void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
           struct pt_regs *regs, struct hlist_head *head, int rctx,
           struct task_struct *task)
{
    struct perf_sample_data data;
    struct perf_event *event;
    struct hlist_node *node;

    struct perf_raw_record raw = {
        .size = entry_size,
        .data = record,
    };

    perf_sample_data_init(&data, addr, 0);
    data.raw = &raw;

    hlist_for_each_entry_rcu(event, node, head, hlist_entry) {
        if (perf_tp_event_match(event, &data, regs))
            perf_swevent_event(event, count, &data, regs);
    }

    /*
     * If we got specified a target task, also iterate its context and
     * deliver this event there too.
     */
    if (task && task != current) {
        struct perf_event_context *ctx;
        struct trace_entry *entry = record;

        rcu_read_lock();
        ctx = rcu_dereference(task->perf_event_ctxp[perf_sw_context]);
        if (!ctx)
            goto unlock;

        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
            if (event->attr.type != PERF_TYPE_TRACEPOINT)
                continue;
            if (event->attr.config != entry->type)
                continue;
            if (perf_tp_event_match(event, &data, regs))
                perf_swevent_event(event, count, &data, regs);
        }
unlock:
        rcu_read_unlock();
    }

    perf_swevent_put_recursion_context(rctx);
}
EXPORT_SYMBOL_GPL(perf_tp_event);

static void tp_perf_event_destroy(struct perf_event *event)
{
    perf_trace_destroy(event);
}

static int perf_tp_event_init(struct perf_event *event)
{
    int err;

    if (event->attr.type != PERF_TYPE_TRACEPOINT)
        return -ENOENT;

    /*
     * no branch sampling for tracepoint events
     */
    if (has_branch_stack(event))
        return -EOPNOTSUPP;

    err = perf_trace_init(event);
    if (err)
        return err;

    event->destroy = tp_perf_event_destroy;

    return 0;
}

static struct pmu perf_tracepoint = {
    .task_ctx_nr    = perf_sw_context,

    .event_init = perf_tp_event_init,
    .add        = perf_trace_add,
    .del        = perf_trace_del,
    .start      = perf_swevent_start,
    .stop       = perf_swevent_stop,
    .read       = perf_swevent_read,

    .event_idx  = perf_swevent_event_idx,
};

static inline void perf_tp_register(void)
{
    perf_pmu_register(&perf_tracepoint, "tracepoint", PERF_TYPE_TRACEPOINT);
}

static int perf_event_set_filter(struct perf_event *event, void __user *arg)
{
    char *filter_str;
    int ret;

    if (event->attr.type != PERF_TYPE_TRACEPOINT)
        return -EINVAL;

    filter_str = strndup_user(arg, PAGE_SIZE);
    if (IS_ERR(filter_str))
        return PTR_ERR(filter_str);

    ret = ftrace_profile_set_filter(event, event->attr.config, filter_str);

    kfree(filter_str);
    return ret;
}

static void perf_event_free_filter(struct perf_event *event)
{
    ftrace_profile_free_filter(event);
}

#else

static inline void perf_tp_register(void)
{
}

static int perf_event_set_filter(struct perf_event *event, void __user *arg)
{
    return -ENOENT;
}

static void perf_event_free_filter(struct perf_event *event)
{
}

#endif /* CONFIG_EVENT_TRACING */

#ifdef CONFIG_HAVE_HW_BREAKPOINT
void perf_bp_event(struct perf_event *bp, void *data)
{
    struct perf_sample_data sample;
    struct pt_regs *regs = data;

    perf_sample_data_init(&sample, bp->attr.bp_addr, 0);

    if (!bp->hw.state && !perf_exclude_event(bp, regs))
        perf_swevent_event(bp, 1, &sample, regs);
}
#endif

/*
 * hrtimer based swevent callback
 */

static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
{
    enum hrtimer_restart ret = HRTIMER_RESTART;
    struct perf_sample_data data;
    struct pt_regs *regs;
    struct perf_event *event;
    u64 period;

    event = container_of(hrtimer, struct perf_event, hw.hrtimer);

    if (event->state != PERF_EVENT_STATE_ACTIVE)
        return HRTIMER_NORESTART;

    event->pmu->read(event);

    perf_sample_data_init(&data, 0, event->hw.last_period);
    regs = get_irq_regs();

    if (regs && !perf_exclude_event(event, regs)) {
        if (!(event->attr.exclude_idle && is_idle_task(current)))
            if (__perf_event_overflow(event, 1, &data, regs))
                ret = HRTIMER_NORESTART;
    }

    period = max_t(u64, 10000, event->hw.sample_period);
    hrtimer_forward_now(hrtimer, ns_to_ktime(period));

    return ret;
}

static void perf_swevent_start_hrtimer(struct perf_event *event)
{
    struct hw_perf_event *hwc = &event->hw;
    s64 period;

    if (!is_sampling_event(event))
        return;

    period = local64_read(&hwc->period_left);
    if (period) {
        if (period < 0)
            period = 10000;

        local64_set(&hwc->period_left, 0);
    } else {
        period = max_t(u64, 10000, hwc->sample_period);
    }
    __hrtimer_start_range_ns(&hwc->hrtimer,
                ns_to_ktime(period), 0,
                HRTIMER_MODE_REL_PINNED, 0);
}

static void perf_swevent_cancel_hrtimer(struct perf_event *event)
{
    struct hw_perf_event *hwc = &event->hw;

    if (is_sampling_event(event)) {
        ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer);
        local64_set(&hwc->period_left, ktime_to_ns(remaining));

        hrtimer_cancel(&hwc->hrtimer);
    }
}

static void perf_swevent_init_hrtimer(struct perf_event *event)
{
    struct hw_perf_event *hwc = &event->hw;

    if (!is_sampling_event(event))
        return;

    hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    hwc->hrtimer.function = perf_swevent_hrtimer;

    /*
     * Since hrtimers have a fixed rate, we can do a static freq->period
     * mapping and avoid the whole period adjust feedback stuff.
     */
    if (event->attr.freq) {
        long freq = event->attr.sample_freq;

        event->attr.sample_period = NSEC_PER_SEC / freq;
        hwc->sample_period = event->attr.sample_period;
        local64_set(&hwc->period_left, hwc->sample_period);
        event->attr.freq = 0;
    }
}

/*
 * Software event: cpu wall time clock
 */

static void cpu_clock_event_update(struct perf_event *event)
{
    s64 prev;
    u64 now;

    now = local_clock();
    prev = local64_xchg(&event->hw.prev_count, now);
    local64_add(now - prev, &event->count);
}

static void cpu_clock_event_start(struct perf_event *event, int flags)
{
    local64_set(&event->hw.prev_count, local_clock());
    perf_swevent_start_hrtimer(event);
}

static void cpu_clock_event_stop(struct perf_event *event, int flags)
{
    perf_swevent_cancel_hrtimer(event);
    cpu_clock_event_update(event);
}

static int cpu_clock_event_add(struct perf_event *event, int flags)
{
    if (flags & PERF_EF_START)
        cpu_clock_event_start(event, flags);

    return 0;
}

static void cpu_clock_event_del(struct perf_event *event, int flags)
{
    cpu_clock_event_stop(event, flags);
}

static void cpu_clock_event_read(struct perf_event *event)
{
    cpu_clock_event_update(event);
}

static int cpu_clock_event_init(struct perf_event *event)
{
    if (event->attr.type != PERF_TYPE_SOFTWARE)
        return -ENOENT;

    if (event->attr.config != PERF_COUNT_SW_CPU_CLOCK)
        return -ENOENT;

    /*
     * no branch sampling for software events
     */
    if (has_branch_stack(event))
        return -EOPNOTSUPP;

    perf_swevent_init_hrtimer(event);

    return 0;
}

static struct pmu perf_cpu_clock = {
    .task_ctx_nr    = perf_sw_context,

    .event_init = cpu_clock_event_init,
    .add        = cpu_clock_event_add,
    .del        = cpu_clock_event_del,
    .start      = cpu_clock_event_start,
    .stop       = cpu_clock_event_stop,
    .read       = cpu_clock_event_read,

    .event_idx  = perf_swevent_event_idx,
};

/*
 * Software event: task time clock
 */

static void task_clock_event_update(struct perf_event *event, u64 now)
{
    u64 prev;
    s64 delta;

    prev = local64_xchg(&event->hw.prev_count, now);
    delta = now - prev;
    local64_add(delta, &event->count);
}

static void task_clock_event_start(struct perf_event *event, int flags)
{
    local64_set(&event->hw.prev_count, event->ctx->time);
    perf_swevent_start_hrtimer(event);
}

static void task_clock_event_stop(struct perf_event *event, int flags)
{
    perf_swevent_cancel_hrtimer(event);
    task_clock_event_update(event, event->ctx->time);
}

static int task_clock_event_add(struct perf_event *event, int flags)
{
    if (flags & PERF_EF_START)
        task_clock_event_start(event, flags);

    return 0;
}

static void task_clock_event_del(struct perf_event *event, int flags)
{
    task_clock_event_stop(event, PERF_EF_UPDATE);
}

static void task_clock_event_read(struct perf_event *event)
{
    u64 now = perf_clock();
    u64 delta = now - event->ctx->timestamp;
    u64 time = event->ctx->time + delta;

    task_clock_event_update(event, time);
}

static int task_clock_event_init(struct perf_event *event)
{
    if (event->attr.type != PERF_TYPE_SOFTWARE)
        return -ENOENT;

    if (event->attr.config != PERF_COUNT_SW_TASK_CLOCK)
        return -ENOENT;

    /*
     * no branch sampling for software events
     */
    if (has_branch_stack(event))
        return -EOPNOTSUPP;

    perf_swevent_init_hrtimer(event);

    return 0;
}

static struct pmu perf_task_clock = {
    .task_ctx_nr    = perf_sw_context,

    .event_init = task_clock_event_init,
    .add        = task_clock_event_add,
    .del        = task_clock_event_del,
    .start      = task_clock_event_start,
    .stop       = task_clock_event_stop,
    .read       = task_clock_event_read,

    .event_idx  = perf_swevent_event_idx,
};

static void perf_pmu_nop_void(struct pmu *pmu)
{
}

static int perf_pmu_nop_int(struct pmu *pmu)
{
    return 0;
}

static void perf_pmu_start_txn(struct pmu *pmu)
{
    perf_pmu_disable(pmu);
}

static int perf_pmu_commit_txn(struct pmu *pmu)
{
    perf_pmu_enable(pmu);
    return 0;
}

static void perf_pmu_cancel_txn(struct pmu *pmu)
{
    perf_pmu_enable(pmu);
}

static int perf_event_idx_default(struct perf_event *event)
{
    return event->hw.idx + 1;
}

/*
 * Ensures all contexts with the same task_ctx_nr have the same
 * pmu_cpu_context too.
 */
static void *find_pmu_context(int ctxn)
{
    struct pmu *pmu;

    if (ctxn < 0)
        return NULL;

    list_for_each_entry(pmu, &pmus, entry) {
        if (pmu->task_ctx_nr == ctxn)
            return pmu->pmu_cpu_context;
    }

    return NULL;
}

static void update_pmu_context(struct pmu *pmu, struct pmu *old_pmu)
{
    int cpu;

    for_each_possible_cpu(cpu) {
        struct perf_cpu_context *cpuctx;

        cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);

        if (cpuctx->unique_pmu == old_pmu)
            cpuctx->unique_pmu = pmu;
    }
}

static void free_pmu_context(struct pmu *pmu)
{
    struct pmu *i;

    mutex_lock(&pmus_lock);
    /*
     * Like a real lame refcount.
     */
    list_for_each_entry(i, &pmus, entry) {
        if (i->pmu_cpu_context == pmu->pmu_cpu_context) {
            update_pmu_context(i, pmu);
            goto out;
        }
    }

    free_percpu(pmu->pmu_cpu_context);
out:
    mutex_unlock(&pmus_lock);
}
static struct idr pmu_idr;

static ssize_t
type_show(struct device *dev, struct device_attribute *attr, char *page)
{
    struct pmu *pmu = dev_get_drvdata(dev);

    return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
}

static struct device_attribute pmu_dev_attrs[] = {
       __ATTR_RO(type),
       __ATTR_NULL,
};

static int pmu_bus_running;
static struct bus_type pmu_bus = {
    .name       = "event_source",
    .dev_attrs  = pmu_dev_attrs,
};

static void pmu_dev_release(struct device *dev)
{
    kfree(dev);
}

static int pmu_dev_alloc(struct pmu *pmu)
{
    int ret = -ENOMEM;

    pmu->dev = kzalloc(sizeof(struct device), GFP_KERNEL);
    if (!pmu->dev)
        goto out;

    pmu->dev->groups = pmu->attr_groups;
    device_initialize(pmu->dev);
    ret = dev_set_name(pmu->dev, "%s", pmu->name);
    if (ret)
        goto free_dev;

    dev_set_drvdata(pmu->dev, pmu);
    pmu->dev->bus = &pmu_bus;
    pmu->dev->release = pmu_dev_release;
    ret = device_add(pmu->dev);
    if (ret)
        goto free_dev;

out:
    return ret;

free_dev:
    put_device(pmu->dev);
    goto out;
}

static struct lock_class_key cpuctx_mutex;
static struct lock_class_key cpuctx_lock;

int perf_pmu_register(struct pmu *pmu, char *name, int type)
{
    int cpu, ret;

    mutex_lock(&pmus_lock);
    ret = -ENOMEM;
    pmu->pmu_disable_count = alloc_percpu(int);
    if (!pmu->pmu_disable_count)
        goto unlock;

    pmu->type = -1;
    if (!name)
        goto skip_type;
    pmu->name = name;

    if (type < 0) {
        int err = idr_pre_get(&pmu_idr, GFP_KERNEL);
        if (!err)
            goto free_pdc;

        err = idr_get_new_above(&pmu_idr, pmu, PERF_TYPE_MAX, &type);
        if (err) {
            ret = err;
            goto free_pdc;
        }
    }
    pmu->type = type;

    if (pmu_bus_running) {
        ret = pmu_dev_alloc(pmu);
        if (ret)
            goto free_idr;
    }

skip_type:
    pmu->pmu_cpu_context = find_pmu_context(pmu->task_ctx_nr);
    if (pmu->pmu_cpu_context)
        goto got_cpu_context;

    pmu->pmu_cpu_context = alloc_percpu(struct perf_cpu_context);
    if (!pmu->pmu_cpu_context)
        goto free_dev;

    for_each_possible_cpu(cpu) {
        struct perf_cpu_context *cpuctx;

        cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
        __perf_event_init_context(&cpuctx->ctx);
        lockdep_set_class(&cpuctx->ctx.mutex, &cpuctx_mutex);
        lockdep_set_class(&cpuctx->ctx.lock, &cpuctx_lock);
        cpuctx->ctx.type = cpu_context;
        cpuctx->ctx.pmu = pmu;
        cpuctx->jiffies_interval = 1;
        INIT_LIST_HEAD(&cpuctx->rotation_list);
        cpuctx->unique_pmu = pmu;
    }

got_cpu_context:
    if (!pmu->start_txn) {
        if (pmu->pmu_enable) {
            /*
             * If we have pmu_enable/pmu_disable calls, install
             * transaction stubs that use that to try and batch
             * hardware accesses.
             */
            pmu->start_txn  = perf_pmu_start_txn;
            pmu->commit_txn = perf_pmu_commit_txn;
            pmu->cancel_txn = perf_pmu_cancel_txn;
        } else {
            pmu->start_txn  = perf_pmu_nop_void;
            pmu->commit_txn = perf_pmu_nop_int;
            pmu->cancel_txn = perf_pmu_nop_void;
        }
    }

    if (!pmu->pmu_enable) {
        pmu->pmu_enable  = perf_pmu_nop_void;
        pmu->pmu_disable = perf_pmu_nop_void;
    }

    if (!pmu->event_idx)
        pmu->event_idx = perf_event_idx_default;

    list_add_rcu(&pmu->entry, &pmus);
    ret = 0;
unlock:
    mutex_unlock(&pmus_lock);

    return ret;

free_dev:
    device_del(pmu->dev);
    put_device(pmu->dev);

free_idr:
    if (pmu->type >= PERF_TYPE_MAX)
        idr_remove(&pmu_idr, pmu->type);

free_pdc:
    free_percpu(pmu->pmu_disable_count);
    goto unlock;
}

void perf_pmu_unregister(struct pmu *pmu)
{
    mutex_lock(&pmus_lock);
    list_del_rcu(&pmu->entry);
    mutex_unlock(&pmus_lock);

    /*
     * We dereference the pmu list under both SRCU and regular RCU, so
     * synchronize against both of those.
     */
    synchronize_srcu(&pmus_srcu);
    synchronize_rcu();

    free_percpu(pmu->pmu_disable_count);
    if (pmu->type >= PERF_TYPE_MAX)
        idr_remove(&pmu_idr, pmu->type);
    device_del(pmu->dev);
    put_device(pmu->dev);
    free_pmu_context(pmu);
}

struct pmu *perf_init_event(struct perf_event *event)
{
    struct pmu *pmu = NULL;
    int idx;
    int ret;

    idx = srcu_read_lock(&pmus_srcu);

    rcu_read_lock();
    pmu = idr_find(&pmu_idr, event->attr.type);
    rcu_read_unlock();
    if (pmu) {
        event->pmu = pmu;
        ret = pmu->event_init(event);
        if (ret)
            pmu = ERR_PTR(ret);
        goto unlock;
    }

    list_for_each_entry_rcu(pmu, &pmus, entry) {
        event->pmu = pmu;
        ret = pmu->event_init(event);
        if (!ret)
            goto unlock;

        if (ret != -ENOENT) {
            pmu = ERR_PTR(ret);
            goto unlock;
        }
    }
    pmu = ERR_PTR(-ENOENT);
unlock:
    srcu_read_unlock(&pmus_srcu, idx);

    return pmu;
}

/*
 * Allocate and initialize a event structure
 */
static struct perf_event *
perf_event_alloc(struct perf_event_attr *attr, int cpu,
         struct task_struct *task,
         struct perf_event *group_leader,
         struct perf_event *parent_event,
         perf_overflow_handler_t overflow_handler,
         void *context)
{
    struct pmu *pmu;
    struct perf_event *event;
    struct hw_perf_event *hwc;
    long err;

    if ((unsigned)cpu >= nr_cpu_ids) {
        if (!task || cpu != -1)
            return ERR_PTR(-EINVAL);
    }

    event = kzalloc(sizeof(*event), GFP_KERNEL);
    if (!event)
        return ERR_PTR(-ENOMEM);

    /*
     * Single events are their own group leaders, with an
     * empty sibling list:
     */
    if (!group_leader)
        group_leader = event;

    mutex_init(&event->child_mutex);
    INIT_LIST_HEAD(&event->child_list);

    INIT_LIST_HEAD(&event->group_entry);
    INIT_LIST_HEAD(&event->event_entry);
    INIT_LIST_HEAD(&event->sibling_list);
    INIT_LIST_HEAD(&event->rb_entry);

    init_waitqueue_head(&event->waitq);
    init_irq_work(&event->pending, perf_pending_event);

    mutex_init(&event->mmap_mutex);

    atomic_long_set(&event->refcount, 1);
    event->cpu      = cpu;
    event->attr     = *attr;
    event->group_leader = group_leader;
    event->pmu      = NULL;
    event->oncpu        = -1;

    event->parent       = parent_event;

    event->ns       = get_pid_ns(current->nsproxy->pid_ns);
    event->id       = atomic64_inc_return(&perf_event_id);

    event->state        = PERF_EVENT_STATE_INACTIVE;

    if (task) {
        event->attach_state = PERF_ATTACH_TASK;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
        /*
         * hw_breakpoint is a bit difficult here..
         */
        if (attr->type == PERF_TYPE_BREAKPOINT)
            event->hw.bp_target = task;
#endif
    }

    if (!overflow_handler && parent_event) {
        overflow_handler = parent_event->overflow_handler;
        context = parent_event->overflow_handler_context;
    }

    event->overflow_handler = overflow_handler;
    event->overflow_handler_context = context;

    if (attr->disabled)
        event->state = PERF_EVENT_STATE_OFF;

    pmu = NULL;

    hwc = &event->hw;
    hwc->sample_period = attr->sample_period;
    if (attr->freq && attr->sample_freq)
        hwc->sample_period = 1;
    hwc->last_period = hwc->sample_period;

    local64_set(&hwc->period_left, hwc->sample_period);

    /*
     * we currently do not support PERF_FORMAT_GROUP on inherited events
     */
    if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
        goto done;

    pmu = perf_init_event(event);

done:
    err = 0;
    if (!pmu)
        err = -EINVAL;
    else if (IS_ERR(pmu))
        err = PTR_ERR(pmu);

    if (err) {
        if (event->ns)
            put_pid_ns(event->ns);
        kfree(event);
        return ERR_PTR(err);
    }

    if (!event->parent) {
        if (event->attach_state & PERF_ATTACH_TASK)
            static_key_slow_inc(&perf_sched_events.key);
        if (event->attr.mmap || event->attr.mmap_data)
            atomic_inc(&nr_mmap_events);
        if (event->attr.comm)
            atomic_inc(&nr_comm_events);
        if (event->attr.task)
            atomic_inc(&nr_task_events);
        if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
            err = get_callchain_buffers();
            if (err) {
                free_event(event);
                return ERR_PTR(err);
            }
        }
        if (has_branch_stack(event)) {
            static_key_slow_inc(&perf_sched_events.key);
            if (!(event->attach_state & PERF_ATTACH_TASK))
                atomic_inc(&per_cpu(perf_branch_stack_events,
                            event->cpu));
        }
    }

    return event;
}

static int perf_copy_attr(struct perf_event_attr __user *uattr,
              struct perf_event_attr *attr)
{
    u32 size;
    int ret;

    if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
        return -EFAULT;

    /*
     * zero the full structure, so that a short copy will be nice.
     */
    memset(attr, 0, sizeof(*attr));

    ret = get_user(size, &uattr->size);
    if (ret)
        return ret;

    if (size > PAGE_SIZE)   /* silly large */
        goto err_size;

    if (!size)      /* abi compat */
        size = PERF_ATTR_SIZE_VER0;

    if (size < PERF_ATTR_SIZE_VER0)
        goto err_size;

    /*
     * If we're handed a bigger struct than we know of,
     * ensure all the unknown bits are 0 - i.e. new
     * user-space does not rely on any kernel feature
     * extensions we dont know about yet.
     */
    if (size > sizeof(*attr)) {
        unsigned char __user *addr;
        unsigned char __user *end;
        unsigned char val;

        addr = (void __user *)uattr + sizeof(*attr);
        end  = (void __user *)uattr + size;

        for (; addr < end; addr++) {
            ret = get_user(val, addr);
            if (ret)
                return ret;
            if (val)
                goto err_size;
        }
        size = sizeof(*attr);
    }

    ret = copy_from_user(attr, uattr, size);
    if (ret)
        return -EFAULT;

    if (attr->__reserved_1)
        return -EINVAL;

    if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))
        return -EINVAL;

    if (attr->read_format & ~(PERF_FORMAT_MAX-1))
        return -EINVAL;

    if (attr->sample_type & PERF_SAMPLE_BRANCH_STACK) {
        u64 mask = attr->branch_sample_type;

        /* only using defined bits */
        if (mask & ~(PERF_SAMPLE_BRANCH_MAX-1))
            return -EINVAL;

        /* at least one branch bit must be set */
        if (!(mask & ~PERF_SAMPLE_BRANCH_PLM_ALL))
            return -EINVAL;

        /* kernel level capture: check permissions */
        if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
            && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
            return -EACCES;

        /* propagate priv level, when not set for branch */
        if (!(mask & PERF_SAMPLE_BRANCH_PLM_ALL)) {

            /* exclude_kernel checked on syscall entry */
            if (!attr->exclude_kernel)
                mask |= PERF_SAMPLE_BRANCH_KERNEL;

            if (!attr->exclude_user)
                mask |= PERF_SAMPLE_BRANCH_USER;

            if (!attr->exclude_hv)
                mask |= PERF_SAMPLE_BRANCH_HV;
            /*
             * adjust user setting (for HW filter setup)
             */
            attr->branch_sample_type = mask;
        }
    }

    if (attr->sample_type & PERF_SAMPLE_REGS_USER) {
        ret = perf_reg_validate(attr->sample_regs_user);
        if (ret)
            return ret;
    }

    if (attr->sample_type & PERF_SAMPLE_STACK_USER) {
        if (!arch_perf_have_user_stack_dump())
            return -ENOSYS;

        /*
         * We have __u32 type for the size, but so far
         * we can only use __u16 as maximum due to the
         * __u16 sample size limit.
         */
        if (attr->sample_stack_user >= USHRT_MAX)
            ret = -EINVAL;
        else if (!IS_ALIGNED(attr->sample_stack_user, sizeof(u64)))
            ret = -EINVAL;
    }

out:
    return ret;

err_size:
    put_user(sizeof(*attr), &uattr->size);
    ret = -E2BIG;
    goto out;
}

static int
perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
{
    struct ring_buffer *rb = NULL, *old_rb = NULL;
    int ret = -EINVAL;

    if (!output_event)
        goto set;

    /* don't allow circular references */
    if (event == output_event)
        goto out;

    /*
     * Don't allow cross-cpu buffers
     */
    if (output_event->cpu != event->cpu)
        goto out;

    /*
     * If its not a per-cpu rb, it must be the same task.
     */
    if (output_event->cpu == -1 && output_event->ctx != event->ctx)
        goto out;

set:
    mutex_lock(&event->mmap_mutex);
    /* Can't redirect output if we've got an active mmap() */
    if (atomic_read(&event->mmap_count))
        goto unlock;

    if (output_event) {
        /* get the rb we want to redirect to */
        rb = ring_buffer_get(output_event);
        if (!rb)
            goto unlock;
    }

    old_rb = event->rb;
    rcu_assign_pointer(event->rb, rb);
    if (old_rb)
        ring_buffer_detach(event, old_rb);
    ret = 0;
unlock:
    mutex_unlock(&event->mmap_mutex);

    if (old_rb)
        ring_buffer_put(old_rb);
out:
    return ret;
}

SYSCALL_DEFINE5(perf_event_open,
        struct perf_event_attr __user *, attr_uptr,
        pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
{
    struct perf_event *group_leader = NULL, *output_event = NULL;
    struct perf_event *event, *sibling;
    struct perf_event_attr attr;
    struct perf_event_context *ctx;
    struct file *event_file = NULL;
    struct fd group = {NULL, 0};
    struct task_struct *task = NULL;
    struct pmu *pmu;
    int event_fd;
    int move_group = 0;
    int err;

    /* for future expandability... */
    if (flags & ~PERF_FLAG_ALL)
        return -EINVAL;

    err = perf_copy_attr(attr_uptr, &attr);
    if (err)
        return err;

    if (!attr.exclude_kernel) {
        if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
            return -EACCES;
    }

    if (attr.freq) {
        if (attr.sample_freq > sysctl_perf_event_sample_rate)
            return -EINVAL;
    }

    /*
     * In cgroup mode, the pid argument is used to pass the fd
     * opened to the cgroup directory in cgroupfs. The cpu argument
     * designates the cpu on which to monitor threads from that
     * cgroup.
     */
    if ((flags & PERF_FLAG_PID_CGROUP) && (pid == -1 || cpu == -1))
        return -EINVAL;

    event_fd = get_unused_fd();
    if (event_fd < 0)
        return event_fd;

    if (group_fd != -1) {
        err = perf_fget_light(group_fd, &group);
        if (err)
            goto err_fd;
        group_leader = group.file->private_data;
        if (flags & PERF_FLAG_FD_OUTPUT)
            output_event = group_leader;
        if (flags & PERF_FLAG_FD_NO_GROUP)
            group_leader = NULL;
    }

    if (pid != -1 && !(flags & PERF_FLAG_PID_CGROUP)) {
        task = find_lively_task_by_vpid(pid);
        if (IS_ERR(task)) {
            err = PTR_ERR(task);
            goto err_group_fd;
        }
    }

    get_online_cpus();

    event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
                 NULL, NULL);
    if (IS_ERR(event)) {
        err = PTR_ERR(event);
        goto err_task;
    }

    if (flags & PERF_FLAG_PID_CGROUP) {
        err = perf_cgroup_connect(pid, event, &attr, group_leader);
        if (err)
            goto err_alloc;
        /*
         * one more event:
         * - that has cgroup constraint on event->cpu
         * - that may need work on context switch
         */
        atomic_inc(&per_cpu(perf_cgroup_events, event->cpu));
        static_key_slow_inc(&perf_sched_events.key);
    }

    /*
     * Special case software events and allow them to be part of
     * any hardware group.
     */
    pmu = event->pmu;

    if (group_leader &&
        (is_software_event(event) != is_software_event(group_leader))) {
        if (is_software_event(event)) {
            /*
             * If event and group_leader are not both a software
             * event, and event is, then group leader is not.
             *
             * Allow the addition of software events to !software
             * groups, this is safe because software events never
             * fail to schedule.
             */
            pmu = group_leader->pmu;
        } else if (is_software_event(group_leader) &&
               (group_leader->group_flags & PERF_GROUP_SOFTWARE)) {
            /*
             * In case the group is a pure software group, and we
             * try to add a hardware event, move the whole group to
             * the hardware context.
             */
            move_group = 1;
        }
    }

    /*
     * Get the target context (task or percpu):
     */
    ctx = find_get_context(pmu, task, event->cpu);
    if (IS_ERR(ctx)) {
        err = PTR_ERR(ctx);
        goto err_alloc;
    }

    if (task) {
        put_task_struct(task);
        task = NULL;
    }

    /*
     * Look up the group leader (we will attach this event to it):
     */
    if (group_leader) {
        err = -EINVAL;

        /*
         * Do not allow a recursive hierarchy (this new sibling
         * becoming part of another group-sibling):
         */
        if (group_leader->group_leader != group_leader)
            goto err_context;
        /*
         * Do not allow to attach to a group in a different
         * task or CPU context:
         */
        if (move_group) {
            if (group_leader->ctx->type != ctx->type)
                goto err_context;
        } else {
            if (group_leader->ctx != ctx)
                goto err_context;
        }

        /*
         * Only a group leader can be exclusive or pinned
         */
        if (attr.exclusive || attr.pinned)
            goto err_context;
    }

    if (output_event) {
        err = perf_event_set_output(event, output_event);
        if (err)
            goto err_context;
    }

    event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, O_RDWR);
    if (IS_ERR(event_file)) {
        err = PTR_ERR(event_file);
        goto err_context;
    }

    if (move_group) {
        struct perf_event_context *gctx = group_leader->ctx;

        mutex_lock(&gctx->mutex);
        perf_remove_from_context(group_leader);
        list_for_each_entry(sibling, &group_leader->sibling_list,
                    group_entry) {
            perf_remove_from_context(sibling);
            put_ctx(gctx);
        }
        mutex_unlock(&gctx->mutex);
        put_ctx(gctx);
    }

    WARN_ON_ONCE(ctx->parent_ctx);
    mutex_lock(&ctx->mutex);

    if (move_group) {
        synchronize_rcu();
        perf_install_in_context(ctx, group_leader, event->cpu);
        get_ctx(ctx);
        list_for_each_entry(sibling, &group_leader->sibling_list,
                    group_entry) {
            perf_install_in_context(ctx, sibling, event->cpu);
            get_ctx(ctx);
        }
    }

    perf_install_in_context(ctx, event, event->cpu);
    ++ctx->generation;
    perf_unpin_context(ctx);
    mutex_unlock(&ctx->mutex);

    put_online_cpus();

    event->owner = current;

    mutex_lock(&current->perf_event_mutex);
    list_add_tail(&event->owner_entry, &current->perf_event_list);
    mutex_unlock(&current->perf_event_mutex);

    /*
     * Precalculate sample_data sizes
     */
    perf_event__header_size(event);
    perf_event__id_header_size(event);

    /*
     * Drop the reference on the group_event after placing the
     * new event on the sibling_list. This ensures destruction
     * of the group leader will find the pointer to itself in
     * perf_group_detach().
     */
    fdput(group);
    fd_install(event_fd, event_file);
    return event_fd;

err_context:
    perf_unpin_context(ctx);
    put_ctx(ctx);
err_alloc:
    free_event(event);
err_task:
    put_online_cpus();
    if (task)
        put_task_struct(task);
err_group_fd:
    fdput(group);
err_fd:
    put_unused_fd(event_fd);
    return err;
}

struct perf_event *
perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
                 struct task_struct *task,
                 perf_overflow_handler_t overflow_handler,
                 void *context)
{
    struct perf_event_context *ctx;
    struct perf_event *event;
    int err;

    /*
     * Get the target context (task or percpu):
     */

    event = perf_event_alloc(attr, cpu, task, NULL, NULL,
                 overflow_handler, context);
    if (IS_ERR(event)) {
        err = PTR_ERR(event);
        goto err;
    }

    ctx = find_get_context(event->pmu, task, cpu);
    if (IS_ERR(ctx)) {
        err = PTR_ERR(ctx);
        goto err_free;
    }

    WARN_ON_ONCE(ctx->parent_ctx);
    mutex_lock(&ctx->mutex);
    perf_install_in_context(ctx, event, cpu);
    ++ctx->generation;
    perf_unpin_context(ctx);
    mutex_unlock(&ctx->mutex);

    return event;

err_free:
    free_event(event);
err:
    return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(perf_event_create_kernel_counter);

void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
{
    struct perf_event_context *src_ctx;
    struct perf_event_context *dst_ctx;
    struct perf_event *event, *tmp;
    LIST_HEAD(events);

    src_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, src_cpu)->ctx;
    dst_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, dst_cpu)->ctx;

    mutex_lock(&src_ctx->mutex);
    list_for_each_entry_safe(event, tmp, &src_ctx->event_list,
                 event_entry) {
        perf_remove_from_context(event);
        put_ctx(src_ctx);
        list_add(&event->event_entry, &events);
    }
    mutex_unlock(&src_ctx->mutex);

    synchronize_rcu();

    mutex_lock(&dst_ctx->mutex);
    list_for_each_entry_safe(event, tmp, &events, event_entry) {
        list_del(&event->event_entry);
        if (event->state >= PERF_EVENT_STATE_OFF)
            event->state = PERF_EVENT_STATE_INACTIVE;
        perf_install_in_context(dst_ctx, event, dst_cpu);
        get_ctx(dst_ctx);
    }
    mutex_unlock(&dst_ctx->mutex);
}
EXPORT_SYMBOL_GPL(perf_pmu_migrate_context);

static void sync_child_event(struct perf_event *child_event,
                   struct task_struct *child)
{
    struct perf_event *parent_event = child_event->parent;
    u64 child_val;

    if (child_event->attr.inherit_stat)
        perf_event_read_event(child_event, child);

    child_val = perf_event_count(child_event);

    /*
     * Add back the child's count to the parent's count:
     */
    atomic64_add(child_val, &parent_event->child_count);
    atomic64_add(child_event->total_time_enabled,
             &parent_event->child_total_time_enabled);
    atomic64_add(child_event->total_time_running,
             &parent_event->child_total_time_running);

    /*
     * Remove this event from the parent's list
     */
    WARN_ON_ONCE(parent_event->ctx->parent_ctx);
    mutex_lock(&parent_event->child_mutex);
    list_del_init(&child_event->child_list);
    mutex_unlock(&parent_event->child_mutex);

    /*
     * Release the parent event, if this was the last
     * reference to it.
     */
    put_event(parent_event);
}

static void
__perf_event_exit_task(struct perf_event *child_event,
             struct perf_event_context *child_ctx,
             struct task_struct *child)
{
    if (child_event->parent) {
        raw_spin_lock_irq(&child_ctx->lock);
        perf_group_detach(child_event);
        raw_spin_unlock_irq(&child_ctx->lock);
    }

    perf_remove_from_context(child_event);

    /*
     * It can happen that the parent exits first, and has events
     * that are still around due to the child reference. These
     * events need to be zapped.
     */
    if (child_event->parent) {
        sync_child_event(child_event, child);
        free_event(child_event);
    }
}

static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
{
    struct perf_event *child_event, *tmp;
    struct perf_event_context *child_ctx;
    unsigned long flags;

    if (likely(!child->perf_event_ctxp[ctxn])) {
        perf_event_task(child, NULL, 0);
        return;
    }

    local_irq_save(flags);
    /*
     * We can't reschedule here because interrupts are disabled,
     * and either child is current or it is a task that can't be
     * scheduled, so we are now safe from rescheduling changing
     * our context.
     */
    child_ctx = rcu_dereference_raw(child->perf_event_ctxp[ctxn]);

    /*
     * Take the context lock here so that if find_get_context is
     * reading child->perf_event_ctxp, we wait until it has
     * incremented the context's refcount before we do put_ctx below.
     */
    raw_spin_lock(&child_ctx->lock);
    task_ctx_sched_out(child_ctx);
    child->perf_event_ctxp[ctxn] = NULL;
    /*
     * If this context is a clone; unclone it so it can't get
     * swapped to another process while we're removing all
     * the events from it.
     */
    unclone_ctx(child_ctx);
    update_context_time(child_ctx);
    raw_spin_unlock_irqrestore(&child_ctx->lock, flags);

    /*
     * Report the task dead after unscheduling the events so that we
     * won't get any samples after PERF_RECORD_EXIT. We can however still
     * get a few PERF_RECORD_READ events.
     */
    perf_event_task(child, child_ctx, 0);

    /*
     * We can recurse on the same lock type through:
     *
     *   __perf_event_exit_task()
     *     sync_child_event()
     *       put_event()
     *         mutex_lock(&ctx->mutex)
     *
     * But since its the parent context it won't be the same instance.
     */
    mutex_lock(&child_ctx->mutex);

again:
    list_for_each_entry_safe(child_event, tmp, &child_ctx->pinned_groups,
                 group_entry)
        __perf_event_exit_task(child_event, child_ctx, child);

    list_for_each_entry_safe(child_event, tmp, &child_ctx->flexible_groups,
                 group_entry)
        __perf_event_exit_task(child_event, child_ctx, child);

    /*
     * If the last event was a group event, it will have appended all
     * its siblings to the list, but we obtained 'tmp' before that which
     * will still point to the list head terminating the iteration.
     */
    if (!list_empty(&child_ctx->pinned_groups) ||
        !list_empty(&child_ctx->flexible_groups))
        goto again;

    mutex_unlock(&child_ctx->mutex);

    put_ctx(child_ctx);
}

/*
 * When a child task exits, feed back event values to parent events.
 */
void perf_event_exit_task(struct task_struct *child)
{
    struct perf_event *event, *tmp;
    int ctxn;

    mutex_lock(&child->perf_event_mutex);
    list_for_each_entry_safe(event, tmp, &child->perf_event_list,
                 owner_entry) {
        list_del_init(&event->owner_entry);

        /*
         * Ensure the list deletion is visible before we clear
         * the owner, closes a race against perf_release() where
         * we need to serialize on the owner->perf_event_mutex.
         */
        smp_wmb();
        event->owner = NULL;
    }
    mutex_unlock(&child->perf_event_mutex);

    for_each_task_context_nr(ctxn)
        perf_event_exit_task_context(child, ctxn);
}

static void perf_free_event(struct perf_event *event,
                struct perf_event_context *ctx)
{
    struct perf_event *parent = event->parent;

    if (WARN_ON_ONCE(!parent))
        return;

    mutex_lock(&parent->child_mutex);
    list_del_init(&event->child_list);
    mutex_unlock(&parent->child_mutex);

    put_event(parent);

    perf_group_detach(event);
    list_del_event(event, ctx);
    free_event(event);
}

/*
 * free an unexposed, unused context as created by inheritance by
 * perf_event_init_task below, used by fork() in case of fail.
 */
void perf_event_free_task(struct task_struct *task)
{
    struct perf_event_context *ctx;
    struct perf_event *event, *tmp;
    int ctxn;

    for_each_task_context_nr(ctxn) {
        ctx = task->perf_event_ctxp[ctxn];
        if (!ctx)
            continue;

        mutex_lock(&ctx->mutex);
again:
        list_for_each_entry_safe(event, tmp, &ctx->pinned_groups,
                group_entry)
            perf_free_event(event, ctx);

        list_for_each_entry_safe(event, tmp, &ctx->flexible_groups,
                group_entry)
            perf_free_event(event, ctx);

        if (!list_empty(&ctx->pinned_groups) ||
                !list_empty(&ctx->flexible_groups))
            goto again;

        mutex_unlock(&ctx->mutex);

        put_ctx(ctx);
    }
}

void perf_event_delayed_put(struct task_struct *task)
{
    int ctxn;

    for_each_task_context_nr(ctxn)
        WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
}

/*
 * inherit a event from parent task to child task:
 */
static struct perf_event *
inherit_event(struct perf_event *parent_event,
          struct task_struct *parent,
          struct perf_event_context *parent_ctx,
          struct task_struct *child,
          struct perf_event *group_leader,
          struct perf_event_context *child_ctx)
{
    struct perf_event *child_event;
    unsigned long flags;

    /*
     * Instead of creating recursive hierarchies of events,
     * we link inherited events back to the original parent,
     * which has a filp for sure, which we use as the reference
     * count:
     */
    if (parent_event->parent)
        parent_event = parent_event->parent;

    child_event = perf_event_alloc(&parent_event->attr,
                       parent_event->cpu,
                       child,
                       group_leader, parent_event,
                           NULL, NULL);
    if (IS_ERR(child_event))
        return child_event;

    if (!atomic_long_inc_not_zero(&parent_event->refcount)) {
        free_event(child_event);
        return NULL;
    }

    get_ctx(child_ctx);

    /*
     * Make the child state follow the state of the parent event,
     * not its attr.disabled bit.  We hold the parent's mutex,
     * so we won't race with perf_event_{en, dis}able_family.
     */
    if (parent_event->state >= PERF_EVENT_STATE_INACTIVE)
        child_event->state = PERF_EVENT_STATE_INACTIVE;
    else
        child_event->state = PERF_EVENT_STATE_OFF;

    if (parent_event->attr.freq) {
        u64 sample_period = parent_event->hw.sample_period;
        struct hw_perf_event *hwc = &child_event->hw;

        hwc->sample_period = sample_period;
        hwc->last_period   = sample_period;

        local64_set(&hwc->period_left, sample_period);
    }

    child_event->ctx = child_ctx;
    child_event->overflow_handler = parent_event->overflow_handler;
    child_event->overflow_handler_context
        = parent_event->overflow_handler_context;

    /*
     * Precalculate sample_data sizes
     */
    perf_event__header_size(child_event);
    perf_event__id_header_size(child_event);

    /*
     * Link it up in the child's context:
     */
    raw_spin_lock_irqsave(&child_ctx->lock, flags);
    add_event_to_ctx(child_event, child_ctx);
    raw_spin_unlock_irqrestore(&child_ctx->lock, flags);

    /*
     * Link this into the parent event's child list
     */
    WARN_ON_ONCE(parent_event->ctx->parent_ctx);
    mutex_lock(&parent_event->child_mutex);
    list_add_tail(&child_event->child_list, &parent_event->child_list);
    mutex_unlock(&parent_event->child_mutex);

    return child_event;
}

static int inherit_group(struct perf_event *parent_event,
          struct task_struct *parent,
          struct perf_event_context *parent_ctx,
          struct task_struct *child,
          struct perf_event_context *child_ctx)
{
    struct perf_event *leader;
    struct perf_event *sub;
    struct perf_event *child_ctr;

    leader = inherit_event(parent_event, parent, parent_ctx,
                 child, NULL, child_ctx);
    if (IS_ERR(leader))
        return PTR_ERR(leader);
    list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
        child_ctr = inherit_event(sub, parent, parent_ctx,
                        child, leader, child_ctx);
        if (IS_ERR(child_ctr))
            return PTR_ERR(child_ctr);
    }
    return 0;
}

static int
inherit_task_group(struct perf_event *event, struct task_struct *parent,
           struct perf_event_context *parent_ctx,
           struct task_struct *child, int ctxn,
           int *inherited_all)
{
    int ret;
    struct perf_event_context *child_ctx;

    if (!event->attr.inherit) {
        *inherited_all = 0;
        return 0;
    }

    child_ctx = child->perf_event_ctxp[ctxn];
    if (!child_ctx) {
        /*
         * This is executed from the parent task context, so
         * inherit events that have been marked for cloning.
         * First allocate and initialize a context for the
         * child.
         */

        child_ctx = alloc_perf_context(event->pmu, child);
        if (!child_ctx)
            return -ENOMEM;

        child->perf_event_ctxp[ctxn] = child_ctx;
    }

    ret = inherit_group(event, parent, parent_ctx,
                child, child_ctx);

    if (ret)
        *inherited_all = 0;

    return ret;
}

/*
 * Initialize the perf_event context in task_struct
 */
int perf_event_init_context(struct task_struct *child, int ctxn)
{
    struct perf_event_context *child_ctx, *parent_ctx;
    struct perf_event_context *cloned_ctx;
    struct perf_event *event;
    struct task_struct *parent = current;
    int inherited_all = 1;
    unsigned long flags;
    int ret = 0;

    if (likely(!parent->perf_event_ctxp[ctxn]))
        return 0;

    /*
     * If the parent's context is a clone, pin it so it won't get
     * swapped under us.
     */
    parent_ctx = perf_pin_task_context(parent, ctxn);

    /*
     * No need to check if parent_ctx != NULL here; since we saw
     * it non-NULL earlier, the only reason for it to become NULL
     * is if we exit, and since we're currently in the middle of
     * a fork we can't be exiting at the same time.
     */

    /*
     * Lock the parent list. No need to lock the child - not PID
     * hashed yet and not running, so nobody can access it.
     */
    mutex_lock(&parent_ctx->mutex);

    /*
     * We dont have to disable NMIs - we are only looking at
     * the list, not manipulating it:
     */
    list_for_each_entry(event, &parent_ctx->pinned_groups, group_entry) {
        ret = inherit_task_group(event, parent, parent_ctx,
                     child, ctxn, &inherited_all);
        if (ret)
            break;
    }

    /*
     * We can't hold ctx->lock when iterating the ->flexible_group list due
     * to allocations, but we need to prevent rotation because
     * rotate_ctx() will change the list from interrupt context.
     */
    raw_spin_lock_irqsave(&parent_ctx->lock, flags);
    parent_ctx->rotate_disable = 1;
    raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);

    list_for_each_entry(event, &parent_ctx->flexible_groups, group_entry) {
        ret = inherit_task_group(event, parent, parent_ctx,
                     child, ctxn, &inherited_all);
        if (ret)
            break;
    }

    raw_spin_lock_irqsave(&parent_ctx->lock, flags);
    parent_ctx->rotate_disable = 0;

    child_ctx = child->perf_event_ctxp[ctxn];

    if (child_ctx && inherited_all) {
        /*
         * Mark the child context as a clone of the parent
         * context, or of whatever the parent is a clone of.
         *
         * Note that if the parent is a clone, the holding of
         * parent_ctx->lock avoids it from being uncloned.
         */
        cloned_ctx = parent_ctx->parent_ctx;
        if (cloned_ctx) {
            child_ctx->parent_ctx = cloned_ctx;
            child_ctx->parent_gen = parent_ctx->parent_gen;
        } else {
            child_ctx->parent_ctx = parent_ctx;
            child_ctx->parent_gen = parent_ctx->generation;
        }
        get_ctx(child_ctx->parent_ctx);
    }

    raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
    mutex_unlock(&parent_ctx->mutex);

    perf_unpin_context(parent_ctx);
    put_ctx(parent_ctx);

    return ret;
}

/*
 * Initialize the perf_event context in task_struct
 */
int perf_event_init_task(struct task_struct *child)
{
    int ctxn, ret;

    memset(child->perf_event_ctxp, 0, sizeof(child->perf_event_ctxp));
    mutex_init(&child->perf_event_mutex);
    INIT_LIST_HEAD(&child->perf_event_list);

    for_each_task_context_nr(ctxn) {
        ret = perf_event_init_context(child, ctxn);
        if (ret)
            return ret;
    }

    return 0;
}

static void __init perf_event_init_all_cpus(void)
{
    struct swevent_htable *swhash;
    int cpu;

    for_each_possible_cpu(cpu) {
        swhash = &per_cpu(swevent_htable, cpu);
        mutex_init(&swhash->hlist_mutex);
        INIT_LIST_HEAD(&per_cpu(rotation_list, cpu));
    }
}

static void __cpuinit perf_event_init_cpu(int cpu)
{
    struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);

    mutex_lock(&swhash->hlist_mutex);
    if (swhash->hlist_refcount > 0) {
        struct swevent_hlist *hlist;

        hlist = kzalloc_node(sizeof(*hlist), GFP_KERNEL, cpu_to_node(cpu));
        WARN_ON(!hlist);
        rcu_assign_pointer(swhash->swevent_hlist, hlist);
    }
    mutex_unlock(&swhash->hlist_mutex);
}

#if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC
static void perf_pmu_rotate_stop(struct pmu *pmu)
{
    struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

    WARN_ON(!irqs_disabled());

    list_del_init(&cpuctx->rotation_list);
}

static void __perf_event_exit_context(void *__info)
{
    struct perf_event_context *ctx = __info;
    struct perf_event *event, *tmp;

    perf_pmu_rotate_stop(ctx->pmu);

    list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
        __perf_remove_from_context(event);
    list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
        __perf_remove_from_context(event);
}

static void perf_event_exit_cpu_context(int cpu)
{
    struct perf_event_context *ctx;
    struct pmu *pmu;
    int idx;

    idx = srcu_read_lock(&pmus_srcu);
    list_for_each_entry_rcu(pmu, &pmus, entry) {
        ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;

        mutex_lock(&ctx->mutex);
        smp_call_function_single(cpu, __perf_event_exit_context, ctx, 1);
        mutex_unlock(&ctx->mutex);
    }
    srcu_read_unlock(&pmus_srcu, idx);
}

static void perf_event_exit_cpu(int cpu)
{
    struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);

    mutex_lock(&swhash->hlist_mutex);
    swevent_hlist_release(swhash);
    mutex_unlock(&swhash->hlist_mutex);

    perf_event_exit_cpu_context(cpu);
}
#else
static inline void perf_event_exit_cpu(int cpu) { }
#endif

static int
perf_reboot(struct notifier_block *notifier, unsigned long val, void *v)
{
    int cpu;

    for_each_online_cpu(cpu)
        perf_event_exit_cpu(cpu);

    return NOTIFY_OK;
}

/*
 * Run the perf reboot notifier at the very last possible moment so that
 * the generic watchdog code runs as long as possible.
 */
static struct notifier_block perf_reboot_notifier = {
    .notifier_call = perf_reboot,
    .priority = INT_MIN,
};

static int __cpuinit
perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
{
    unsigned int cpu = (long)hcpu;

    switch (action & ~CPU_TASKS_FROZEN) {

    case CPU_UP_PREPARE:
    case CPU_DOWN_FAILED:
        perf_event_init_cpu(cpu);
        break;

    case CPU_UP_CANCELED:
    case CPU_DOWN_PREPARE:
        perf_event_exit_cpu(cpu);
        break;

    default:
        break;
    }

    return NOTIFY_OK;
}

void __init perf_event_init(void)
{
    int ret;

    idr_init(&pmu_idr);

    perf_event_init_all_cpus();
    init_srcu_struct(&pmus_srcu);
    perf_pmu_register(&perf_swevent, "software", PERF_TYPE_SOFTWARE);
    perf_pmu_register(&perf_cpu_clock, NULL, -1);
    perf_pmu_register(&perf_task_clock, NULL, -1);
    perf_tp_register();
    perf_cpu_notifier(perf_cpu_notify);
    register_reboot_notifier(&perf_reboot_notifier);

    ret = init_hw_breakpoint();
    WARN(ret, "hw_breakpoint initialization failed with: %d", ret);

    /* do not patch jump label more than once per second */
    jump_label_rate_limit(&perf_sched_events, HZ);

    /*
     * Build time assertion that we keep the data_head at the intended
     * location.  IOW, validation we got the __reserved[] size right.
     */
    BUILD_BUG_ON((offsetof(struct perf_event_mmap_page, data_head))
             != 1024);
}

static int __init perf_event_sysfs_init(void)
{
    struct pmu *pmu;
    int ret;

    mutex_lock(&pmus_lock);

    ret = bus_register(&pmu_bus);
    if (ret)
        goto unlock;

    list_for_each_entry(pmu, &pmus, entry) {
        if (!pmu->name || pmu->type < 0)
            continue;

        ret = pmu_dev_alloc(pmu);
        WARN(ret, "Failed to register pmu: %s, reason %d\n", pmu->name, ret);
    }
    pmu_bus_running = 1;
    ret = 0;

unlock:
    mutex_unlock(&pmus_lock);

    return ret;
}
device_initcall(perf_event_sysfs_init);

#ifdef CONFIG_CGROUP_PERF
static struct cgroup_subsys_state *perf_cgroup_create(struct cgroup *cont)
{
    struct perf_cgroup *jc;

    jc = kzalloc(sizeof(*jc), GFP_KERNEL);
    if (!jc)
        return ERR_PTR(-ENOMEM);

    jc->info = alloc_percpu(struct perf_cgroup_info);
    if (!jc->info) {
        kfree(jc);
        return ERR_PTR(-ENOMEM);
    }

    return &jc->css;
}

static void perf_cgroup_destroy(struct cgroup *cont)
{
    struct perf_cgroup *jc;
    jc = container_of(cgroup_subsys_state(cont, perf_subsys_id),
              struct perf_cgroup, css);
    free_percpu(jc->info);
    kfree(jc);
}

static int __perf_cgroup_move(void *info)
{
    struct task_struct *task = info;
    perf_cgroup_switch(task, PERF_CGROUP_SWOUT | PERF_CGROUP_SWIN);
    return 0;
}

static void perf_cgroup_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
    struct task_struct *task;

    cgroup_taskset_for_each(task, cgrp, tset)
        task_function_call(task, __perf_cgroup_move, task);
}

static void perf_cgroup_exit(struct cgroup *cgrp, struct cgroup *old_cgrp,
                 struct task_struct *task)
{
    /*
     * cgroup_exit() is called in the copy_process() failure path.
     * Ignore this case since the task hasn't ran yet, this avoids
     * trying to poke a half freed task state from generic code.
     */
    if (!(task->flags & PF_EXITING))
        return;

    task_function_call(task, __perf_cgroup_move, task);
}

struct cgroup_subsys perf_subsys = {
    .name       = "perf_event",
    .subsys_id  = perf_subsys_id,
    .create     = perf_cgroup_create,
    .destroy    = perf_cgroup_destroy,
    .exit       = perf_cgroup_exit,
    .attach     = perf_cgroup_attach,

    /*
     * perf_event cgroup doesn't handle nesting correctly.
     * ctx->nr_cgroups adjustments should be propagated through the
     * cgroup hierarchy.  Fix it and remove the following.
     */
    .broken_hierarchy = true,
};
#endif /* CONFIG_CGROUP_PERF */