ftrace.c

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/*
 * Infrastructure for profiling code inserted by 'gcc -pg'.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
 * Copyright (C) 2004-2008 Ingo Molnar <[email protected]>
 *
 * Originally ported from the -rt patch by:
 *   Copyright (C) 2007 Arnaldo Carvalho de Melo <[email protected]>
 *
 * Based on code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */

#include <linux/stop_machine.h>
#include <linux/clocksource.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/suspend.h>
#include <linux/debugfs.h>
#include <linux/hardirq.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <linux/bsearch.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/sort.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/rcupdate.h>

#include <trace/events/sched.h>

#include <asm/setup.h>

#include "trace_output.h"
#include "trace_stat.h"

#define FTRACE_WARN_ON(cond)            \
    ({                  \
        int ___r = cond;        \
        if (WARN_ON(___r))      \
            ftrace_kill();      \
        ___r;               \
    })

#define FTRACE_WARN_ON_ONCE(cond)       \
    ({                  \
        int ___r = cond;        \
        if (WARN_ON_ONCE(___r))     \
            ftrace_kill();      \
        ___r;               \
    })

/* hash bits for specific function selection */
#define FTRACE_HASH_BITS 7
#define FTRACE_FUNC_HASHSIZE (1 << FTRACE_HASH_BITS)
#define FTRACE_HASH_DEFAULT_BITS 10
#define FTRACE_HASH_MAX_BITS 12

#define FL_GLOBAL_CONTROL_MASK (FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_CONTROL)

static struct ftrace_ops ftrace_list_end __read_mostly = {
    .func       = ftrace_stub,
    .flags      = FTRACE_OPS_FL_RECURSION_SAFE,
};

/* ftrace_enabled is a method to turn ftrace on or off */
int ftrace_enabled __read_mostly;
static int last_ftrace_enabled;

/* Quick disabling of function tracer. */
int function_trace_stop __read_mostly;

/* Current function tracing op */
struct ftrace_ops *function_trace_op __read_mostly = &ftrace_list_end;

/* List for set_ftrace_pid's pids. */
LIST_HEAD(ftrace_pids);
struct ftrace_pid {
    struct list_head list;
    struct pid *pid;
};

/*
 * ftrace_disabled is set when an anomaly is discovered.
 * ftrace_disabled is much stronger than ftrace_enabled.
 */
static int ftrace_disabled __read_mostly;

static DEFINE_MUTEX(ftrace_lock);

static struct ftrace_ops *ftrace_global_list __read_mostly = &ftrace_list_end;
static struct ftrace_ops *ftrace_control_list __read_mostly = &ftrace_list_end;
static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
static struct ftrace_ops global_ops;
static struct ftrace_ops control_ops;

#if ARCH_SUPPORTS_FTRACE_OPS
static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
                 struct ftrace_ops *op, struct pt_regs *regs);
#else
/* See comment below, where ftrace_ops_list_func is defined */
static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
#endif

int ftrace_nr_registered_ops(void)
{
    struct ftrace_ops *ops;
    int cnt = 0;

    mutex_lock(&ftrace_lock);

    for (ops = ftrace_ops_list;
         ops != &ftrace_list_end; ops = ops->next)
        cnt++;

    mutex_unlock(&ftrace_lock);

    return cnt;
}

/*
 * Traverse the ftrace_global_list, invoking all entries.  The reason that we
 * can use rcu_dereference_raw() is that elements removed from this list
 * are simply leaked, so there is no need to interact with a grace-period
 * mechanism.  The rcu_dereference_raw() calls are needed to handle
 * concurrent insertions into the ftrace_global_list.
 *
 * Silly Alpha and silly pointer-speculation compiler optimizations!
 */
static void
ftrace_global_list_func(unsigned long ip, unsigned long parent_ip,
            struct ftrace_ops *op, struct pt_regs *regs)
{
    if (unlikely(trace_recursion_test(TRACE_GLOBAL_BIT)))
        return;

    trace_recursion_set(TRACE_GLOBAL_BIT);
    op = rcu_dereference_raw(ftrace_global_list); /*see above*/
    while (op != &ftrace_list_end) {
        op->func(ip, parent_ip, op, regs);
        op = rcu_dereference_raw(op->next); /*see above*/
    };
    trace_recursion_clear(TRACE_GLOBAL_BIT);
}

static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
                struct ftrace_ops *op, struct pt_regs *regs)
{
    if (!test_tsk_trace_trace(current))
        return;

    ftrace_pid_function(ip, parent_ip, op, regs);
}

static void set_ftrace_pid_function(ftrace_func_t func)
{
    /* do not set ftrace_pid_function to itself! */
    if (func != ftrace_pid_func)
        ftrace_pid_function = func;
}

void clear_ftrace_function(void)
{
    ftrace_trace_function = ftrace_stub;
    ftrace_pid_function = ftrace_stub;
}

static void control_ops_disable_all(struct ftrace_ops *ops)
{
    int cpu;

    for_each_possible_cpu(cpu)
        *per_cpu_ptr(ops->disabled, cpu) = 1;
}

static int control_ops_alloc(struct ftrace_ops *ops)
{
    int __percpu *disabled;

    disabled = alloc_percpu(int);
    if (!disabled)
        return -ENOMEM;

    ops->disabled = disabled;
    control_ops_disable_all(ops);
    return 0;
}

static void control_ops_free(struct ftrace_ops *ops)
{
    free_percpu(ops->disabled);
}

static void update_global_ops(void)
{
    ftrace_func_t func;

    /*
     * If there's only one function registered, then call that
     * function directly. Otherwise, we need to iterate over the
     * registered callers.
     */
    if (ftrace_global_list == &ftrace_list_end ||
        ftrace_global_list->next == &ftrace_list_end)
        func = ftrace_global_list->func;
    else
        func = ftrace_global_list_func;

    /* If we filter on pids, update to use the pid function */
    if (!list_empty(&ftrace_pids)) {
        set_ftrace_pid_function(func);
        func = ftrace_pid_func;
    }

    global_ops.func = func;
}

static void update_ftrace_function(void)
{
    ftrace_func_t func;

    update_global_ops();

    /*
     * If we are at the end of the list and this ops is
     * recursion safe and not dynamic and the arch supports passing ops,
     * then have the mcount trampoline call the function directly.
     */
    if (ftrace_ops_list == &ftrace_list_end ||
        (ftrace_ops_list->next == &ftrace_list_end &&
         !(ftrace_ops_list->flags & FTRACE_OPS_FL_DYNAMIC) &&
         (ftrace_ops_list->flags & FTRACE_OPS_FL_RECURSION_SAFE) &&
         !FTRACE_FORCE_LIST_FUNC)) {
        /* Set the ftrace_ops that the arch callback uses */
        if (ftrace_ops_list == &global_ops)
            function_trace_op = ftrace_global_list;
        else
            function_trace_op = ftrace_ops_list;
        func = ftrace_ops_list->func;
    } else {
        /* Just use the default ftrace_ops */
        function_trace_op = &ftrace_list_end;
        func = ftrace_ops_list_func;
    }

    ftrace_trace_function = func;
}

static void add_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops)
{
    ops->next = *list;
    /*
     * We are entering ops into the list but another
     * CPU might be walking that list. We need to make sure
     * the ops->next pointer is valid before another CPU sees
     * the ops pointer included into the list.
     */
    rcu_assign_pointer(*list, ops);
}

static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops)
{
    struct ftrace_ops **p;

    /*
     * If we are removing the last function, then simply point
     * to the ftrace_stub.
     */
    if (*list == ops && ops->next == &ftrace_list_end) {
        *list = &ftrace_list_end;
        return 0;
    }

    for (p = list; *p != &ftrace_list_end; p = &(*p)->next)
        if (*p == ops)
            break;

    if (*p != ops)
        return -1;

    *p = (*p)->next;
    return 0;
}

static void add_ftrace_list_ops(struct ftrace_ops **list,
                struct ftrace_ops *main_ops,
                struct ftrace_ops *ops)
{
    int first = *list == &ftrace_list_end;
    add_ftrace_ops(list, ops);
    if (first)
        add_ftrace_ops(&ftrace_ops_list, main_ops);
}

static int remove_ftrace_list_ops(struct ftrace_ops **list,
                  struct ftrace_ops *main_ops,
                  struct ftrace_ops *ops)
{
    int ret = remove_ftrace_ops(list, ops);
    if (!ret && *list == &ftrace_list_end)
        ret = remove_ftrace_ops(&ftrace_ops_list, main_ops);
    return ret;
}

static int __register_ftrace_function(struct ftrace_ops *ops)
{
    if (unlikely(ftrace_disabled))
        return -ENODEV;

    if (FTRACE_WARN_ON(ops == &global_ops))
        return -EINVAL;

    if (WARN_ON(ops->flags & FTRACE_OPS_FL_ENABLED))
        return -EBUSY;

    /* We don't support both control and global flags set. */
    if ((ops->flags & FL_GLOBAL_CONTROL_MASK) == FL_GLOBAL_CONTROL_MASK)
        return -EINVAL;

#ifndef ARCH_SUPPORTS_FTRACE_SAVE_REGS
    /*
     * If the ftrace_ops specifies SAVE_REGS, then it only can be used
     * if the arch supports it, or SAVE_REGS_IF_SUPPORTED is also set.
     * Setting SAVE_REGS_IF_SUPPORTED makes SAVE_REGS irrelevant.
     */
    if (ops->flags & FTRACE_OPS_FL_SAVE_REGS &&
        !(ops->flags & FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED))
        return -EINVAL;

    if (ops->flags & FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED)
        ops->flags |= FTRACE_OPS_FL_SAVE_REGS;
#endif

    if (!core_kernel_data((unsigned long)ops))
        ops->flags |= FTRACE_OPS_FL_DYNAMIC;

    if (ops->flags & FTRACE_OPS_FL_GLOBAL) {
        add_ftrace_list_ops(&ftrace_global_list, &global_ops, ops);
        ops->flags |= FTRACE_OPS_FL_ENABLED;
    } else if (ops->flags & FTRACE_OPS_FL_CONTROL) {
        if (control_ops_alloc(ops))
            return -ENOMEM;
        add_ftrace_list_ops(&ftrace_control_list, &control_ops, ops);
    } else
        add_ftrace_ops(&ftrace_ops_list, ops);

    if (ftrace_enabled)
        update_ftrace_function();

    return 0;
}

static int __unregister_ftrace_function(struct ftrace_ops *ops)
{
    int ret;

    if (ftrace_disabled)
        return -ENODEV;

    if (WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED)))
        return -EBUSY;

    if (FTRACE_WARN_ON(ops == &global_ops))
        return -EINVAL;

    if (ops->flags & FTRACE_OPS_FL_GLOBAL) {
        ret = remove_ftrace_list_ops(&ftrace_global_list,
                         &global_ops, ops);
        if (!ret)
            ops->flags &= ~FTRACE_OPS_FL_ENABLED;
    } else if (ops->flags & FTRACE_OPS_FL_CONTROL) {
        ret = remove_ftrace_list_ops(&ftrace_control_list,
                         &control_ops, ops);
        if (!ret) {
            /*
             * The ftrace_ops is now removed from the list,
             * so there'll be no new users. We must ensure
             * all current users are done before we free
             * the control data.
             */
            synchronize_sched();
            control_ops_free(ops);
        }
    } else
        ret = remove_ftrace_ops(&ftrace_ops_list, ops);

    if (ret < 0)
        return ret;

    if (ftrace_enabled)
        update_ftrace_function();

    /*
     * Dynamic ops may be freed, we must make sure that all
     * callers are done before leaving this function.
     */
    if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
        synchronize_sched();

    return 0;
}

static void ftrace_update_pid_func(void)
{
    /* Only do something if we are tracing something */
    if (ftrace_trace_function == ftrace_stub)
        return;

    update_ftrace_function();
}

#ifdef CONFIG_FUNCTION_PROFILER
struct ftrace_profile {
    struct hlist_node       node;
    unsigned long           ip;
    unsigned long           counter;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    unsigned long long      time;
    unsigned long long      time_squared;
#endif
};

struct ftrace_profile_page {
    struct ftrace_profile_page  *next;
    unsigned long           index;
    struct ftrace_profile       records[];
};

struct ftrace_profile_stat {
    atomic_t            disabled;
    struct hlist_head       *hash;
    struct ftrace_profile_page  *pages;
    struct ftrace_profile_page  *start;
    struct tracer_stat      stat;
};

#define PROFILE_RECORDS_SIZE                        \
    (PAGE_SIZE - offsetof(struct ftrace_profile_page, records))

#define PROFILES_PER_PAGE                   \
    (PROFILE_RECORDS_SIZE / sizeof(struct ftrace_profile))

static int ftrace_profile_bits __read_mostly;
static int ftrace_profile_enabled __read_mostly;

/* ftrace_profile_lock - synchronize the enable and disable of the profiler */
static DEFINE_MUTEX(ftrace_profile_lock);

static DEFINE_PER_CPU(struct ftrace_profile_stat, ftrace_profile_stats);

#define FTRACE_PROFILE_HASH_SIZE 1024 /* must be power of 2 */

static void *
function_stat_next(void *v, int idx)
{
    struct ftrace_profile *rec = v;
    struct ftrace_profile_page *pg;

    pg = (struct ftrace_profile_page *)((unsigned long)rec & PAGE_MASK);

 again:
    if (idx != 0)
        rec++;

    if ((void *)rec >= (void *)&pg->records[pg->index]) {
        pg = pg->next;
        if (!pg)
            return NULL;
        rec = &pg->records[0];
        if (!rec->counter)
            goto again;
    }

    return rec;
}

static void *function_stat_start(struct tracer_stat *trace)
{
    struct ftrace_profile_stat *stat =
        container_of(trace, struct ftrace_profile_stat, stat);

    if (!stat || !stat->start)
        return NULL;

    return function_stat_next(&stat->start->records[0], 0);
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* function graph compares on total time */
static int function_stat_cmp(void *p1, void *p2)
{
    struct ftrace_profile *a = p1;
    struct ftrace_profile *b = p2;

    if (a->time < b->time)
        return -1;
    if (a->time > b->time)
        return 1;
    else
        return 0;
}
#else
/* not function graph compares against hits */
static int function_stat_cmp(void *p1, void *p2)
{
    struct ftrace_profile *a = p1;
    struct ftrace_profile *b = p2;

    if (a->counter < b->counter)
        return -1;
    if (a->counter > b->counter)
        return 1;
    else
        return 0;
}
#endif

static int function_stat_headers(struct seq_file *m)
{
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    seq_printf(m, "  Function                               "
           "Hit    Time            Avg             s^2\n"
              "  --------                               "
           "---    ----            ---             ---\n");
#else
    seq_printf(m, "  Function                               Hit\n"
              "  --------                               ---\n");
#endif
    return 0;
}

static int function_stat_show(struct seq_file *m, void *v)
{
    struct ftrace_profile *rec = v;
    char str[KSYM_SYMBOL_LEN];
    int ret = 0;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    static struct trace_seq s;
    unsigned long long avg;
    unsigned long long stddev;
#endif
    mutex_lock(&ftrace_profile_lock);

    /* we raced with function_profile_reset() */
    if (unlikely(rec->counter == 0)) {
        ret = -EBUSY;
        goto out;
    }

    kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
    seq_printf(m, "  %-30.30s  %10lu", str, rec->counter);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    seq_printf(m, "    ");
    avg = rec->time;
    do_div(avg, rec->counter);

    /* Sample standard deviation (s^2) */
    if (rec->counter <= 1)
        stddev = 0;
    else {
        stddev = rec->time_squared - rec->counter * avg * avg;
        /*
         * Divide only 1000 for ns^2 -> us^2 conversion.
         * trace_print_graph_duration will divide 1000 again.
         */
        do_div(stddev, (rec->counter - 1) * 1000);
    }

    trace_seq_init(&s);
    trace_print_graph_duration(rec->time, &s);
    trace_seq_puts(&s, "    ");
    trace_print_graph_duration(avg, &s);
    trace_seq_puts(&s, "    ");
    trace_print_graph_duration(stddev, &s);
    trace_print_seq(m, &s);
#endif
    seq_putc(m, '\n');
out:
    mutex_unlock(&ftrace_profile_lock);

    return ret;
}

static void ftrace_profile_reset(struct ftrace_profile_stat *stat)
{
    struct ftrace_profile_page *pg;

    pg = stat->pages = stat->start;

    while (pg) {
        memset(pg->records, 0, PROFILE_RECORDS_SIZE);
        pg->index = 0;
        pg = pg->next;
    }

    memset(stat->hash, 0,
           FTRACE_PROFILE_HASH_SIZE * sizeof(struct hlist_head));
}

int ftrace_profile_pages_init(struct ftrace_profile_stat *stat)
{
    struct ftrace_profile_page *pg;
    int functions;
    int pages;
    int i;

    /* If we already allocated, do nothing */
    if (stat->pages)
        return 0;

    stat->pages = (void *)get_zeroed_page(GFP_KERNEL);
    if (!stat->pages)
        return -ENOMEM;

#ifdef CONFIG_DYNAMIC_FTRACE
    functions = ftrace_update_tot_cnt;
#else
    /*
     * We do not know the number of functions that exist because
     * dynamic tracing is what counts them. With past experience
     * we have around 20K functions. That should be more than enough.
     * It is highly unlikely we will execute every function in
     * the kernel.
     */
    functions = 20000;
#endif

    pg = stat->start = stat->pages;

    pages = DIV_ROUND_UP(functions, PROFILES_PER_PAGE);

    for (i = 0; i < pages; i++) {
        pg->next = (void *)get_zeroed_page(GFP_KERNEL);
        if (!pg->next)
            goto out_free;
        pg = pg->next;
    }

    return 0;

 out_free:
    pg = stat->start;
    while (pg) {
        unsigned long tmp = (unsigned long)pg;

        pg = pg->next;
        free_page(tmp);
    }

    free_page((unsigned long)stat->pages);
    stat->pages = NULL;
    stat->start = NULL;

    return -ENOMEM;
}

static int ftrace_profile_init_cpu(int cpu)
{
    struct ftrace_profile_stat *stat;
    int size;

    stat = &per_cpu(ftrace_profile_stats, cpu);

    if (stat->hash) {
        /* If the profile is already created, simply reset it */
        ftrace_profile_reset(stat);
        return 0;
    }

    /*
     * We are profiling all functions, but usually only a few thousand
     * functions are hit. We'll make a hash of 1024 items.
     */
    size = FTRACE_PROFILE_HASH_SIZE;

    stat->hash = kzalloc(sizeof(struct hlist_head) * size, GFP_KERNEL);

    if (!stat->hash)
        return -ENOMEM;

    if (!ftrace_profile_bits) {
        size--;

        for (; size; size >>= 1)
            ftrace_profile_bits++;
    }

    /* Preallocate the function profiling pages */
    if (ftrace_profile_pages_init(stat) < 0) {
        kfree(stat->hash);
        stat->hash = NULL;
        return -ENOMEM;
    }

    return 0;
}

static int ftrace_profile_init(void)
{
    int cpu;
    int ret = 0;

    for_each_online_cpu(cpu) {
        ret = ftrace_profile_init_cpu(cpu);
        if (ret)
            break;
    }

    return ret;
}

/* interrupts must be disabled */
static struct ftrace_profile *
ftrace_find_profiled_func(struct ftrace_profile_stat *stat, unsigned long ip)
{
    struct ftrace_profile *rec;
    struct hlist_head *hhd;
    struct hlist_node *n;
    unsigned long key;

    key = hash_long(ip, ftrace_profile_bits);
    hhd = &stat->hash[key];

    if (hlist_empty(hhd))
        return NULL;

    hlist_for_each_entry_rcu(rec, n, hhd, node) {
        if (rec->ip == ip)
            return rec;
    }

    return NULL;
}

static void ftrace_add_profile(struct ftrace_profile_stat *stat,
                   struct ftrace_profile *rec)
{
    unsigned long key;

    key = hash_long(rec->ip, ftrace_profile_bits);
    hlist_add_head_rcu(&rec->node, &stat->hash[key]);
}

/*
 * The memory is already allocated, this simply finds a new record to use.
 */
static struct ftrace_profile *
ftrace_profile_alloc(struct ftrace_profile_stat *stat, unsigned long ip)
{
    struct ftrace_profile *rec = NULL;

    /* prevent recursion (from NMIs) */
    if (atomic_inc_return(&stat->disabled) != 1)
        goto out;

    /*
     * Try to find the function again since an NMI
     * could have added it
     */
    rec = ftrace_find_profiled_func(stat, ip);
    if (rec)
        goto out;

    if (stat->pages->index == PROFILES_PER_PAGE) {
        if (!stat->pages->next)
            goto out;
        stat->pages = stat->pages->next;
    }

    rec = &stat->pages->records[stat->pages->index++];
    rec->ip = ip;
    ftrace_add_profile(stat, rec);

 out:
    atomic_dec(&stat->disabled);

    return rec;
}

static void
function_profile_call(unsigned long ip, unsigned long parent_ip,
              struct ftrace_ops *ops, struct pt_regs *regs)
{
    struct ftrace_profile_stat *stat;
    struct ftrace_profile *rec;
    unsigned long flags;

    if (!ftrace_profile_enabled)
        return;

    local_irq_save(flags);

    stat = &__get_cpu_var(ftrace_profile_stats);
    if (!stat->hash || !ftrace_profile_enabled)
        goto out;

    rec = ftrace_find_profiled_func(stat, ip);
    if (!rec) {
        rec = ftrace_profile_alloc(stat, ip);
        if (!rec)
            goto out;
    }

    rec->counter++;
 out:
    local_irq_restore(flags);
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int profile_graph_entry(struct ftrace_graph_ent *trace)
{
    function_profile_call(trace->func, 0, NULL, NULL);
    return 1;
}

static void profile_graph_return(struct ftrace_graph_ret *trace)
{
    struct ftrace_profile_stat *stat;
    unsigned long long calltime;
    struct ftrace_profile *rec;
    unsigned long flags;

    local_irq_save(flags);
    stat = &__get_cpu_var(ftrace_profile_stats);
    if (!stat->hash || !ftrace_profile_enabled)
        goto out;

    /* If the calltime was zero'd ignore it */
    if (!trace->calltime)
        goto out;

    calltime = trace->rettime - trace->calltime;

    if (!(trace_flags & TRACE_ITER_GRAPH_TIME)) {
        int index;

        index = trace->depth;

        /* Append this call time to the parent time to subtract */
        if (index)
            current->ret_stack[index - 1].subtime += calltime;

        if (current->ret_stack[index].subtime < calltime)
            calltime -= current->ret_stack[index].subtime;
        else
            calltime = 0;
    }

    rec = ftrace_find_profiled_func(stat, trace->func);
    if (rec) {
        rec->time += calltime;
        rec->time_squared += calltime * calltime;
    }

 out:
    local_irq_restore(flags);
}

static int register_ftrace_profiler(void)
{
    return register_ftrace_graph(&profile_graph_return,
                     &profile_graph_entry);
}

static void unregister_ftrace_profiler(void)
{
    unregister_ftrace_graph();
}
#else
static struct ftrace_ops ftrace_profile_ops __read_mostly = {
    .func       = function_profile_call,
    .flags      = FTRACE_OPS_FL_RECURSION_SAFE,
};

static int register_ftrace_profiler(void)
{
    return register_ftrace_function(&ftrace_profile_ops);
}

static void unregister_ftrace_profiler(void)
{
    unregister_ftrace_function(&ftrace_profile_ops);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

static ssize_t
ftrace_profile_write(struct file *filp, const char __user *ubuf,
             size_t cnt, loff_t *ppos)
{
    unsigned long val;
    int ret;

    ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
    if (ret)
        return ret;

    val = !!val;

    mutex_lock(&ftrace_profile_lock);
    if (ftrace_profile_enabled ^ val) {
        if (val) {
            ret = ftrace_profile_init();
            if (ret < 0) {
                cnt = ret;
                goto out;
            }

            ret = register_ftrace_profiler();
            if (ret < 0) {
                cnt = ret;
                goto out;
            }
            ftrace_profile_enabled = 1;
        } else {
            ftrace_profile_enabled = 0;
            /*
             * unregister_ftrace_profiler calls stop_machine
             * so this acts like an synchronize_sched.
             */
            unregister_ftrace_profiler();
        }
    }
 out:
    mutex_unlock(&ftrace_profile_lock);

    *ppos += cnt;

    return cnt;
}

static ssize_t
ftrace_profile_read(struct file *filp, char __user *ubuf,
             size_t cnt, loff_t *ppos)
{
    char buf[64];       /* big enough to hold a number */
    int r;

    r = sprintf(buf, "%u\n", ftrace_profile_enabled);
    return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static const struct file_operations ftrace_profile_fops = {
    .open       = tracing_open_generic,
    .read       = ftrace_profile_read,
    .write      = ftrace_profile_write,
    .llseek     = default_llseek,
};

/* used to initialize the real stat files */
static struct tracer_stat function_stats __initdata = {
    .name       = "functions",
    .stat_start = function_stat_start,
    .stat_next  = function_stat_next,
    .stat_cmp   = function_stat_cmp,
    .stat_headers   = function_stat_headers,
    .stat_show  = function_stat_show
};

static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
{
    struct ftrace_profile_stat *stat;
    struct dentry *entry;
    char *name;
    int ret;
    int cpu;

    for_each_possible_cpu(cpu) {
        stat = &per_cpu(ftrace_profile_stats, cpu);

        /* allocate enough for function name + cpu number */
        name = kmalloc(32, GFP_KERNEL);
        if (!name) {
            /*
             * The files created are permanent, if something happens
             * we still do not free memory.
             */
            WARN(1,
                 "Could not allocate stat file for cpu %d\n",
                 cpu);
            return;
        }
        stat->stat = function_stats;
        snprintf(name, 32, "function%d", cpu);
        stat->stat.name = name;
        ret = register_stat_tracer(&stat->stat);
        if (ret) {
            WARN(1,
                 "Could not register function stat for cpu %d\n",
                 cpu);
            kfree(name);
            return;
        }
    }

    entry = debugfs_create_file("function_profile_enabled", 0644,
                    d_tracer, NULL, &ftrace_profile_fops);
    if (!entry)
        pr_warning("Could not create debugfs "
               "'function_profile_enabled' entry\n");
}

#else /* CONFIG_FUNCTION_PROFILER */
static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
{
}
#endif /* CONFIG_FUNCTION_PROFILER */

static struct pid * const ftrace_swapper_pid = &init_struct_pid;

#ifdef CONFIG_DYNAMIC_FTRACE

#ifndef CONFIG_FTRACE_MCOUNT_RECORD
# error Dynamic ftrace depends on MCOUNT_RECORD
#endif

static struct hlist_head ftrace_func_hash[FTRACE_FUNC_HASHSIZE] __read_mostly;

struct ftrace_func_probe {
    struct hlist_node   node;
    struct ftrace_probe_ops *ops;
    unsigned long       flags;
    unsigned long       ip;
    void            *data;
    struct rcu_head     rcu;
};

struct ftrace_func_entry {
    struct hlist_node hlist;
    unsigned long ip;
};

struct ftrace_hash {
    unsigned long       size_bits;
    struct hlist_head   *buckets;
    unsigned long       count;
    struct rcu_head     rcu;
};

/*
 * We make these constant because no one should touch them,
 * but they are used as the default "empty hash", to avoid allocating
 * it all the time. These are in a read only section such that if
 * anyone does try to modify it, it will cause an exception.
 */
static const struct hlist_head empty_buckets[1];
static const struct ftrace_hash empty_hash = {
    .buckets = (struct hlist_head *)empty_buckets,
};
#define EMPTY_HASH  ((struct ftrace_hash *)&empty_hash)

static struct ftrace_ops global_ops = {
    .func           = ftrace_stub,
    .notrace_hash       = EMPTY_HASH,
    .filter_hash        = EMPTY_HASH,
    .flags          = FTRACE_OPS_FL_RECURSION_SAFE,
};

static DEFINE_MUTEX(ftrace_regex_lock);

struct ftrace_page {
    struct ftrace_page  *next;
    struct dyn_ftrace   *records;
    int         index;
    int         size;
};

static struct ftrace_page *ftrace_new_pgs;

#define ENTRY_SIZE sizeof(struct dyn_ftrace)
#define ENTRIES_PER_PAGE (PAGE_SIZE / ENTRY_SIZE)

/* estimate from running different kernels */
#define NR_TO_INIT      10000

static struct ftrace_page   *ftrace_pages_start;
static struct ftrace_page   *ftrace_pages;

static bool ftrace_hash_empty(struct ftrace_hash *hash)
{
    return !hash || !hash->count;
}

static struct ftrace_func_entry *
ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip)
{
    unsigned long key;
    struct ftrace_func_entry *entry;
    struct hlist_head *hhd;
    struct hlist_node *n;

    if (ftrace_hash_empty(hash))
        return NULL;

    if (hash->size_bits > 0)
        key = hash_long(ip, hash->size_bits);
    else
        key = 0;

    hhd = &hash->buckets[key];

    hlist_for_each_entry_rcu(entry, n, hhd, hlist) {
        if (entry->ip == ip)
            return entry;
    }
    return NULL;
}

static void __add_hash_entry(struct ftrace_hash *hash,
                 struct ftrace_func_entry *entry)
{
    struct hlist_head *hhd;
    unsigned long key;

    if (hash->size_bits)
        key = hash_long(entry->ip, hash->size_bits);
    else
        key = 0;

    hhd = &hash->buckets[key];
    hlist_add_head(&entry->hlist, hhd);
    hash->count++;
}

static int add_hash_entry(struct ftrace_hash *hash, unsigned long ip)
{
    struct ftrace_func_entry *entry;

    entry = kmalloc(sizeof(*entry), GFP_KERNEL);
    if (!entry)
        return -ENOMEM;

    entry->ip = ip;
    __add_hash_entry(hash, entry);

    return 0;
}

static void
free_hash_entry(struct ftrace_hash *hash,
          struct ftrace_func_entry *entry)
{
    hlist_del(&entry->hlist);
    kfree(entry);
    hash->count--;
}

static void
remove_hash_entry(struct ftrace_hash *hash,
          struct ftrace_func_entry *entry)
{
    hlist_del(&entry->hlist);
    hash->count--;
}

static void ftrace_hash_clear(struct ftrace_hash *hash)
{
    struct hlist_head *hhd;
    struct hlist_node *tp, *tn;
    struct ftrace_func_entry *entry;
    int size = 1 << hash->size_bits;
    int i;

    if (!hash->count)
        return;

    for (i = 0; i < size; i++) {
        hhd = &hash->buckets[i];
        hlist_for_each_entry_safe(entry, tp, tn, hhd, hlist)
            free_hash_entry(hash, entry);
    }
    FTRACE_WARN_ON(hash->count);
}

static void free_ftrace_hash(struct ftrace_hash *hash)
{
    if (!hash || hash == EMPTY_HASH)
        return;
    ftrace_hash_clear(hash);
    kfree(hash->buckets);
    kfree(hash);
}

static void __free_ftrace_hash_rcu(struct rcu_head *rcu)
{
    struct ftrace_hash *hash;

    hash = container_of(rcu, struct ftrace_hash, rcu);
    free_ftrace_hash(hash);
}

static void free_ftrace_hash_rcu(struct ftrace_hash *hash)
{
    if (!hash || hash == EMPTY_HASH)
        return;
    call_rcu_sched(&hash->rcu, __free_ftrace_hash_rcu);
}

void ftrace_free_filter(struct ftrace_ops *ops)
{
    free_ftrace_hash(ops->filter_hash);
    free_ftrace_hash(ops->notrace_hash);
}

static struct ftrace_hash *alloc_ftrace_hash(int size_bits)
{
    struct ftrace_hash *hash;
    int size;

    hash = kzalloc(sizeof(*hash), GFP_KERNEL);
    if (!hash)
        return NULL;

    size = 1 << size_bits;
    hash->buckets = kcalloc(size, sizeof(*hash->buckets), GFP_KERNEL);

    if (!hash->buckets) {
        kfree(hash);
        return NULL;
    }

    hash->size_bits = size_bits;

    return hash;
}

static struct ftrace_hash *
alloc_and_copy_ftrace_hash(int size_bits, struct ftrace_hash *hash)
{
    struct ftrace_func_entry *entry;
    struct ftrace_hash *new_hash;
    struct hlist_node *tp;
    int size;
    int ret;
    int i;

    new_hash = alloc_ftrace_hash(size_bits);
    if (!new_hash)
        return NULL;

    /* Empty hash? */
    if (ftrace_hash_empty(hash))
        return new_hash;

    size = 1 << hash->size_bits;
    for (i = 0; i < size; i++) {
        hlist_for_each_entry(entry, tp, &hash->buckets[i], hlist) {
            ret = add_hash_entry(new_hash, entry->ip);
            if (ret < 0)
                goto free_hash;
        }
    }

    FTRACE_WARN_ON(new_hash->count != hash->count);

    return new_hash;

 free_hash:
    free_ftrace_hash(new_hash);
    return NULL;
}

static void
ftrace_hash_rec_disable(struct ftrace_ops *ops, int filter_hash);
static void
ftrace_hash_rec_enable(struct ftrace_ops *ops, int filter_hash);

static int
ftrace_hash_move(struct ftrace_ops *ops, int enable,
         struct ftrace_hash **dst, struct ftrace_hash *src)
{
    struct ftrace_func_entry *entry;
    struct hlist_node *tp, *tn;
    struct hlist_head *hhd;
    struct ftrace_hash *old_hash;
    struct ftrace_hash *new_hash;
    unsigned long key;
    int size = src->count;
    int bits = 0;
    int ret;
    int i;

    /*
     * Remove the current set, update the hash and add
     * them back.
     */
    ftrace_hash_rec_disable(ops, enable);

    /*
     * If the new source is empty, just free dst and assign it
     * the empty_hash.
     */
    if (!src->count) {
        free_ftrace_hash_rcu(*dst);
        rcu_assign_pointer(*dst, EMPTY_HASH);
        /* still need to update the function records */
        ret = 0;
        goto out;
    }

    /*
     * Make the hash size about 1/2 the # found
     */
    for (size /= 2; size; size >>= 1)
        bits++;

    /* Don't allocate too much */
    if (bits > FTRACE_HASH_MAX_BITS)
        bits = FTRACE_HASH_MAX_BITS;

    ret = -ENOMEM;
    new_hash = alloc_ftrace_hash(bits);
    if (!new_hash)
        goto out;

    size = 1 << src->size_bits;
    for (i = 0; i < size; i++) {
        hhd = &src->buckets[i];
        hlist_for_each_entry_safe(entry, tp, tn, hhd, hlist) {
            if (bits > 0)
                key = hash_long(entry->ip, bits);
            else
                key = 0;
            remove_hash_entry(src, entry);
            __add_hash_entry(new_hash, entry);
        }
    }

    old_hash = *dst;
    rcu_assign_pointer(*dst, new_hash);
    free_ftrace_hash_rcu(old_hash);

    ret = 0;
 out:
    /*
     * Enable regardless of ret:
     *  On success, we enable the new hash.
     *  On failure, we re-enable the original hash.
     */
    ftrace_hash_rec_enable(ops, enable);

    return ret;
}

/*
 * Test the hashes for this ops to see if we want to call
 * the ops->func or not.
 *
 * It's a match if the ip is in the ops->filter_hash or
 * the filter_hash does not exist or is empty,
 *  AND
 * the ip is not in the ops->notrace_hash.
 *
 * This needs to be called with preemption disabled as
 * the hashes are freed with call_rcu_sched().
 */
static int
ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip)
{
    struct ftrace_hash *filter_hash;
    struct ftrace_hash *notrace_hash;
    int ret;

    filter_hash = rcu_dereference_raw(ops->filter_hash);
    notrace_hash = rcu_dereference_raw(ops->notrace_hash);

    if ((ftrace_hash_empty(filter_hash) ||
         ftrace_lookup_ip(filter_hash, ip)) &&
        (ftrace_hash_empty(notrace_hash) ||
         !ftrace_lookup_ip(notrace_hash, ip)))
        ret = 1;
    else
        ret = 0;

    return ret;
}

/*
 * This is a double for. Do not use 'break' to break out of the loop,
 * you must use a goto.
 */
#define do_for_each_ftrace_rec(pg, rec)                 \
    for (pg = ftrace_pages_start; pg; pg = pg->next) {      \
        int _____i;                     \
        for (_____i = 0; _____i < pg->index; _____i++) {    \
            rec = &pg->records[_____i];

#define while_for_each_ftrace_rec()     \
        }               \
    }


static int ftrace_cmp_recs(const void *a, const void *b)
{
    const struct dyn_ftrace *key = a;
    const struct dyn_ftrace *rec = b;

    if (key->flags < rec->ip)
        return -1;
    if (key->ip >= rec->ip + MCOUNT_INSN_SIZE)
        return 1;
    return 0;
}

static unsigned long ftrace_location_range(unsigned long start, unsigned long end)
{
    struct ftrace_page *pg;
    struct dyn_ftrace *rec;
    struct dyn_ftrace key;

    key.ip = start;
    key.flags = end;    /* overload flags, as it is unsigned long */

    for (pg = ftrace_pages_start; pg; pg = pg->next) {
        if (end < pg->records[0].ip ||
            start >= (pg->records[pg->index - 1].ip + MCOUNT_INSN_SIZE))
            continue;
        rec = bsearch(&key, pg->records, pg->index,
                  sizeof(struct dyn_ftrace),
                  ftrace_cmp_recs);
        if (rec)
            return rec->ip;
    }

    return 0;
}

unsigned long ftrace_location(unsigned long ip)
{
    return ftrace_location_range(ip, ip);
}

int ftrace_text_reserved(void *start, void *end)
{
    unsigned long ret;

    ret = ftrace_location_range((unsigned long)start,
                    (unsigned long)end);

    return (int)!!ret;
}

static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
                     int filter_hash,
                     bool inc)
{
    struct ftrace_hash *hash;
    struct ftrace_hash *other_hash;
    struct ftrace_page *pg;
    struct dyn_ftrace *rec;
    int count = 0;
    int all = 0;

    /* Only update if the ops has been registered */
    if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
        return;

    /*
     * In the filter_hash case:
     *   If the count is zero, we update all records.
     *   Otherwise we just update the items in the hash.
     *
     * In the notrace_hash case:
     *   We enable the update in the hash.
     *   As disabling notrace means enabling the tracing,
     *   and enabling notrace means disabling, the inc variable
     *   gets inversed.
     */
    if (filter_hash) {
        hash = ops->filter_hash;
        other_hash = ops->notrace_hash;
        if (ftrace_hash_empty(hash))
            all = 1;
    } else {
        inc = !inc;
        hash = ops->notrace_hash;
        other_hash = ops->filter_hash;
        /*
         * If the notrace hash has no items,
         * then there's nothing to do.
         */
        if (ftrace_hash_empty(hash))
            return;
    }

    do_for_each_ftrace_rec(pg, rec) {
        int in_other_hash = 0;
        int in_hash = 0;
        int match = 0;

        if (all) {
            /*
             * Only the filter_hash affects all records.
             * Update if the record is not in the notrace hash.
             */
            if (!other_hash || !ftrace_lookup_ip(other_hash, rec->ip))
                match = 1;
        } else {
            in_hash = !!ftrace_lookup_ip(hash, rec->ip);
            in_other_hash = !!ftrace_lookup_ip(other_hash, rec->ip);

            /*
             *
             */
            if (filter_hash && in_hash && !in_other_hash)
                match = 1;
            else if (!filter_hash && in_hash &&
                 (in_other_hash || ftrace_hash_empty(other_hash)))
                match = 1;
        }
        if (!match)
            continue;

        if (inc) {
            rec->flags++;
            if (FTRACE_WARN_ON((rec->flags & ~FTRACE_FL_MASK) == FTRACE_REF_MAX))
                return;
            /*
             * If any ops wants regs saved for this function
             * then all ops will get saved regs.
             */
            if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
                rec->flags |= FTRACE_FL_REGS;
        } else {
            if (FTRACE_WARN_ON((rec->flags & ~FTRACE_FL_MASK) == 0))
                return;
            rec->flags--;
        }
        count++;
        /* Shortcut, if we handled all records, we are done. */
        if (!all && count == hash->count)
            return;
    } while_for_each_ftrace_rec();
}

static void ftrace_hash_rec_disable(struct ftrace_ops *ops,
                    int filter_hash)
{
    __ftrace_hash_rec_update(ops, filter_hash, 0);
}

static void ftrace_hash_rec_enable(struct ftrace_ops *ops,
                   int filter_hash)
{
    __ftrace_hash_rec_update(ops, filter_hash, 1);
}

static void print_ip_ins(const char *fmt, unsigned char *p)
{
    int i;

    printk(KERN_CONT "%s", fmt);

    for (i = 0; i < MCOUNT_INSN_SIZE; i++)
        printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);
}

void ftrace_bug(int failed, unsigned long ip)
{
    switch (failed) {
    case -EFAULT:
        FTRACE_WARN_ON_ONCE(1);
        pr_info("ftrace faulted on modifying ");
        print_ip_sym(ip);
        break;
    case -EINVAL:
        FTRACE_WARN_ON_ONCE(1);
        pr_info("ftrace failed to modify ");
        print_ip_sym(ip);
        print_ip_ins(" actual: ", (unsigned char *)ip);
        printk(KERN_CONT "\n");
        break;
    case -EPERM:
        FTRACE_WARN_ON_ONCE(1);
        pr_info("ftrace faulted on writing ");
        print_ip_sym(ip);
        break;
    default:
        FTRACE_WARN_ON_ONCE(1);
        pr_info("ftrace faulted on unknown error ");
        print_ip_sym(ip);
    }
}

static int ftrace_check_record(struct dyn_ftrace *rec, int enable, int update)
{
    unsigned long flag = 0UL;

    /*
     * If we are updating calls:
     *
     *   If the record has a ref count, then we need to enable it
     *   because someone is using it.
     *
     *   Otherwise we make sure its disabled.
     *
     * If we are disabling calls, then disable all records that
     * are enabled.
     */
    if (enable && (rec->flags & ~FTRACE_FL_MASK))
        flag = FTRACE_FL_ENABLED;

    /*
     * If enabling and the REGS flag does not match the REGS_EN, then
     * do not ignore this record. Set flags to fail the compare against
     * ENABLED.
     */
    if (flag &&
        (!(rec->flags & FTRACE_FL_REGS) != !(rec->flags & FTRACE_FL_REGS_EN)))
        flag |= FTRACE_FL_REGS;

    /* If the state of this record hasn't changed, then do nothing */
    if ((rec->flags & FTRACE_FL_ENABLED) == flag)
        return FTRACE_UPDATE_IGNORE;

    if (flag) {
        /* Save off if rec is being enabled (for return value) */
        flag ^= rec->flags & FTRACE_FL_ENABLED;

        if (update) {
            rec->flags |= FTRACE_FL_ENABLED;
            if (flag & FTRACE_FL_REGS) {
                if (rec->flags & FTRACE_FL_REGS)
                    rec->flags |= FTRACE_FL_REGS_EN;
                else
                    rec->flags &= ~FTRACE_FL_REGS_EN;
            }
        }

        /*
         * If this record is being updated from a nop, then
         *   return UPDATE_MAKE_CALL.
         * Otherwise, if the EN flag is set, then return
         *   UPDATE_MODIFY_CALL_REGS to tell the caller to convert
         *   from the non-save regs, to a save regs function.
         * Otherwise,
         *   return UPDATE_MODIFY_CALL to tell the caller to convert
         *   from the save regs, to a non-save regs function.
         */
        if (flag & FTRACE_FL_ENABLED)
            return FTRACE_UPDATE_MAKE_CALL;
        else if (rec->flags & FTRACE_FL_REGS_EN)
            return FTRACE_UPDATE_MODIFY_CALL_REGS;
        else
            return FTRACE_UPDATE_MODIFY_CALL;
    }

    if (update) {
        /* If there's no more users, clear all flags */
        if (!(rec->flags & ~FTRACE_FL_MASK))
            rec->flags = 0;
        else
            /* Just disable the record (keep REGS state) */
            rec->flags &= ~FTRACE_FL_ENABLED;
    }

    return FTRACE_UPDATE_MAKE_NOP;
}

int ftrace_update_record(struct dyn_ftrace *rec, int enable)
{
    return ftrace_check_record(rec, enable, 1);
}

int ftrace_test_record(struct dyn_ftrace *rec, int enable)
{
    return ftrace_check_record(rec, enable, 0);
}

static int
__ftrace_replace_code(struct dyn_ftrace *rec, int enable)
{
    unsigned long ftrace_old_addr;
    unsigned long ftrace_addr;
    int ret;

    ret = ftrace_update_record(rec, enable);

    if (rec->flags & FTRACE_FL_REGS)
        ftrace_addr = (unsigned long)FTRACE_REGS_ADDR;
    else
        ftrace_addr = (unsigned long)FTRACE_ADDR;

    switch (ret) {
    case FTRACE_UPDATE_IGNORE:
        return 0;

    case FTRACE_UPDATE_MAKE_CALL:
        return ftrace_make_call(rec, ftrace_addr);

    case FTRACE_UPDATE_MAKE_NOP:
        return ftrace_make_nop(NULL, rec, ftrace_addr);

    case FTRACE_UPDATE_MODIFY_CALL_REGS:
    case FTRACE_UPDATE_MODIFY_CALL:
        if (rec->flags & FTRACE_FL_REGS)
            ftrace_old_addr = (unsigned long)FTRACE_ADDR;
        else
            ftrace_old_addr = (unsigned long)FTRACE_REGS_ADDR;

        return ftrace_modify_call(rec, ftrace_old_addr, ftrace_addr);
    }

    return -1; /* unknow ftrace bug */
}

void __weak ftrace_replace_code(int enable)
{
    struct dyn_ftrace *rec;
    struct ftrace_page *pg;
    int failed;

    if (unlikely(ftrace_disabled))
        return;

    do_for_each_ftrace_rec(pg, rec) {
        failed = __ftrace_replace_code(rec, enable);
        if (failed) {
            ftrace_bug(failed, rec->ip);
            /* Stop processing */
            return;
        }
    } while_for_each_ftrace_rec();
}

struct ftrace_rec_iter {
    struct ftrace_page  *pg;
    int         index;
};

struct ftrace_rec_iter *ftrace_rec_iter_start(void)
{
    /*
     * We only use a single iterator.
     * Protected by the ftrace_lock mutex.
     */
    static struct ftrace_rec_iter ftrace_rec_iter;
    struct ftrace_rec_iter *iter = &ftrace_rec_iter;

    iter->pg = ftrace_pages_start;
    iter->index = 0;

    /* Could have empty pages */
    while (iter->pg && !iter->pg->index)
        iter->pg = iter->pg->next;

    if (!iter->pg)
        return NULL;

    return iter;
}

struct ftrace_rec_iter *ftrace_rec_iter_next(struct ftrace_rec_iter *iter)
{
    iter->index++;

    if (iter->index >= iter->pg->index) {
        iter->pg = iter->pg->next;
        iter->index = 0;

        /* Could have empty pages */
        while (iter->pg && !iter->pg->index)
            iter->pg = iter->pg->next;
    }

    if (!iter->pg)
        return NULL;

    return iter;
}

struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter)
{
    return &iter->pg->records[iter->index];
}

static int
ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
{
    unsigned long ip;
    int ret;

    ip = rec->ip;

    if (unlikely(ftrace_disabled))
        return 0;

    ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
    if (ret) {
        ftrace_bug(ret, ip);
        return 0;
    }
    return 1;
}

/*
 * archs can override this function if they must do something
 * before the modifying code is performed.
 */
int __weak ftrace_arch_code_modify_prepare(void)
{
    return 0;
}

/*
 * archs can override this function if they must do something
 * after the modifying code is performed.
 */
int __weak ftrace_arch_code_modify_post_process(void)
{
    return 0;
}

void ftrace_modify_all_code(int command)
{
    if (command & FTRACE_UPDATE_CALLS)
        ftrace_replace_code(1);
    else if (command & FTRACE_DISABLE_CALLS)
        ftrace_replace_code(0);

    if (command & FTRACE_UPDATE_TRACE_FUNC)
        ftrace_update_ftrace_func(ftrace_trace_function);

    if (command & FTRACE_START_FUNC_RET)
        ftrace_enable_ftrace_graph_caller();
    else if (command & FTRACE_STOP_FUNC_RET)
        ftrace_disable_ftrace_graph_caller();
}

static int __ftrace_modify_code(void *data)
{
    int *command = data;

    ftrace_modify_all_code(*command);

    return 0;
}

void ftrace_run_stop_machine(int command)
{
    stop_machine(__ftrace_modify_code, &command, NULL);
}

void __weak arch_ftrace_update_code(int command)
{
    ftrace_run_stop_machine(command);
}

static void ftrace_run_update_code(int command)
{
    int ret;

    ret = ftrace_arch_code_modify_prepare();
    FTRACE_WARN_ON(ret);
    if (ret)
        return;
    /*
     * Do not call function tracer while we update the code.
     * We are in stop machine.
     */
    function_trace_stop++;

    /*
     * By default we use stop_machine() to modify the code.
     * But archs can do what ever they want as long as it
     * is safe. The stop_machine() is the safest, but also
     * produces the most overhead.
     */
    arch_ftrace_update_code(command);

    function_trace_stop--;

    ret = ftrace_arch_code_modify_post_process();
    FTRACE_WARN_ON(ret);
}

static ftrace_func_t saved_ftrace_func;
static int ftrace_start_up;
static int global_start_up;

static void ftrace_startup_enable(int command)
{
    if (saved_ftrace_func != ftrace_trace_function) {
        saved_ftrace_func = ftrace_trace_function;
        command |= FTRACE_UPDATE_TRACE_FUNC;
    }

    if (!command || !ftrace_enabled)
        return;

    ftrace_run_update_code(command);
}

static int ftrace_startup(struct ftrace_ops *ops, int command)
{
    bool hash_enable = true;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    ftrace_start_up++;
    command |= FTRACE_UPDATE_CALLS;

    /* ops marked global share the filter hashes */
    if (ops->flags & FTRACE_OPS_FL_GLOBAL) {
        ops = &global_ops;
        /* Don't update hash if global is already set */
        if (global_start_up)
            hash_enable = false;
        global_start_up++;
    }

    ops->flags |= FTRACE_OPS_FL_ENABLED;
    if (hash_enable)
        ftrace_hash_rec_enable(ops, 1);

    ftrace_startup_enable(command);

    return 0;
}

static void ftrace_shutdown(struct ftrace_ops *ops, int command)
{
    bool hash_disable = true;

    if (unlikely(ftrace_disabled))
        return;

    ftrace_start_up--;
    /*
     * Just warn in case of unbalance, no need to kill ftrace, it's not
     * critical but the ftrace_call callers may be never nopped again after
     * further ftrace uses.
     */
    WARN_ON_ONCE(ftrace_start_up < 0);

    if (ops->flags & FTRACE_OPS_FL_GLOBAL) {
        ops = &global_ops;
        global_start_up--;
        WARN_ON_ONCE(global_start_up < 0);
        /* Don't update hash if global still has users */
        if (global_start_up) {
            WARN_ON_ONCE(!ftrace_start_up);
            hash_disable = false;
        }
    }

    if (hash_disable)
        ftrace_hash_rec_disable(ops, 1);

    if (ops != &global_ops || !global_start_up)
        ops->flags &= ~FTRACE_OPS_FL_ENABLED;

    command |= FTRACE_UPDATE_CALLS;

    if (saved_ftrace_func != ftrace_trace_function) {
        saved_ftrace_func = ftrace_trace_function;
        command |= FTRACE_UPDATE_TRACE_FUNC;
    }

    if (!command || !ftrace_enabled)
        return;

    ftrace_run_update_code(command);
}

static void ftrace_startup_sysctl(void)
{
    if (unlikely(ftrace_disabled))
        return;

    /* Force update next time */
    saved_ftrace_func = NULL;
    /* ftrace_start_up is true if we want ftrace running */
    if (ftrace_start_up)
        ftrace_run_update_code(FTRACE_UPDATE_CALLS);
}

static void ftrace_shutdown_sysctl(void)
{
    if (unlikely(ftrace_disabled))
        return;

    /* ftrace_start_up is true if ftrace is running */
    if (ftrace_start_up)
        ftrace_run_update_code(FTRACE_DISABLE_CALLS);
}

static cycle_t      ftrace_update_time;
static unsigned long    ftrace_update_cnt;
unsigned long       ftrace_update_tot_cnt;

static int ops_traces_mod(struct ftrace_ops *ops)
{
    struct ftrace_hash *hash;

    hash = ops->filter_hash;
    return ftrace_hash_empty(hash);
}

static int ftrace_update_code(struct module *mod)
{
    struct ftrace_page *pg;
    struct dyn_ftrace *p;
    cycle_t start, stop;
    unsigned long ref = 0;
    int i;

    /*
     * When adding a module, we need to check if tracers are
     * currently enabled and if they are set to trace all functions.
     * If they are, we need to enable the module functions as well
     * as update the reference counts for those function records.
     */
    if (mod) {
        struct ftrace_ops *ops;

        for (ops = ftrace_ops_list;
             ops != &ftrace_list_end; ops = ops->next) {
            if (ops->flags & FTRACE_OPS_FL_ENABLED &&
                ops_traces_mod(ops))
                ref++;
        }
    }

    start = ftrace_now(raw_smp_processor_id());
    ftrace_update_cnt = 0;

    for (pg = ftrace_new_pgs; pg; pg = pg->next) {

        for (i = 0; i < pg->index; i++) {
            /* If something went wrong, bail without enabling anything */
            if (unlikely(ftrace_disabled))
                return -1;

            p = &pg->records[i];
            p->flags = ref;

            /*
             * Do the initial record conversion from mcount jump
             * to the NOP instructions.
             */
            if (!ftrace_code_disable(mod, p))
                break;

            ftrace_update_cnt++;

            /*
             * If the tracing is enabled, go ahead and enable the record.
             *
             * The reason not to enable the record immediatelly is the
             * inherent check of ftrace_make_nop/ftrace_make_call for
             * correct previous instructions.  Making first the NOP
             * conversion puts the module to the correct state, thus
             * passing the ftrace_make_call check.
             */
            if (ftrace_start_up && ref) {
                int failed = __ftrace_replace_code(p, 1);
                if (failed)
                    ftrace_bug(failed, p->ip);
            }
        }
    }

    ftrace_new_pgs = NULL;

    stop = ftrace_now(raw_smp_processor_id());
    ftrace_update_time = stop - start;
    ftrace_update_tot_cnt += ftrace_update_cnt;

    return 0;
}

static int ftrace_allocate_records(struct ftrace_page *pg, int count)
{
    int order;
    int cnt;

    if (WARN_ON(!count))
        return -EINVAL;

    order = get_count_order(DIV_ROUND_UP(count, ENTRIES_PER_PAGE));

    /*
     * We want to fill as much as possible. No more than a page
     * may be empty.
     */
    while ((PAGE_SIZE << order) / ENTRY_SIZE >= count + ENTRIES_PER_PAGE)
        order--;

 again:
    pg->records = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, order);

    if (!pg->records) {
        /* if we can't allocate this size, try something smaller */
        if (!order)
            return -ENOMEM;
        order >>= 1;
        goto again;
    }

    cnt = (PAGE_SIZE << order) / ENTRY_SIZE;
    pg->size = cnt;

    if (cnt > count)
        cnt = count;

    return cnt;
}

static struct ftrace_page *
ftrace_allocate_pages(unsigned long num_to_init)
{
    struct ftrace_page *start_pg;
    struct ftrace_page *pg;
    int order;
    int cnt;

    if (!num_to_init)
        return 0;

    start_pg = pg = kzalloc(sizeof(*pg), GFP_KERNEL);
    if (!pg)
        return NULL;

    /*
     * Try to allocate as much as possible in one continues
     * location that fills in all of the space. We want to
     * waste as little space as possible.
     */
    for (;;) {
        cnt = ftrace_allocate_records(pg, num_to_init);
        if (cnt < 0)
            goto free_pages;

        num_to_init -= cnt;
        if (!num_to_init)
            break;

        pg->next = kzalloc(sizeof(*pg), GFP_KERNEL);
        if (!pg->next)
            goto free_pages;

        pg = pg->next;
    }

    return start_pg;

 free_pages:
    while (start_pg) {
        order = get_count_order(pg->size / ENTRIES_PER_PAGE);
        free_pages((unsigned long)pg->records, order);
        start_pg = pg->next;
        kfree(pg);
        pg = start_pg;
    }
    pr_info("ftrace: FAILED to allocate memory for functions\n");
    return NULL;
}

static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
{
    int cnt;

    if (!num_to_init) {
        pr_info("ftrace: No functions to be traced?\n");
        return -1;
    }

    cnt = num_to_init / ENTRIES_PER_PAGE;
    pr_info("ftrace: allocating %ld entries in %d pages\n",
        num_to_init, cnt + 1);

    return 0;
}

#define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */

struct ftrace_iterator {
    loff_t              pos;
    loff_t              func_pos;
    struct ftrace_page      *pg;
    struct dyn_ftrace       *func;
    struct ftrace_func_probe    *probe;
    struct trace_parser     parser;
    struct ftrace_hash      *hash;
    struct ftrace_ops       *ops;
    int             hidx;
    int             idx;
    unsigned            flags;
};

static void *
t_hash_next(struct seq_file *m, loff_t *pos)
{
    struct ftrace_iterator *iter = m->private;
    struct hlist_node *hnd = NULL;
    struct hlist_head *hhd;

    (*pos)++;
    iter->pos = *pos;

    if (iter->probe)
        hnd = &iter->probe->node;
 retry:
    if (iter->hidx >= FTRACE_FUNC_HASHSIZE)
        return NULL;

    hhd = &ftrace_func_hash[iter->hidx];

    if (hlist_empty(hhd)) {
        iter->hidx++;
        hnd = NULL;
        goto retry;
    }

    if (!hnd)
        hnd = hhd->first;
    else {
        hnd = hnd->next;
        if (!hnd) {
            iter->hidx++;
            goto retry;
        }
    }

    if (WARN_ON_ONCE(!hnd))
        return NULL;

    iter->probe = hlist_entry(hnd, struct ftrace_func_probe, node);

    return iter;
}

static void *t_hash_start(struct seq_file *m, loff_t *pos)
{
    struct ftrace_iterator *iter = m->private;
    void *p = NULL;
    loff_t l;

    if (!(iter->flags & FTRACE_ITER_DO_HASH))
        return NULL;

    if (iter->func_pos > *pos)
        return NULL;

    iter->hidx = 0;
    for (l = 0; l <= (*pos - iter->func_pos); ) {
        p = t_hash_next(m, &l);
        if (!p)
            break;
    }
    if (!p)
        return NULL;

    /* Only set this if we have an item */
    iter->flags |= FTRACE_ITER_HASH;

    return iter;
}

static int
t_hash_show(struct seq_file *m, struct ftrace_iterator *iter)
{
    struct ftrace_func_probe *rec;

    rec = iter->probe;
    if (WARN_ON_ONCE(!rec))
        return -EIO;

    if (rec->ops->print)
        return rec->ops->print(m, rec->ip, rec->ops, rec->data);

    seq_printf(m, "%ps:%ps", (void *)rec->ip, (void *)rec->ops->func);

    if (rec->data)
        seq_printf(m, ":%p", rec->data);
    seq_putc(m, '\n');

    return 0;
}

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
    struct ftrace_iterator *iter = m->private;
    struct ftrace_ops *ops = iter->ops;
    struct dyn_ftrace *rec = NULL;

    if (unlikely(ftrace_disabled))
        return NULL;

    if (iter->flags & FTRACE_ITER_HASH)
        return t_hash_next(m, pos);

    (*pos)++;
    iter->pos = iter->func_pos = *pos;

    if (iter->flags & FTRACE_ITER_PRINTALL)
        return t_hash_start(m, pos);

 retry:
    if (iter->idx >= iter->pg->index) {
        if (iter->pg->next) {
            iter->pg = iter->pg->next;
            iter->idx = 0;
            goto retry;
        }
    } else {
        rec = &iter->pg->records[iter->idx++];
        if (((iter->flags & FTRACE_ITER_FILTER) &&
             !(ftrace_lookup_ip(ops->filter_hash, rec->ip))) ||

            ((iter->flags & FTRACE_ITER_NOTRACE) &&
             !ftrace_lookup_ip(ops->notrace_hash, rec->ip)) ||

            ((iter->flags & FTRACE_ITER_ENABLED) &&
             !(rec->flags & ~FTRACE_FL_MASK))) {

            rec = NULL;
            goto retry;
        }
    }

    if (!rec)
        return t_hash_start(m, pos);

    iter->func = rec;

    return iter;
}

static void reset_iter_read(struct ftrace_iterator *iter)
{
    iter->pos = 0;
    iter->func_pos = 0;
    iter->flags &= ~(FTRACE_ITER_PRINTALL | FTRACE_ITER_HASH);
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
    struct ftrace_iterator *iter = m->private;
    struct ftrace_ops *ops = iter->ops;
    void *p = NULL;
    loff_t l;

    mutex_lock(&ftrace_lock);

    if (unlikely(ftrace_disabled))
        return NULL;

    /*
     * If an lseek was done, then reset and start from beginning.
     */
    if (*pos < iter->pos)
        reset_iter_read(iter);

    /*
     * For set_ftrace_filter reading, if we have the filter
     * off, we can short cut and just print out that all
     * functions are enabled.
     */
    if (iter->flags & FTRACE_ITER_FILTER &&
        ftrace_hash_empty(ops->filter_hash)) {
        if (*pos > 0)
            return t_hash_start(m, pos);
        iter->flags |= FTRACE_ITER_PRINTALL;
        /* reset in case of seek/pread */
        iter->flags &= ~FTRACE_ITER_HASH;
        return iter;
    }

    if (iter->flags & FTRACE_ITER_HASH)
        return t_hash_start(m, pos);

    /*
     * Unfortunately, we need to restart at ftrace_pages_start
     * every time we let go of the ftrace_mutex. This is because
     * those pointers can change without the lock.
     */
    iter->pg = ftrace_pages_start;
    iter->idx = 0;
    for (l = 0; l <= *pos; ) {
        p = t_next(m, p, &l);
        if (!p)
            break;
    }

    if (!p)
        return t_hash_start(m, pos);

    return iter;
}

static void t_stop(struct seq_file *m, void *p)
{
    mutex_unlock(&ftrace_lock);
}

static int t_show(struct seq_file *m, void *v)
{
    struct ftrace_iterator *iter = m->private;
    struct dyn_ftrace *rec;

    if (iter->flags & FTRACE_ITER_HASH)
        return t_hash_show(m, iter);

    if (iter->flags & FTRACE_ITER_PRINTALL) {
        seq_printf(m, "#### all functions enabled ####\n");
        return 0;
    }

    rec = iter->func;

    if (!rec)
        return 0;

    seq_printf(m, "%ps", (void *)rec->ip);
    if (iter->flags & FTRACE_ITER_ENABLED)
        seq_printf(m, " (%ld)%s",
               rec->flags & ~FTRACE_FL_MASK,
               rec->flags & FTRACE_FL_REGS ? " R" : "");
    seq_printf(m, "\n");

    return 0;
}

static const struct seq_operations show_ftrace_seq_ops = {
    .start = t_start,
    .next = t_next,
    .stop = t_stop,
    .show = t_show,
};

static int
ftrace_avail_open(struct inode *inode, struct file *file)
{
    struct ftrace_iterator *iter;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
    if (iter) {
        iter->pg = ftrace_pages_start;
        iter->ops = &global_ops;
    }

    return iter ? 0 : -ENOMEM;
}

static int
ftrace_enabled_open(struct inode *inode, struct file *file)
{
    struct ftrace_iterator *iter;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
    if (iter) {
        iter->pg = ftrace_pages_start;
        iter->flags = FTRACE_ITER_ENABLED;
        iter->ops = &global_ops;
    }

    return iter ? 0 : -ENOMEM;
}

static void ftrace_filter_reset(struct ftrace_hash *hash)
{
    mutex_lock(&ftrace_lock);
    ftrace_hash_clear(hash);
    mutex_unlock(&ftrace_lock);
}

int
ftrace_regex_open(struct ftrace_ops *ops, int flag,
          struct inode *inode, struct file *file)
{
    struct ftrace_iterator *iter;
    struct ftrace_hash *hash;
    int ret = 0;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    iter = kzalloc(sizeof(*iter), GFP_KERNEL);
    if (!iter)
        return -ENOMEM;

    if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) {
        kfree(iter);
        return -ENOMEM;
    }

    if (flag & FTRACE_ITER_NOTRACE)
        hash = ops->notrace_hash;
    else
        hash = ops->filter_hash;

    iter->ops = ops;
    iter->flags = flag;

    if (file->f_mode & FMODE_WRITE) {
        mutex_lock(&ftrace_lock);
        iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
        mutex_unlock(&ftrace_lock);

        if (!iter->hash) {
            trace_parser_put(&iter->parser);
            kfree(iter);
            return -ENOMEM;
        }
    }

    mutex_lock(&ftrace_regex_lock);

    if ((file->f_mode & FMODE_WRITE) &&
        (file->f_flags & O_TRUNC))
        ftrace_filter_reset(iter->hash);

    if (file->f_mode & FMODE_READ) {
        iter->pg = ftrace_pages_start;

        ret = seq_open(file, &show_ftrace_seq_ops);
        if (!ret) {
            struct seq_file *m = file->private_data;
            m->private = iter;
        } else {
            /* Failed */
            free_ftrace_hash(iter->hash);
            trace_parser_put(&iter->parser);
            kfree(iter);
        }
    } else
        file->private_data = iter;
    mutex_unlock(&ftrace_regex_lock);

    return ret;
}

static int
ftrace_filter_open(struct inode *inode, struct file *file)
{
    return ftrace_regex_open(&global_ops,
            FTRACE_ITER_FILTER | FTRACE_ITER_DO_HASH,
            inode, file);
}

static int
ftrace_notrace_open(struct inode *inode, struct file *file)
{
    return ftrace_regex_open(&global_ops, FTRACE_ITER_NOTRACE,
                 inode, file);
}

loff_t
ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
{
    loff_t ret;

    if (file->f_mode & FMODE_READ)
        ret = seq_lseek(file, offset, origin);
    else
        file->f_pos = ret = 1;

    return ret;
}

static int ftrace_match(char *str, char *regex, int len, int type)
{
    int matched = 0;
    int slen;

    switch (type) {
    case MATCH_FULL:
        if (strcmp(str, regex) == 0)
            matched = 1;
        break;
    case MATCH_FRONT_ONLY:
        if (strncmp(str, regex, len) == 0)
            matched = 1;
        break;
    case MATCH_MIDDLE_ONLY:
        if (strstr(str, regex))
            matched = 1;
        break;
    case MATCH_END_ONLY:
        slen = strlen(str);
        if (slen >= len && memcmp(str + slen - len, regex, len) == 0)
            matched = 1;
        break;
    }

    return matched;
}

static int
enter_record(struct ftrace_hash *hash, struct dyn_ftrace *rec, int not)
{
    struct ftrace_func_entry *entry;
    int ret = 0;

    entry = ftrace_lookup_ip(hash, rec->ip);
    if (not) {
        /* Do nothing if it doesn't exist */
        if (!entry)
            return 0;

        free_hash_entry(hash, entry);
    } else {
        /* Do nothing if it exists */
        if (entry)
            return 0;

        ret = add_hash_entry(hash, rec->ip);
    }
    return ret;
}

static int
ftrace_match_record(struct dyn_ftrace *rec, char *mod,
            char *regex, int len, int type)
{
    char str[KSYM_SYMBOL_LEN];
    char *modname;

    kallsyms_lookup(rec->ip, NULL, NULL, &modname, str);

    if (mod) {
        /* module lookup requires matching the module */
        if (!modname || strcmp(modname, mod))
            return 0;

        /* blank search means to match all funcs in the mod */
        if (!len)
            return 1;
    }

    return ftrace_match(str, regex, len, type);
}

static int
match_records(struct ftrace_hash *hash, char *buff,
          int len, char *mod, int not)
{
    unsigned search_len = 0;
    struct ftrace_page *pg;
    struct dyn_ftrace *rec;
    int type = MATCH_FULL;
    char *search = buff;
    int found = 0;
    int ret;

    if (len) {
        type = filter_parse_regex(buff, len, &search, &not);
        search_len = strlen(search);
    }

    mutex_lock(&ftrace_lock);

    if (unlikely(ftrace_disabled))
        goto out_unlock;

    do_for_each_ftrace_rec(pg, rec) {
        if (ftrace_match_record(rec, mod, search, search_len, type)) {
            ret = enter_record(hash, rec, not);
            if (ret < 0) {
                found = ret;
                goto out_unlock;
            }
            found = 1;
        }
    } while_for_each_ftrace_rec();
 out_unlock:
    mutex_unlock(&ftrace_lock);

    return found;
}

static int
ftrace_match_records(struct ftrace_hash *hash, char *buff, int len)
{
    return match_records(hash, buff, len, NULL, 0);
}

static int
ftrace_match_module_records(struct ftrace_hash *hash, char *buff, char *mod)
{
    int not = 0;

    /* blank or '*' mean the same */
    if (strcmp(buff, "*") == 0)
        buff[0] = 0;

    /* handle the case of 'dont filter this module' */
    if (strcmp(buff, "!") == 0 || strcmp(buff, "!*") == 0) {
        buff[0] = 0;
        not = 1;
    }

    return match_records(hash, buff, strlen(buff), mod, not);
}

/*
 * We register the module command as a template to show others how
 * to register the a command as well.
 */

static int
ftrace_mod_callback(struct ftrace_hash *hash,
            char *func, char *cmd, char *param, int enable)
{
    char *mod;
    int ret = -EINVAL;

    /*
     * cmd == 'mod' because we only registered this func
     * for the 'mod' ftrace_func_command.
     * But if you register one func with multiple commands,
     * you can tell which command was used by the cmd
     * parameter.
     */

    /* we must have a module name */
    if (!param)
        return ret;

    mod = strsep(&param, ":");
    if (!strlen(mod))
        return ret;

    ret = ftrace_match_module_records(hash, func, mod);
    if (!ret)
        ret = -EINVAL;
    if (ret < 0)
        return ret;

    return 0;
}

static struct ftrace_func_command ftrace_mod_cmd = {
    .name           = "mod",
    .func           = ftrace_mod_callback,
};

static int __init ftrace_mod_cmd_init(void)
{
    return register_ftrace_command(&ftrace_mod_cmd);
}
device_initcall(ftrace_mod_cmd_init);

static void function_trace_probe_call(unsigned long ip, unsigned long parent_ip,
                      struct ftrace_ops *op, struct pt_regs *pt_regs)
{
    struct ftrace_func_probe *entry;
    struct hlist_head *hhd;
    struct hlist_node *n;
    unsigned long key;

    key = hash_long(ip, FTRACE_HASH_BITS);

    hhd = &ftrace_func_hash[key];

    if (hlist_empty(hhd))
        return;

    /*
     * Disable preemption for these calls to prevent a RCU grace
     * period. This syncs the hash iteration and freeing of items
     * on the hash. rcu_read_lock is too dangerous here.
     */
    preempt_disable_notrace();
    hlist_for_each_entry_rcu(entry, n, hhd, node) {
        if (entry->ip == ip)
            entry->ops->func(ip, parent_ip, &entry->data);
    }
    preempt_enable_notrace();
}

static struct ftrace_ops trace_probe_ops __read_mostly =
{
    .func       = function_trace_probe_call,
};

static int ftrace_probe_registered;

static void __enable_ftrace_function_probe(void)
{
    int ret;
    int i;

    if (ftrace_probe_registered)
        return;

    for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
        struct hlist_head *hhd = &ftrace_func_hash[i];
        if (hhd->first)
            break;
    }
    /* Nothing registered? */
    if (i == FTRACE_FUNC_HASHSIZE)
        return;

    ret = __register_ftrace_function(&trace_probe_ops);
    if (!ret)
        ret = ftrace_startup(&trace_probe_ops, 0);

    ftrace_probe_registered = 1;
}

static void __disable_ftrace_function_probe(void)
{
    int ret;
    int i;

    if (!ftrace_probe_registered)
        return;

    for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
        struct hlist_head *hhd = &ftrace_func_hash[i];
        if (hhd->first)
            return;
    }

    /* no more funcs left */
    ret = __unregister_ftrace_function(&trace_probe_ops);
    if (!ret)
        ftrace_shutdown(&trace_probe_ops, 0);

    ftrace_probe_registered = 0;
}


static void ftrace_free_entry_rcu(struct rcu_head *rhp)
{
    struct ftrace_func_probe *entry =
        container_of(rhp, struct ftrace_func_probe, rcu);

    if (entry->ops->free)
        entry->ops->free(&entry->data);
    kfree(entry);
}


int
register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                  void *data)
{
    struct ftrace_func_probe *entry;
    struct ftrace_page *pg;
    struct dyn_ftrace *rec;
    int type, len, not;
    unsigned long key;
    int count = 0;
    char *search;

    type = filter_parse_regex(glob, strlen(glob), &search, &not);
    len = strlen(search);

    /* we do not support '!' for function probes */
    if (WARN_ON(not))
        return -EINVAL;

    mutex_lock(&ftrace_lock);

    if (unlikely(ftrace_disabled))
        goto out_unlock;

    do_for_each_ftrace_rec(pg, rec) {

        if (!ftrace_match_record(rec, NULL, search, len, type))
            continue;

        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry) {
            /* If we did not process any, then return error */
            if (!count)
                count = -ENOMEM;
            goto out_unlock;
        }

        count++;

        entry->data = data;

        /*
         * The caller might want to do something special
         * for each function we find. We call the callback
         * to give the caller an opportunity to do so.
         */
        if (ops->callback) {
            if (ops->callback(rec->ip, &entry->data) < 0) {
                /* caller does not like this func */
                kfree(entry);
                continue;
            }
        }

        entry->ops = ops;
        entry->ip = rec->ip;

        key = hash_long(entry->ip, FTRACE_HASH_BITS);
        hlist_add_head_rcu(&entry->node, &ftrace_func_hash[key]);

    } while_for_each_ftrace_rec();
    __enable_ftrace_function_probe();

 out_unlock:
    mutex_unlock(&ftrace_lock);

    return count;
}

enum {
    PROBE_TEST_FUNC     = 1,
    PROBE_TEST_DATA     = 2
};

static void
__unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                  void *data, int flags)
{
    struct ftrace_func_probe *entry;
    struct hlist_node *n, *tmp;
    char str[KSYM_SYMBOL_LEN];
    int type = MATCH_FULL;
    int i, len = 0;
    char *search;

    if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
        glob = NULL;
    else if (glob) {
        int not;

        type = filter_parse_regex(glob, strlen(glob), &search, &not);
        len = strlen(search);

        /* we do not support '!' for function probes */
        if (WARN_ON(not))
            return;
    }

    mutex_lock(&ftrace_lock);
    for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
        struct hlist_head *hhd = &ftrace_func_hash[i];

        hlist_for_each_entry_safe(entry, n, tmp, hhd, node) {

            /* break up if statements for readability */
            if ((flags & PROBE_TEST_FUNC) && entry->ops != ops)
                continue;

            if ((flags & PROBE_TEST_DATA) && entry->data != data)
                continue;

            /* do this last, since it is the most expensive */
            if (glob) {
                kallsyms_lookup(entry->ip, NULL, NULL,
                        NULL, str);
                if (!ftrace_match(str, glob, len, type))
                    continue;
            }

            hlist_del(&entry->node);
            call_rcu(&entry->rcu, ftrace_free_entry_rcu);
        }
    }
    __disable_ftrace_function_probe();
    mutex_unlock(&ftrace_lock);
}

void
unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                void *data)
{
    __unregister_ftrace_function_probe(glob, ops, data,
                      PROBE_TEST_FUNC | PROBE_TEST_DATA);
}

void
unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
{
    __unregister_ftrace_function_probe(glob, ops, NULL, PROBE_TEST_FUNC);
}

void unregister_ftrace_function_probe_all(char *glob)
{
    __unregister_ftrace_function_probe(glob, NULL, NULL, 0);
}

static LIST_HEAD(ftrace_commands);
static DEFINE_MUTEX(ftrace_cmd_mutex);

int register_ftrace_command(struct ftrace_func_command *cmd)
{
    struct ftrace_func_command *p;
    int ret = 0;

    mutex_lock(&ftrace_cmd_mutex);
    list_for_each_entry(p, &ftrace_commands, list) {
        if (strcmp(cmd->name, p->name) == 0) {
            ret = -EBUSY;
            goto out_unlock;
        }
    }
    list_add(&cmd->list, &ftrace_commands);
 out_unlock:
    mutex_unlock(&ftrace_cmd_mutex);

    return ret;
}

int unregister_ftrace_command(struct ftrace_func_command *cmd)
{
    struct ftrace_func_command *p, *n;
    int ret = -ENODEV;

    mutex_lock(&ftrace_cmd_mutex);
    list_for_each_entry_safe(p, n, &ftrace_commands, list) {
        if (strcmp(cmd->name, p->name) == 0) {
            ret = 0;
            list_del_init(&p->list);
            goto out_unlock;
        }
    }
 out_unlock:
    mutex_unlock(&ftrace_cmd_mutex);

    return ret;
}

static int ftrace_process_regex(struct ftrace_hash *hash,
                char *buff, int len, int enable)
{
    char *func, *command, *next = buff;
    struct ftrace_func_command *p;
    int ret = -EINVAL;

    func = strsep(&next, ":");

    if (!next) {
        ret = ftrace_match_records(hash, func, len);
        if (!ret)
            ret = -EINVAL;
        if (ret < 0)
            return ret;
        return 0;
    }

    /* command found */

    command = strsep(&next, ":");

    mutex_lock(&ftrace_cmd_mutex);
    list_for_each_entry(p, &ftrace_commands, list) {
        if (strcmp(p->name, command) == 0) {
            ret = p->func(hash, func, command, next, enable);
            goto out_unlock;
        }
    }
 out_unlock:
    mutex_unlock(&ftrace_cmd_mutex);

    return ret;
}

static ssize_t
ftrace_regex_write(struct file *file, const char __user *ubuf,
           size_t cnt, loff_t *ppos, int enable)
{
    struct ftrace_iterator *iter;
    struct trace_parser *parser;
    ssize_t ret, read;

    if (!cnt)
        return 0;

    mutex_lock(&ftrace_regex_lock);

    ret = -ENODEV;
    if (unlikely(ftrace_disabled))
        goto out_unlock;

    if (file->f_mode & FMODE_READ) {
        struct seq_file *m = file->private_data;
        iter = m->private;
    } else
        iter = file->private_data;

    parser = &iter->parser;
    read = trace_get_user(parser, ubuf, cnt, ppos);

    if (read >= 0 && trace_parser_loaded(parser) &&
        !trace_parser_cont(parser)) {
        ret = ftrace_process_regex(iter->hash, parser->buffer,
                       parser->idx, enable);
        trace_parser_clear(parser);
        if (ret)
            goto out_unlock;
    }

    ret = read;
out_unlock:
    mutex_unlock(&ftrace_regex_lock);

    return ret;
}

ssize_t
ftrace_filter_write(struct file *file, const char __user *ubuf,
            size_t cnt, loff_t *ppos)
{
    return ftrace_regex_write(file, ubuf, cnt, ppos, 1);
}

ssize_t
ftrace_notrace_write(struct file *file, const char __user *ubuf,
             size_t cnt, loff_t *ppos)
{
    return ftrace_regex_write(file, ubuf, cnt, ppos, 0);
}

static int
ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
{
    struct ftrace_func_entry *entry;

    if (!ftrace_location(ip))
        return -EINVAL;

    if (remove) {
        entry = ftrace_lookup_ip(hash, ip);
        if (!entry)
            return -ENOENT;
        free_hash_entry(hash, entry);
        return 0;
    }

    return add_hash_entry(hash, ip);
}

static int
ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
        unsigned long ip, int remove, int reset, int enable)
{
    struct ftrace_hash **orig_hash;
    struct ftrace_hash *hash;
    int ret;

    /* All global ops uses the global ops filters */
    if (ops->flags & FTRACE_OPS_FL_GLOBAL)
        ops = &global_ops;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    if (enable)
        orig_hash = &ops->filter_hash;
    else
        orig_hash = &ops->notrace_hash;

    hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
    if (!hash)
        return -ENOMEM;

    mutex_lock(&ftrace_regex_lock);
    if (reset)
        ftrace_filter_reset(hash);
    if (buf && !ftrace_match_records(hash, buf, len)) {
        ret = -EINVAL;
        goto out_regex_unlock;
    }
    if (ip) {
        ret = ftrace_match_addr(hash, ip, remove);
        if (ret < 0)
            goto out_regex_unlock;
    }

    mutex_lock(&ftrace_lock);
    ret = ftrace_hash_move(ops, enable, orig_hash, hash);
    if (!ret && ops->flags & FTRACE_OPS_FL_ENABLED
        && ftrace_enabled)
        ftrace_run_update_code(FTRACE_UPDATE_CALLS);

    mutex_unlock(&ftrace_lock);

 out_regex_unlock:
    mutex_unlock(&ftrace_regex_lock);

    free_ftrace_hash(hash);
    return ret;
}

static int
ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove,
        int reset, int enable)
{
    return ftrace_set_hash(ops, 0, 0, ip, remove, reset, enable);
}

int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
             int remove, int reset)
{
    return ftrace_set_addr(ops, ip, remove, reset, 1);
}
EXPORT_SYMBOL_GPL(ftrace_set_filter_ip);

static int
ftrace_set_regex(struct ftrace_ops *ops, unsigned char *buf, int len,
         int reset, int enable)
{
    return ftrace_set_hash(ops, buf, len, 0, 0, reset, enable);
}

int ftrace_set_filter(struct ftrace_ops *ops, unsigned char *buf,
               int len, int reset)
{
    return ftrace_set_regex(ops, buf, len, reset, 1);
}
EXPORT_SYMBOL_GPL(ftrace_set_filter);

int ftrace_set_notrace(struct ftrace_ops *ops, unsigned char *buf,
            int len, int reset)
{
    return ftrace_set_regex(ops, buf, len, reset, 0);
}
EXPORT_SYMBOL_GPL(ftrace_set_notrace);
void ftrace_set_global_filter(unsigned char *buf, int len, int reset)
{
    ftrace_set_regex(&global_ops, buf, len, reset, 1);
}
EXPORT_SYMBOL_GPL(ftrace_set_global_filter);

void ftrace_set_global_notrace(unsigned char *buf, int len, int reset)
{
    ftrace_set_regex(&global_ops, buf, len, reset, 0);
}
EXPORT_SYMBOL_GPL(ftrace_set_global_notrace);

/*
 * command line interface to allow users to set filters on boot up.
 */
#define FTRACE_FILTER_SIZE      COMMAND_LINE_SIZE
static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;

static int __init set_ftrace_notrace(char *str)
{
    strncpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
    return 1;
}
__setup("ftrace_notrace=", set_ftrace_notrace);

static int __init set_ftrace_filter(char *str)
{
    strncpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
    return 1;
}
__setup("ftrace_filter=", set_ftrace_filter);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);

static int __init set_graph_function(char *str)
{
    strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
    return 1;
}
__setup("ftrace_graph_filter=", set_graph_function);

static void __init set_ftrace_early_graph(char *buf)
{
    int ret;
    char *func;

    while (buf) {
        func = strsep(&buf, ",");
        /* we allow only one expression at a time */
        ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
                      func);
        if (ret)
            printk(KERN_DEBUG "ftrace: function %s not "
                      "traceable\n", func);
    }
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

void __init
ftrace_set_early_filter(struct ftrace_ops *ops, char *buf, int enable)
{
    char *func;

    while (buf) {
        func = strsep(&buf, ",");
        ftrace_set_regex(ops, func, strlen(func), 0, enable);
    }
}

static void __init set_ftrace_early_filters(void)
{
    if (ftrace_filter_buf[0])
        ftrace_set_early_filter(&global_ops, ftrace_filter_buf, 1);
    if (ftrace_notrace_buf[0])
        ftrace_set_early_filter(&global_ops, ftrace_notrace_buf, 0);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    if (ftrace_graph_buf[0])
        set_ftrace_early_graph(ftrace_graph_buf);
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
}

int ftrace_regex_release(struct inode *inode, struct file *file)
{
    struct seq_file *m = (struct seq_file *)file->private_data;
    struct ftrace_iterator *iter;
    struct ftrace_hash **orig_hash;
    struct trace_parser *parser;
    int filter_hash;
    int ret;

    mutex_lock(&ftrace_regex_lock);
    if (file->f_mode & FMODE_READ) {
        iter = m->private;

        seq_release(inode, file);
    } else
        iter = file->private_data;

    parser = &iter->parser;
    if (trace_parser_loaded(parser)) {
        parser->buffer[parser->idx] = 0;
        ftrace_match_records(iter->hash, parser->buffer, parser->idx);
    }

    trace_parser_put(parser);

    if (file->f_mode & FMODE_WRITE) {
        filter_hash = !!(iter->flags & FTRACE_ITER_FILTER);

        if (filter_hash)
            orig_hash = &iter->ops->filter_hash;
        else
            orig_hash = &iter->ops->notrace_hash;

        mutex_lock(&ftrace_lock);
        ret = ftrace_hash_move(iter->ops, filter_hash,
                       orig_hash, iter->hash);
        if (!ret && (iter->ops->flags & FTRACE_OPS_FL_ENABLED)
            && ftrace_enabled)
            ftrace_run_update_code(FTRACE_UPDATE_CALLS);

        mutex_unlock(&ftrace_lock);
    }
    free_ftrace_hash(iter->hash);
    kfree(iter);

    mutex_unlock(&ftrace_regex_lock);
    return 0;
}

static const struct file_operations ftrace_avail_fops = {
    .open = ftrace_avail_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release_private,
};

static const struct file_operations ftrace_enabled_fops = {
    .open = ftrace_enabled_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release_private,
};

static const struct file_operations ftrace_filter_fops = {
    .open = ftrace_filter_open,
    .read = seq_read,
    .write = ftrace_filter_write,
    .llseek = ftrace_regex_lseek,
    .release = ftrace_regex_release,
};

static const struct file_operations ftrace_notrace_fops = {
    .open = ftrace_notrace_open,
    .read = seq_read,
    .write = ftrace_notrace_write,
    .llseek = ftrace_regex_lseek,
    .release = ftrace_regex_release,
};

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static DEFINE_MUTEX(graph_lock);

int ftrace_graph_count;
int ftrace_graph_filter_enabled;
unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;

static void *
__g_next(struct seq_file *m, loff_t *pos)
{
    if (*pos >= ftrace_graph_count)
        return NULL;
    return &ftrace_graph_funcs[*pos];
}

static void *
g_next(struct seq_file *m, void *v, loff_t *pos)
{
    (*pos)++;
    return __g_next(m, pos);
}

static void *g_start(struct seq_file *m, loff_t *pos)
{
    mutex_lock(&graph_lock);

    /* Nothing, tell g_show to print all functions are enabled */
    if (!ftrace_graph_filter_enabled && !*pos)
        return (void *)1;

    return __g_next(m, pos);
}

static void g_stop(struct seq_file *m, void *p)
{
    mutex_unlock(&graph_lock);
}

static int g_show(struct seq_file *m, void *v)
{
    unsigned long *ptr = v;

    if (!ptr)
        return 0;

    if (ptr == (unsigned long *)1) {
        seq_printf(m, "#### all functions enabled ####\n");
        return 0;
    }

    seq_printf(m, "%ps\n", (void *)*ptr);

    return 0;
}

static const struct seq_operations ftrace_graph_seq_ops = {
    .start = g_start,
    .next = g_next,
    .stop = g_stop,
    .show = g_show,
};

static int
ftrace_graph_open(struct inode *inode, struct file *file)
{
    int ret = 0;

    if (unlikely(ftrace_disabled))
        return -ENODEV;

    mutex_lock(&graph_lock);
    if ((file->f_mode & FMODE_WRITE) &&
        (file->f_flags & O_TRUNC)) {
        ftrace_graph_filter_enabled = 0;
        ftrace_graph_count = 0;
        memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
    }
    mutex_unlock(&graph_lock);

    if (file->f_mode & FMODE_READ)
        ret = seq_open(file, &ftrace_graph_seq_ops);

    return ret;
}

static int
ftrace_graph_release(struct inode *inode, struct file *file)
{
    if (file->f_mode & FMODE_READ)
        seq_release(inode, file);
    return 0;
}

static int
ftrace_set_func(unsigned long *array, int *idx, char *buffer)
{
    struct dyn_ftrace *rec;
    struct ftrace_page *pg;
    int search_len;
    int fail = 1;
    int type, not;
    char *search;
    bool exists;
    int i;

    /* decode regex */
    type = filter_parse_regex(buffer, strlen(buffer), &search, &not);
    if (!not && *idx >= FTRACE_GRAPH_MAX_FUNCS)
        return -EBUSY;

    search_len = strlen(search);

    mutex_lock(&ftrace_lock);

    if (unlikely(ftrace_disabled)) {
        mutex_unlock(&ftrace_lock);
        return -ENODEV;
    }

    do_for_each_ftrace_rec(pg, rec) {

        if (ftrace_match_record(rec, NULL, search, search_len, type)) {
            /* if it is in the array */
            exists = false;
            for (i = 0; i < *idx; i++) {
                if (array[i] == rec->ip) {
                    exists = true;
                    break;
                }
            }

            if (!not) {
                fail = 0;
                if (!exists) {
                    array[(*idx)++] = rec->ip;
                    if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
                        goto out;
                }
            } else {
                if (exists) {
                    array[i] = array[--(*idx)];
                    array[*idx] = 0;
                    fail = 0;
                }
            }
        }
    } while_for_each_ftrace_rec();
out:
    mutex_unlock(&ftrace_lock);

    if (fail)
        return -EINVAL;

    ftrace_graph_filter_enabled = 1;
    return 0;
}

static ssize_t
ftrace_graph_write(struct file *file, const char __user *ubuf,
           size_t cnt, loff_t *ppos)
{
    struct trace_parser parser;
    ssize_t read, ret;

    if (!cnt)
        return 0;

    mutex_lock(&graph_lock);

    if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
        ret = -ENOMEM;
        goto out_unlock;
    }

    read = trace_get_user(&parser, ubuf, cnt, ppos);

    if (read >= 0 && trace_parser_loaded((&parser))) {
        parser.buffer[parser.idx] = 0;

        /* we allow only one expression at a time */
        ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
                    parser.buffer);
        if (ret)
            goto out_free;
    }

    ret = read;

out_free:
    trace_parser_put(&parser);
out_unlock:
    mutex_unlock(&graph_lock);

    return ret;
}

static const struct file_operations ftrace_graph_fops = {
    .open       = ftrace_graph_open,
    .read       = seq_read,
    .write      = ftrace_graph_write,
    .release    = ftrace_graph_release,
    .llseek     = seq_lseek,
};
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
{

    trace_create_file("available_filter_functions", 0444,
            d_tracer, NULL, &ftrace_avail_fops);

    trace_create_file("enabled_functions", 0444,
            d_tracer, NULL, &ftrace_enabled_fops);

    trace_create_file("set_ftrace_filter", 0644, d_tracer,
            NULL, &ftrace_filter_fops);

    trace_create_file("set_ftrace_notrace", 0644, d_tracer,
                    NULL, &ftrace_notrace_fops);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    trace_create_file("set_graph_function", 0444, d_tracer,
                    NULL,
                    &ftrace_graph_fops);
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

    return 0;
}

static int ftrace_cmp_ips(const void *a, const void *b)
{
    const unsigned long *ipa = a;
    const unsigned long *ipb = b;

    if (*ipa > *ipb)
        return 1;
    if (*ipa < *ipb)
        return -1;
    return 0;
}

static void ftrace_swap_ips(void *a, void *b, int size)
{
    unsigned long *ipa = a;
    unsigned long *ipb = b;
    unsigned long t;

    t = *ipa;
    *ipa = *ipb;
    *ipb = t;
}

static int ftrace_process_locs(struct module *mod,
                   unsigned long *start,
                   unsigned long *end)
{
    struct ftrace_page *start_pg;
    struct ftrace_page *pg;
    struct dyn_ftrace *rec;
    unsigned long count;
    unsigned long *p;
    unsigned long addr;
    unsigned long flags = 0; /* Shut up gcc */
    int ret = -ENOMEM;

    count = end - start;

    if (!count)
        return 0;

    sort(start, count, sizeof(*start),
         ftrace_cmp_ips, ftrace_swap_ips);

    start_pg = ftrace_allocate_pages(count);
    if (!start_pg)
        return -ENOMEM;

    mutex_lock(&ftrace_lock);

    /*
     * Core and each module needs their own pages, as
     * modules will free them when they are removed.
     * Force a new page to be allocated for modules.
     */
    if (!mod) {
        WARN_ON(ftrace_pages || ftrace_pages_start);
        /* First initialization */
        ftrace_pages = ftrace_pages_start = start_pg;
    } else {
        if (!ftrace_pages)
            goto out;

        if (WARN_ON(ftrace_pages->next)) {
            /* Hmm, we have free pages? */
            while (ftrace_pages->next)
                ftrace_pages = ftrace_pages->next;
        }

        ftrace_pages->next = start_pg;
    }

    p = start;
    pg = start_pg;
    while (p < end) {
        addr = ftrace_call_adjust(*p++);
        /*
         * Some architecture linkers will pad between
         * the different mcount_loc sections of different
         * object files to satisfy alignments.
         * Skip any NULL pointers.
         */
        if (!addr)
            continue;

        if (pg->index == pg->size) {
            /* We should have allocated enough */
            if (WARN_ON(!pg->next))
                break;
            pg = pg->next;
        }

        rec = &pg->records[pg->index++];
        rec->ip = addr;
    }

    /* We should have used all pages */
    WARN_ON(pg->next);

    /* Assign the last page to ftrace_pages */
    ftrace_pages = pg;

    /* These new locations need to be initialized */
    ftrace_new_pgs = start_pg;

    /*
     * We only need to disable interrupts on start up
     * because we are modifying code that an interrupt
     * may execute, and the modification is not atomic.
     * But for modules, nothing runs the code we modify
     * until we are finished with it, and there's no
     * reason to cause large interrupt latencies while we do it.
     */
    if (!mod)
        local_irq_save(flags);
    ftrace_update_code(mod);
    if (!mod)
        local_irq_restore(flags);
    ret = 0;
 out:
    mutex_unlock(&ftrace_lock);

    return ret;
}

#ifdef CONFIG_MODULES

#define next_to_ftrace_page(p) container_of(p, struct ftrace_page, next)

void ftrace_release_mod(struct module *mod)
{
    struct dyn_ftrace *rec;
    struct ftrace_page **last_pg;
    struct ftrace_page *pg;
    int order;

    mutex_lock(&ftrace_lock);

    if (ftrace_disabled)
        goto out_unlock;

    /*
     * Each module has its own ftrace_pages, remove
     * them from the list.
     */
    last_pg = &ftrace_pages_start;
    for (pg = ftrace_pages_start; pg; pg = *last_pg) {
        rec = &pg->records[0];
        if (within_module_core(rec->ip, mod)) {
            /*
             * As core pages are first, the first
             * page should never be a module page.
             */
            if (WARN_ON(pg == ftrace_pages_start))
                goto out_unlock;

            /* Check if we are deleting the last page */
            if (pg == ftrace_pages)
                ftrace_pages = next_to_ftrace_page(last_pg);

            *last_pg = pg->next;
            order = get_count_order(pg->size / ENTRIES_PER_PAGE);
            free_pages((unsigned long)pg->records, order);
            kfree(pg);
        } else
            last_pg = &pg->next;
    }
 out_unlock:
    mutex_unlock(&ftrace_lock);
}

static void ftrace_init_module(struct module *mod,
                   unsigned long *start, unsigned long *end)
{
    if (ftrace_disabled || start == end)
        return;
    ftrace_process_locs(mod, start, end);
}

static int ftrace_module_notify(struct notifier_block *self,
                unsigned long val, void *data)
{
    struct module *mod = data;

    switch (val) {
    case MODULE_STATE_COMING:
        ftrace_init_module(mod, mod->ftrace_callsites,
                   mod->ftrace_callsites +
                   mod->num_ftrace_callsites);
        break;
    case MODULE_STATE_GOING:
        ftrace_release_mod(mod);
        break;
    }

    return 0;
}
#else
static int ftrace_module_notify(struct notifier_block *self,
                unsigned long val, void *data)
{
    return 0;
}
#endif /* CONFIG_MODULES */

struct notifier_block ftrace_module_nb = {
    .notifier_call = ftrace_module_notify,
    .priority = 0,
};

extern unsigned long __start_mcount_loc[];
extern unsigned long __stop_mcount_loc[];

void __init ftrace_init(void)
{
    unsigned long count, addr, flags;
    int ret;

    /* Keep the ftrace pointer to the stub */
    addr = (unsigned long)ftrace_stub;

    local_irq_save(flags);
    ftrace_dyn_arch_init(&addr);
    local_irq_restore(flags);

    /* ftrace_dyn_arch_init places the return code in addr */
    if (addr)
        goto failed;

    count = __stop_mcount_loc - __start_mcount_loc;

    ret = ftrace_dyn_table_alloc(count);
    if (ret)
        goto failed;

    last_ftrace_enabled = ftrace_enabled = 1;

    ret = ftrace_process_locs(NULL,
                  __start_mcount_loc,
                  __stop_mcount_loc);

    ret = register_module_notifier(&ftrace_module_nb);
    if (ret)
        pr_warning("Failed to register trace ftrace module notifier\n");

    set_ftrace_early_filters();

    return;
 failed:
    ftrace_disabled = 1;
}

#else

static struct ftrace_ops global_ops = {
    .func           = ftrace_stub,
    .flags          = FTRACE_OPS_FL_RECURSION_SAFE,
};

static int __init ftrace_nodyn_init(void)
{
    ftrace_enabled = 1;
    return 0;
}
device_initcall(ftrace_nodyn_init);

static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }
static inline void ftrace_startup_enable(int command) { }
/* Keep as macros so we do not need to define the commands */
# define ftrace_startup(ops, command)           \
    ({                      \
        (ops)->flags |= FTRACE_OPS_FL_ENABLED;  \
        0;                  \
    })
# define ftrace_shutdown(ops, command)  do { } while (0)
# define ftrace_startup_sysctl()    do { } while (0)
# define ftrace_shutdown_sysctl()   do { } while (0)

static inline int
ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip)
{
    return 1;
}

#endif /* CONFIG_DYNAMIC_FTRACE */

static void
ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip,
            struct ftrace_ops *op, struct pt_regs *regs)
{
    if (unlikely(trace_recursion_test(TRACE_CONTROL_BIT)))
        return;

    /*
     * Some of the ops may be dynamically allocated,
     * they must be freed after a synchronize_sched().
     */
    preempt_disable_notrace();
    trace_recursion_set(TRACE_CONTROL_BIT);
    op = rcu_dereference_raw(ftrace_control_list);
    while (op != &ftrace_list_end) {
        if (!ftrace_function_local_disabled(op) &&
            ftrace_ops_test(op, ip))
            op->func(ip, parent_ip, op, regs);

        op = rcu_dereference_raw(op->next);
    };
    trace_recursion_clear(TRACE_CONTROL_BIT);
    preempt_enable_notrace();
}

static struct ftrace_ops control_ops = {
    .func = ftrace_ops_control_func,
    .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};

static inline void
__ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
               struct ftrace_ops *ignored, struct pt_regs *regs)
{
    struct ftrace_ops *op;

    if (function_trace_stop)
        return;

    if (unlikely(trace_recursion_test(TRACE_INTERNAL_BIT)))
        return;

    trace_recursion_set(TRACE_INTERNAL_BIT);
    /*
     * Some of the ops may be dynamically allocated,
     * they must be freed after a synchronize_sched().
     */
    preempt_disable_notrace();
    op = rcu_dereference_raw(ftrace_ops_list);
    while (op != &ftrace_list_end) {
        if (ftrace_ops_test(op, ip))
            op->func(ip, parent_ip, op, regs);
        op = rcu_dereference_raw(op->next);
    };
    preempt_enable_notrace();
    trace_recursion_clear(TRACE_INTERNAL_BIT);
}

/*
 * Some archs only support passing ip and parent_ip. Even though
 * the list function ignores the op parameter, we do not want any
 * C side effects, where a function is called without the caller
 * sending a third parameter.
 * Archs are to support both the regs and ftrace_ops at the same time.
 * If they support ftrace_ops, it is assumed they support regs.
 * If call backs want to use regs, they must either check for regs
 * being NULL, or ARCH_SUPPORTS_FTRACE_SAVE_REGS.
 * Note, ARCH_SUPPORT_SAVE_REGS expects a full regs to be saved.
 * An architecture can pass partial regs with ftrace_ops and still
 * set the ARCH_SUPPORT_FTARCE_OPS.
 */
#if ARCH_SUPPORTS_FTRACE_OPS
static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
                 struct ftrace_ops *op, struct pt_regs *regs)
{
    __ftrace_ops_list_func(ip, parent_ip, NULL, regs);
}
#else
static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
{
    __ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
}
#endif

static void clear_ftrace_swapper(void)
{
    struct task_struct *p;
    int cpu;

    get_online_cpus();
    for_each_online_cpu(cpu) {
        p = idle_task(cpu);
        clear_tsk_trace_trace(p);
    }
    put_online_cpus();
}

static void set_ftrace_swapper(void)
{
    struct task_struct *p;
    int cpu;

    get_online_cpus();
    for_each_online_cpu(cpu) {
        p = idle_task(cpu);
        set_tsk_trace_trace(p);
    }
    put_online_cpus();
}

static void clear_ftrace_pid(struct pid *pid)
{
    struct task_struct *p;

    rcu_read_lock();
    do_each_pid_task(pid, PIDTYPE_PID, p) {
        clear_tsk_trace_trace(p);
    } while_each_pid_task(pid, PIDTYPE_PID, p);
    rcu_read_unlock();

    put_pid(pid);
}

static void set_ftrace_pid(struct pid *pid)
{
    struct task_struct *p;

    rcu_read_lock();
    do_each_pid_task(pid, PIDTYPE_PID, p) {
        set_tsk_trace_trace(p);
    } while_each_pid_task(pid, PIDTYPE_PID, p);
    rcu_read_unlock();
}

static void clear_ftrace_pid_task(struct pid *pid)
{
    if (pid == ftrace_swapper_pid)
        clear_ftrace_swapper();
    else
        clear_ftrace_pid(pid);
}

static void set_ftrace_pid_task(struct pid *pid)
{
    if (pid == ftrace_swapper_pid)
        set_ftrace_swapper();
    else
        set_ftrace_pid(pid);
}

static int ftrace_pid_add(int p)
{
    struct pid *pid;
    struct ftrace_pid *fpid;
    int ret = -EINVAL;

    mutex_lock(&ftrace_lock);

    if (!p)
        pid = ftrace_swapper_pid;
    else
        pid = find_get_pid(p);

    if (!pid)
        goto out;

    ret = 0;

    list_for_each_entry(fpid, &ftrace_pids, list)
        if (fpid->pid == pid)
            goto out_put;

    ret = -ENOMEM;

    fpid = kmalloc(sizeof(*fpid), GFP_KERNEL);
    if (!fpid)
        goto out_put;

    list_add(&fpid->list, &ftrace_pids);
    fpid->pid = pid;

    set_ftrace_pid_task(pid);

    ftrace_update_pid_func();
    ftrace_startup_enable(0);

    mutex_unlock(&ftrace_lock);
    return 0;

out_put:
    if (pid != ftrace_swapper_pid)
        put_pid(pid);

out:
    mutex_unlock(&ftrace_lock);
    return ret;
}

static void ftrace_pid_reset(void)
{
    struct ftrace_pid *fpid, *safe;

    mutex_lock(&ftrace_lock);
    list_for_each_entry_safe(fpid, safe, &ftrace_pids, list) {
        struct pid *pid = fpid->pid;

        clear_ftrace_pid_task(pid);

        list_del(&fpid->list);
        kfree(fpid);
    }

    ftrace_update_pid_func();
    ftrace_startup_enable(0);

    mutex_unlock(&ftrace_lock);
}

static void *fpid_start(struct seq_file *m, loff_t *pos)
{
    mutex_lock(&ftrace_lock);

    if (list_empty(&ftrace_pids) && (!*pos))
        return (void *) 1;

    return seq_list_start(&ftrace_pids, *pos);
}

static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
{
    if (v == (void *)1)
        return NULL;

    return seq_list_next(v, &ftrace_pids, pos);
}

static void fpid_stop(struct seq_file *m, void *p)
{
    mutex_unlock(&ftrace_lock);
}

static int fpid_show(struct seq_file *m, void *v)
{
    const struct ftrace_pid *fpid = list_entry(v, struct ftrace_pid, list);

    if (v == (void *)1) {
        seq_printf(m, "no pid\n");
        return 0;
    }

    if (fpid->pid == ftrace_swapper_pid)
        seq_printf(m, "swapper tasks\n");
    else
        seq_printf(m, "%u\n", pid_vnr(fpid->pid));

    return 0;
}

static const struct seq_operations ftrace_pid_sops = {
    .start = fpid_start,
    .next = fpid_next,
    .stop = fpid_stop,
    .show = fpid_show,
};

static int
ftrace_pid_open(struct inode *inode, struct file *file)
{
    int ret = 0;

    if ((file->f_mode & FMODE_WRITE) &&
        (file->f_flags & O_TRUNC))
        ftrace_pid_reset();

    if (file->f_mode & FMODE_READ)
        ret = seq_open(file, &ftrace_pid_sops);

    return ret;
}

static ssize_t
ftrace_pid_write(struct file *filp, const char __user *ubuf,
           size_t cnt, loff_t *ppos)
{
    char buf[64], *tmp;
    long val;
    int ret;

    if (cnt >= sizeof(buf))
        return -EINVAL;

    if (copy_from_user(&buf, ubuf, cnt))
        return -EFAULT;

    buf[cnt] = 0;

    /*
     * Allow "echo > set_ftrace_pid" or "echo -n '' > set_ftrace_pid"
     * to clean the filter quietly.
     */
    tmp = strstrip(buf);
    if (strlen(tmp) == 0)
        return 1;

    ret = strict_strtol(tmp, 10, &val);
    if (ret < 0)
        return ret;

    ret = ftrace_pid_add(val);

    return ret ? ret : cnt;
}

static int
ftrace_pid_release(struct inode *inode, struct file *file)
{
    if (file->f_mode & FMODE_READ)
        seq_release(inode, file);

    return 0;
}

static const struct file_operations ftrace_pid_fops = {
    .open       = ftrace_pid_open,
    .write      = ftrace_pid_write,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = ftrace_pid_release,
};

static __init int ftrace_init_debugfs(void)
{
    struct dentry *d_tracer;

    d_tracer = tracing_init_dentry();
    if (!d_tracer)
        return 0;

    ftrace_init_dyn_debugfs(d_tracer);

    trace_create_file("set_ftrace_pid", 0644, d_tracer,
                NULL, &ftrace_pid_fops);

    ftrace_profile_debugfs(d_tracer);

    return 0;
}
fs_initcall(ftrace_init_debugfs);

void ftrace_kill(void)
{
    ftrace_disabled = 1;
    ftrace_enabled = 0;
    clear_ftrace_function();
}

int ftrace_is_dead(void)
{
    return ftrace_disabled;
}

int register_ftrace_function(struct ftrace_ops *ops)
{
    int ret = -1;

    mutex_lock(&ftrace_lock);

    ret = __register_ftrace_function(ops);
    if (!ret)
        ret = ftrace_startup(ops, 0);

    mutex_unlock(&ftrace_lock);

    return ret;
}
EXPORT_SYMBOL_GPL(register_ftrace_function);

int unregister_ftrace_function(struct ftrace_ops *ops)
{
    int ret;

    mutex_lock(&ftrace_lock);
    ret = __unregister_ftrace_function(ops);
    if (!ret)
        ftrace_shutdown(ops, 0);
    mutex_unlock(&ftrace_lock);

    return ret;
}
EXPORT_SYMBOL_GPL(unregister_ftrace_function);

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

    mutex_lock(&ftrace_lock);

    if (unlikely(ftrace_disabled))
        goto out;

    ret = proc_dointvec(table, write, buffer, lenp, ppos);

    if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))
        goto out;

    last_ftrace_enabled = !!ftrace_enabled;

    if (ftrace_enabled) {

        ftrace_startup_sysctl();

        /* we are starting ftrace again */
        if (ftrace_ops_list != &ftrace_list_end) {
            if (ftrace_ops_list->next == &ftrace_list_end)
                ftrace_trace_function = ftrace_ops_list->func;
            else
                ftrace_trace_function = ftrace_ops_list_func;
        }

    } else {
        /* stopping ftrace calls (just send to ftrace_stub) */
        ftrace_trace_function = ftrace_stub;

        ftrace_shutdown_sysctl();
    }

 out:
    mutex_unlock(&ftrace_lock);
    return ret;
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static int ftrace_graph_active;
static struct notifier_block ftrace_suspend_notifier;

int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace)
{
    return 0;
}

/* The callbacks that hook a function */
trace_func_graph_ret_t ftrace_graph_return =
            (trace_func_graph_ret_t)ftrace_stub;
trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;

/* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
{
    int i;
    int ret = 0;
    unsigned long flags;
    int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
    struct task_struct *g, *t;

    for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
        ret_stack_list[i] = kmalloc(FTRACE_RETFUNC_DEPTH
                    * sizeof(struct ftrace_ret_stack),
                    GFP_KERNEL);
        if (!ret_stack_list[i]) {
            start = 0;
            end = i;
            ret = -ENOMEM;
            goto free;
        }
    }

    read_lock_irqsave(&tasklist_lock, flags);
    do_each_thread(g, t) {
        if (start == end) {
            ret = -EAGAIN;
            goto unlock;
        }

        if (t->ret_stack == NULL) {
            atomic_set(&t->tracing_graph_pause, 0);
            atomic_set(&t->trace_overrun, 0);
            t->curr_ret_stack = -1;
            /* Make sure the tasks see the -1 first: */
            smp_wmb();
            t->ret_stack = ret_stack_list[start++];
        }
    } while_each_thread(g, t);

unlock:
    read_unlock_irqrestore(&tasklist_lock, flags);
free:
    for (i = start; i < end; i++)
        kfree(ret_stack_list[i]);
    return ret;
}

static void
ftrace_graph_probe_sched_switch(void *ignore,
            struct task_struct *prev, struct task_struct *next)
{
    unsigned long long timestamp;
    int index;

    /*
     * Does the user want to count the time a function was asleep.
     * If so, do not update the time stamps.
     */
    if (trace_flags & TRACE_ITER_SLEEP_TIME)
        return;

    timestamp = trace_clock_local();

    prev->ftrace_timestamp = timestamp;

    /* only process tasks that we timestamped */
    if (!next->ftrace_timestamp)
        return;

    /*
     * Update all the counters in next to make up for the
     * time next was sleeping.
     */
    timestamp -= next->ftrace_timestamp;

    for (index = next->curr_ret_stack; index >= 0; index--)
        next->ret_stack[index].calltime += timestamp;
}

/* Allocate a return stack for each task */
static int start_graph_tracing(void)
{
    struct ftrace_ret_stack **ret_stack_list;
    int ret, cpu;

    ret_stack_list = kmalloc(FTRACE_RETSTACK_ALLOC_SIZE *
                sizeof(struct ftrace_ret_stack *),
                GFP_KERNEL);

    if (!ret_stack_list)
        return -ENOMEM;

    /* The cpu_boot init_task->ret_stack will never be freed */
    for_each_online_cpu(cpu) {
        if (!idle_task(cpu)->ret_stack)
            ftrace_graph_init_idle_task(idle_task(cpu), cpu);
    }

    do {
        ret = alloc_retstack_tasklist(ret_stack_list);
    } while (ret == -EAGAIN);

    if (!ret) {
        ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
        if (ret)
            pr_info("ftrace_graph: Couldn't activate tracepoint"
                " probe to kernel_sched_switch\n");
    }

    kfree(ret_stack_list);
    return ret;
}

/*
 * Hibernation protection.
 * The state of the current task is too much unstable during
 * suspend/restore to disk. We want to protect against that.
 */
static int
ftrace_suspend_notifier_call(struct notifier_block *bl, unsigned long state,
                            void *unused)
{
    switch (state) {
    case PM_HIBERNATION_PREPARE:
        pause_graph_tracing();
        break;

    case PM_POST_HIBERNATION:
        unpause_graph_tracing();
        break;
    }
    return NOTIFY_DONE;
}

int register_ftrace_graph(trace_func_graph_ret_t retfunc,
            trace_func_graph_ent_t entryfunc)
{
    int ret = 0;

    mutex_lock(&ftrace_lock);

    /* we currently allow only one tracer registered at a time */
    if (ftrace_graph_active) {
        ret = -EBUSY;
        goto out;
    }

    ftrace_suspend_notifier.notifier_call = ftrace_suspend_notifier_call;
    register_pm_notifier(&ftrace_suspend_notifier);

    ftrace_graph_active++;
    ret = start_graph_tracing();
    if (ret) {
        ftrace_graph_active--;
        goto out;
    }

    ftrace_graph_return = retfunc;
    ftrace_graph_entry = entryfunc;

    ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);

out:
    mutex_unlock(&ftrace_lock);
    return ret;
}

void unregister_ftrace_graph(void)
{
    mutex_lock(&ftrace_lock);

    if (unlikely(!ftrace_graph_active))
        goto out;

    ftrace_graph_active--;
    ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
    ftrace_graph_entry = ftrace_graph_entry_stub;
    ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET);
    unregister_pm_notifier(&ftrace_suspend_notifier);
    unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);

 out:
    mutex_unlock(&ftrace_lock);
}

static DEFINE_PER_CPU(struct ftrace_ret_stack *, idle_ret_stack);

static void
graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack)
{
    atomic_set(&t->tracing_graph_pause, 0);
    atomic_set(&t->trace_overrun, 0);
    t->ftrace_timestamp = 0;
    /* make curr_ret_stack visible before we add the ret_stack */
    smp_wmb();
    t->ret_stack = ret_stack;
}

/*
 * Allocate a return stack for the idle task. May be the first
 * time through, or it may be done by CPU hotplug online.
 */
void ftrace_graph_init_idle_task(struct task_struct *t, int cpu)
{
    t->curr_ret_stack = -1;
    /*
     * The idle task has no parent, it either has its own
     * stack or no stack at all.
     */
    if (t->ret_stack)
        WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu));

    if (ftrace_graph_active) {
        struct ftrace_ret_stack *ret_stack;

        ret_stack = per_cpu(idle_ret_stack, cpu);
        if (!ret_stack) {
            ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
                        * sizeof(struct ftrace_ret_stack),
                        GFP_KERNEL);
            if (!ret_stack)
                return;
            per_cpu(idle_ret_stack, cpu) = ret_stack;
        }
        graph_init_task(t, ret_stack);
    }
}

/* Allocate a return stack for newly created task */
void ftrace_graph_init_task(struct task_struct *t)
{
    /* Make sure we do not use the parent ret_stack */
    t->ret_stack = NULL;
    t->curr_ret_stack = -1;

    if (ftrace_graph_active) {
        struct ftrace_ret_stack *ret_stack;

        ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
                * sizeof(struct ftrace_ret_stack),
                GFP_KERNEL);
        if (!ret_stack)
            return;
        graph_init_task(t, ret_stack);
    }
}

void ftrace_graph_exit_task(struct task_struct *t)
{
    struct ftrace_ret_stack *ret_stack = t->ret_stack;

    t->ret_stack = NULL;
    /* NULL must become visible to IRQs before we free it: */
    barrier();

    kfree(ret_stack);
}

void ftrace_graph_stop(void)
{
    ftrace_stop();
}
#endif