trace.c

Go to the documentation of this file.

/*
 * ring buffer based function tracer
 *
 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
 * Copyright (C) 2008 Ingo Molnar <[email protected]>
 *
 * Originally taken from the RT patch by:
 *    Arnaldo Carvalho de Melo <[email protected]>
 *
 * Based on code from the latency_tracer, that is:
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/ring_buffer.h>
#include <generated/utsrelease.h>
#include <linux/stacktrace.h>
#include <linux/writeback.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/notifier.h>
#include <linux/irqflags.h>
#include <linux/debugfs.h>
#include <linux/pagemap.h>
#include <linux/hardirq.h>
#include <linux/linkage.h>
#include <linux/uaccess.h>
#include <linux/kprobes.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/splice.h>
#include <linux/kdebug.h>
#include <linux/string.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/nmi.h>
#include <linux/fs.h>

#include "trace.h"
#include "trace_output.h"

/*
 * On boot up, the ring buffer is set to the minimum size, so that
 * we do not waste memory on systems that are not using tracing.
 */
int ring_buffer_expanded;

/*
 * We need to change this state when a selftest is running.
 * A selftest will lurk into the ring-buffer to count the
 * entries inserted during the selftest although some concurrent
 * insertions into the ring-buffer such as trace_printk could occurred
 * at the same time, giving false positive or negative results.
 */
static bool __read_mostly tracing_selftest_running;

/*
 * If a tracer is running, we do not want to run SELFTEST.
 */
bool __read_mostly tracing_selftest_disabled;

/* For tracers that don't implement custom flags */
static struct tracer_opt dummy_tracer_opt[] = {
    { }
};

static struct tracer_flags dummy_tracer_flags = {
    .val = 0,
    .opts = dummy_tracer_opt
};

static int dummy_set_flag(u32 old_flags, u32 bit, int set)
{
    return 0;
}

/*
 * Kill all tracing for good (never come back).
 * It is initialized to 1 but will turn to zero if the initialization
 * of the tracer is successful. But that is the only place that sets
 * this back to zero.
 */
static int tracing_disabled = 1;

DEFINE_PER_CPU(int, ftrace_cpu_disabled);

cpumask_var_t __read_mostly tracing_buffer_mask;

/*
 * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
 *
 * If there is an oops (or kernel panic) and the ftrace_dump_on_oops
 * is set, then ftrace_dump is called. This will output the contents
 * of the ftrace buffers to the console.  This is very useful for
 * capturing traces that lead to crashes and outputing it to a
 * serial console.
 *
 * It is default off, but you can enable it with either specifying
 * "ftrace_dump_on_oops" in the kernel command line, or setting
 * /proc/sys/kernel/ftrace_dump_on_oops
 * Set 1 if you want to dump buffers of all CPUs
 * Set 2 if you want to dump the buffer of the CPU that triggered oops
 */

enum ftrace_dump_mode ftrace_dump_on_oops;

static int tracing_set_tracer(const char *buf);

#define MAX_TRACER_SIZE     100
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
static char *default_bootup_tracer;

static int __init set_cmdline_ftrace(char *str)
{
    strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
    default_bootup_tracer = bootup_tracer_buf;
    /* We are using ftrace early, expand it */
    ring_buffer_expanded = 1;
    return 1;
}
__setup("ftrace=", set_cmdline_ftrace);

static int __init set_ftrace_dump_on_oops(char *str)
{
    if (*str++ != '=' || !*str) {
        ftrace_dump_on_oops = DUMP_ALL;
        return 1;
    }

    if (!strcmp("orig_cpu", str)) {
        ftrace_dump_on_oops = DUMP_ORIG;
                return 1;
        }

        return 0;
}
__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);

unsigned long long ns2usecs(cycle_t nsec)
{
    nsec += 500;
    do_div(nsec, 1000);
    return nsec;
}

/*
 * The global_trace is the descriptor that holds the tracing
 * buffers for the live tracing. For each CPU, it contains
 * a link list of pages that will store trace entries. The
 * page descriptor of the pages in the memory is used to hold
 * the link list by linking the lru item in the page descriptor
 * to each of the pages in the buffer per CPU.
 *
 * For each active CPU there is a data field that holds the
 * pages for the buffer for that CPU. Each CPU has the same number
 * of pages allocated for its buffer.
 */
static struct trace_array   global_trace;

static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);

int filter_current_check_discard(struct ring_buffer *buffer,
                 struct ftrace_event_call *call, void *rec,
                 struct ring_buffer_event *event)
{
    return filter_check_discard(call, rec, buffer, event);
}
EXPORT_SYMBOL_GPL(filter_current_check_discard);

cycle_t ftrace_now(int cpu)
{
    u64 ts;

    /* Early boot up does not have a buffer yet */
    if (!global_trace.buffer)
        return trace_clock_local();

    ts = ring_buffer_time_stamp(global_trace.buffer, cpu);
    ring_buffer_normalize_time_stamp(global_trace.buffer, cpu, &ts);

    return ts;
}

/*
 * The max_tr is used to snapshot the global_trace when a maximum
 * latency is reached. Some tracers will use this to store a maximum
 * trace while it continues examining live traces.
 *
 * The buffers for the max_tr are set up the same as the global_trace.
 * When a snapshot is taken, the link list of the max_tr is swapped
 * with the link list of the global_trace and the buffers are reset for
 * the global_trace so the tracing can continue.
 */
static struct trace_array   max_tr;

static DEFINE_PER_CPU(struct trace_array_cpu, max_tr_data);

/* tracer_enabled is used to toggle activation of a tracer */
static int          tracer_enabled = 1;

int tracing_is_enabled(void)
{
    return tracer_enabled;
}

/*
 * trace_buf_size is the size in bytes that is allocated
 * for a buffer. Note, the number of bytes is always rounded
 * to page size.
 *
 * This number is purposely set to a low number of 16384.
 * If the dump on oops happens, it will be much appreciated
 * to not have to wait for all that output. Anyway this can be
 * boot time and run time configurable.
 */
#define TRACE_BUF_SIZE_DEFAULT  1441792UL /* 16384 * 88 (sizeof(entry)) */

static unsigned long        trace_buf_size = TRACE_BUF_SIZE_DEFAULT;

/* trace_types holds a link list of available tracers. */
static struct tracer        *trace_types __read_mostly;

/* current_trace points to the tracer that is currently active */
static struct tracer        *current_trace __read_mostly;

/*
 * trace_types_lock is used to protect the trace_types list.
 */
static DEFINE_MUTEX(trace_types_lock);

/*
 * serialize the access of the ring buffer
 *
 * ring buffer serializes readers, but it is low level protection.
 * The validity of the events (which returns by ring_buffer_peek() ..etc)
 * are not protected by ring buffer.
 *
 * The content of events may become garbage if we allow other process consumes
 * these events concurrently:
 *   A) the page of the consumed events may become a normal page
 *      (not reader page) in ring buffer, and this page will be rewrited
 *      by events producer.
 *   B) The page of the consumed events may become a page for splice_read,
 *      and this page will be returned to system.
 *
 * These primitives allow multi process access to different cpu ring buffer
 * concurrently.
 *
 * These primitives don't distinguish read-only and read-consume access.
 * Multi read-only access are also serialized.
 */

#ifdef CONFIG_SMP
static DECLARE_RWSEM(all_cpu_access_lock);
static DEFINE_PER_CPU(struct mutex, cpu_access_lock);

static inline void trace_access_lock(int cpu)
{
    if (cpu == TRACE_PIPE_ALL_CPU) {
        /* gain it for accessing the whole ring buffer. */
        down_write(&all_cpu_access_lock);
    } else {
        /* gain it for accessing a cpu ring buffer. */

        /* Firstly block other trace_access_lock(TRACE_PIPE_ALL_CPU). */
        down_read(&all_cpu_access_lock);

        /* Secondly block other access to this @cpu ring buffer. */
        mutex_lock(&per_cpu(cpu_access_lock, cpu));
    }
}

static inline void trace_access_unlock(int cpu)
{
    if (cpu == TRACE_PIPE_ALL_CPU) {
        up_write(&all_cpu_access_lock);
    } else {
        mutex_unlock(&per_cpu(cpu_access_lock, cpu));
        up_read(&all_cpu_access_lock);
    }
}

static inline void trace_access_lock_init(void)
{
    int cpu;

    for_each_possible_cpu(cpu)
        mutex_init(&per_cpu(cpu_access_lock, cpu));
}

#else

static DEFINE_MUTEX(access_lock);

static inline void trace_access_lock(int cpu)
{
    (void)cpu;
    mutex_lock(&access_lock);
}

static inline void trace_access_unlock(int cpu)
{
    (void)cpu;
    mutex_unlock(&access_lock);
}

static inline void trace_access_lock_init(void)
{
}

#endif

/* trace_wait is a waitqueue for tasks blocked on trace_poll */
static DECLARE_WAIT_QUEUE_HEAD(trace_wait);

/* trace_flags holds trace_options default values */
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
    TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
    TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |
    TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS;

static int trace_stop_count;
static DEFINE_RAW_SPINLOCK(tracing_start_lock);

static void wakeup_work_handler(struct work_struct *work)
{
    wake_up(&trace_wait);
}

static DECLARE_DELAYED_WORK(wakeup_work, wakeup_work_handler);

void tracing_on(void)
{
    if (global_trace.buffer)
        ring_buffer_record_on(global_trace.buffer);
    /*
     * This flag is only looked at when buffers haven't been
     * allocated yet. We don't really care about the race
     * between setting this flag and actually turning
     * on the buffer.
     */
    global_trace.buffer_disabled = 0;
}
EXPORT_SYMBOL_GPL(tracing_on);

void tracing_off(void)
{
    if (global_trace.buffer)
        ring_buffer_record_off(global_trace.buffer);
    /*
     * This flag is only looked at when buffers haven't been
     * allocated yet. We don't really care about the race
     * between setting this flag and actually turning
     * on the buffer.
     */
    global_trace.buffer_disabled = 1;
}
EXPORT_SYMBOL_GPL(tracing_off);

int tracing_is_on(void)
{
    if (global_trace.buffer)
        return ring_buffer_record_is_on(global_trace.buffer);
    return !global_trace.buffer_disabled;
}
EXPORT_SYMBOL_GPL(tracing_is_on);

void trace_wake_up(void)
{
    const unsigned long delay = msecs_to_jiffies(2);

    if (trace_flags & TRACE_ITER_BLOCK)
        return;
    schedule_delayed_work(&wakeup_work, delay);
}

static int __init set_buf_size(char *str)
{
    unsigned long buf_size;

    if (!str)
        return 0;
    buf_size = memparse(str, &str);
    /* nr_entries can not be zero */
    if (buf_size == 0)
        return 0;
    trace_buf_size = buf_size;
    return 1;
}
__setup("trace_buf_size=", set_buf_size);

static int __init set_tracing_thresh(char *str)
{
    unsigned long threshold;
    int ret;

    if (!str)
        return 0;
    ret = strict_strtoul(str, 0, &threshold);
    if (ret < 0)
        return 0;
    tracing_thresh = threshold * 1000;
    return 1;
}
__setup("tracing_thresh=", set_tracing_thresh);

unsigned long nsecs_to_usecs(unsigned long nsecs)
{
    return nsecs / 1000;
}

/* These must match the bit postions in trace_iterator_flags */
static const char *trace_options[] = {
    "print-parent",
    "sym-offset",
    "sym-addr",
    "verbose",
    "raw",
    "hex",
    "bin",
    "block",
    "stacktrace",
    "trace_printk",
    "ftrace_preempt",
    "branch",
    "annotate",
    "userstacktrace",
    "sym-userobj",
    "printk-msg-only",
    "context-info",
    "latency-format",
    "sleep-time",
    "graph-time",
    "record-cmd",
    "overwrite",
    "disable_on_free",
    "irq-info",
    "markers",
    NULL
};

static struct {
    u64 (*func)(void);
    const char *name;
} trace_clocks[] = {
    { trace_clock_local,    "local" },
    { trace_clock_global,   "global" },
    { trace_clock_counter,  "counter" },
};

int trace_clock_id;

/*
 * trace_parser_get_init - gets the buffer for trace parser
 */
int trace_parser_get_init(struct trace_parser *parser, int size)
{
    memset(parser, 0, sizeof(*parser));

    parser->buffer = kmalloc(size, GFP_KERNEL);
    if (!parser->buffer)
        return 1;

    parser->size = size;
    return 0;
}

/*
 * trace_parser_put - frees the buffer for trace parser
 */
void trace_parser_put(struct trace_parser *parser)
{
    kfree(parser->buffer);
}

/*
 * trace_get_user - reads the user input string separated by  space
 * (matched by isspace(ch))
 *
 * For each string found the 'struct trace_parser' is updated,
 * and the function returns.
 *
 * Returns number of bytes read.
 *
 * See kernel/trace/trace.h for 'struct trace_parser' details.
 */
int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
    size_t cnt, loff_t *ppos)
{
    char ch;
    size_t read = 0;
    ssize_t ret;

    if (!*ppos)
        trace_parser_clear(parser);

    ret = get_user(ch, ubuf++);
    if (ret)
        goto out;

    read++;
    cnt--;

    /*
     * The parser is not finished with the last write,
     * continue reading the user input without skipping spaces.
     */
    if (!parser->cont) {
        /* skip white space */
        while (cnt && isspace(ch)) {
            ret = get_user(ch, ubuf++);
            if (ret)
                goto out;
            read++;
            cnt--;
        }

        /* only spaces were written */
        if (isspace(ch)) {
            *ppos += read;
            ret = read;
            goto out;
        }

        parser->idx = 0;
    }

    /* read the non-space input */
    while (cnt && !isspace(ch)) {
        if (parser->idx < parser->size - 1)
            parser->buffer[parser->idx++] = ch;
        else {
            ret = -EINVAL;
            goto out;
        }
        ret = get_user(ch, ubuf++);
        if (ret)
            goto out;
        read++;
        cnt--;
    }

    /* We either got finished input or we have to wait for another call. */
    if (isspace(ch)) {
        parser->buffer[parser->idx] = 0;
        parser->cont = false;
    } else {
        parser->cont = true;
        parser->buffer[parser->idx++] = ch;
    }

    *ppos += read;
    ret = read;

out:
    return ret;
}

ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
{
    int len;
    int ret;

    if (!cnt)
        return 0;

    if (s->len <= s->readpos)
        return -EBUSY;

    len = s->len - s->readpos;
    if (cnt > len)
        cnt = len;
    ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
    if (ret == cnt)
        return -EFAULT;

    cnt -= ret;

    s->readpos += cnt;
    return cnt;
}

static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
{
    int len;

    if (s->len <= s->readpos)
        return -EBUSY;

    len = s->len - s->readpos;
    if (cnt > len)
        cnt = len;
    memcpy(buf, s->buffer + s->readpos, cnt);

    s->readpos += cnt;
    return cnt;
}

/*
 * ftrace_max_lock is used to protect the swapping of buffers
 * when taking a max snapshot. The buffers themselves are
 * protected by per_cpu spinlocks. But the action of the swap
 * needs its own lock.
 *
 * This is defined as a arch_spinlock_t in order to help
 * with performance when lockdep debugging is enabled.
 *
 * It is also used in other places outside the update_max_tr
 * so it needs to be defined outside of the
 * CONFIG_TRACER_MAX_TRACE.
 */
static arch_spinlock_t ftrace_max_lock =
    (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

unsigned long __read_mostly tracing_thresh;

#ifdef CONFIG_TRACER_MAX_TRACE
unsigned long __read_mostly tracing_max_latency;

/*
 * Copy the new maximum trace into the separate maximum-trace
 * structure. (this way the maximum trace is permanently saved,
 * for later retrieval via /sys/kernel/debug/tracing/latency_trace)
 */
static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
    struct trace_array_cpu *data = tr->data[cpu];
    struct trace_array_cpu *max_data;

    max_tr.cpu = cpu;
    max_tr.time_start = data->preempt_timestamp;

    max_data = max_tr.data[cpu];
    max_data->saved_latency = tracing_max_latency;
    max_data->critical_start = data->critical_start;
    max_data->critical_end = data->critical_end;

    memcpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
    max_data->pid = tsk->pid;
    max_data->uid = task_uid(tsk);
    max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
    max_data->policy = tsk->policy;
    max_data->rt_priority = tsk->rt_priority;

    /* record this tasks comm */
    tracing_record_cmdline(tsk);
}

void
update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
    struct ring_buffer *buf = tr->buffer;

    if (trace_stop_count)
        return;

    WARN_ON_ONCE(!irqs_disabled());
    if (!current_trace->use_max_tr) {
        WARN_ON_ONCE(1);
        return;
    }
    arch_spin_lock(&ftrace_max_lock);

    tr->buffer = max_tr.buffer;
    max_tr.buffer = buf;

    __update_max_tr(tr, tsk, cpu);
    arch_spin_unlock(&ftrace_max_lock);
}

void
update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
    int ret;

    if (trace_stop_count)
        return;

    WARN_ON_ONCE(!irqs_disabled());
    if (!current_trace->use_max_tr) {
        WARN_ON_ONCE(1);
        return;
    }

    arch_spin_lock(&ftrace_max_lock);

    ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu);

    if (ret == -EBUSY) {
        /*
         * We failed to swap the buffer due to a commit taking
         * place on this CPU. We fail to record, but we reset
         * the max trace buffer (no one writes directly to it)
         * and flag that it failed.
         */
        trace_array_printk(&max_tr, _THIS_IP_,
            "Failed to swap buffers due to commit in progress\n");
    }

    WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);

    __update_max_tr(tr, tsk, cpu);
    arch_spin_unlock(&ftrace_max_lock);
}
#endif /* CONFIG_TRACER_MAX_TRACE */

int register_tracer(struct tracer *type)
{
    struct tracer *t;
    int ret = 0;

    if (!type->name) {
        pr_info("Tracer must have a name\n");
        return -1;
    }

    if (strlen(type->name) >= MAX_TRACER_SIZE) {
        pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
        return -1;
    }

    mutex_lock(&trace_types_lock);

    tracing_selftest_running = true;

    for (t = trace_types; t; t = t->next) {
        if (strcmp(type->name, t->name) == 0) {
            /* already found */
            pr_info("Tracer %s already registered\n",
                type->name);
            ret = -1;
            goto out;
        }
    }

    if (!type->set_flag)
        type->set_flag = &dummy_set_flag;
    if (!type->flags)
        type->flags = &dummy_tracer_flags;
    else
        if (!type->flags->opts)
            type->flags->opts = dummy_tracer_opt;
    if (!type->wait_pipe)
        type->wait_pipe = default_wait_pipe;


#ifdef CONFIG_FTRACE_STARTUP_TEST
    if (type->selftest && !tracing_selftest_disabled) {
        struct tracer *saved_tracer = current_trace;
        struct trace_array *tr = &global_trace;

        /*
         * Run a selftest on this tracer.
         * Here we reset the trace buffer, and set the current
         * tracer to be this tracer. The tracer can then run some
         * internal tracing to verify that everything is in order.
         * If we fail, we do not register this tracer.
         */
        tracing_reset_online_cpus(tr);

        current_trace = type;

        /* If we expanded the buffers, make sure the max is expanded too */
        if (ring_buffer_expanded && type->use_max_tr)
            ring_buffer_resize(max_tr.buffer, trace_buf_size,
                        RING_BUFFER_ALL_CPUS);

        /* the test is responsible for initializing and enabling */
        pr_info("Testing tracer %s: ", type->name);
        ret = type->selftest(type, tr);
        /* the test is responsible for resetting too */
        current_trace = saved_tracer;
        if (ret) {
            printk(KERN_CONT "FAILED!\n");
            /* Add the warning after printing 'FAILED' */
            WARN_ON(1);
            goto out;
        }
        /* Only reset on passing, to avoid touching corrupted buffers */
        tracing_reset_online_cpus(tr);

        /* Shrink the max buffer again */
        if (ring_buffer_expanded && type->use_max_tr)
            ring_buffer_resize(max_tr.buffer, 1,
                        RING_BUFFER_ALL_CPUS);

        printk(KERN_CONT "PASSED\n");
    }
#endif

    type->next = trace_types;
    trace_types = type;

 out:
    tracing_selftest_running = false;
    mutex_unlock(&trace_types_lock);

    if (ret || !default_bootup_tracer)
        goto out_unlock;

    if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
        goto out_unlock;

    printk(KERN_INFO "Starting tracer '%s'\n", type->name);
    /* Do we want this tracer to start on bootup? */
    tracing_set_tracer(type->name);
    default_bootup_tracer = NULL;
    /* disable other selftests, since this will break it. */
    tracing_selftest_disabled = 1;
#ifdef CONFIG_FTRACE_STARTUP_TEST
    printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
           type->name);
#endif

 out_unlock:
    return ret;
}

void unregister_tracer(struct tracer *type)
{
    struct tracer **t;

    mutex_lock(&trace_types_lock);
    for (t = &trace_types; *t; t = &(*t)->next) {
        if (*t == type)
            goto found;
    }
    pr_info("Tracer %s not registered\n", type->name);
    goto out;

 found:
    *t = (*t)->next;

    if (type == current_trace && tracer_enabled) {
        tracer_enabled = 0;
        tracing_stop();
        if (current_trace->stop)
            current_trace->stop(&global_trace);
        current_trace = &nop_trace;
    }
out:
    mutex_unlock(&trace_types_lock);
}

void tracing_reset(struct trace_array *tr, int cpu)
{
    struct ring_buffer *buffer = tr->buffer;

    ring_buffer_record_disable(buffer);

    /* Make sure all commits have finished */
    synchronize_sched();
    ring_buffer_reset_cpu(buffer, cpu);

    ring_buffer_record_enable(buffer);
}

void tracing_reset_online_cpus(struct trace_array *tr)
{
    struct ring_buffer *buffer = tr->buffer;
    int cpu;

    ring_buffer_record_disable(buffer);

    /* Make sure all commits have finished */
    synchronize_sched();

    tr->time_start = ftrace_now(tr->cpu);

    for_each_online_cpu(cpu)
        ring_buffer_reset_cpu(buffer, cpu);

    ring_buffer_record_enable(buffer);
}

void tracing_reset_current(int cpu)
{
    tracing_reset(&global_trace, cpu);
}

void tracing_reset_current_online_cpus(void)
{
    tracing_reset_online_cpus(&global_trace);
}

#define SAVED_CMDLINES 128
#define NO_CMDLINE_MAP UINT_MAX
static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
static int cmdline_idx;
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;

/* temporary disable recording */
static atomic_t trace_record_cmdline_disabled __read_mostly;

static void trace_init_cmdlines(void)
{
    memset(&map_pid_to_cmdline, NO_CMDLINE_MAP, sizeof(map_pid_to_cmdline));
    memset(&map_cmdline_to_pid, NO_CMDLINE_MAP, sizeof(map_cmdline_to_pid));
    cmdline_idx = 0;
}

int is_tracing_stopped(void)
{
    return trace_stop_count;
}

void ftrace_off_permanent(void)
{
    tracing_disabled = 1;
    ftrace_stop();
    tracing_off_permanent();
}

void tracing_start(void)
{
    struct ring_buffer *buffer;
    unsigned long flags;

    if (tracing_disabled)
        return;

    raw_spin_lock_irqsave(&tracing_start_lock, flags);
    if (--trace_stop_count) {
        if (trace_stop_count < 0) {
            /* Someone screwed up their debugging */
            WARN_ON_ONCE(1);
            trace_stop_count = 0;
        }
        goto out;
    }

    /* Prevent the buffers from switching */
    arch_spin_lock(&ftrace_max_lock);

    buffer = global_trace.buffer;
    if (buffer)
        ring_buffer_record_enable(buffer);

    buffer = max_tr.buffer;
    if (buffer)
        ring_buffer_record_enable(buffer);

    arch_spin_unlock(&ftrace_max_lock);

    ftrace_start();
 out:
    raw_spin_unlock_irqrestore(&tracing_start_lock, flags);
}

void tracing_stop(void)
{
    struct ring_buffer *buffer;
    unsigned long flags;

    ftrace_stop();
    raw_spin_lock_irqsave(&tracing_start_lock, flags);
    if (trace_stop_count++)
        goto out;

    /* Prevent the buffers from switching */
    arch_spin_lock(&ftrace_max_lock);

    buffer = global_trace.buffer;
    if (buffer)
        ring_buffer_record_disable(buffer);

    buffer = max_tr.buffer;
    if (buffer)
        ring_buffer_record_disable(buffer);

    arch_spin_unlock(&ftrace_max_lock);

 out:
    raw_spin_unlock_irqrestore(&tracing_start_lock, flags);
}

void trace_stop_cmdline_recording(void);

static void trace_save_cmdline(struct task_struct *tsk)
{
    unsigned pid, idx;

    if (!tsk->pid || unlikely(tsk->pid > PID_MAX_DEFAULT))
        return;

    /*
     * It's not the end of the world if we don't get
     * the lock, but we also don't want to spin
     * nor do we want to disable interrupts,
     * so if we miss here, then better luck next time.
     */
    if (!arch_spin_trylock(&trace_cmdline_lock))
        return;

    idx = map_pid_to_cmdline[tsk->pid];
    if (idx == NO_CMDLINE_MAP) {
        idx = (cmdline_idx + 1) % SAVED_CMDLINES;

        /*
         * Check whether the cmdline buffer at idx has a pid
         * mapped. We are going to overwrite that entry so we
         * need to clear the map_pid_to_cmdline. Otherwise we
         * would read the new comm for the old pid.
         */
        pid = map_cmdline_to_pid[idx];
        if (pid != NO_CMDLINE_MAP)
            map_pid_to_cmdline[pid] = NO_CMDLINE_MAP;

        map_cmdline_to_pid[idx] = tsk->pid;
        map_pid_to_cmdline[tsk->pid] = idx;

        cmdline_idx = idx;
    }

    memcpy(&saved_cmdlines[idx], tsk->comm, TASK_COMM_LEN);

    arch_spin_unlock(&trace_cmdline_lock);
}

void trace_find_cmdline(int pid, char comm[])
{
    unsigned map;

    if (!pid) {
        strcpy(comm, "<idle>");
        return;
    }

    if (WARN_ON_ONCE(pid < 0)) {
        strcpy(comm, "<XXX>");
        return;
    }

    if (pid > PID_MAX_DEFAULT) {
        strcpy(comm, "<...>");
        return;
    }

    preempt_disable();
    arch_spin_lock(&trace_cmdline_lock);
    map = map_pid_to_cmdline[pid];
    if (map != NO_CMDLINE_MAP)
        strcpy(comm, saved_cmdlines[map]);
    else
        strcpy(comm, "<...>");

    arch_spin_unlock(&trace_cmdline_lock);
    preempt_enable();
}

void tracing_record_cmdline(struct task_struct *tsk)
{
    if (atomic_read(&trace_record_cmdline_disabled) || !tracer_enabled ||
        !tracing_is_on())
        return;

    trace_save_cmdline(tsk);
}

void
tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
                 int pc)
{
    struct task_struct *tsk = current;

    entry->preempt_count        = pc & 0xff;
    entry->pid          = (tsk) ? tsk->pid : 0;
    entry->padding          = 0;
    entry->flags =
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
        (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
#else
        TRACE_FLAG_IRQS_NOSUPPORT |
#endif
        ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
        ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
        (need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
}
EXPORT_SYMBOL_GPL(tracing_generic_entry_update);

struct ring_buffer_event *
trace_buffer_lock_reserve(struct ring_buffer *buffer,
              int type,
              unsigned long len,
              unsigned long flags, int pc)
{
    struct ring_buffer_event *event;

    event = ring_buffer_lock_reserve(buffer, len);
    if (event != NULL) {
        struct trace_entry *ent = ring_buffer_event_data(event);

        tracing_generic_entry_update(ent, flags, pc);
        ent->type = type;
    }

    return event;
}

static inline void
__trace_buffer_unlock_commit(struct ring_buffer *buffer,
                 struct ring_buffer_event *event,
                 unsigned long flags, int pc,
                 int wake)
{
    ring_buffer_unlock_commit(buffer, event);

    ftrace_trace_stack(buffer, flags, 6, pc);
    ftrace_trace_userstack(buffer, flags, pc);

    if (wake)
        trace_wake_up();
}

void trace_buffer_unlock_commit(struct ring_buffer *buffer,
                struct ring_buffer_event *event,
                unsigned long flags, int pc)
{
    __trace_buffer_unlock_commit(buffer, event, flags, pc, 1);
}

struct ring_buffer_event *
trace_current_buffer_lock_reserve(struct ring_buffer **current_rb,
                  int type, unsigned long len,
                  unsigned long flags, int pc)
{
    *current_rb = global_trace.buffer;
    return trace_buffer_lock_reserve(*current_rb,
                     type, len, flags, pc);
}
EXPORT_SYMBOL_GPL(trace_current_buffer_lock_reserve);

void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
                    struct ring_buffer_event *event,
                    unsigned long flags, int pc)
{
    __trace_buffer_unlock_commit(buffer, event, flags, pc, 1);
}
EXPORT_SYMBOL_GPL(trace_current_buffer_unlock_commit);

void trace_nowake_buffer_unlock_commit(struct ring_buffer *buffer,
                       struct ring_buffer_event *event,
                       unsigned long flags, int pc)
{
    __trace_buffer_unlock_commit(buffer, event, flags, pc, 0);
}
EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit);

void trace_nowake_buffer_unlock_commit_regs(struct ring_buffer *buffer,
                        struct ring_buffer_event *event,
                        unsigned long flags, int pc,
                        struct pt_regs *regs)
{
    ring_buffer_unlock_commit(buffer, event);

    ftrace_trace_stack_regs(buffer, flags, 0, pc, regs);
    ftrace_trace_userstack(buffer, flags, pc);
}
EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit_regs);

void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
                     struct ring_buffer_event *event)
{
    ring_buffer_discard_commit(buffer, event);
}
EXPORT_SYMBOL_GPL(trace_current_buffer_discard_commit);

void
trace_function(struct trace_array *tr,
           unsigned long ip, unsigned long parent_ip, unsigned long flags,
           int pc)
{
    struct ftrace_event_call *call = &event_function;
    struct ring_buffer *buffer = tr->buffer;
    struct ring_buffer_event *event;
    struct ftrace_entry *entry;

    /* If we are reading the ring buffer, don't trace */
    if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
        return;

    event = trace_buffer_lock_reserve(buffer, TRACE_FN, sizeof(*entry),
                      flags, pc);
    if (!event)
        return;
    entry   = ring_buffer_event_data(event);
    entry->ip           = ip;
    entry->parent_ip        = parent_ip;

    if (!filter_check_discard(call, entry, buffer, event))
        ring_buffer_unlock_commit(buffer, event);
}

void
ftrace(struct trace_array *tr, struct trace_array_cpu *data,
       unsigned long ip, unsigned long parent_ip, unsigned long flags,
       int pc)
{
    if (likely(!atomic_read(&data->disabled)))
        trace_function(tr, ip, parent_ip, flags, pc);
}

#ifdef CONFIG_STACKTRACE

#define FTRACE_STACK_MAX_ENTRIES (PAGE_SIZE / sizeof(unsigned long))
struct ftrace_stack {
    unsigned long       calls[FTRACE_STACK_MAX_ENTRIES];
};

static DEFINE_PER_CPU(struct ftrace_stack, ftrace_stack);
static DEFINE_PER_CPU(int, ftrace_stack_reserve);

static void __ftrace_trace_stack(struct ring_buffer *buffer,
                 unsigned long flags,
                 int skip, int pc, struct pt_regs *regs)
{
    struct ftrace_event_call *call = &event_kernel_stack;
    struct ring_buffer_event *event;
    struct stack_entry *entry;
    struct stack_trace trace;
    int use_stack;
    int size = FTRACE_STACK_ENTRIES;

    trace.nr_entries    = 0;
    trace.skip      = skip;

    /*
     * Since events can happen in NMIs there's no safe way to
     * use the per cpu ftrace_stacks. We reserve it and if an interrupt
     * or NMI comes in, it will just have to use the default
     * FTRACE_STACK_SIZE.
     */
    preempt_disable_notrace();

    use_stack = ++__get_cpu_var(ftrace_stack_reserve);
    /*
     * We don't need any atomic variables, just a barrier.
     * If an interrupt comes in, we don't care, because it would
     * have exited and put the counter back to what we want.
     * We just need a barrier to keep gcc from moving things
     * around.
     */
    barrier();
    if (use_stack == 1) {
        trace.entries       = &__get_cpu_var(ftrace_stack).calls[0];
        trace.max_entries   = FTRACE_STACK_MAX_ENTRIES;

        if (regs)
            save_stack_trace_regs(regs, &trace);
        else
            save_stack_trace(&trace);

        if (trace.nr_entries > size)
            size = trace.nr_entries;
    } else
        /* From now on, use_stack is a boolean */
        use_stack = 0;

    size *= sizeof(unsigned long);

    event = trace_buffer_lock_reserve(buffer, TRACE_STACK,
                      sizeof(*entry) + size, flags, pc);
    if (!event)
        goto out;
    entry = ring_buffer_event_data(event);

    memset(&entry->caller, 0, size);

    if (use_stack)
        memcpy(&entry->caller, trace.entries,
               trace.nr_entries * sizeof(unsigned long));
    else {
        trace.max_entries   = FTRACE_STACK_ENTRIES;
        trace.entries       = entry->caller;
        if (regs)
            save_stack_trace_regs(regs, &trace);
        else
            save_stack_trace(&trace);
    }

    entry->size = trace.nr_entries;

    if (!filter_check_discard(call, entry, buffer, event))
        ring_buffer_unlock_commit(buffer, event);

 out:
    /* Again, don't let gcc optimize things here */
    barrier();
    __get_cpu_var(ftrace_stack_reserve)--;
    preempt_enable_notrace();

}

void ftrace_trace_stack_regs(struct ring_buffer *buffer, unsigned long flags,
                 int skip, int pc, struct pt_regs *regs)
{
    if (!(trace_flags & TRACE_ITER_STACKTRACE))
        return;

    __ftrace_trace_stack(buffer, flags, skip, pc, regs);
}

void ftrace_trace_stack(struct ring_buffer *buffer, unsigned long flags,
            int skip, int pc)
{
    if (!(trace_flags & TRACE_ITER_STACKTRACE))
        return;

    __ftrace_trace_stack(buffer, flags, skip, pc, NULL);
}

void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
           int pc)
{
    __ftrace_trace_stack(tr->buffer, flags, skip, pc, NULL);
}

void trace_dump_stack(void)
{
    unsigned long flags;

    if (tracing_disabled || tracing_selftest_running)
        return;

    local_save_flags(flags);

    /* skipping 3 traces, seems to get us at the caller of this function */
    __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count(), NULL);
}

static DEFINE_PER_CPU(int, user_stack_count);

void
ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
{
    struct ftrace_event_call *call = &event_user_stack;
    struct ring_buffer_event *event;
    struct userstack_entry *entry;
    struct stack_trace trace;

    if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
        return;

    /*
     * NMIs can not handle page faults, even with fix ups.
     * The save user stack can (and often does) fault.
     */
    if (unlikely(in_nmi()))
        return;

    /*
     * prevent recursion, since the user stack tracing may
     * trigger other kernel events.
     */
    preempt_disable();
    if (__this_cpu_read(user_stack_count))
        goto out;

    __this_cpu_inc(user_stack_count);

    event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                      sizeof(*entry), flags, pc);
    if (!event)
        goto out_drop_count;
    entry   = ring_buffer_event_data(event);

    entry->tgid     = current->tgid;
    memset(&entry->caller, 0, sizeof(entry->caller));

    trace.nr_entries    = 0;
    trace.max_entries   = FTRACE_STACK_ENTRIES;
    trace.skip      = 0;
    trace.entries       = entry->caller;

    save_stack_trace_user(&trace);
    if (!filter_check_discard(call, entry, buffer, event))
        ring_buffer_unlock_commit(buffer, event);

 out_drop_count:
    __this_cpu_dec(user_stack_count);
 out:
    preempt_enable();
}

#ifdef UNUSED
static void __trace_userstack(struct trace_array *tr, unsigned long flags)
{
    ftrace_trace_userstack(tr, flags, preempt_count());
}
#endif /* UNUSED */

#endif /* CONFIG_STACKTRACE */

/* created for use with alloc_percpu */
struct trace_buffer_struct {
    char buffer[TRACE_BUF_SIZE];
};

static struct trace_buffer_struct *trace_percpu_buffer;
static struct trace_buffer_struct *trace_percpu_sirq_buffer;
static struct trace_buffer_struct *trace_percpu_irq_buffer;
static struct trace_buffer_struct *trace_percpu_nmi_buffer;

/*
 * The buffer used is dependent on the context. There is a per cpu
 * buffer for normal context, softirq contex, hard irq context and
 * for NMI context. Thise allows for lockless recording.
 *
 * Note, if the buffers failed to be allocated, then this returns NULL
 */
static char *get_trace_buf(void)
{
    struct trace_buffer_struct *percpu_buffer;
    struct trace_buffer_struct *buffer;

    /*
     * If we have allocated per cpu buffers, then we do not
     * need to do any locking.
     */
    if (in_nmi())
        percpu_buffer = trace_percpu_nmi_buffer;
    else if (in_irq())
        percpu_buffer = trace_percpu_irq_buffer;
    else if (in_softirq())
        percpu_buffer = trace_percpu_sirq_buffer;
    else
        percpu_buffer = trace_percpu_buffer;

    if (!percpu_buffer)
        return NULL;

    buffer = per_cpu_ptr(percpu_buffer, smp_processor_id());

    return buffer->buffer;
}

static int alloc_percpu_trace_buffer(void)
{
    struct trace_buffer_struct *buffers;
    struct trace_buffer_struct *sirq_buffers;
    struct trace_buffer_struct *irq_buffers;
    struct trace_buffer_struct *nmi_buffers;

    buffers = alloc_percpu(struct trace_buffer_struct);
    if (!buffers)
        goto err_warn;

    sirq_buffers = alloc_percpu(struct trace_buffer_struct);
    if (!sirq_buffers)
        goto err_sirq;

    irq_buffers = alloc_percpu(struct trace_buffer_struct);
    if (!irq_buffers)
        goto err_irq;

    nmi_buffers = alloc_percpu(struct trace_buffer_struct);
    if (!nmi_buffers)
        goto err_nmi;

    trace_percpu_buffer = buffers;
    trace_percpu_sirq_buffer = sirq_buffers;
    trace_percpu_irq_buffer = irq_buffers;
    trace_percpu_nmi_buffer = nmi_buffers;

    return 0;

 err_nmi:
    free_percpu(irq_buffers);
 err_irq:
    free_percpu(sirq_buffers);
 err_sirq:
    free_percpu(buffers);
 err_warn:
    WARN(1, "Could not allocate percpu trace_printk buffer");
    return -ENOMEM;
}

void trace_printk_init_buffers(void)
{
    static int buffers_allocated;

    if (buffers_allocated)
        return;

    if (alloc_percpu_trace_buffer())
        return;

    pr_info("ftrace: Allocated trace_printk buffers\n");

    buffers_allocated = 1;
}

int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
{
    struct ftrace_event_call *call = &event_bprint;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    struct trace_array *tr = &global_trace;
    struct bprint_entry *entry;
    unsigned long flags;
    char *tbuffer;
    int len = 0, size, pc;

    if (unlikely(tracing_selftest_running || tracing_disabled))
        return 0;

    /* Don't pollute graph traces with trace_vprintk internals */
    pause_graph_tracing();

    pc = preempt_count();
    preempt_disable_notrace();

    tbuffer = get_trace_buf();
    if (!tbuffer) {
        len = 0;
        goto out;
    }

    len = vbin_printf((u32 *)tbuffer, TRACE_BUF_SIZE/sizeof(int), fmt, args);

    if (len > TRACE_BUF_SIZE/sizeof(int) || len < 0)
        goto out;

    local_save_flags(flags);
    size = sizeof(*entry) + sizeof(u32) * len;
    buffer = tr->buffer;
    event = trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
                      flags, pc);
    if (!event)
        goto out;
    entry = ring_buffer_event_data(event);
    entry->ip           = ip;
    entry->fmt          = fmt;

    memcpy(entry->buf, tbuffer, sizeof(u32) * len);
    if (!filter_check_discard(call, entry, buffer, event)) {
        ring_buffer_unlock_commit(buffer, event);
        ftrace_trace_stack(buffer, flags, 6, pc);
    }

out:
    preempt_enable_notrace();
    unpause_graph_tracing();

    return len;
}
EXPORT_SYMBOL_GPL(trace_vbprintk);

int trace_array_printk(struct trace_array *tr,
               unsigned long ip, const char *fmt, ...)
{
    int ret;
    va_list ap;

    if (!(trace_flags & TRACE_ITER_PRINTK))
        return 0;

    va_start(ap, fmt);
    ret = trace_array_vprintk(tr, ip, fmt, ap);
    va_end(ap);
    return ret;
}

int trace_array_vprintk(struct trace_array *tr,
            unsigned long ip, const char *fmt, va_list args)
{
    struct ftrace_event_call *call = &event_print;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    int len = 0, size, pc;
    struct print_entry *entry;
    unsigned long flags;
    char *tbuffer;

    if (tracing_disabled || tracing_selftest_running)
        return 0;

    /* Don't pollute graph traces with trace_vprintk internals */
    pause_graph_tracing();

    pc = preempt_count();
    preempt_disable_notrace();


    tbuffer = get_trace_buf();
    if (!tbuffer) {
        len = 0;
        goto out;
    }

    len = vsnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
    if (len > TRACE_BUF_SIZE)
        goto out;

    local_save_flags(flags);
    size = sizeof(*entry) + len + 1;
    buffer = tr->buffer;
    event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
                      flags, pc);
    if (!event)
        goto out;
    entry = ring_buffer_event_data(event);
    entry->ip = ip;

    memcpy(&entry->buf, tbuffer, len);
    entry->buf[len] = '\0';
    if (!filter_check_discard(call, entry, buffer, event)) {
        ring_buffer_unlock_commit(buffer, event);
        ftrace_trace_stack(buffer, flags, 6, pc);
    }
 out:
    preempt_enable_notrace();
    unpause_graph_tracing();

    return len;
}

int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
{
    return trace_array_vprintk(&global_trace, ip, fmt, args);
}
EXPORT_SYMBOL_GPL(trace_vprintk);

static void trace_iterator_increment(struct trace_iterator *iter)
{
    struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, iter->cpu);

    iter->idx++;
    if (buf_iter)
        ring_buffer_read(buf_iter, NULL);
}

static struct trace_entry *
peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts,
        unsigned long *lost_events)
{
    struct ring_buffer_event *event;
    struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, cpu);

    if (buf_iter)
        event = ring_buffer_iter_peek(buf_iter, ts);
    else
        event = ring_buffer_peek(iter->tr->buffer, cpu, ts,
                     lost_events);

    if (event) {
        iter->ent_size = ring_buffer_event_length(event);
        return ring_buffer_event_data(event);
    }
    iter->ent_size = 0;
    return NULL;
}

static struct trace_entry *
__find_next_entry(struct trace_iterator *iter, int *ent_cpu,
          unsigned long *missing_events, u64 *ent_ts)
{
    struct ring_buffer *buffer = iter->tr->buffer;
    struct trace_entry *ent, *next = NULL;
    unsigned long lost_events = 0, next_lost = 0;
    int cpu_file = iter->cpu_file;
    u64 next_ts = 0, ts;
    int next_cpu = -1;
    int next_size = 0;
    int cpu;

    /*
     * If we are in a per_cpu trace file, don't bother by iterating over
     * all cpu and peek directly.
     */
    if (cpu_file > TRACE_PIPE_ALL_CPU) {
        if (ring_buffer_empty_cpu(buffer, cpu_file))
            return NULL;
        ent = peek_next_entry(iter, cpu_file, ent_ts, missing_events);
        if (ent_cpu)
            *ent_cpu = cpu_file;

        return ent;
    }

    for_each_tracing_cpu(cpu) {

        if (ring_buffer_empty_cpu(buffer, cpu))
            continue;

        ent = peek_next_entry(iter, cpu, &ts, &lost_events);

        /*
         * Pick the entry with the smallest timestamp:
         */
        if (ent && (!next || ts < next_ts)) {
            next = ent;
            next_cpu = cpu;
            next_ts = ts;
            next_lost = lost_events;
            next_size = iter->ent_size;
        }
    }

    iter->ent_size = next_size;

    if (ent_cpu)
        *ent_cpu = next_cpu;

    if (ent_ts)
        *ent_ts = next_ts;

    if (missing_events)
        *missing_events = next_lost;

    return next;
}

/* Find the next real entry, without updating the iterator itself */
struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,
                      int *ent_cpu, u64 *ent_ts)
{
    return __find_next_entry(iter, ent_cpu, NULL, ent_ts);
}

/* Find the next real entry, and increment the iterator to the next entry */
void *trace_find_next_entry_inc(struct trace_iterator *iter)
{
    iter->ent = __find_next_entry(iter, &iter->cpu,
                      &iter->lost_events, &iter->ts);

    if (iter->ent)
        trace_iterator_increment(iter);

    return iter->ent ? iter : NULL;
}

static void trace_consume(struct trace_iterator *iter)
{
    ring_buffer_consume(iter->tr->buffer, iter->cpu, &iter->ts,
                &iter->lost_events);
}

static void *s_next(struct seq_file *m, void *v, loff_t *pos)
{
    struct trace_iterator *iter = m->private;
    int i = (int)*pos;
    void *ent;

    WARN_ON_ONCE(iter->leftover);

    (*pos)++;

    /* can't go backwards */
    if (iter->idx > i)
        return NULL;

    if (iter->idx < 0)
        ent = trace_find_next_entry_inc(iter);
    else
        ent = iter;

    while (ent && iter->idx < i)
        ent = trace_find_next_entry_inc(iter);

    iter->pos = *pos;

    return ent;
}

void tracing_iter_reset(struct trace_iterator *iter, int cpu)
{
    struct trace_array *tr = iter->tr;
    struct ring_buffer_event *event;
    struct ring_buffer_iter *buf_iter;
    unsigned long entries = 0;
    u64 ts;

    tr->data[cpu]->skipped_entries = 0;

    buf_iter = trace_buffer_iter(iter, cpu);
    if (!buf_iter)
        return;

    ring_buffer_iter_reset(buf_iter);

    /*
     * We could have the case with the max latency tracers
     * that a reset never took place on a cpu. This is evident
     * by the timestamp being before the start of the buffer.
     */
    while ((event = ring_buffer_iter_peek(buf_iter, &ts))) {
        if (ts >= iter->tr->time_start)
            break;
        entries++;
        ring_buffer_read(buf_iter, NULL);
    }

    tr->data[cpu]->skipped_entries = entries;
}

/*
 * The current tracer is copied to avoid a global locking
 * all around.
 */
static void *s_start(struct seq_file *m, loff_t *pos)
{
    struct trace_iterator *iter = m->private;
    static struct tracer *old_tracer;
    int cpu_file = iter->cpu_file;
    void *p = NULL;
    loff_t l = 0;
    int cpu;

    /* copy the tracer to avoid using a global lock all around */
    mutex_lock(&trace_types_lock);
    if (unlikely(old_tracer != current_trace && current_trace)) {
        old_tracer = current_trace;
        *iter->trace = *current_trace;
    }
    mutex_unlock(&trace_types_lock);

    atomic_inc(&trace_record_cmdline_disabled);

    if (*pos != iter->pos) {
        iter->ent = NULL;
        iter->cpu = 0;
        iter->idx = -1;

        if (cpu_file == TRACE_PIPE_ALL_CPU) {
            for_each_tracing_cpu(cpu)
                tracing_iter_reset(iter, cpu);
        } else
            tracing_iter_reset(iter, cpu_file);

        iter->leftover = 0;
        for (p = iter; p && l < *pos; p = s_next(m, p, &l))
            ;

    } else {
        /*
         * If we overflowed the seq_file before, then we want
         * to just reuse the trace_seq buffer again.
         */
        if (iter->leftover)
            p = iter;
        else {
            l = *pos - 1;
            p = s_next(m, p, &l);
        }
    }

    trace_event_read_lock();
    trace_access_lock(cpu_file);
    return p;
}

static void s_stop(struct seq_file *m, void *p)
{
    struct trace_iterator *iter = m->private;

    atomic_dec(&trace_record_cmdline_disabled);
    trace_access_unlock(iter->cpu_file);
    trace_event_read_unlock();
}

static void
get_total_entries(struct trace_array *tr, unsigned long *total, unsigned long *entries)
{
    unsigned long count;
    int cpu;

    *total = 0;
    *entries = 0;

    for_each_tracing_cpu(cpu) {
        count = ring_buffer_entries_cpu(tr->buffer, cpu);
        /*
         * If this buffer has skipped entries, then we hold all
         * entries for the trace and we need to ignore the
         * ones before the time stamp.
         */
        if (tr->data[cpu]->skipped_entries) {
            count -= tr->data[cpu]->skipped_entries;
            /* total is the same as the entries */
            *total += count;
        } else
            *total += count +
                ring_buffer_overrun_cpu(tr->buffer, cpu);
        *entries += count;
    }
}

static void print_lat_help_header(struct seq_file *m)
{
    seq_puts(m, "#                  _------=> CPU#            \n");
    seq_puts(m, "#                 / _-----=> irqs-off        \n");
    seq_puts(m, "#                | / _----=> need-resched    \n");
    seq_puts(m, "#                || / _---=> hardirq/softirq \n");
    seq_puts(m, "#                ||| / _--=> preempt-depth   \n");
    seq_puts(m, "#                |||| /     delay             \n");
    seq_puts(m, "#  cmd     pid   ||||| time  |   caller      \n");
    seq_puts(m, "#     \\   /      |||||  \\    |   /           \n");
}

static void print_event_info(struct trace_array *tr, struct seq_file *m)
{
    unsigned long total;
    unsigned long entries;

    get_total_entries(tr, &total, &entries);
    seq_printf(m, "# entries-in-buffer/entries-written: %lu/%lu   #P:%d\n",
           entries, total, num_online_cpus());
    seq_puts(m, "#\n");
}

static void print_func_help_header(struct trace_array *tr, struct seq_file *m)
{
    print_event_info(tr, m);
    seq_puts(m, "#           TASK-PID   CPU#      TIMESTAMP  FUNCTION\n");
    seq_puts(m, "#              | |       |          |         |\n");
}

static void print_func_help_header_irq(struct trace_array *tr, struct seq_file *m)
{
    print_event_info(tr, m);
    seq_puts(m, "#                              _-----=> irqs-off\n");
    seq_puts(m, "#                             / _----=> need-resched\n");
    seq_puts(m, "#                            | / _---=> hardirq/softirq\n");
    seq_puts(m, "#                            || / _--=> preempt-depth\n");
    seq_puts(m, "#                            ||| /     delay\n");
    seq_puts(m, "#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION\n");
    seq_puts(m, "#              | |       |   ||||       |         |\n");
}

void
print_trace_header(struct seq_file *m, struct trace_iterator *iter)
{
    unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
    struct trace_array *tr = iter->tr;
    struct trace_array_cpu *data = tr->data[tr->cpu];
    struct tracer *type = current_trace;
    unsigned long entries;
    unsigned long total;
    const char *name = "preemption";

    if (type)
        name = type->name;

    get_total_entries(tr, &total, &entries);

    seq_printf(m, "# %s latency trace v1.1.5 on %s\n",
           name, UTS_RELEASE);
    seq_puts(m, "# -----------------------------------"
         "---------------------------------\n");
    seq_printf(m, "# latency: %lu us, #%lu/%lu, CPU#%d |"
           " (M:%s VP:%d, KP:%d, SP:%d HP:%d",
           nsecs_to_usecs(data->saved_latency),
           entries,
           total,
           tr->cpu,
#if defined(CONFIG_PREEMPT_NONE)
           "server",
#elif defined(CONFIG_PREEMPT_VOLUNTARY)
           "desktop",
#elif defined(CONFIG_PREEMPT)
           "preempt",
#else
           "unknown",
#endif
           /* These are reserved for later use */
           0, 0, 0, 0);
#ifdef CONFIG_SMP
    seq_printf(m, " #P:%d)\n", num_online_cpus());
#else
    seq_puts(m, ")\n");
#endif
    seq_puts(m, "#    -----------------\n");
    seq_printf(m, "#    | task: %.16s-%d "
           "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
           data->comm, data->pid,
           from_kuid_munged(seq_user_ns(m), data->uid), data->nice,
           data->policy, data->rt_priority);
    seq_puts(m, "#    -----------------\n");

    if (data->critical_start) {
        seq_puts(m, "#  => started at: ");
        seq_print_ip_sym(&iter->seq, data->critical_start, sym_flags);
        trace_print_seq(m, &iter->seq);
        seq_puts(m, "\n#  => ended at:   ");
        seq_print_ip_sym(&iter->seq, data->critical_end, sym_flags);
        trace_print_seq(m, &iter->seq);
        seq_puts(m, "\n#\n");
    }

    seq_puts(m, "#\n");
}

static void test_cpu_buff_start(struct trace_iterator *iter)
{
    struct trace_seq *s = &iter->seq;

    if (!(trace_flags & TRACE_ITER_ANNOTATE))
        return;

    if (!(iter->iter_flags & TRACE_FILE_ANNOTATE))
        return;

    if (cpumask_test_cpu(iter->cpu, iter->started))
        return;

    if (iter->tr->data[iter->cpu]->skipped_entries)
        return;

    cpumask_set_cpu(iter->cpu, iter->started);

    /* Don't print started cpu buffer for the first entry of the trace */
    if (iter->idx > 1)
        trace_seq_printf(s, "##### CPU %u buffer started ####\n",
                iter->cpu);
}

static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
{
    struct trace_seq *s = &iter->seq;
    unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
    struct trace_entry *entry;
    struct trace_event *event;

    entry = iter->ent;

    test_cpu_buff_start(iter);

    event = ftrace_find_event(entry->type);

    if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
        if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
            if (!trace_print_lat_context(iter))
                goto partial;
        } else {
            if (!trace_print_context(iter))
                goto partial;
        }
    }

    if (event)
        return event->funcs->trace(iter, sym_flags, event);

    if (!trace_seq_printf(s, "Unknown type %d\n", entry->type))
        goto partial;

    return TRACE_TYPE_HANDLED;
partial:
    return TRACE_TYPE_PARTIAL_LINE;
}

static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
{
    struct trace_seq *s = &iter->seq;
    struct trace_entry *entry;
    struct trace_event *event;

    entry = iter->ent;

    if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
        if (!trace_seq_printf(s, "%d %d %llu ",
                      entry->pid, iter->cpu, iter->ts))
            goto partial;
    }

    event = ftrace_find_event(entry->type);
    if (event)
        return event->funcs->raw(iter, 0, event);

    if (!trace_seq_printf(s, "%d ?\n", entry->type))
        goto partial;

    return TRACE_TYPE_HANDLED;
partial:
    return TRACE_TYPE_PARTIAL_LINE;
}

static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
{
    struct trace_seq *s = &iter->seq;
    unsigned char newline = '\n';
    struct trace_entry *entry;
    struct trace_event *event;

    entry = iter->ent;

    if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
        SEQ_PUT_HEX_FIELD_RET(s, entry->pid);
        SEQ_PUT_HEX_FIELD_RET(s, iter->cpu);
        SEQ_PUT_HEX_FIELD_RET(s, iter->ts);
    }

    event = ftrace_find_event(entry->type);
    if (event) {
        enum print_line_t ret = event->funcs->hex(iter, 0, event);
        if (ret != TRACE_TYPE_HANDLED)
            return ret;
    }

    SEQ_PUT_FIELD_RET(s, newline);

    return TRACE_TYPE_HANDLED;
}

static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
{
    struct trace_seq *s = &iter->seq;
    struct trace_entry *entry;
    struct trace_event *event;

    entry = iter->ent;

    if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
        SEQ_PUT_FIELD_RET(s, entry->pid);
        SEQ_PUT_FIELD_RET(s, iter->cpu);
        SEQ_PUT_FIELD_RET(s, iter->ts);
    }

    event = ftrace_find_event(entry->type);
    return event ? event->funcs->binary(iter, 0, event) :
        TRACE_TYPE_HANDLED;
}

int trace_empty(struct trace_iterator *iter)
{
    struct ring_buffer_iter *buf_iter;
    int cpu;

    /* If we are looking at one CPU buffer, only check that one */
    if (iter->cpu_file != TRACE_PIPE_ALL_CPU) {
        cpu = iter->cpu_file;
        buf_iter = trace_buffer_iter(iter, cpu);
        if (buf_iter) {
            if (!ring_buffer_iter_empty(buf_iter))
                return 0;
        } else {
            if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
                return 0;
        }
        return 1;
    }

    for_each_tracing_cpu(cpu) {
        buf_iter = trace_buffer_iter(iter, cpu);
        if (buf_iter) {
            if (!ring_buffer_iter_empty(buf_iter))
                return 0;
        } else {
            if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
                return 0;
        }
    }

    return 1;
}

/*  Called with trace_event_read_lock() held. */
enum print_line_t print_trace_line(struct trace_iterator *iter)
{
    enum print_line_t ret;

    if (iter->lost_events &&
        !trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n",
                 iter->cpu, iter->lost_events))
        return TRACE_TYPE_PARTIAL_LINE;

    if (iter->trace && iter->trace->print_line) {
        ret = iter->trace->print_line(iter);
        if (ret != TRACE_TYPE_UNHANDLED)
            return ret;
    }

    if (iter->ent->type == TRACE_BPRINT &&
            trace_flags & TRACE_ITER_PRINTK &&
            trace_flags & TRACE_ITER_PRINTK_MSGONLY)
        return trace_print_bprintk_msg_only(iter);

    if (iter->ent->type == TRACE_PRINT &&
            trace_flags & TRACE_ITER_PRINTK &&
            trace_flags & TRACE_ITER_PRINTK_MSGONLY)
        return trace_print_printk_msg_only(iter);

    if (trace_flags & TRACE_ITER_BIN)
        return print_bin_fmt(iter);

    if (trace_flags & TRACE_ITER_HEX)
        return print_hex_fmt(iter);

    if (trace_flags & TRACE_ITER_RAW)
        return print_raw_fmt(iter);

    return print_trace_fmt(iter);
}

void trace_latency_header(struct seq_file *m)
{
    struct trace_iterator *iter = m->private;

    /* print nothing if the buffers are empty */
    if (trace_empty(iter))
        return;

    if (iter->iter_flags & TRACE_FILE_LAT_FMT)
        print_trace_header(m, iter);

    if (!(trace_flags & TRACE_ITER_VERBOSE))
        print_lat_help_header(m);
}

void trace_default_header(struct seq_file *m)
{
    struct trace_iterator *iter = m->private;

    if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
        return;

    if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
        /* print nothing if the buffers are empty */
        if (trace_empty(iter))
            return;
        print_trace_header(m, iter);
        if (!(trace_flags & TRACE_ITER_VERBOSE))
            print_lat_help_header(m);
    } else {
        if (!(trace_flags & TRACE_ITER_VERBOSE)) {
            if (trace_flags & TRACE_ITER_IRQ_INFO)
                print_func_help_header_irq(iter->tr, m);
            else
                print_func_help_header(iter->tr, m);
        }
    }
}

static void test_ftrace_alive(struct seq_file *m)
{
    if (!ftrace_is_dead())
        return;
    seq_printf(m, "# WARNING: FUNCTION TRACING IS CORRUPTED\n");
    seq_printf(m, "#          MAY BE MISSING FUNCTION EVENTS\n");
}

static int s_show(struct seq_file *m, void *v)
{
    struct trace_iterator *iter = v;
    int ret;

    if (iter->ent == NULL) {
        if (iter->tr) {
            seq_printf(m, "# tracer: %s\n", iter->trace->name);
            seq_puts(m, "#\n");
            test_ftrace_alive(m);
        }
        if (iter->trace && iter->trace->print_header)
            iter->trace->print_header(m);
        else
            trace_default_header(m);

    } else if (iter->leftover) {
        /*
         * If we filled the seq_file buffer earlier, we
         * want to just show it now.
         */
        ret = trace_print_seq(m, &iter->seq);

        /* ret should this time be zero, but you never know */
        iter->leftover = ret;

    } else {
        print_trace_line(iter);
        ret = trace_print_seq(m, &iter->seq);
        /*
         * If we overflow the seq_file buffer, then it will
         * ask us for this data again at start up.
         * Use that instead.
         *  ret is 0 if seq_file write succeeded.
         *        -1 otherwise.
         */
        iter->leftover = ret;
    }

    return 0;
}

static const struct seq_operations tracer_seq_ops = {
    .start      = s_start,
    .next       = s_next,
    .stop       = s_stop,
    .show       = s_show,
};

static struct trace_iterator *
__tracing_open(struct inode *inode, struct file *file)
{
    long cpu_file = (long) inode->i_private;
    struct trace_iterator *iter;
    int cpu;

    if (tracing_disabled)
        return ERR_PTR(-ENODEV);

    iter = __seq_open_private(file, &tracer_seq_ops, sizeof(*iter));
    if (!iter)
        return ERR_PTR(-ENOMEM);

    iter->buffer_iter = kzalloc(sizeof(*iter->buffer_iter) * num_possible_cpus(),
                    GFP_KERNEL);
    if (!iter->buffer_iter)
        goto release;

    /*
     * We make a copy of the current tracer to avoid concurrent
     * changes on it while we are reading.
     */
    mutex_lock(&trace_types_lock);
    iter->trace = kzalloc(sizeof(*iter->trace), GFP_KERNEL);
    if (!iter->trace)
        goto fail;

    if (current_trace)
        *iter->trace = *current_trace;

    if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL))
        goto fail;

    if (current_trace && current_trace->print_max)
        iter->tr = &max_tr;
    else
        iter->tr = &global_trace;
    iter->pos = -1;
    mutex_init(&iter->mutex);
    iter->cpu_file = cpu_file;

    /* Notify the tracer early; before we stop tracing. */
    if (iter->trace && iter->trace->open)
        iter->trace->open(iter);

    /* Annotate start of buffers if we had overruns */
    if (ring_buffer_overruns(iter->tr->buffer))
        iter->iter_flags |= TRACE_FILE_ANNOTATE;

    /* stop the trace while dumping */
    tracing_stop();

    if (iter->cpu_file == TRACE_PIPE_ALL_CPU) {
        for_each_tracing_cpu(cpu) {
            iter->buffer_iter[cpu] =
                ring_buffer_read_prepare(iter->tr->buffer, cpu);
        }
        ring_buffer_read_prepare_sync();
        for_each_tracing_cpu(cpu) {
            ring_buffer_read_start(iter->buffer_iter[cpu]);
            tracing_iter_reset(iter, cpu);
        }
    } else {
        cpu = iter->cpu_file;
        iter->buffer_iter[cpu] =
            ring_buffer_read_prepare(iter->tr->buffer, cpu);
        ring_buffer_read_prepare_sync();
        ring_buffer_read_start(iter->buffer_iter[cpu]);
        tracing_iter_reset(iter, cpu);
    }

    mutex_unlock(&trace_types_lock);

    return iter;

 fail:
    mutex_unlock(&trace_types_lock);
    kfree(iter->trace);
    kfree(iter->buffer_iter);
release:
    seq_release_private(inode, file);
    return ERR_PTR(-ENOMEM);
}

int tracing_open_generic(struct inode *inode, struct file *filp)
{
    if (tracing_disabled)
        return -ENODEV;

    filp->private_data = inode->i_private;
    return 0;
}

static int tracing_release(struct inode *inode, struct file *file)
{
    struct seq_file *m = file->private_data;
    struct trace_iterator *iter;
    int cpu;

    if (!(file->f_mode & FMODE_READ))
        return 0;

    iter = m->private;

    mutex_lock(&trace_types_lock);
    for_each_tracing_cpu(cpu) {
        if (iter->buffer_iter[cpu])
            ring_buffer_read_finish(iter->buffer_iter[cpu]);
    }

    if (iter->trace && iter->trace->close)
        iter->trace->close(iter);

    /* reenable tracing if it was previously enabled */
    tracing_start();
    mutex_unlock(&trace_types_lock);

    mutex_destroy(&iter->mutex);
    free_cpumask_var(iter->started);
    kfree(iter->trace);
    kfree(iter->buffer_iter);
    seq_release_private(inode, file);
    return 0;
}

static int tracing_open(struct inode *inode, struct file *file)
{
    struct trace_iterator *iter;
    int ret = 0;

    /* If this file was open for write, then erase contents */
    if ((file->f_mode & FMODE_WRITE) &&
        (file->f_flags & O_TRUNC)) {
        long cpu = (long) inode->i_private;

        if (cpu == TRACE_PIPE_ALL_CPU)
            tracing_reset_online_cpus(&global_trace);
        else
            tracing_reset(&global_trace, cpu);
    }

    if (file->f_mode & FMODE_READ) {
        iter = __tracing_open(inode, file);
        if (IS_ERR(iter))
            ret = PTR_ERR(iter);
        else if (trace_flags & TRACE_ITER_LATENCY_FMT)
            iter->iter_flags |= TRACE_FILE_LAT_FMT;
    }
    return ret;
}

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
    struct tracer *t = v;

    (*pos)++;

    if (t)
        t = t->next;

    return t;
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
    struct tracer *t;
    loff_t l = 0;

    mutex_lock(&trace_types_lock);
    for (t = trace_types; t && l < *pos; t = t_next(m, t, &l))
        ;

    return t;
}

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

static int t_show(struct seq_file *m, void *v)
{
    struct tracer *t = v;

    if (!t)
        return 0;

    seq_printf(m, "%s", t->name);
    if (t->next)
        seq_putc(m, ' ');
    else
        seq_putc(m, '\n');

    return 0;
}

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

static int show_traces_open(struct inode *inode, struct file *file)
{
    if (tracing_disabled)
        return -ENODEV;

    return seq_open(file, &show_traces_seq_ops);
}

static ssize_t
tracing_write_stub(struct file *filp, const char __user *ubuf,
           size_t count, loff_t *ppos)
{
    return count;
}

static loff_t tracing_seek(struct file *file, loff_t offset, int origin)
{
    if (file->f_mode & FMODE_READ)
        return seq_lseek(file, offset, origin);
    else
        return 0;
}

static const struct file_operations tracing_fops = {
    .open       = tracing_open,
    .read       = seq_read,
    .write      = tracing_write_stub,
    .llseek     = tracing_seek,
    .release    = tracing_release,
};

static const struct file_operations show_traces_fops = {
    .open       = show_traces_open,
    .read       = seq_read,
    .release    = seq_release,
    .llseek     = seq_lseek,
};

/*
 * Only trace on a CPU if the bitmask is set:
 */
static cpumask_var_t tracing_cpumask;

/*
 * The tracer itself will not take this lock, but still we want
 * to provide a consistent cpumask to user-space:
 */
static DEFINE_MUTEX(tracing_cpumask_update_lock);

/*
 * Temporary storage for the character representation of the
 * CPU bitmask (and one more byte for the newline):
 */
static char mask_str[NR_CPUS + 1];

static ssize_t
tracing_cpumask_read(struct file *filp, char __user *ubuf,
             size_t count, loff_t *ppos)
{
    int len;

    mutex_lock(&tracing_cpumask_update_lock);

    len = cpumask_scnprintf(mask_str, count, tracing_cpumask);
    if (count - len < 2) {
        count = -EINVAL;
        goto out_err;
    }
    len += sprintf(mask_str + len, "\n");
    count = simple_read_from_buffer(ubuf, count, ppos, mask_str, NR_CPUS+1);

out_err:
    mutex_unlock(&tracing_cpumask_update_lock);

    return count;
}

static ssize_t
tracing_cpumask_write(struct file *filp, const char __user *ubuf,
              size_t count, loff_t *ppos)
{
    int err, cpu;
    cpumask_var_t tracing_cpumask_new;

    if (!alloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
        return -ENOMEM;

    err = cpumask_parse_user(ubuf, count, tracing_cpumask_new);
    if (err)
        goto err_unlock;

    mutex_lock(&tracing_cpumask_update_lock);

    local_irq_disable();
    arch_spin_lock(&ftrace_max_lock);
    for_each_tracing_cpu(cpu) {
        /*
         * Increase/decrease the disabled counter if we are
         * about to flip a bit in the cpumask:
         */
        if (cpumask_test_cpu(cpu, tracing_cpumask) &&
                !cpumask_test_cpu(cpu, tracing_cpumask_new)) {
            atomic_inc(&global_trace.data[cpu]->disabled);
            ring_buffer_record_disable_cpu(global_trace.buffer, cpu);
        }
        if (!cpumask_test_cpu(cpu, tracing_cpumask) &&
                cpumask_test_cpu(cpu, tracing_cpumask_new)) {
            atomic_dec(&global_trace.data[cpu]->disabled);
            ring_buffer_record_enable_cpu(global_trace.buffer, cpu);
        }
    }
    arch_spin_unlock(&ftrace_max_lock);
    local_irq_enable();

    cpumask_copy(tracing_cpumask, tracing_cpumask_new);

    mutex_unlock(&tracing_cpumask_update_lock);
    free_cpumask_var(tracing_cpumask_new);

    return count;

err_unlock:
    free_cpumask_var(tracing_cpumask_new);

    return err;
}

static const struct file_operations tracing_cpumask_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_cpumask_read,
    .write      = tracing_cpumask_write,
    .llseek     = generic_file_llseek,
};

static int tracing_trace_options_show(struct seq_file *m, void *v)
{
    struct tracer_opt *trace_opts;
    u32 tracer_flags;
    int i;

    mutex_lock(&trace_types_lock);
    tracer_flags = current_trace->flags->val;
    trace_opts = current_trace->flags->opts;

    for (i = 0; trace_options[i]; i++) {
        if (trace_flags & (1 << i))
            seq_printf(m, "%s\n", trace_options[i]);
        else
            seq_printf(m, "no%s\n", trace_options[i]);
    }

    for (i = 0; trace_opts[i].name; i++) {
        if (tracer_flags & trace_opts[i].bit)
            seq_printf(m, "%s\n", trace_opts[i].name);
        else
            seq_printf(m, "no%s\n", trace_opts[i].name);
    }
    mutex_unlock(&trace_types_lock);

    return 0;
}

static int __set_tracer_option(struct tracer *trace,
                   struct tracer_flags *tracer_flags,
                   struct tracer_opt *opts, int neg)
{
    int ret;

    ret = trace->set_flag(tracer_flags->val, opts->bit, !neg);
    if (ret)
        return ret;

    if (neg)
        tracer_flags->val &= ~opts->bit;
    else
        tracer_flags->val |= opts->bit;
    return 0;
}

/* Try to assign a tracer specific option */
static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
{
    struct tracer_flags *tracer_flags = trace->flags;
    struct tracer_opt *opts = NULL;
    int i;

    for (i = 0; tracer_flags->opts[i].name; i++) {
        opts = &tracer_flags->opts[i];

        if (strcmp(cmp, opts->name) == 0)
            return __set_tracer_option(trace, trace->flags,
                           opts, neg);
    }

    return -EINVAL;
}

static void set_tracer_flags(unsigned int mask, int enabled)
{
    /* do nothing if flag is already set */
    if (!!(trace_flags & mask) == !!enabled)
        return;

    if (enabled)
        trace_flags |= mask;
    else
        trace_flags &= ~mask;

    if (mask == TRACE_ITER_RECORD_CMD)
        trace_event_enable_cmd_record(enabled);

    if (mask == TRACE_ITER_OVERWRITE)
        ring_buffer_change_overwrite(global_trace.buffer, enabled);
}

static ssize_t
tracing_trace_options_write(struct file *filp, const char __user *ubuf,
            size_t cnt, loff_t *ppos)
{
    char buf[64];
    char *cmp;
    int neg = 0;
    int ret;
    int i;

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

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

    buf[cnt] = 0;
    cmp = strstrip(buf);

    if (strncmp(cmp, "no", 2) == 0) {
        neg = 1;
        cmp += 2;
    }

    for (i = 0; trace_options[i]; i++) {
        if (strcmp(cmp, trace_options[i]) == 0) {
            set_tracer_flags(1 << i, !neg);
            break;
        }
    }

    /* If no option could be set, test the specific tracer options */
    if (!trace_options[i]) {
        mutex_lock(&trace_types_lock);
        ret = set_tracer_option(current_trace, cmp, neg);
        mutex_unlock(&trace_types_lock);
        if (ret)
            return ret;
    }

    *ppos += cnt;

    return cnt;
}

static int tracing_trace_options_open(struct inode *inode, struct file *file)
{
    if (tracing_disabled)
        return -ENODEV;
    return single_open(file, tracing_trace_options_show, NULL);
}

static const struct file_operations tracing_iter_fops = {
    .open       = tracing_trace_options_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
    .write      = tracing_trace_options_write,
};

static const char readme_msg[] =
    "tracing mini-HOWTO:\n\n"
    "# mount -t debugfs nodev /sys/kernel/debug\n\n"
    "# cat /sys/kernel/debug/tracing/available_tracers\n"
    "wakeup wakeup_rt preemptirqsoff preemptoff irqsoff function nop\n\n"
    "# cat /sys/kernel/debug/tracing/current_tracer\n"
    "nop\n"
    "# echo wakeup > /sys/kernel/debug/tracing/current_tracer\n"
    "# cat /sys/kernel/debug/tracing/current_tracer\n"
    "wakeup\n"
    "# cat /sys/kernel/debug/tracing/trace_options\n"
    "noprint-parent nosym-offset nosym-addr noverbose\n"
    "# echo print-parent > /sys/kernel/debug/tracing/trace_options\n"
    "# echo 1 > /sys/kernel/debug/tracing/tracing_on\n"
    "# cat /sys/kernel/debug/tracing/trace > /tmp/trace.txt\n"
    "# echo 0 > /sys/kernel/debug/tracing/tracing_on\n"
;

static ssize_t
tracing_readme_read(struct file *filp, char __user *ubuf,
               size_t cnt, loff_t *ppos)
{
    return simple_read_from_buffer(ubuf, cnt, ppos,
                    readme_msg, strlen(readme_msg));
}

static const struct file_operations tracing_readme_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_readme_read,
    .llseek     = generic_file_llseek,
};

static ssize_t
tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,
                size_t cnt, loff_t *ppos)
{
    char *buf_comm;
    char *file_buf;
    char *buf;
    int len = 0;
    int pid;
    int i;

    file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);
    if (!file_buf)
        return -ENOMEM;

    buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);
    if (!buf_comm) {
        kfree(file_buf);
        return -ENOMEM;
    }

    buf = file_buf;

    for (i = 0; i < SAVED_CMDLINES; i++) {
        int r;

        pid = map_cmdline_to_pid[i];
        if (pid == -1 || pid == NO_CMDLINE_MAP)
            continue;

        trace_find_cmdline(pid, buf_comm);
        r = sprintf(buf, "%d %s\n", pid, buf_comm);
        buf += r;
        len += r;
    }

    len = simple_read_from_buffer(ubuf, cnt, ppos,
                      file_buf, len);

    kfree(file_buf);
    kfree(buf_comm);

    return len;
}

static const struct file_operations tracing_saved_cmdlines_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_saved_cmdlines_read,
    .llseek = generic_file_llseek,
};

static ssize_t
tracing_ctrl_read(struct file *filp, char __user *ubuf,
          size_t cnt, loff_t *ppos)
{
    char buf[64];
    int r;

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

static ssize_t
tracing_ctrl_write(struct file *filp, const char __user *ubuf,
           size_t cnt, loff_t *ppos)
{
    struct trace_array *tr = filp->private_data;
    unsigned long val;
    int ret;

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

    val = !!val;

    mutex_lock(&trace_types_lock);
    if (tracer_enabled ^ val) {

        /* Only need to warn if this is used to change the state */
        WARN_ONCE(1, "tracing_enabled is deprecated. Use tracing_on");

        if (val) {
            tracer_enabled = 1;
            if (current_trace->start)
                current_trace->start(tr);
            tracing_start();
        } else {
            tracer_enabled = 0;
            tracing_stop();
            if (current_trace->stop)
                current_trace->stop(tr);
        }
    }
    mutex_unlock(&trace_types_lock);

    *ppos += cnt;

    return cnt;
}

static ssize_t
tracing_set_trace_read(struct file *filp, char __user *ubuf,
               size_t cnt, loff_t *ppos)
{
    char buf[MAX_TRACER_SIZE+2];
    int r;

    mutex_lock(&trace_types_lock);
    if (current_trace)
        r = sprintf(buf, "%s\n", current_trace->name);
    else
        r = sprintf(buf, "\n");
    mutex_unlock(&trace_types_lock);

    return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

int tracer_init(struct tracer *t, struct trace_array *tr)
{
    tracing_reset_online_cpus(tr);
    return t->init(tr);
}

static void set_buffer_entries(struct trace_array *tr, unsigned long val)
{
    int cpu;
    for_each_tracing_cpu(cpu)
        tr->data[cpu]->entries = val;
}

static int __tracing_resize_ring_buffer(unsigned long size, int cpu)
{
    int ret;

    /*
     * If kernel or user changes the size of the ring buffer
     * we use the size that was given, and we can forget about
     * expanding it later.
     */
    ring_buffer_expanded = 1;

    ret = ring_buffer_resize(global_trace.buffer, size, cpu);
    if (ret < 0)
        return ret;

    if (!current_trace->use_max_tr)
        goto out;

    ret = ring_buffer_resize(max_tr.buffer, size, cpu);
    if (ret < 0) {
        int r = 0;

        if (cpu == RING_BUFFER_ALL_CPUS) {
            int i;
            for_each_tracing_cpu(i) {
                r = ring_buffer_resize(global_trace.buffer,
                        global_trace.data[i]->entries,
                        i);
                if (r < 0)
                    break;
            }
        } else {
            r = ring_buffer_resize(global_trace.buffer,
                        global_trace.data[cpu]->entries,
                        cpu);
        }

        if (r < 0) {
            /*
             * AARGH! We are left with different
             * size max buffer!!!!
             * The max buffer is our "snapshot" buffer.
             * When a tracer needs a snapshot (one of the
             * latency tracers), it swaps the max buffer
             * with the saved snap shot. We succeeded to
             * update the size of the main buffer, but failed to
             * update the size of the max buffer. But when we tried
             * to reset the main buffer to the original size, we
             * failed there too. This is very unlikely to
             * happen, but if it does, warn and kill all
             * tracing.
             */
            WARN_ON(1);
            tracing_disabled = 1;
        }
        return ret;
    }

    if (cpu == RING_BUFFER_ALL_CPUS)
        set_buffer_entries(&max_tr, size);
    else
        max_tr.data[cpu]->entries = size;

 out:
    if (cpu == RING_BUFFER_ALL_CPUS)
        set_buffer_entries(&global_trace, size);
    else
        global_trace.data[cpu]->entries = size;

    return ret;
}

static ssize_t tracing_resize_ring_buffer(unsigned long size, int cpu_id)
{
    int ret = size;

    mutex_lock(&trace_types_lock);

    if (cpu_id != RING_BUFFER_ALL_CPUS) {
        /* make sure, this cpu is enabled in the mask */
        if (!cpumask_test_cpu(cpu_id, tracing_buffer_mask)) {
            ret = -EINVAL;
            goto out;
        }
    }

    ret = __tracing_resize_ring_buffer(size, cpu_id);
    if (ret < 0)
        ret = -ENOMEM;

out:
    mutex_unlock(&trace_types_lock);

    return ret;
}


int tracing_update_buffers(void)
{
    int ret = 0;

    mutex_lock(&trace_types_lock);
    if (!ring_buffer_expanded)
        ret = __tracing_resize_ring_buffer(trace_buf_size,
                        RING_BUFFER_ALL_CPUS);
    mutex_unlock(&trace_types_lock);

    return ret;
}

struct trace_option_dentry;

static struct trace_option_dentry *
create_trace_option_files(struct tracer *tracer);

static void
destroy_trace_option_files(struct trace_option_dentry *topts);

static int tracing_set_tracer(const char *buf)
{
    static struct trace_option_dentry *topts;
    struct trace_array *tr = &global_trace;
    struct tracer *t;
    int ret = 0;

    mutex_lock(&trace_types_lock);

    if (!ring_buffer_expanded) {
        ret = __tracing_resize_ring_buffer(trace_buf_size,
                        RING_BUFFER_ALL_CPUS);
        if (ret < 0)
            goto out;
        ret = 0;
    }

    for (t = trace_types; t; t = t->next) {
        if (strcmp(t->name, buf) == 0)
            break;
    }
    if (!t) {
        ret = -EINVAL;
        goto out;
    }
    if (t == current_trace)
        goto out;

    trace_branch_disable();
    if (current_trace && current_trace->reset)
        current_trace->reset(tr);
    if (current_trace && current_trace->use_max_tr) {
        /*
         * We don't free the ring buffer. instead, resize it because
         * The max_tr ring buffer has some state (e.g. ring->clock) and
         * we want preserve it.
         */
        ring_buffer_resize(max_tr.buffer, 1, RING_BUFFER_ALL_CPUS);
        set_buffer_entries(&max_tr, 1);
    }
    destroy_trace_option_files(topts);

    current_trace = &nop_trace;

    topts = create_trace_option_files(t);
    if (t->use_max_tr) {
        int cpu;
        /* we need to make per cpu buffer sizes equivalent */
        for_each_tracing_cpu(cpu) {
            ret = ring_buffer_resize(max_tr.buffer,
                        global_trace.data[cpu]->entries,
                        cpu);
            if (ret < 0)
                goto out;
            max_tr.data[cpu]->entries =
                    global_trace.data[cpu]->entries;
        }
    }

    if (t->init) {
        ret = tracer_init(t, tr);
        if (ret)
            goto out;
    }

    current_trace = t;
    trace_branch_enable(tr);
 out:
    mutex_unlock(&trace_types_lock);

    return ret;
}

static ssize_t
tracing_set_trace_write(struct file *filp, const char __user *ubuf,
            size_t cnt, loff_t *ppos)
{
    char buf[MAX_TRACER_SIZE+1];
    int i;
    size_t ret;
    int err;

    ret = cnt;

    if (cnt > MAX_TRACER_SIZE)
        cnt = MAX_TRACER_SIZE;

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

    buf[cnt] = 0;

    /* strip ending whitespace. */
    for (i = cnt - 1; i > 0 && isspace(buf[i]); i--)
        buf[i] = 0;

    err = tracing_set_tracer(buf);
    if (err)
        return err;

    *ppos += ret;

    return ret;
}

static ssize_t
tracing_max_lat_read(struct file *filp, char __user *ubuf,
             size_t cnt, loff_t *ppos)
{
    unsigned long *ptr = filp->private_data;
    char buf[64];
    int r;

    r = snprintf(buf, sizeof(buf), "%ld\n",
             *ptr == (unsigned long)-1 ? -1 : nsecs_to_usecs(*ptr));
    if (r > sizeof(buf))
        r = sizeof(buf);
    return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static ssize_t
tracing_max_lat_write(struct file *filp, const char __user *ubuf,
              size_t cnt, loff_t *ppos)
{
    unsigned long *ptr = filp->private_data;
    unsigned long val;
    int ret;

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

    *ptr = val * 1000;

    return cnt;
}

static int tracing_open_pipe(struct inode *inode, struct file *filp)
{
    long cpu_file = (long) inode->i_private;
    struct trace_iterator *iter;
    int ret = 0;

    if (tracing_disabled)
        return -ENODEV;

    mutex_lock(&trace_types_lock);

    /* create a buffer to store the information to pass to userspace */
    iter = kzalloc(sizeof(*iter), GFP_KERNEL);
    if (!iter) {
        ret = -ENOMEM;
        goto out;
    }

    /*
     * We make a copy of the current tracer to avoid concurrent
     * changes on it while we are reading.
     */
    iter->trace = kmalloc(sizeof(*iter->trace), GFP_KERNEL);
    if (!iter->trace) {
        ret = -ENOMEM;
        goto fail;
    }
    if (current_trace)
        *iter->trace = *current_trace;

    if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
        ret = -ENOMEM;
        goto fail;
    }

    /* trace pipe does not show start of buffer */
    cpumask_setall(iter->started);

    if (trace_flags & TRACE_ITER_LATENCY_FMT)
        iter->iter_flags |= TRACE_FILE_LAT_FMT;

    iter->cpu_file = cpu_file;
    iter->tr = &global_trace;
    mutex_init(&iter->mutex);
    filp->private_data = iter;

    if (iter->trace->pipe_open)
        iter->trace->pipe_open(iter);

    nonseekable_open(inode, filp);
out:
    mutex_unlock(&trace_types_lock);
    return ret;

fail:
    kfree(iter->trace);
    kfree(iter);
    mutex_unlock(&trace_types_lock);
    return ret;
}

static int tracing_release_pipe(struct inode *inode, struct file *file)
{
    struct trace_iterator *iter = file->private_data;

    mutex_lock(&trace_types_lock);

    if (iter->trace->pipe_close)
        iter->trace->pipe_close(iter);

    mutex_unlock(&trace_types_lock);

    free_cpumask_var(iter->started);
    mutex_destroy(&iter->mutex);
    kfree(iter->trace);
    kfree(iter);

    return 0;
}

static unsigned int
tracing_poll_pipe(struct file *filp, poll_table *poll_table)
{
    struct trace_iterator *iter = filp->private_data;

    if (trace_flags & TRACE_ITER_BLOCK) {
        /*
         * Always select as readable when in blocking mode
         */
        return POLLIN | POLLRDNORM;
    } else {
        if (!trace_empty(iter))
            return POLLIN | POLLRDNORM;
        poll_wait(filp, &trace_wait, poll_table);
        if (!trace_empty(iter))
            return POLLIN | POLLRDNORM;

        return 0;
    }
}


void default_wait_pipe(struct trace_iterator *iter)
{
    DEFINE_WAIT(wait);

    prepare_to_wait(&trace_wait, &wait, TASK_INTERRUPTIBLE);

    if (trace_empty(iter))
        schedule();

    finish_wait(&trace_wait, &wait);
}

/*
 * This is a make-shift waitqueue.
 * A tracer might use this callback on some rare cases:
 *
 *  1) the current tracer might hold the runqueue lock when it wakes up
 *     a reader, hence a deadlock (sched, function, and function graph tracers)
 *  2) the function tracers, trace all functions, we don't want
 *     the overhead of calling wake_up and friends
 *     (and tracing them too)
 *
 *     Anyway, this is really very primitive wakeup.
 */
void poll_wait_pipe(struct trace_iterator *iter)
{
    set_current_state(TASK_INTERRUPTIBLE);
    /* sleep for 100 msecs, and try again. */
    schedule_timeout(HZ / 10);
}

/* Must be called with trace_types_lock mutex held. */
static int tracing_wait_pipe(struct file *filp)
{
    struct trace_iterator *iter = filp->private_data;

    while (trace_empty(iter)) {

        if ((filp->f_flags & O_NONBLOCK)) {
            return -EAGAIN;
        }

        mutex_unlock(&iter->mutex);

        iter->trace->wait_pipe(iter);

        mutex_lock(&iter->mutex);

        if (signal_pending(current))
            return -EINTR;

        /*
         * We block until we read something and tracing is disabled.
         * We still block if tracing is disabled, but we have never
         * read anything. This allows a user to cat this file, and
         * then enable tracing. But after we have read something,
         * we give an EOF when tracing is again disabled.
         *
         * iter->pos will be 0 if we haven't read anything.
         */
        if (!tracer_enabled && iter->pos)
            break;
    }

    return 1;
}

/*
 * Consumer reader.
 */
static ssize_t
tracing_read_pipe(struct file *filp, char __user *ubuf,
          size_t cnt, loff_t *ppos)
{
    struct trace_iterator *iter = filp->private_data;
    static struct tracer *old_tracer;
    ssize_t sret;

    /* return any leftover data */
    sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
    if (sret != -EBUSY)
        return sret;

    trace_seq_init(&iter->seq);

    /* copy the tracer to avoid using a global lock all around */
    mutex_lock(&trace_types_lock);
    if (unlikely(old_tracer != current_trace && current_trace)) {
        old_tracer = current_trace;
        *iter->trace = *current_trace;
    }
    mutex_unlock(&trace_types_lock);

    /*
     * Avoid more than one consumer on a single file descriptor
     * This is just a matter of traces coherency, the ring buffer itself
     * is protected.
     */
    mutex_lock(&iter->mutex);
    if (iter->trace->read) {
        sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
        if (sret)
            goto out;
    }

waitagain:
    sret = tracing_wait_pipe(filp);
    if (sret <= 0)
        goto out;

    /* stop when tracing is finished */
    if (trace_empty(iter)) {
        sret = 0;
        goto out;
    }

    if (cnt >= PAGE_SIZE)
        cnt = PAGE_SIZE - 1;

    /* reset all but tr, trace, and overruns */
    memset(&iter->seq, 0,
           sizeof(struct trace_iterator) -
           offsetof(struct trace_iterator, seq));
    iter->pos = -1;

    trace_event_read_lock();
    trace_access_lock(iter->cpu_file);
    while (trace_find_next_entry_inc(iter) != NULL) {
        enum print_line_t ret;
        int len = iter->seq.len;

        ret = print_trace_line(iter);
        if (ret == TRACE_TYPE_PARTIAL_LINE) {
            /* don't print partial lines */
            iter->seq.len = len;
            break;
        }
        if (ret != TRACE_TYPE_NO_CONSUME)
            trace_consume(iter);

        if (iter->seq.len >= cnt)
            break;

        /*
         * Setting the full flag means we reached the trace_seq buffer
         * size and we should leave by partial output condition above.
         * One of the trace_seq_* functions is not used properly.
         */
        WARN_ONCE(iter->seq.full, "full flag set for trace type %d",
              iter->ent->type);
    }
    trace_access_unlock(iter->cpu_file);
    trace_event_read_unlock();

    /* Now copy what we have to the user */
    sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
    if (iter->seq.readpos >= iter->seq.len)
        trace_seq_init(&iter->seq);

    /*
     * If there was nothing to send to user, in spite of consuming trace
     * entries, go back to wait for more entries.
     */
    if (sret == -EBUSY)
        goto waitagain;

out:
    mutex_unlock(&iter->mutex);

    return sret;
}

static void tracing_pipe_buf_release(struct pipe_inode_info *pipe,
                     struct pipe_buffer *buf)
{
    __free_page(buf->page);
}

static void tracing_spd_release_pipe(struct splice_pipe_desc *spd,
                     unsigned int idx)
{
    __free_page(spd->pages[idx]);
}

static const struct pipe_buf_operations tracing_pipe_buf_ops = {
    .can_merge      = 0,
    .map            = generic_pipe_buf_map,
    .unmap          = generic_pipe_buf_unmap,
    .confirm        = generic_pipe_buf_confirm,
    .release        = tracing_pipe_buf_release,
    .steal          = generic_pipe_buf_steal,
    .get            = generic_pipe_buf_get,
};

static size_t
tracing_fill_pipe_page(size_t rem, struct trace_iterator *iter)
{
    size_t count;
    int ret;

    /* Seq buffer is page-sized, exactly what we need. */
    for (;;) {
        count = iter->seq.len;
        ret = print_trace_line(iter);
        count = iter->seq.len - count;
        if (rem < count) {
            rem = 0;
            iter->seq.len -= count;
            break;
        }
        if (ret == TRACE_TYPE_PARTIAL_LINE) {
            iter->seq.len -= count;
            break;
        }

        if (ret != TRACE_TYPE_NO_CONSUME)
            trace_consume(iter);
        rem -= count;
        if (!trace_find_next_entry_inc(iter))   {
            rem = 0;
            iter->ent = NULL;
            break;
        }
    }

    return rem;
}

static ssize_t tracing_splice_read_pipe(struct file *filp,
                    loff_t *ppos,
                    struct pipe_inode_info *pipe,
                    size_t len,
                    unsigned int flags)
{
    struct page *pages_def[PIPE_DEF_BUFFERS];
    struct partial_page partial_def[PIPE_DEF_BUFFERS];
    struct trace_iterator *iter = filp->private_data;
    struct splice_pipe_desc spd = {
        .pages      = pages_def,
        .partial    = partial_def,
        .nr_pages   = 0, /* This gets updated below. */
        .nr_pages_max   = PIPE_DEF_BUFFERS,
        .flags      = flags,
        .ops        = &tracing_pipe_buf_ops,
        .spd_release    = tracing_spd_release_pipe,
    };
    static struct tracer *old_tracer;
    ssize_t ret;
    size_t rem;
    unsigned int i;

    if (splice_grow_spd(pipe, &spd))
        return -ENOMEM;

    /* copy the tracer to avoid using a global lock all around */
    mutex_lock(&trace_types_lock);
    if (unlikely(old_tracer != current_trace && current_trace)) {
        old_tracer = current_trace;
        *iter->trace = *current_trace;
    }
    mutex_unlock(&trace_types_lock);

    mutex_lock(&iter->mutex);

    if (iter->trace->splice_read) {
        ret = iter->trace->splice_read(iter, filp,
                           ppos, pipe, len, flags);
        if (ret)
            goto out_err;
    }

    ret = tracing_wait_pipe(filp);
    if (ret <= 0)
        goto out_err;

    if (!iter->ent && !trace_find_next_entry_inc(iter)) {
        ret = -EFAULT;
        goto out_err;
    }

    trace_event_read_lock();
    trace_access_lock(iter->cpu_file);

    /* Fill as many pages as possible. */
    for (i = 0, rem = len; i < pipe->buffers && rem; i++) {
        spd.pages[i] = alloc_page(GFP_KERNEL);
        if (!spd.pages[i])
            break;

        rem = tracing_fill_pipe_page(rem, iter);

        /* Copy the data into the page, so we can start over. */
        ret = trace_seq_to_buffer(&iter->seq,
                      page_address(spd.pages[i]),
                      iter->seq.len);
        if (ret < 0) {
            __free_page(spd.pages[i]);
            break;
        }
        spd.partial[i].offset = 0;
        spd.partial[i].len = iter->seq.len;

        trace_seq_init(&iter->seq);
    }

    trace_access_unlock(iter->cpu_file);
    trace_event_read_unlock();
    mutex_unlock(&iter->mutex);

    spd.nr_pages = i;

    ret = splice_to_pipe(pipe, &spd);
out:
    splice_shrink_spd(&spd);
    return ret;

out_err:
    mutex_unlock(&iter->mutex);
    goto out;
}

struct ftrace_entries_info {
    struct trace_array  *tr;
    int         cpu;
};

static int tracing_entries_open(struct inode *inode, struct file *filp)
{
    struct ftrace_entries_info *info;

    if (tracing_disabled)
        return -ENODEV;

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

    info->tr = &global_trace;
    info->cpu = (unsigned long)inode->i_private;

    filp->private_data = info;

    return 0;
}

static ssize_t
tracing_entries_read(struct file *filp, char __user *ubuf,
             size_t cnt, loff_t *ppos)
{
    struct ftrace_entries_info *info = filp->private_data;
    struct trace_array *tr = info->tr;
    char buf[64];
    int r = 0;
    ssize_t ret;

    mutex_lock(&trace_types_lock);

    if (info->cpu == RING_BUFFER_ALL_CPUS) {
        int cpu, buf_size_same;
        unsigned long size;

        size = 0;
        buf_size_same = 1;
        /* check if all cpu sizes are same */
        for_each_tracing_cpu(cpu) {
            /* fill in the size from first enabled cpu */
            if (size == 0)
                size = tr->data[cpu]->entries;
            if (size != tr->data[cpu]->entries) {
                buf_size_same = 0;
                break;
            }
        }

        if (buf_size_same) {
            if (!ring_buffer_expanded)
                r = sprintf(buf, "%lu (expanded: %lu)\n",
                        size >> 10,
                        trace_buf_size >> 10);
            else
                r = sprintf(buf, "%lu\n", size >> 10);
        } else
            r = sprintf(buf, "X\n");
    } else
        r = sprintf(buf, "%lu\n", tr->data[info->cpu]->entries >> 10);

    mutex_unlock(&trace_types_lock);

    ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
    return ret;
}

static ssize_t
tracing_entries_write(struct file *filp, const char __user *ubuf,
              size_t cnt, loff_t *ppos)
{
    struct ftrace_entries_info *info = filp->private_data;
    unsigned long val;
    int ret;

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

    /* must have at least 1 entry */
    if (!val)
        return -EINVAL;

    /* value is in KB */
    val <<= 10;

    ret = tracing_resize_ring_buffer(val, info->cpu);
    if (ret < 0)
        return ret;

    *ppos += cnt;

    return cnt;
}

static int
tracing_entries_release(struct inode *inode, struct file *filp)
{
    struct ftrace_entries_info *info = filp->private_data;

    kfree(info);

    return 0;
}

static ssize_t
tracing_total_entries_read(struct file *filp, char __user *ubuf,
                size_t cnt, loff_t *ppos)
{
    struct trace_array *tr = filp->private_data;
    char buf[64];
    int r, cpu;
    unsigned long size = 0, expanded_size = 0;

    mutex_lock(&trace_types_lock);
    for_each_tracing_cpu(cpu) {
        size += tr->data[cpu]->entries >> 10;
        if (!ring_buffer_expanded)
            expanded_size += trace_buf_size >> 10;
    }
    if (ring_buffer_expanded)
        r = sprintf(buf, "%lu\n", size);
    else
        r = sprintf(buf, "%lu (expanded: %lu)\n", size, expanded_size);
    mutex_unlock(&trace_types_lock);

    return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static ssize_t
tracing_free_buffer_write(struct file *filp, const char __user *ubuf,
              size_t cnt, loff_t *ppos)
{
    /*
     * There is no need to read what the user has written, this function
     * is just to make sure that there is no error when "echo" is used
     */

    *ppos += cnt;

    return cnt;
}

static int
tracing_free_buffer_release(struct inode *inode, struct file *filp)
{
    /* disable tracing ? */
    if (trace_flags & TRACE_ITER_STOP_ON_FREE)
        tracing_off();
    /* resize the ring buffer to 0 */
    tracing_resize_ring_buffer(0, RING_BUFFER_ALL_CPUS);

    return 0;
}

static ssize_t
tracing_mark_write(struct file *filp, const char __user *ubuf,
                    size_t cnt, loff_t *fpos)
{
    unsigned long addr = (unsigned long)ubuf;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    struct print_entry *entry;
    unsigned long irq_flags;
    struct page *pages[2];
    void *map_page[2];
    int nr_pages = 1;
    ssize_t written;
    int offset;
    int size;
    int len;
    int ret;
    int i;

    if (tracing_disabled)
        return -EINVAL;

    if (!(trace_flags & TRACE_ITER_MARKERS))
        return -EINVAL;

    if (cnt > TRACE_BUF_SIZE)
        cnt = TRACE_BUF_SIZE;

    /*
     * Userspace is injecting traces into the kernel trace buffer.
     * We want to be as non intrusive as possible.
     * To do so, we do not want to allocate any special buffers
     * or take any locks, but instead write the userspace data
     * straight into the ring buffer.
     *
     * First we need to pin the userspace buffer into memory,
     * which, most likely it is, because it just referenced it.
     * But there's no guarantee that it is. By using get_user_pages_fast()
     * and kmap_atomic/kunmap_atomic() we can get access to the
     * pages directly. We then write the data directly into the
     * ring buffer.
     */
    BUILD_BUG_ON(TRACE_BUF_SIZE >= PAGE_SIZE);

    /* check if we cross pages */
    if ((addr & PAGE_MASK) != ((addr + cnt) & PAGE_MASK))
        nr_pages = 2;

    offset = addr & (PAGE_SIZE - 1);
    addr &= PAGE_MASK;

    ret = get_user_pages_fast(addr, nr_pages, 0, pages);
    if (ret < nr_pages) {
        while (--ret >= 0)
            put_page(pages[ret]);
        written = -EFAULT;
        goto out;
    }

    for (i = 0; i < nr_pages; i++)
        map_page[i] = kmap_atomic(pages[i]);

    local_save_flags(irq_flags);
    size = sizeof(*entry) + cnt + 2; /* possible \n added */
    buffer = global_trace.buffer;
    event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
                      irq_flags, preempt_count());
    if (!event) {
        /* Ring buffer disabled, return as if not open for write */
        written = -EBADF;
        goto out_unlock;
    }

    entry = ring_buffer_event_data(event);
    entry->ip = _THIS_IP_;

    if (nr_pages == 2) {
        len = PAGE_SIZE - offset;
        memcpy(&entry->buf, map_page[0] + offset, len);
        memcpy(&entry->buf[len], map_page[1], cnt - len);
    } else
        memcpy(&entry->buf, map_page[0] + offset, cnt);

    if (entry->buf[cnt - 1] != '\n') {
        entry->buf[cnt] = '\n';
        entry->buf[cnt + 1] = '\0';
    } else
        entry->buf[cnt] = '\0';

    ring_buffer_unlock_commit(buffer, event);

    written = cnt;

    *fpos += written;

 out_unlock:
    for (i = 0; i < nr_pages; i++){
        kunmap_atomic(map_page[i]);
        put_page(pages[i]);
    }
 out:
    return written;
}

static int tracing_clock_show(struct seq_file *m, void *v)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(trace_clocks); i++)
        seq_printf(m,
            "%s%s%s%s", i ? " " : "",
            i == trace_clock_id ? "[" : "", trace_clocks[i].name,
            i == trace_clock_id ? "]" : "");
    seq_putc(m, '\n');

    return 0;
}

static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
                   size_t cnt, loff_t *fpos)
{
    char buf[64];
    const char *clockstr;
    int i;

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

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

    buf[cnt] = 0;

    clockstr = strstrip(buf);

    for (i = 0; i < ARRAY_SIZE(trace_clocks); i++) {
        if (strcmp(trace_clocks[i].name, clockstr) == 0)
            break;
    }
    if (i == ARRAY_SIZE(trace_clocks))
        return -EINVAL;

    trace_clock_id = i;

    mutex_lock(&trace_types_lock);

    ring_buffer_set_clock(global_trace.buffer, trace_clocks[i].func);
    if (max_tr.buffer)
        ring_buffer_set_clock(max_tr.buffer, trace_clocks[i].func);

    mutex_unlock(&trace_types_lock);

    *fpos += cnt;

    return cnt;
}

static int tracing_clock_open(struct inode *inode, struct file *file)
{
    if (tracing_disabled)
        return -ENODEV;
    return single_open(file, tracing_clock_show, NULL);
}

static const struct file_operations tracing_max_lat_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_max_lat_read,
    .write      = tracing_max_lat_write,
    .llseek     = generic_file_llseek,
};

static const struct file_operations tracing_ctrl_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_ctrl_read,
    .write      = tracing_ctrl_write,
    .llseek     = generic_file_llseek,
};

static const struct file_operations set_tracer_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_set_trace_read,
    .write      = tracing_set_trace_write,
    .llseek     = generic_file_llseek,
};

static const struct file_operations tracing_pipe_fops = {
    .open       = tracing_open_pipe,
    .poll       = tracing_poll_pipe,
    .read       = tracing_read_pipe,
    .splice_read    = tracing_splice_read_pipe,
    .release    = tracing_release_pipe,
    .llseek     = no_llseek,
};

static const struct file_operations tracing_entries_fops = {
    .open       = tracing_entries_open,
    .read       = tracing_entries_read,
    .write      = tracing_entries_write,
    .release    = tracing_entries_release,
    .llseek     = generic_file_llseek,
};

static const struct file_operations tracing_total_entries_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_total_entries_read,
    .llseek     = generic_file_llseek,
};

static const struct file_operations tracing_free_buffer_fops = {
    .write      = tracing_free_buffer_write,
    .release    = tracing_free_buffer_release,
};

static const struct file_operations tracing_mark_fops = {
    .open       = tracing_open_generic,
    .write      = tracing_mark_write,
    .llseek     = generic_file_llseek,
};

static const struct file_operations trace_clock_fops = {
    .open       = tracing_clock_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
    .write      = tracing_clock_write,
};

struct ftrace_buffer_info {
    struct trace_array  *tr;
    void            *spare;
    int         cpu;
    unsigned int        read;
};

static int tracing_buffers_open(struct inode *inode, struct file *filp)
{
    int cpu = (int)(long)inode->i_private;
    struct ftrace_buffer_info *info;

    if (tracing_disabled)
        return -ENODEV;

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

    info->tr    = &global_trace;
    info->cpu   = cpu;
    info->spare = NULL;
    /* Force reading ring buffer for first read */
    info->read  = (unsigned int)-1;

    filp->private_data = info;

    return nonseekable_open(inode, filp);
}

static ssize_t
tracing_buffers_read(struct file *filp, char __user *ubuf,
             size_t count, loff_t *ppos)
{
    struct ftrace_buffer_info *info = filp->private_data;
    ssize_t ret;
    size_t size;

    if (!count)
        return 0;

    if (!info->spare)
        info->spare = ring_buffer_alloc_read_page(info->tr->buffer, info->cpu);
    if (!info->spare)
        return -ENOMEM;

    /* Do we have previous read data to read? */
    if (info->read < PAGE_SIZE)
        goto read;

    trace_access_lock(info->cpu);
    ret = ring_buffer_read_page(info->tr->buffer,
                    &info->spare,
                    count,
                    info->cpu, 0);
    trace_access_unlock(info->cpu);
    if (ret < 0)
        return 0;

    info->read = 0;

read:
    size = PAGE_SIZE - info->read;
    if (size > count)
        size = count;

    ret = copy_to_user(ubuf, info->spare + info->read, size);
    if (ret == size)
        return -EFAULT;
    size -= ret;

    *ppos += size;
    info->read += size;

    return size;
}

static int tracing_buffers_release(struct inode *inode, struct file *file)
{
    struct ftrace_buffer_info *info = file->private_data;

    if (info->spare)
        ring_buffer_free_read_page(info->tr->buffer, info->spare);
    kfree(info);

    return 0;
}

struct buffer_ref {
    struct ring_buffer  *buffer;
    void            *page;
    int         ref;
};

static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
                    struct pipe_buffer *buf)
{
    struct buffer_ref *ref = (struct buffer_ref *)buf->private;

    if (--ref->ref)
        return;

    ring_buffer_free_read_page(ref->buffer, ref->page);
    kfree(ref);
    buf->private = 0;
}

static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
                struct pipe_buffer *buf)
{
    struct buffer_ref *ref = (struct buffer_ref *)buf->private;

    ref->ref++;
}

/* Pipe buffer operations for a buffer. */
static const struct pipe_buf_operations buffer_pipe_buf_ops = {
    .can_merge      = 0,
    .map            = generic_pipe_buf_map,
    .unmap          = generic_pipe_buf_unmap,
    .confirm        = generic_pipe_buf_confirm,
    .release        = buffer_pipe_buf_release,
    .steal          = generic_pipe_buf_steal,
    .get            = buffer_pipe_buf_get,
};

/*
 * Callback from splice_to_pipe(), if we need to release some pages
 * at the end of the spd in case we error'ed out in filling the pipe.
 */
static void buffer_spd_release(struct splice_pipe_desc *spd, unsigned int i)
{
    struct buffer_ref *ref =
        (struct buffer_ref *)spd->partial[i].private;

    if (--ref->ref)
        return;

    ring_buffer_free_read_page(ref->buffer, ref->page);
    kfree(ref);
    spd->partial[i].private = 0;
}

static ssize_t
tracing_buffers_splice_read(struct file *file, loff_t *ppos,
                struct pipe_inode_info *pipe, size_t len,
                unsigned int flags)
{
    struct ftrace_buffer_info *info = file->private_data;
    struct partial_page partial_def[PIPE_DEF_BUFFERS];
    struct page *pages_def[PIPE_DEF_BUFFERS];
    struct splice_pipe_desc spd = {
        .pages      = pages_def,
        .partial    = partial_def,
        .nr_pages_max   = PIPE_DEF_BUFFERS,
        .flags      = flags,
        .ops        = &buffer_pipe_buf_ops,
        .spd_release    = buffer_spd_release,
    };
    struct buffer_ref *ref;
    int entries, size, i;
    size_t ret;

    if (splice_grow_spd(pipe, &spd))
        return -ENOMEM;

    if (*ppos & (PAGE_SIZE - 1)) {
        WARN_ONCE(1, "Ftrace: previous read must page-align\n");
        ret = -EINVAL;
        goto out;
    }

    if (len & (PAGE_SIZE - 1)) {
        WARN_ONCE(1, "Ftrace: splice_read should page-align\n");
        if (len < PAGE_SIZE) {
            ret = -EINVAL;
            goto out;
        }
        len &= PAGE_MASK;
    }

    trace_access_lock(info->cpu);
    entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);

    for (i = 0; i < pipe->buffers && len && entries; i++, len -= PAGE_SIZE) {
        struct page *page;
        int r;

        ref = kzalloc(sizeof(*ref), GFP_KERNEL);
        if (!ref)
            break;

        ref->ref = 1;
        ref->buffer = info->tr->buffer;
        ref->page = ring_buffer_alloc_read_page(ref->buffer, info->cpu);
        if (!ref->page) {
            kfree(ref);
            break;
        }

        r = ring_buffer_read_page(ref->buffer, &ref->page,
                      len, info->cpu, 1);
        if (r < 0) {
            ring_buffer_free_read_page(ref->buffer, ref->page);
            kfree(ref);
            break;
        }

        /*
         * zero out any left over data, this is going to
         * user land.
         */
        size = ring_buffer_page_len(ref->page);
        if (size < PAGE_SIZE)
            memset(ref->page + size, 0, PAGE_SIZE - size);

        page = virt_to_page(ref->page);

        spd.pages[i] = page;
        spd.partial[i].len = PAGE_SIZE;
        spd.partial[i].offset = 0;
        spd.partial[i].private = (unsigned long)ref;
        spd.nr_pages++;
        *ppos += PAGE_SIZE;

        entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);
    }

    trace_access_unlock(info->cpu);
    spd.nr_pages = i;

    /* did we read anything? */
    if (!spd.nr_pages) {
        if (flags & SPLICE_F_NONBLOCK)
            ret = -EAGAIN;
        else
            ret = 0;
        /* TODO: block */
        goto out;
    }

    ret = splice_to_pipe(pipe, &spd);
    splice_shrink_spd(&spd);
out:
    return ret;
}

static const struct file_operations tracing_buffers_fops = {
    .open       = tracing_buffers_open,
    .read       = tracing_buffers_read,
    .release    = tracing_buffers_release,
    .splice_read    = tracing_buffers_splice_read,
    .llseek     = no_llseek,
};

static ssize_t
tracing_stats_read(struct file *filp, char __user *ubuf,
           size_t count, loff_t *ppos)
{
    unsigned long cpu = (unsigned long)filp->private_data;
    struct trace_array *tr = &global_trace;
    struct trace_seq *s;
    unsigned long cnt;
    unsigned long long t;
    unsigned long usec_rem;

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

    trace_seq_init(s);

    cnt = ring_buffer_entries_cpu(tr->buffer, cpu);
    trace_seq_printf(s, "entries: %ld\n", cnt);

    cnt = ring_buffer_overrun_cpu(tr->buffer, cpu);
    trace_seq_printf(s, "overrun: %ld\n", cnt);

    cnt = ring_buffer_commit_overrun_cpu(tr->buffer, cpu);
    trace_seq_printf(s, "commit overrun: %ld\n", cnt);

    cnt = ring_buffer_bytes_cpu(tr->buffer, cpu);
    trace_seq_printf(s, "bytes: %ld\n", cnt);

    t = ns2usecs(ring_buffer_oldest_event_ts(tr->buffer, cpu));
    usec_rem = do_div(t, USEC_PER_SEC);
    trace_seq_printf(s, "oldest event ts: %5llu.%06lu\n", t, usec_rem);

    t = ns2usecs(ring_buffer_time_stamp(tr->buffer, cpu));
    usec_rem = do_div(t, USEC_PER_SEC);
    trace_seq_printf(s, "now ts: %5llu.%06lu\n", t, usec_rem);

    count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);

    kfree(s);

    return count;
}

static const struct file_operations tracing_stats_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_stats_read,
    .llseek     = generic_file_llseek,
};

#ifdef CONFIG_DYNAMIC_FTRACE

int __weak ftrace_arch_read_dyn_info(char *buf, int size)
{
    return 0;
}

static ssize_t
tracing_read_dyn_info(struct file *filp, char __user *ubuf,
          size_t cnt, loff_t *ppos)
{
    static char ftrace_dyn_info_buffer[1024];
    static DEFINE_MUTEX(dyn_info_mutex);
    unsigned long *p = filp->private_data;
    char *buf = ftrace_dyn_info_buffer;
    int size = ARRAY_SIZE(ftrace_dyn_info_buffer);
    int r;

    mutex_lock(&dyn_info_mutex);
    r = sprintf(buf, "%ld ", *p);

    r += ftrace_arch_read_dyn_info(buf+r, (size-1)-r);
    buf[r++] = '\n';

    r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);

    mutex_unlock(&dyn_info_mutex);

    return r;
}

static const struct file_operations tracing_dyn_info_fops = {
    .open       = tracing_open_generic,
    .read       = tracing_read_dyn_info,
    .llseek     = generic_file_llseek,
};
#endif

static struct dentry *d_tracer;

struct dentry *tracing_init_dentry(void)
{
    static int once;

    if (d_tracer)
        return d_tracer;

    if (!debugfs_initialized())
        return NULL;

    d_tracer = debugfs_create_dir("tracing", NULL);

    if (!d_tracer && !once) {
        once = 1;
        pr_warning("Could not create debugfs directory 'tracing'\n");
        return NULL;
    }

    return d_tracer;
}

static struct dentry *d_percpu;

struct dentry *tracing_dentry_percpu(void)
{
    static int once;
    struct dentry *d_tracer;

    if (d_percpu)
        return d_percpu;

    d_tracer = tracing_init_dentry();

    if (!d_tracer)
        return NULL;

    d_percpu = debugfs_create_dir("per_cpu", d_tracer);

    if (!d_percpu && !once) {
        once = 1;
        pr_warning("Could not create debugfs directory 'per_cpu'\n");
        return NULL;
    }

    return d_percpu;
}

static void tracing_init_debugfs_percpu(long cpu)
{
    struct dentry *d_percpu = tracing_dentry_percpu();
    struct dentry *d_cpu;
    char cpu_dir[30]; /* 30 characters should be more than enough */

    if (!d_percpu)
        return;

    snprintf(cpu_dir, 30, "cpu%ld", cpu);
    d_cpu = debugfs_create_dir(cpu_dir, d_percpu);
    if (!d_cpu) {
        pr_warning("Could not create debugfs '%s' entry\n", cpu_dir);
        return;
    }

    /* per cpu trace_pipe */
    trace_create_file("trace_pipe", 0444, d_cpu,
            (void *) cpu, &tracing_pipe_fops);

    /* per cpu trace */
    trace_create_file("trace", 0644, d_cpu,
            (void *) cpu, &tracing_fops);

    trace_create_file("trace_pipe_raw", 0444, d_cpu,
            (void *) cpu, &tracing_buffers_fops);

    trace_create_file("stats", 0444, d_cpu,
            (void *) cpu, &tracing_stats_fops);

    trace_create_file("buffer_size_kb", 0444, d_cpu,
            (void *) cpu, &tracing_entries_fops);
}

#ifdef CONFIG_FTRACE_SELFTEST
/* Let selftest have access to static functions in this file */
#include "trace_selftest.c"
#endif

struct trace_option_dentry {
    struct tracer_opt       *opt;
    struct tracer_flags     *flags;
    struct dentry           *entry;
};

static ssize_t
trace_options_read(struct file *filp, char __user *ubuf, size_t cnt,
            loff_t *ppos)
{
    struct trace_option_dentry *topt = filp->private_data;
    char *buf;

    if (topt->flags->val & topt->opt->bit)
        buf = "1\n";
    else
        buf = "0\n";

    return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
}

static ssize_t
trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt,
             loff_t *ppos)
{
    struct trace_option_dentry *topt = filp->private_data;
    unsigned long val;
    int ret;

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

    if (val != 0 && val != 1)
        return -EINVAL;

    if (!!(topt->flags->val & topt->opt->bit) != val) {
        mutex_lock(&trace_types_lock);
        ret = __set_tracer_option(current_trace, topt->flags,
                      topt->opt, !val);
        mutex_unlock(&trace_types_lock);
        if (ret)
            return ret;
    }

    *ppos += cnt;

    return cnt;
}


static const struct file_operations trace_options_fops = {
    .open = tracing_open_generic,
    .read = trace_options_read,
    .write = trace_options_write,
    .llseek = generic_file_llseek,
};

static ssize_t
trace_options_core_read(struct file *filp, char __user *ubuf, size_t cnt,
            loff_t *ppos)
{
    long index = (long)filp->private_data;
    char *buf;

    if (trace_flags & (1 << index))
        buf = "1\n";
    else
        buf = "0\n";

    return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
}

static ssize_t
trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
             loff_t *ppos)
{
    long index = (long)filp->private_data;
    unsigned long val;
    int ret;

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

    if (val != 0 && val != 1)
        return -EINVAL;
    set_tracer_flags(1 << index, val);

    *ppos += cnt;

    return cnt;
}

static const struct file_operations trace_options_core_fops = {
    .open = tracing_open_generic,
    .read = trace_options_core_read,
    .write = trace_options_core_write,
    .llseek = generic_file_llseek,
};

struct dentry *trace_create_file(const char *name,
                 umode_t mode,
                 struct dentry *parent,
                 void *data,
                 const struct file_operations *fops)
{
    struct dentry *ret;

    ret = debugfs_create_file(name, mode, parent, data, fops);
    if (!ret)
        pr_warning("Could not create debugfs '%s' entry\n", name);

    return ret;
}


static struct dentry *trace_options_init_dentry(void)
{
    struct dentry *d_tracer;
    static struct dentry *t_options;

    if (t_options)
        return t_options;

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

    t_options = debugfs_create_dir("options", d_tracer);
    if (!t_options) {
        pr_warning("Could not create debugfs directory 'options'\n");
        return NULL;
    }

    return t_options;
}

static void
create_trace_option_file(struct trace_option_dentry *topt,
             struct tracer_flags *flags,
             struct tracer_opt *opt)
{
    struct dentry *t_options;

    t_options = trace_options_init_dentry();
    if (!t_options)
        return;

    topt->flags = flags;
    topt->opt = opt;

    topt->entry = trace_create_file(opt->name, 0644, t_options, topt,
                    &trace_options_fops);

}

static struct trace_option_dentry *
create_trace_option_files(struct tracer *tracer)
{
    struct trace_option_dentry *topts;
    struct tracer_flags *flags;
    struct tracer_opt *opts;
    int cnt;

    if (!tracer)
        return NULL;

    flags = tracer->flags;

    if (!flags || !flags->opts)
        return NULL;

    opts = flags->opts;

    for (cnt = 0; opts[cnt].name; cnt++)
        ;

    topts = kcalloc(cnt + 1, sizeof(*topts), GFP_KERNEL);
    if (!topts)
        return NULL;

    for (cnt = 0; opts[cnt].name; cnt++)
        create_trace_option_file(&topts[cnt], flags,
                     &opts[cnt]);

    return topts;
}

static void
destroy_trace_option_files(struct trace_option_dentry *topts)
{
    int cnt;

    if (!topts)
        return;

    for (cnt = 0; topts[cnt].opt; cnt++) {
        if (topts[cnt].entry)
            debugfs_remove(topts[cnt].entry);
    }

    kfree(topts);
}

static struct dentry *
create_trace_option_core_file(const char *option, long index)
{
    struct dentry *t_options;

    t_options = trace_options_init_dentry();
    if (!t_options)
        return NULL;

    return trace_create_file(option, 0644, t_options, (void *)index,
                    &trace_options_core_fops);
}

static __init void create_trace_options_dir(void)
{
    struct dentry *t_options;
    int i;

    t_options = trace_options_init_dentry();
    if (!t_options)
        return;

    for (i = 0; trace_options[i]; i++)
        create_trace_option_core_file(trace_options[i], i);
}

static ssize_t
rb_simple_read(struct file *filp, char __user *ubuf,
           size_t cnt, loff_t *ppos)
{
    struct trace_array *tr = filp->private_data;
    struct ring_buffer *buffer = tr->buffer;
    char buf[64];
    int r;

    if (buffer)
        r = ring_buffer_record_is_on(buffer);
    else
        r = 0;

    r = sprintf(buf, "%d\n", r);

    return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static ssize_t
rb_simple_write(struct file *filp, const char __user *ubuf,
        size_t cnt, loff_t *ppos)
{
    struct trace_array *tr = filp->private_data;
    struct ring_buffer *buffer = tr->buffer;
    unsigned long val;
    int ret;

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

    if (buffer) {
        if (val)
            ring_buffer_record_on(buffer);
        else
            ring_buffer_record_off(buffer);
    }

    (*ppos)++;

    return cnt;
}

static const struct file_operations rb_simple_fops = {
    .open       = tracing_open_generic,
    .read       = rb_simple_read,
    .write      = rb_simple_write,
    .llseek     = default_llseek,
};

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

    trace_access_lock_init();

    d_tracer = tracing_init_dentry();

    trace_create_file("tracing_enabled", 0644, d_tracer,
            &global_trace, &tracing_ctrl_fops);

    trace_create_file("trace_options", 0644, d_tracer,
            NULL, &tracing_iter_fops);

    trace_create_file("tracing_cpumask", 0644, d_tracer,
            NULL, &tracing_cpumask_fops);

    trace_create_file("trace", 0644, d_tracer,
            (void *) TRACE_PIPE_ALL_CPU, &tracing_fops);

    trace_create_file("available_tracers", 0444, d_tracer,
            &global_trace, &show_traces_fops);

    trace_create_file("current_tracer", 0644, d_tracer,
            &global_trace, &set_tracer_fops);

#ifdef CONFIG_TRACER_MAX_TRACE
    trace_create_file("tracing_max_latency", 0644, d_tracer,
            &tracing_max_latency, &tracing_max_lat_fops);
#endif

    trace_create_file("tracing_thresh", 0644, d_tracer,
            &tracing_thresh, &tracing_max_lat_fops);

    trace_create_file("README", 0444, d_tracer,
            NULL, &tracing_readme_fops);

    trace_create_file("trace_pipe", 0444, d_tracer,
            (void *) TRACE_PIPE_ALL_CPU, &tracing_pipe_fops);

    trace_create_file("buffer_size_kb", 0644, d_tracer,
            (void *) RING_BUFFER_ALL_CPUS, &tracing_entries_fops);

    trace_create_file("buffer_total_size_kb", 0444, d_tracer,
            &global_trace, &tracing_total_entries_fops);

    trace_create_file("free_buffer", 0644, d_tracer,
            &global_trace, &tracing_free_buffer_fops);

    trace_create_file("trace_marker", 0220, d_tracer,
            NULL, &tracing_mark_fops);

    trace_create_file("saved_cmdlines", 0444, d_tracer,
            NULL, &tracing_saved_cmdlines_fops);

    trace_create_file("trace_clock", 0644, d_tracer, NULL,
              &trace_clock_fops);

    trace_create_file("tracing_on", 0644, d_tracer,
                &global_trace, &rb_simple_fops);

#ifdef CONFIG_DYNAMIC_FTRACE
    trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
            &ftrace_update_tot_cnt, &tracing_dyn_info_fops);
#endif

    create_trace_options_dir();

    for_each_tracing_cpu(cpu)
        tracing_init_debugfs_percpu(cpu);

    return 0;
}

static int trace_panic_handler(struct notifier_block *this,
                   unsigned long event, void *unused)
{
    if (ftrace_dump_on_oops)
        ftrace_dump(ftrace_dump_on_oops);
    return NOTIFY_OK;
}

static struct notifier_block trace_panic_notifier = {
    .notifier_call  = trace_panic_handler,
    .next           = NULL,
    .priority       = 150   /* priority: INT_MAX >= x >= 0 */
};

static int trace_die_handler(struct notifier_block *self,
                 unsigned long val,
                 void *data)
{
    switch (val) {
    case DIE_OOPS:
        if (ftrace_dump_on_oops)
            ftrace_dump(ftrace_dump_on_oops);
        break;
    default:
        break;
    }
    return NOTIFY_OK;
}

static struct notifier_block trace_die_notifier = {
    .notifier_call = trace_die_handler,
    .priority = 200
};

/*
 * printk is set to max of 1024, we really don't need it that big.
 * Nothing should be printing 1000 characters anyway.
 */
#define TRACE_MAX_PRINT     1000

/*
 * Define here KERN_TRACE so that we have one place to modify
 * it if we decide to change what log level the ftrace dump
 * should be at.
 */
#define KERN_TRACE      KERN_EMERG

void
trace_printk_seq(struct trace_seq *s)
{
    /* Probably should print a warning here. */
    if (s->len >= 1000)
        s->len = 1000;

    /* should be zero ended, but we are paranoid. */
    s->buffer[s->len] = 0;

    printk(KERN_TRACE "%s", s->buffer);

    trace_seq_init(s);
}

void trace_init_global_iter(struct trace_iterator *iter)
{
    iter->tr = &global_trace;
    iter->trace = current_trace;
    iter->cpu_file = TRACE_PIPE_ALL_CPU;
}

static void
__ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode)
{
    static arch_spinlock_t ftrace_dump_lock =
        (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
    /* use static because iter can be a bit big for the stack */
    static struct trace_iterator iter;
    unsigned int old_userobj;
    static int dump_ran;
    unsigned long flags;
    int cnt = 0, cpu;

    /* only one dump */
    local_irq_save(flags);
    arch_spin_lock(&ftrace_dump_lock);
    if (dump_ran)
        goto out;

    dump_ran = 1;

    tracing_off();

    /* Did function tracer already get disabled? */
    if (ftrace_is_dead()) {
        printk("# WARNING: FUNCTION TRACING IS CORRUPTED\n");
        printk("#          MAY BE MISSING FUNCTION EVENTS\n");
    }

    if (disable_tracing)
        ftrace_kill();

    trace_init_global_iter(&iter);

    for_each_tracing_cpu(cpu) {
        atomic_inc(&iter.tr->data[cpu]->disabled);
    }

    old_userobj = trace_flags & TRACE_ITER_SYM_USEROBJ;

    /* don't look at user memory in panic mode */
    trace_flags &= ~TRACE_ITER_SYM_USEROBJ;

    /* Simulate the iterator */
    iter.tr = &global_trace;
    iter.trace = current_trace;

    switch (oops_dump_mode) {
    case DUMP_ALL:
        iter.cpu_file = TRACE_PIPE_ALL_CPU;
        break;
    case DUMP_ORIG:
        iter.cpu_file = raw_smp_processor_id();
        break;
    case DUMP_NONE:
        goto out_enable;
    default:
        printk(KERN_TRACE "Bad dumping mode, switching to all CPUs dump\n");
        iter.cpu_file = TRACE_PIPE_ALL_CPU;
    }

    printk(KERN_TRACE "Dumping ftrace buffer:\n");

    /*
     * We need to stop all tracing on all CPUS to read the
     * the next buffer. This is a bit expensive, but is
     * not done often. We fill all what we can read,
     * and then release the locks again.
     */

    while (!trace_empty(&iter)) {

        if (!cnt)
            printk(KERN_TRACE "---------------------------------\n");

        cnt++;

        /* reset all but tr, trace, and overruns */
        memset(&iter.seq, 0,
               sizeof(struct trace_iterator) -
               offsetof(struct trace_iterator, seq));
        iter.iter_flags |= TRACE_FILE_LAT_FMT;
        iter.pos = -1;

        if (trace_find_next_entry_inc(&iter) != NULL) {
            int ret;

            ret = print_trace_line(&iter);
            if (ret != TRACE_TYPE_NO_CONSUME)
                trace_consume(&iter);
        }
        touch_nmi_watchdog();

        trace_printk_seq(&iter.seq);
    }

    if (!cnt)
        printk(KERN_TRACE "   (ftrace buffer empty)\n");
    else
        printk(KERN_TRACE "---------------------------------\n");

 out_enable:
    /* Re-enable tracing if requested */
    if (!disable_tracing) {
        trace_flags |= old_userobj;

        for_each_tracing_cpu(cpu) {
            atomic_dec(&iter.tr->data[cpu]->disabled);
        }
        tracing_on();
    }

 out:
    arch_spin_unlock(&ftrace_dump_lock);
    local_irq_restore(flags);
}

/* By default: disable tracing after the dump */
void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
{
    __ftrace_dump(true, oops_dump_mode);
}
EXPORT_SYMBOL_GPL(ftrace_dump);

__init static int tracer_alloc_buffers(void)
{
    int ring_buf_size;
    enum ring_buffer_flags rb_flags;
    int i;
    int ret = -ENOMEM;


    if (!alloc_cpumask_var(&tracing_buffer_mask, GFP_KERNEL))
        goto out;

    if (!alloc_cpumask_var(&tracing_cpumask, GFP_KERNEL))
        goto out_free_buffer_mask;

    /* Only allocate trace_printk buffers if a trace_printk exists */
    if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
        trace_printk_init_buffers();

    /* To save memory, keep the ring buffer size to its minimum */
    if (ring_buffer_expanded)
        ring_buf_size = trace_buf_size;
    else
        ring_buf_size = 1;

    rb_flags = trace_flags & TRACE_ITER_OVERWRITE ? RB_FL_OVERWRITE : 0;

    cpumask_copy(tracing_buffer_mask, cpu_possible_mask);
    cpumask_copy(tracing_cpumask, cpu_all_mask);

    /* TODO: make the number of buffers hot pluggable with CPUS */
    global_trace.buffer = ring_buffer_alloc(ring_buf_size, rb_flags);
    if (!global_trace.buffer) {
        printk(KERN_ERR "tracer: failed to allocate ring buffer!\n");
        WARN_ON(1);
        goto out_free_cpumask;
    }
    if (global_trace.buffer_disabled)
        tracing_off();


#ifdef CONFIG_TRACER_MAX_TRACE
    max_tr.buffer = ring_buffer_alloc(1, rb_flags);
    if (!max_tr.buffer) {
        printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n");
        WARN_ON(1);
        ring_buffer_free(global_trace.buffer);
        goto out_free_cpumask;
    }
#endif

    /* Allocate the first page for all buffers */
    for_each_tracing_cpu(i) {
        global_trace.data[i] = &per_cpu(global_trace_cpu, i);
        max_tr.data[i] = &per_cpu(max_tr_data, i);
    }

    set_buffer_entries(&global_trace,
               ring_buffer_size(global_trace.buffer, 0));
#ifdef CONFIG_TRACER_MAX_TRACE
    set_buffer_entries(&max_tr, 1);
#endif

    trace_init_cmdlines();

    register_tracer(&nop_trace);
    current_trace = &nop_trace;
    /* All seems OK, enable tracing */
    tracing_disabled = 0;

    atomic_notifier_chain_register(&panic_notifier_list,
                       &trace_panic_notifier);

    register_die_notifier(&trace_die_notifier);

    return 0;

out_free_cpumask:
    free_cpumask_var(tracing_cpumask);
out_free_buffer_mask:
    free_cpumask_var(tracing_buffer_mask);
out:
    return ret;
}

__init static int clear_boot_tracer(void)
{
    /*
     * The default tracer at boot buffer is an init section.
     * This function is called in lateinit. If we did not
     * find the boot tracer, then clear it out, to prevent
     * later registration from accessing the buffer that is
     * about to be freed.
     */
    if (!default_bootup_tracer)
        return 0;

    printk(KERN_INFO "ftrace bootup tracer '%s' not registered.\n",
           default_bootup_tracer);
    default_bootup_tracer = NULL;

    return 0;
}

early_initcall(tracer_alloc_buffers);
fs_initcall(tracer_init_debugfs);
late_initcall(clear_boot_tracer);