ftrace: fix build failure

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / trace / ftrace.c

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

#include <linux/stop_machine.h>
#include <linux/clocksource.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/hardirq.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <linux/kprobes.h>
#include <linux/ftrace.h>
#include <linux/sysctl.h>
#include <linux/ctype.h>
#include <linux/hash.h>
#include <linux/list.h>

#include <asm/ftrace.h>

#include "trace.h"

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

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

static DEFINE_SPINLOCK(ftrace_lock);
static DEFINE_MUTEX(ftrace_sysctl_lock);

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

static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;

static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
{
        struct ftrace_ops *op = ftrace_list;

        /* in case someone actually ports this to alpha! */
        read_barrier_depends();

        while (op != &ftrace_list_end) {
                /* silly alpha */
                read_barrier_depends();
                op->func(ip, parent_ip);
                op = op->next;
        };
}

/**
 * clear_ftrace_function - reset the ftrace function
 *
 * This NULLs the ftrace function and in essence stops
 * tracing.  There may be lag
 */
void clear_ftrace_function(void)
{
        ftrace_trace_function = ftrace_stub;
}

static int __register_ftrace_function(struct ftrace_ops *ops)
{
        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);

        ops->next = ftrace_list;
        /*
         * We are entering ops into the ftrace_list but another
         * CPU might be walking that list. We need to make sure
         * the ops->next pointer is valid before another CPU sees
         * the ops pointer included into the ftrace_list.
         */
        smp_wmb();
        ftrace_list = ops;

        if (ftrace_enabled) {
                /*
                 * For one func, simply call it directly.
                 * For more than one func, call the chain.
                 */
                if (ops->next == &ftrace_list_end)
                        ftrace_trace_function = ops->func;
                else
                        ftrace_trace_function = ftrace_list_func;
        }

        spin_unlock(&ftrace_lock);

        return 0;
}

static int __unregister_ftrace_function(struct ftrace_ops *ops)
{
        struct ftrace_ops **p;
        int ret = 0;

        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);

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

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

        if (*p != ops) {
                ret = -1;
                goto out;
        }

        *p = (*p)->next;

        if (ftrace_enabled) {
                /* If we only have one func left, then call that directly */
                if (ftrace_list == &ftrace_list_end ||
                    ftrace_list->next == &ftrace_list_end)
                        ftrace_trace_function = ftrace_list->func;
        }

 out:
        spin_unlock(&ftrace_lock);

        return ret;
}

#ifdef CONFIG_DYNAMIC_FTRACE

#ifndef CONFIG_FTRACE_MCOUNT_RECORD
/*
 * The hash lock is only needed when the recording of the mcount
 * callers are dynamic. That is, by the caller themselves and
 * not recorded via the compilation.
 */
static DEFINE_SPINLOCK(ftrace_hash_lock);
#define ftrace_hash_lock(flags)   spin_lock_irqsave(&ftrace_hash_lock, flags)
#define ftrace_hash_unlock(flags) spin_lock_irqsave(&ftrace_hash_lock, flags)
#else
/* This is protected via the ftrace_lock with MCOUNT_RECORD. */
#define ftrace_hash_lock(flags)   do { (void)flags; } while (0)
#define ftrace_hash_unlock(flags) do { } while(0)
#endif

static struct task_struct *ftraced_task;

enum {
        FTRACE_ENABLE_CALLS             = (1 << 0),
        FTRACE_DISABLE_CALLS            = (1 << 1),
        FTRACE_UPDATE_TRACE_FUNC        = (1 << 2),
        FTRACE_ENABLE_MCOUNT            = (1 << 3),
        FTRACE_DISABLE_MCOUNT           = (1 << 4),
};

static int ftrace_filtered;
static int tracing_on;
static int frozen_record_count;

static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];

static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);

static DEFINE_MUTEX(ftraced_lock);
static DEFINE_MUTEX(ftrace_regex_lock);

struct ftrace_page {
        struct ftrace_page      *next;
        unsigned long           index;
        struct dyn_ftrace       records[];
};

#define ENTRIES_PER_PAGE \
  ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))

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

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

static int ftraced_trigger;
static int ftraced_suspend;
static int ftraced_stop;

static int ftrace_record_suspend;

static struct dyn_ftrace *ftrace_free_records;


#ifdef CONFIG_KPROBES
static inline void freeze_record(struct dyn_ftrace *rec)
{
        if (!(rec->flags & FTRACE_FL_FROZEN)) {
                rec->flags |= FTRACE_FL_FROZEN;
                frozen_record_count++;
        }
}

static inline void unfreeze_record(struct dyn_ftrace *rec)
{
        if (rec->flags & FTRACE_FL_FROZEN) {
                rec->flags &= ~FTRACE_FL_FROZEN;
                frozen_record_count--;
        }
}

static inline int record_frozen(struct dyn_ftrace *rec)
{
        return rec->flags & FTRACE_FL_FROZEN;
}
#else
# define freeze_record(rec)                     ({ 0; })
# define unfreeze_record(rec)                   ({ 0; })
# define record_frozen(rec)                     ({ 0; })
#endif /* CONFIG_KPROBES */

int skip_trace(unsigned long ip)
{
        unsigned long fl;
        struct dyn_ftrace *rec;
        struct hlist_node *t;
        struct hlist_head *head;

        if (frozen_record_count == 0)
                return 0;

        head = &ftrace_hash[hash_long(ip, FTRACE_HASHBITS)];
        hlist_for_each_entry_rcu(rec, t, head, node) {
                if (rec->ip == ip) {
                        if (record_frozen(rec)) {
                                if (rec->flags & FTRACE_FL_FAILED)
                                        return 1;

                                if (!(rec->flags & FTRACE_FL_CONVERTED))
                                        return 1;

                                if (!tracing_on || !ftrace_enabled)
                                        return 1;

                                if (ftrace_filtered) {
                                        fl = rec->flags & (FTRACE_FL_FILTER |
                                                           FTRACE_FL_NOTRACE);
                                        if (!fl || (fl & FTRACE_FL_NOTRACE))
                                                return 1;
                                }
                        }
                        break;
                }
        }

        return 0;
}

static inline int
ftrace_ip_in_hash(unsigned long ip, unsigned long key)
{
        struct dyn_ftrace *p;
        struct hlist_node *t;
        int found = 0;

        hlist_for_each_entry_rcu(p, t, &ftrace_hash[key], node) {
                if (p->ip == ip) {
                        found = 1;
                        break;
                }
        }

        return found;
}

static inline void
ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
{
        hlist_add_head_rcu(&node->node, &ftrace_hash[key]);
}

/* called from kstop_machine */
static inline void ftrace_del_hash(struct dyn_ftrace *node)
{
        hlist_del(&node->node);
}

static void ftrace_free_rec(struct dyn_ftrace *rec)
{
        rec->ip = (unsigned long)ftrace_free_records;
        ftrace_free_records = rec;
        rec->flags |= FTRACE_FL_FREE;
}

void ftrace_release(void *start, unsigned long size)
{
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
        unsigned long s = (unsigned long)start;
        unsigned long e = s + size;
        int i;

        if (ftrace_disabled || !start)
                return;

        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);

        for (pg = ftrace_pages_start; pg; pg = pg->next) {
                for (i = 0; i < pg->index; i++) {
                        rec = &pg->records[i];

                        if ((rec->ip >= s) && (rec->ip < e))
                                ftrace_free_rec(rec);
                }
        }
        spin_unlock(&ftrace_lock);

}

static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
{
        struct dyn_ftrace *rec;

        /* First check for freed records */
        if (ftrace_free_records) {
                rec = ftrace_free_records;

                if (unlikely(!(rec->flags & FTRACE_FL_FREE))) {
                        WARN_ON_ONCE(1);
                        ftrace_free_records = NULL;
                        ftrace_disabled = 1;
                        ftrace_enabled = 0;
                        return NULL;
                }

                ftrace_free_records = (void *)rec->ip;
                memset(rec, 0, sizeof(*rec));
                return rec;
        }

        if (ftrace_pages->index == ENTRIES_PER_PAGE) {
                if (!ftrace_pages->next)
                        return NULL;
                ftrace_pages = ftrace_pages->next;
        }

        return &ftrace_pages->records[ftrace_pages->index++];
}

static void
ftrace_record_ip(unsigned long ip)
{
        struct dyn_ftrace *node;
        unsigned long flags;
        unsigned long key;
        int resched;
        int cpu;

        if (!ftrace_enabled || ftrace_disabled)
                return;

        resched = need_resched();
        preempt_disable_notrace();

        /*
         * We simply need to protect against recursion.
         * Use the the raw version of smp_processor_id and not
         * __get_cpu_var which can call debug hooks that can
         * cause a recursive crash here.
         */
        cpu = raw_smp_processor_id();
        per_cpu(ftrace_shutdown_disable_cpu, cpu)++;
        if (per_cpu(ftrace_shutdown_disable_cpu, cpu) != 1)
                goto out;

        if (unlikely(ftrace_record_suspend))
                goto out;

        key = hash_long(ip, FTRACE_HASHBITS);

        WARN_ON_ONCE(key >= FTRACE_HASHSIZE);

        if (ftrace_ip_in_hash(ip, key))
                goto out;

        ftrace_hash_lock(flags);

        /* This ip may have hit the hash before the lock */
        if (ftrace_ip_in_hash(ip, key))
                goto out_unlock;

        node = ftrace_alloc_dyn_node(ip);
        if (!node)
                goto out_unlock;

        node->ip = ip;

        ftrace_add_hash(node, key);

        ftraced_trigger = 1;

 out_unlock:
        ftrace_hash_unlock(flags);
 out:
        per_cpu(ftrace_shutdown_disable_cpu, cpu)--;

        /* prevent recursion with scheduler */
        if (resched)
                preempt_enable_no_resched_notrace();
        else
                preempt_enable_notrace();
}

#define FTRACE_ADDR ((long)(ftrace_caller))

static int
__ftrace_replace_code(struct dyn_ftrace *rec,
                      unsigned char *old, unsigned char *new, int enable)
{
        unsigned long ip, fl;

        ip = rec->ip;

        if (ftrace_filtered && enable) {
                /*
                 * If filtering is on:
                 *
                 * If this record is set to be filtered and
                 * is enabled then do nothing.
                 *
                 * If this record is set to be filtered and
                 * it is not enabled, enable it.
                 *
                 * If this record is not set to be filtered
                 * and it is not enabled do nothing.
                 *
                 * If this record is set not to trace then
                 * do nothing.
                 *
                 * If this record is set not to trace and
                 * it is enabled then disable it.
                 *
                 * If this record is not set to be filtered and
                 * it is enabled, disable it.
                 */

                fl = rec->flags & (FTRACE_FL_FILTER | FTRACE_FL_NOTRACE |
                                   FTRACE_FL_ENABLED);

                if ((fl ==  (FTRACE_FL_FILTER | FTRACE_FL_ENABLED)) ||
                    (fl ==  (FTRACE_FL_FILTER | FTRACE_FL_NOTRACE)) ||
                    !fl || (fl == FTRACE_FL_NOTRACE))
                        return 0;

                /*
                 * If it is enabled disable it,
                 * otherwise enable it!
                 */
                if (fl & FTRACE_FL_ENABLED) {
                        /* swap new and old */
                        new = old;
                        old = ftrace_call_replace(ip, FTRACE_ADDR);
                        rec->flags &= ~FTRACE_FL_ENABLED;
                } else {
                        new = ftrace_call_replace(ip, FTRACE_ADDR);
                        rec->flags |= FTRACE_FL_ENABLED;
                }
        } else {

                if (enable) {
                        /*
                         * If this record is set not to trace and is
                         * not enabled, do nothing.
                         */
                        fl = rec->flags & (FTRACE_FL_NOTRACE | FTRACE_FL_ENABLED);
                        if (fl == FTRACE_FL_NOTRACE)
                                return 0;

                        new = ftrace_call_replace(ip, FTRACE_ADDR);
                } else
                        old = ftrace_call_replace(ip, FTRACE_ADDR);

                if (enable) {
                        if (rec->flags & FTRACE_FL_ENABLED)
                                return 0;
                        rec->flags |= FTRACE_FL_ENABLED;
                } else {
                        if (!(rec->flags & FTRACE_FL_ENABLED))
                                return 0;
                        rec->flags &= ~FTRACE_FL_ENABLED;
                }
        }

        return ftrace_modify_code(ip, old, new);
}

static void ftrace_replace_code(int enable)
{
        int i, failed;
        unsigned char *new = NULL, *old = NULL;
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;

        if (enable)
                old = ftrace_nop_replace();
        else
                new = ftrace_nop_replace();

        for (pg = ftrace_pages_start; pg; pg = pg->next) {
                for (i = 0; i < pg->index; i++) {
                        rec = &pg->records[i];

                        /* don't modify code that has already faulted */
                        if (rec->flags & FTRACE_FL_FAILED)
                                continue;

                        /* ignore updates to this record's mcount site */
                        if (get_kprobe((void *)rec->ip)) {
                                freeze_record(rec);
                                continue;
                        } else {
                                unfreeze_record(rec);
                        }

                        failed = __ftrace_replace_code(rec, old, new, enable);
                        if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {
                                rec->flags |= FTRACE_FL_FAILED;
                                if ((system_state == SYSTEM_BOOTING) ||
                                    !core_kernel_text(rec->ip)) {
                                        ftrace_del_hash(rec);
                                        ftrace_free_rec(rec);
                                }
                        }
                }
        }
}

static void ftrace_shutdown_replenish(void)
{
        if (ftrace_pages->next)
                return;

        /* allocate another page */
        ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
}

static int
ftrace_code_disable(struct dyn_ftrace *rec)
{
        unsigned long ip;
        unsigned char *nop, *call;
        int failed;

        ip = rec->ip;

        nop = ftrace_nop_replace();
        call = ftrace_call_replace(ip, MCOUNT_ADDR);

        failed = ftrace_modify_code(ip, call, nop);
        if (failed) {
                rec->flags |= FTRACE_FL_FAILED;
                return 0;
        }
        return 1;
}

static int __ftrace_update_code(void *ignore);

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

        if (*command & FTRACE_ENABLE_CALLS) {
                /*
                 * Update any recorded ips now that we have the
                 * machine stopped
                 */
                __ftrace_update_code(NULL);
                ftrace_replace_code(1);
                tracing_on = 1;
        } else if (*command & FTRACE_DISABLE_CALLS) {
                ftrace_replace_code(0);
                tracing_on = 0;
        }

        if (*command & FTRACE_UPDATE_TRACE_FUNC)
                ftrace_update_ftrace_func(ftrace_trace_function);

        if (*command & FTRACE_ENABLE_MCOUNT) {
                addr = (unsigned long)ftrace_record_ip;
                ftrace_mcount_set(&addr);
        } else if (*command & FTRACE_DISABLE_MCOUNT) {
                addr = (unsigned long)ftrace_stub;
                ftrace_mcount_set(&addr);
        }

        return 0;
}

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

void ftrace_disable_daemon(void)
{
        /* Stop the daemon from calling kstop_machine */
        mutex_lock(&ftraced_lock);
        ftraced_stop = 1;
        mutex_unlock(&ftraced_lock);

        ftrace_force_update();
}

void ftrace_enable_daemon(void)
{
        mutex_lock(&ftraced_lock);
        ftraced_stop = 0;
        mutex_unlock(&ftraced_lock);

        ftrace_force_update();
}

static ftrace_func_t saved_ftrace_func;

static void ftrace_startup(void)
{
        int command = 0;

        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftraced_lock);
        ftraced_suspend++;
        if (ftraced_suspend == 1)
                command |= FTRACE_ENABLE_CALLS;

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

        if (!command || !ftrace_enabled)
                goto out;

        ftrace_run_update_code(command);
 out:
        mutex_unlock(&ftraced_lock);
}

static void ftrace_shutdown(void)
{
        int command = 0;

        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftraced_lock);
        ftraced_suspend--;
        if (!ftraced_suspend)
                command |= FTRACE_DISABLE_CALLS;

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

        if (!command || !ftrace_enabled)
                goto out;

        ftrace_run_update_code(command);
 out:
        mutex_unlock(&ftraced_lock);
}

static void ftrace_startup_sysctl(void)
{
        int command = FTRACE_ENABLE_MCOUNT;

        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftraced_lock);
        /* Force update next time */
        saved_ftrace_func = NULL;
        /* ftraced_suspend is true if we want ftrace running */
        if (ftraced_suspend)
                command |= FTRACE_ENABLE_CALLS;

        ftrace_run_update_code(command);
        mutex_unlock(&ftraced_lock);
}

static void ftrace_shutdown_sysctl(void)
{
        int command = FTRACE_DISABLE_MCOUNT;

        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftraced_lock);
        /* ftraced_suspend is true if ftrace is running */
        if (ftraced_suspend)
                command |= FTRACE_DISABLE_CALLS;

        ftrace_run_update_code(command);
        mutex_unlock(&ftraced_lock);
}

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

static int __ftrace_update_code(void *ignore)
{
        int i, save_ftrace_enabled;
        cycle_t start, stop;
        struct dyn_ftrace *p;
        struct hlist_node *t, *n;
        struct hlist_head *head, temp_list;

        /* Don't be recording funcs now */
        ftrace_record_suspend++;
        save_ftrace_enabled = ftrace_enabled;
        ftrace_enabled = 0;

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

        /* No locks needed, the machine is stopped! */
        for (i = 0; i < FTRACE_HASHSIZE; i++) {
                INIT_HLIST_HEAD(&temp_list);
                head = &ftrace_hash[i];

                /* all CPUS are stopped, we are safe to modify code */
                hlist_for_each_entry_safe(p, t, n, head, node) {
                        /* Skip over failed records which have not been
                         * freed. */
                        if (p->flags & FTRACE_FL_FAILED)
                                continue;

                        /* Unconverted records are always at the head of the
                         * hash bucket. Once we encounter a converted record,
                         * simply skip over to the next bucket. Saves ftraced
                         * some processor cycles (ftrace does its bid for
                         * global warming :-p ). */
                        if (p->flags & (FTRACE_FL_CONVERTED))
                                break;

                        /* Ignore updates to this record's mcount site.
                         * Reintroduce this record at the head of this
                         * bucket to attempt to "convert" it again if
                         * the kprobe on it is unregistered before the
                         * next run. */
                        if (get_kprobe((void *)p->ip)) {
                                ftrace_del_hash(p);
                                INIT_HLIST_NODE(&p->node);
                                hlist_add_head(&p->node, &temp_list);
                                freeze_record(p);
                                continue;
                        } else {
                                unfreeze_record(p);
                        }

                        /* convert record (i.e, patch mcount-call with NOP) */
                        if (ftrace_code_disable(p)) {
                                p->flags |= FTRACE_FL_CONVERTED;
                                ftrace_update_cnt++;
                        } else {
                                if ((system_state == SYSTEM_BOOTING) ||
                                    !core_kernel_text(p->ip)) {
                                        ftrace_del_hash(p);
                                        ftrace_free_rec(p);
                                }
                        }
                }

                hlist_for_each_entry_safe(p, t, n, &temp_list, node) {
                        hlist_del(&p->node);
                        INIT_HLIST_NODE(&p->node);
                        hlist_add_head(&p->node, head);
                }
        }

        stop = ftrace_now(raw_smp_processor_id());
        ftrace_update_time = stop - start;
        ftrace_update_tot_cnt += ftrace_update_cnt;
        ftraced_trigger = 0;

        ftrace_enabled = save_ftrace_enabled;
        ftrace_record_suspend--;

        return 0;
}

static int ftrace_update_code(void)
{
        if (unlikely(ftrace_disabled) ||
            !ftrace_enabled || !ftraced_trigger)
                return 0;

        stop_machine(__ftrace_update_code, NULL, NULL);

        return 1;
}

static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
{
        struct ftrace_page *pg;
        int cnt;
        int i;

        /* allocate a few pages */
        ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
        if (!ftrace_pages_start)
                return -1;

        /*
         * Allocate a few more pages.
         *
         * TODO: have some parser search vmlinux before
         *   final linking to find all calls to ftrace.
         *   Then we can:
         *    a) know how many pages to allocate.
         *     and/or
         *    b) set up the table then.
         *
         *  The dynamic code is still necessary for
         *  modules.
         */

        pg = ftrace_pages = ftrace_pages_start;

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

        for (i = 0; i < cnt; i++) {
                pg->next = (void *)get_zeroed_page(GFP_KERNEL);

                /* If we fail, we'll try later anyway */
                if (!pg->next)
                        break;

                pg = pg->next;
        }

        return 0;
}

enum {
        FTRACE_ITER_FILTER      = (1 << 0),
        FTRACE_ITER_CONT        = (1 << 1),
        FTRACE_ITER_NOTRACE     = (1 << 2),
        FTRACE_ITER_FAILURES    = (1 << 3),
};

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

struct ftrace_iterator {
        loff_t                  pos;
        struct ftrace_page      *pg;
        unsigned                idx;
        unsigned                flags;
        unsigned char           buffer[FTRACE_BUFF_MAX+1];
        unsigned                buffer_idx;
        unsigned                filtered;
};

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

        (*pos)++;

        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);
 retry:
        if (iter->idx >= iter->pg->index) {
                if (iter->pg->next) {
                        iter->pg = iter->pg->next;
                        iter->idx = 0;
                        goto retry;
                }
        } else {
                rec = &iter->pg->records[iter->idx++];
                if ((rec->flags & FTRACE_FL_FREE) ||

                    (!(iter->flags & FTRACE_ITER_FAILURES) &&
                     (rec->flags & FTRACE_FL_FAILED)) ||

                    ((iter->flags & FTRACE_ITER_FAILURES) &&
                     !(rec->flags & FTRACE_FL_FAILED)) ||

                    ((iter->flags & FTRACE_ITER_NOTRACE) &&
                     !(rec->flags & FTRACE_FL_NOTRACE))) {
                        rec = NULL;
                        goto retry;
                }
        }
        spin_unlock(&ftrace_lock);

        iter->pos = *pos;

        return rec;
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
        struct ftrace_iterator *iter = m->private;
        void *p = NULL;
        loff_t l = -1;

        if (*pos != iter->pos) {
                for (p = t_next(m, p, &l); p && l < *pos; p = t_next(m, p, &l))
                        ;
        } else {
                l = *pos;
                p = t_next(m, p, &l);
        }

        return p;
}

static void t_stop(struct seq_file *m, void *p)
{
}

static int t_show(struct seq_file *m, void *v)
{
        struct dyn_ftrace *rec = v;
        char str[KSYM_SYMBOL_LEN];

        if (!rec)
                return 0;

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

        seq_printf(m, "%s\n", str);

        return 0;
}

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

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

        if (unlikely(ftrace_disabled))
                return -ENODEV;

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

        iter->pg = ftrace_pages_start;
        iter->pos = -1;

        ret = seq_open(file, &show_ftrace_seq_ops);
        if (!ret) {
                struct seq_file *m = file->private_data;

                m->private = iter;
        } else {
                kfree(iter);
        }

        return ret;
}

int ftrace_avail_release(struct inode *inode, struct file *file)
{
        struct seq_file *m = (struct seq_file *)file->private_data;
        struct ftrace_iterator *iter = m->private;

        seq_release(inode, file);
        kfree(iter);

        return 0;
}

static int
ftrace_failures_open(struct inode *inode, struct file *file)
{
        int ret;
        struct seq_file *m;
        struct ftrace_iterator *iter;

        ret = ftrace_avail_open(inode, file);
        if (!ret) {
                m = (struct seq_file *)file->private_data;
                iter = (struct ftrace_iterator *)m->private;
                iter->flags = FTRACE_ITER_FAILURES;
        }

        return ret;
}


static void ftrace_filter_reset(int enable)
{
        struct ftrace_page *pg;
        struct dyn_ftrace *rec;
        unsigned long type = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
        unsigned i;

        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);
        if (enable)
                ftrace_filtered = 0;
        pg = ftrace_pages_start;
        while (pg) {
                for (i = 0; i < pg->index; i++) {
                        rec = &pg->records[i];
                        if (rec->flags & FTRACE_FL_FAILED)
                                continue;
                        rec->flags &= ~type;
                }
                pg = pg->next;
        }
        spin_unlock(&ftrace_lock);
}

static int
ftrace_regex_open(struct inode *inode, struct file *file, int enable)
{
        struct ftrace_iterator *iter;
        int ret = 0;

        if (unlikely(ftrace_disabled))
                return -ENODEV;

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

        mutex_lock(&ftrace_regex_lock);
        if ((file->f_mode & FMODE_WRITE) &&
            !(file->f_flags & O_APPEND))
                ftrace_filter_reset(enable);

        if (file->f_mode & FMODE_READ) {
                iter->pg = ftrace_pages_start;
                iter->pos = -1;
                iter->flags = enable ? FTRACE_ITER_FILTER :
                        FTRACE_ITER_NOTRACE;

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

        return ret;
}

static int
ftrace_filter_open(struct inode *inode, struct file *file)
{
        return ftrace_regex_open(inode, file, 1);
}

static int
ftrace_notrace_open(struct inode *inode, struct file *file)
{
        return ftrace_regex_open(inode, file, 0);
}

static ssize_t
ftrace_regex_read(struct file *file, char __user *ubuf,
                       size_t cnt, loff_t *ppos)
{
        if (file->f_mode & FMODE_READ)
                return seq_read(file, ubuf, cnt, ppos);
        else
                return -EPERM;
}

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

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

        return ret;
}

enum {
        MATCH_FULL,
        MATCH_FRONT_ONLY,
        MATCH_MIDDLE_ONLY,
        MATCH_END_ONLY,
};

static void
ftrace_match(unsigned char *buff, int len, int enable)
{
        char str[KSYM_SYMBOL_LEN];
        char *search = NULL;
        struct ftrace_page *pg;
        struct dyn_ftrace *rec;
        int type = MATCH_FULL;
        unsigned long flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
        unsigned i, match = 0, search_len = 0;

        for (i = 0; i < len; i++) {
                if (buff[i] == '*') {
                        if (!i) {
                                search = buff + i + 1;
                                type = MATCH_END_ONLY;
                                search_len = len - (i + 1);
                        } else {
                                if (type == MATCH_END_ONLY) {
                                        type = MATCH_MIDDLE_ONLY;
                                } else {
                                        match = i;
                                        type = MATCH_FRONT_ONLY;
                                }
                                buff[i] = 0;
                                break;
                        }
                }
        }

        /* should not be called from interrupt context */
        spin_lock(&ftrace_lock);
        if (enable)
                ftrace_filtered = 1;
        pg = ftrace_pages_start;
        while (pg) {
                for (i = 0; i < pg->index; i++) {
                        int matched = 0;
                        char *ptr;

                        rec = &pg->records[i];
                        if (rec->flags & FTRACE_FL_FAILED)
                                continue;
                        kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
                        switch (type) {
                        case MATCH_FULL:
                                if (strcmp(str, buff) == 0)
                                        matched = 1;
                                break;
                        case MATCH_FRONT_ONLY:
                                if (memcmp(str, buff, match) == 0)
                                        matched = 1;
                                break;
                        case MATCH_MIDDLE_ONLY:
                                if (strstr(str, search))
                                        matched = 1;
                                break;
                        case MATCH_END_ONLY:
                                ptr = strstr(str, search);
                                if (ptr && (ptr[search_len] == 0))
                                        matched = 1;
                                break;
                        }
                        if (matched)
                                rec->flags |= flag;
                }
                pg = pg->next;
        }
        spin_unlock(&ftrace_lock);
}

static ssize_t
ftrace_regex_write(struct file *file, const char __user *ubuf,
                   size_t cnt, loff_t *ppos, int enable)
{
        struct ftrace_iterator *iter;
        char ch;
        size_t read = 0;
        ssize_t ret;

        if (!cnt || cnt < 0)
                return 0;

        mutex_lock(&ftrace_regex_lock);

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

        if (!*ppos) {
                iter->flags &= ~FTRACE_ITER_CONT;
                iter->buffer_idx = 0;
        }

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

        if (!(iter->flags & ~FTRACE_ITER_CONT)) {
                /* skip white space */
                while (cnt && isspace(ch)) {
                        ret = get_user(ch, ubuf++);
                        if (ret)
                                goto out;
                        read++;
                        cnt--;
                }

                if (isspace(ch)) {
                        file->f_pos += read;
                        ret = read;
                        goto out;
                }

                iter->buffer_idx = 0;
        }

        while (cnt && !isspace(ch)) {
                if (iter->buffer_idx < FTRACE_BUFF_MAX)
                        iter->buffer[iter->buffer_idx++] = ch;
                else {
                        ret = -EINVAL;
                        goto out;
                }
                ret = get_user(ch, ubuf++);
                if (ret)
                        goto out;
                read++;
                cnt--;
        }

        if (isspace(ch)) {
                iter->filtered++;
                iter->buffer[iter->buffer_idx] = 0;
                ftrace_match(iter->buffer, iter->buffer_idx, enable);
                iter->buffer_idx = 0;
        } else
                iter->flags |= FTRACE_ITER_CONT;


        file->f_pos += read;

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

        return ret;
}

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

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

static void
ftrace_set_regex(unsigned char *buf, int len, int reset, int enable)
{
        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftrace_regex_lock);
        if (reset)
                ftrace_filter_reset(enable);
        if (buf)
                ftrace_match(buf, len, enable);
        mutex_unlock(&ftrace_regex_lock);
}

/**
 * ftrace_set_filter - set a function to filter on in ftrace
 * @buf - the string that holds the function filter text.
 * @len - the length of the string.
 * @reset - non zero to reset all filters before applying this filter.
 *
 * Filters denote which functions should be enabled when tracing is enabled.
 * If @buf is NULL and reset is set, all functions will be enabled for tracing.
 */
void ftrace_set_filter(unsigned char *buf, int len, int reset)
{
        ftrace_set_regex(buf, len, reset, 1);
}

/**
 * ftrace_set_notrace - set a function to not trace in ftrace
 * @buf - the string that holds the function notrace text.
 * @len - the length of the string.
 * @reset - non zero to reset all filters before applying this filter.
 *
 * Notrace Filters denote which functions should not be enabled when tracing
 * is enabled. If @buf is NULL and reset is set, all functions will be enabled
 * for tracing.
 */
void ftrace_set_notrace(unsigned char *buf, int len, int reset)
{
        ftrace_set_regex(buf, len, reset, 0);
}

static int
ftrace_regex_release(struct inode *inode, struct file *file, int enable)
{
        struct seq_file *m = (struct seq_file *)file->private_data;
        struct ftrace_iterator *iter;

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

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

        if (iter->buffer_idx) {
                iter->filtered++;
                iter->buffer[iter->buffer_idx] = 0;
                ftrace_match(iter->buffer, iter->buffer_idx, enable);
        }

        mutex_lock(&ftrace_sysctl_lock);
        mutex_lock(&ftraced_lock);
        if (iter->filtered && ftraced_suspend && ftrace_enabled)
                ftrace_run_update_code(FTRACE_ENABLE_CALLS);
        mutex_unlock(&ftraced_lock);
        mutex_unlock(&ftrace_sysctl_lock);

        kfree(iter);
        mutex_unlock(&ftrace_regex_lock);
        return 0;
}

static int
ftrace_filter_release(struct inode *inode, struct file *file)
{
        return ftrace_regex_release(inode, file, 1);
}

static int
ftrace_notrace_release(struct inode *inode, struct file *file)
{
        return ftrace_regex_release(inode, file, 0);
}

static ssize_t
ftraced_read(struct file *filp, char __user *ubuf,
                     size_t cnt, loff_t *ppos)
{
        /* don't worry about races */
        char *buf = ftraced_stop ? "disabled\n" : "enabled\n";
        int r = strlen(buf);

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

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

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

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

        if (strncmp(buf, "enable", 6) == 0)
                val = 1;
        else if (strncmp(buf, "disable", 7) == 0)
                val = 0;
        else {
                buf[cnt] = 0;

                ret = strict_strtoul(buf, 10, &val);
                if (ret < 0)
                        return ret;

                val = !!val;
        }

        if (val)
                ftrace_enable_daemon();
        else
                ftrace_disable_daemon();

        filp->f_pos += cnt;

        return cnt;
}

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

static struct file_operations ftrace_failures_fops = {
        .open = ftrace_failures_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = ftrace_avail_release,
};

static struct file_operations ftrace_filter_fops = {
        .open = ftrace_filter_open,
        .read = ftrace_regex_read,
        .write = ftrace_filter_write,
        .llseek = ftrace_regex_lseek,
        .release = ftrace_filter_release,
};

static struct file_operations ftrace_notrace_fops = {
        .open = ftrace_notrace_open,
        .read = ftrace_regex_read,
        .write = ftrace_notrace_write,
        .llseek = ftrace_regex_lseek,
        .release = ftrace_notrace_release,
};

static struct file_operations ftraced_fops = {
        .open = tracing_open_generic,
        .read = ftraced_read,
        .write = ftraced_write,
};

/**
 * ftrace_force_update - force an update to all recording ftrace functions
 */
int ftrace_force_update(void)
{
        int ret = 0;

        if (unlikely(ftrace_disabled))
                return -ENODEV;

        mutex_lock(&ftrace_sysctl_lock);
        mutex_lock(&ftraced_lock);

        /*
         * If ftraced_trigger is not set, then there is nothing
         * to update.
         */
        if (ftraced_trigger && !ftrace_update_code())
                ret = -EBUSY;

        mutex_unlock(&ftraced_lock);
        mutex_unlock(&ftrace_sysctl_lock);

        return ret;
}

static void ftrace_force_shutdown(void)
{
        struct task_struct *task;
        int command = FTRACE_DISABLE_CALLS | FTRACE_UPDATE_TRACE_FUNC;

        mutex_lock(&ftraced_lock);
        task = ftraced_task;
        ftraced_task = NULL;
        ftraced_suspend = -1;
        ftrace_run_update_code(command);
        mutex_unlock(&ftraced_lock);

        if (task)
                kthread_stop(task);
}

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

        d_tracer = tracing_init_dentry();

        entry = debugfs_create_file("available_filter_functions", 0444,
                                    d_tracer, NULL, &ftrace_avail_fops);
        if (!entry)
                pr_warning("Could not create debugfs "
                           "'available_filter_functions' entry\n");

        entry = debugfs_create_file("failures", 0444,
                                    d_tracer, NULL, &ftrace_failures_fops);
        if (!entry)
                pr_warning("Could not create debugfs 'failures' entry\n");

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

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

        entry = debugfs_create_file("ftraced_enabled", 0644, d_tracer,
                                    NULL, &ftraced_fops);
        if (!entry)
                pr_warning("Could not create debugfs "
                           "'ftraced_enabled' entry\n");
        return 0;
}

fs_initcall(ftrace_init_debugfs);

#ifdef CONFIG_FTRACE_MCOUNT_RECORD
static int ftrace_convert_nops(unsigned long *start,
                               unsigned long *end)
{
        unsigned long *p;
        unsigned long addr;
        unsigned long flags;

        p = start;
        while (p < end) {
                addr = ftrace_call_adjust(*p++);
                /* should not be called from interrupt context */
                spin_lock(&ftrace_lock);
                ftrace_record_ip(addr);
                spin_unlock(&ftrace_lock);
                ftrace_shutdown_replenish();
        }

        /* p is ignored */
        local_irq_save(flags);
        __ftrace_update_code(p);
        local_irq_restore(flags);

        return 0;
}

void ftrace_init_module(unsigned long *start, unsigned long *end)
{
        if (ftrace_disabled || start == end)
                return;
        ftrace_convert_nops(start, end);
}

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

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

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

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

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

        count = __stop_mcount_loc - __start_mcount_loc;

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

        last_ftrace_enabled = ftrace_enabled = 1;

        ret = ftrace_convert_nops(__start_mcount_loc,
                                  __stop_mcount_loc);

        return;
 failed:
        ftrace_disabled = 1;
}
#else /* CONFIG_FTRACE_MCOUNT_RECORD */
static int ftraced(void *ignore)
{
        unsigned long usecs;

        while (!kthread_should_stop()) {

                set_current_state(TASK_INTERRUPTIBLE);

                /* check once a second */
                schedule_timeout(HZ);

                if (unlikely(ftrace_disabled))
                        continue;

                mutex_lock(&ftrace_sysctl_lock);
                mutex_lock(&ftraced_lock);
                if (!ftraced_suspend && !ftraced_stop &&
                    ftrace_update_code()) {
                        usecs = nsecs_to_usecs(ftrace_update_time);
                        if (ftrace_update_tot_cnt > 100000) {
                                ftrace_update_tot_cnt = 0;
                                pr_info("hm, dftrace overflow: %lu change%s"
                                        " (%lu total) in %lu usec%s\n",
                                        ftrace_update_cnt,
                                        ftrace_update_cnt != 1 ? "s" : "",
                                        ftrace_update_tot_cnt,
                                        usecs, usecs != 1 ? "s" : "");
                                ftrace_disabled = 1;
                                WARN_ON_ONCE(1);
                        }
                }
                mutex_unlock(&ftraced_lock);
                mutex_unlock(&ftrace_sysctl_lock);

                ftrace_shutdown_replenish();
        }
        __set_current_state(TASK_RUNNING);
        return 0;
}

static int __init ftrace_dynamic_init(void)
{
        struct task_struct *p;
        unsigned long addr;
        int ret;

        addr = (unsigned long)ftrace_record_ip;

        stop_machine(ftrace_dyn_arch_init, &addr, NULL);

        /* ftrace_dyn_arch_init places the return code in addr */
        if (addr) {
                ret = (int)addr;
                goto failed;
        }

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

        p = kthread_run(ftraced, NULL, "ftraced");
        if (IS_ERR(p)) {
                ret = -1;
                goto failed;
        }

        last_ftrace_enabled = ftrace_enabled = 1;
        ftraced_task = p;

        return 0;

 failed:
        ftrace_disabled = 1;
        return ret;
}

core_initcall(ftrace_dynamic_init);
#endif /* CONFIG_FTRACE_MCOUNT_RECORD */

#else
# define ftrace_startup()               do { } while (0)
# define ftrace_shutdown()              do { } while (0)
# define ftrace_startup_sysctl()        do { } while (0)
# define ftrace_shutdown_sysctl()       do { } while (0)
# define ftrace_force_shutdown()        do { } while (0)
#endif /* CONFIG_DYNAMIC_FTRACE */

/**
 * ftrace_kill_atomic - kill ftrace from critical sections
 *
 * This function should be used by panic code. It stops ftrace
 * but in a not so nice way. If you need to simply kill ftrace
 * from a non-atomic section, use ftrace_kill.
 */
void ftrace_kill_atomic(void)
{
        ftrace_disabled = 1;
        ftrace_enabled = 0;
#ifdef CONFIG_DYNAMIC_FTRACE
        ftraced_suspend = -1;
#endif
        clear_ftrace_function();
}

/**
 * ftrace_kill - totally shutdown ftrace
 *
 * This is a safety measure. If something was detected that seems
 * wrong, calling this function will keep ftrace from doing
 * any more modifications, and updates.
 * used when something went wrong.
 */
void ftrace_kill(void)
{
        mutex_lock(&ftrace_sysctl_lock);
        ftrace_disabled = 1;
        ftrace_enabled = 0;

        clear_ftrace_function();
        mutex_unlock(&ftrace_sysctl_lock);

        /* Try to totally disable ftrace */
        ftrace_force_shutdown();
}

/**
 * register_ftrace_function - register a function for profiling
 * @ops - ops structure that holds the function for profiling.
 *
 * Register a function to be called by all functions in the
 * kernel.
 *
 * Note: @ops->func and all the functions it calls must be labeled
 *       with "notrace", otherwise it will go into a
 *       recursive loop.
 */
int register_ftrace_function(struct ftrace_ops *ops)
{
        int ret;

        if (unlikely(ftrace_disabled))
                return -1;

        mutex_lock(&ftrace_sysctl_lock);
        ret = __register_ftrace_function(ops);
        ftrace_startup();
        mutex_unlock(&ftrace_sysctl_lock);

        return ret;
}

/**
 * unregister_ftrace_function - unresgister a function for profiling.
 * @ops - ops structure that holds the function to unregister
 *
 * Unregister a function that was added to be called by ftrace profiling.
 */
int unregister_ftrace_function(struct ftrace_ops *ops)
{
        int ret;

        mutex_lock(&ftrace_sysctl_lock);
        ret = __unregister_ftrace_function(ops);
        ftrace_shutdown();
        mutex_unlock(&ftrace_sysctl_lock);

        return ret;
}

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

        if (unlikely(ftrace_disabled))
                return -ENODEV;

        mutex_lock(&ftrace_sysctl_lock);

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

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

        last_ftrace_enabled = ftrace_enabled;

        if (ftrace_enabled) {

                ftrace_startup_sysctl();

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

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

                ftrace_shutdown_sysctl();
        }

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