ftrace: break out modify loop immediately on detection of error

[mirror_ubuntu-zesty-kernel.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/suspend.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/list.h>

#include <asm/ftrace.h>

#include "trace.h"

#define FTRACE_WARN_ON(cond)                    \
        do {                                    \
                if (WARN_ON(cond))              \
                        ftrace_kill();          \
        } while (0)

#define FTRACE_WARN_ON_ONCE(cond)               \
        do {                                    \
                if (WARN_ON_ONCE(cond))         \
                        ftrace_kill();          \
        } while (0)

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

/* set when tracing only a pid */
struct pid *ftrace_pid_trace;
static struct pid * const ftrace_swapper_pid = &init_struct_pid;

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

/*
 * 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 DEFINE_MUTEX(ftrace_start_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;
ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_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;
        };
}

static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip)
{
        if (!test_tsk_trace_trace(current))
                return;

        ftrace_pid_function(ip, parent_ip);
}

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

/**
 * 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;
        __ftrace_trace_function = ftrace_stub;
        ftrace_pid_function = ftrace_stub;
}

#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
/*
 * For those archs that do not test ftrace_trace_stop in their
 * mcount call site, we need to do it from C.
 */
static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
{
        if (function_trace_stop)
                return;

        __ftrace_trace_function(ip, parent_ip);
}
#endif

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) {
                ftrace_func_t func;

                if (ops->next == &ftrace_list_end)
                        func = ops->func;
                else
                        func = ftrace_list_func;

                if (ftrace_pid_trace) {
                        set_ftrace_pid_function(func);
                        func = ftrace_pid_func;
                }

                /*
                 * For one func, simply call it directly.
                 * For more than one func, call the chain.
                 */
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
                ftrace_trace_function = func;
#else
                __ftrace_trace_function = func;
                ftrace_trace_function = ftrace_test_stop_func;
#endif
        }

        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->next == &ftrace_list_end) {
                        ftrace_func_t func = ftrace_list->func;

                        if (ftrace_pid_trace) {
                                set_ftrace_pid_function(func);
                                func = ftrace_pid_func;
                        }
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
                        ftrace_trace_function = func;
#else
                        __ftrace_trace_function = func;
#endif
                }
        }

 out:
        spin_unlock(&ftrace_lock);

        return ret;
}

static void ftrace_update_pid_func(void)
{
        ftrace_func_t func;

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

        if (ftrace_trace_function == ftrace_stub)
                goto out;

        func = ftrace_trace_function;

        if (ftrace_pid_trace) {
                set_ftrace_pid_function(func);
                func = ftrace_pid_func;
        } else {
                if (func == ftrace_pid_func)
                        func = ftrace_pid_function;
        }

#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
        ftrace_trace_function = func;
#else
        __ftrace_trace_function = func;
#endif

 out:
        spin_unlock(&ftrace_lock);
}

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

/*
 * Since MCOUNT_ADDR may point to mcount itself, we do not want
 * to get it confused by reading a reference in the code as we
 * are parsing on objcopy output of text. Use a variable for
 * it instead.
 */
static unsigned long mcount_addr = MCOUNT_ADDR;

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),
        FTRACE_START_FUNC_RET           = (1 << 5),
        FTRACE_STOP_FUNC_RET            = (1 << 6),
};

static int ftrace_filtered;

static LIST_HEAD(ftrace_new_addrs);

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 struct dyn_ftrace *ftrace_free_records;


#ifdef CONFIG_KPROBES

static int frozen_record_count;

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 */

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))) {
                        FTRACE_WARN_ON_ONCE(1);
                        ftrace_free_records = NULL;
                        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) {
                        /* allocate another page */
                        ftrace_pages->next =
                                (void *)get_zeroed_page(GFP_KERNEL);
                        if (!ftrace_pages->next)
                                return NULL;
                }
                ftrace_pages = ftrace_pages->next;
        }

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

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

        if (ftrace_disabled)
                return NULL;

        rec = ftrace_alloc_dyn_node(ip);
        if (!rec)
                return NULL;

        rec->ip = ip;

        list_add(&rec->list, &ftrace_new_addrs);

        return rec;
}

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

        printk(KERN_CONT "%s", fmt);

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

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


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

        ftrace_addr = (unsigned long)ftrace_caller;

        ip = rec->ip;

        /*
         * If this record is not to be traced and
         * it is not enabled then do nothing.
         *
         * If this record is not to be traced and
         * it is enabled then disabled it.
         *
         */
        if (rec->flags & FTRACE_FL_NOTRACE) {
                if (rec->flags & FTRACE_FL_ENABLED)
                        rec->flags &= ~FTRACE_FL_ENABLED;
                else
                        return 0;

        } else if (ftrace_filtered && enable) {
                /*
                 * Filtering is on:
                 */

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

                /* Record is filtered and enabled, do nothing */
                if (fl == (FTRACE_FL_FILTER | FTRACE_FL_ENABLED))
                        return 0;

                /* Record is not filtered and is not enabled do nothing */
                if (!fl)
                        return 0;

                /* Record is not filtered but enabled, disable it */
                if (fl == FTRACE_FL_ENABLED)
                        rec->flags &= ~FTRACE_FL_ENABLED;
                else
                /* Otherwise record is filtered but not enabled, enable it */
                        rec->flags |= FTRACE_FL_ENABLED;
        } else {
                /* Disable or not filtered */

                if (enable) {
                        /* if record is enabled, do nothing */
                        if (rec->flags & FTRACE_FL_ENABLED)
                                return 0;

                        rec->flags |= FTRACE_FL_ENABLED;

                } else {

                        /* if record is not enabled do nothing */
                        if (!(rec->flags & FTRACE_FL_ENABLED))
                                return 0;

                        rec->flags &= ~FTRACE_FL_ENABLED;
                }
        }

        if (rec->flags & FTRACE_FL_ENABLED)
                return ftrace_make_call(rec, ftrace_addr);
        else
                return ftrace_make_nop(NULL, rec, ftrace_addr);
}

static void ftrace_replace_code(int enable)
{
        int i, failed;
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;

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

                        /*
                         * Skip over free records and records that have
                         * failed.
                         */
                        if (rec->flags & FTRACE_FL_FREE ||
                            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, enable);
                        if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {
                                rec->flags |= FTRACE_FL_FAILED;
                                if ((system_state == SYSTEM_BOOTING) ||
                                    !core_kernel_text(rec->ip)) {
                                        ftrace_free_rec(rec);
                                } else {
                                        ftrace_bug(failed, rec->ip);
                                        /* Stop processing */
                                        return;
                                }
                        }
                }
        }
}

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

        ip = rec->ip;

        ret = ftrace_make_nop(mod, rec, mcount_addr);
        if (ret) {
                ftrace_bug(ret, ip);
                rec->flags |= FTRACE_FL_FAILED;
                return 0;
        }
        return 1;
}

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

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

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

        if (*command & FTRACE_ENABLE_CALLS)
                ftrace_replace_code(1);
        else if (*command & FTRACE_DISABLE_CALLS)
                ftrace_replace_code(0);

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

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

        return 0;
}

static void ftrace_run_update_code(int command)
{
        int ret;

        ret = ftrace_arch_code_modify_prepare();
        FTRACE_WARN_ON(ret);
        if (ret)
                return;

        stop_machine(__ftrace_modify_code, &command, NULL);

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

static ftrace_func_t saved_ftrace_func;
static int ftrace_start_up;

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

        if (!command || !ftrace_enabled)
                return;

        ftrace_run_update_code(command);
}

static void ftrace_startup(int command)
{
        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftrace_start_lock);
        ftrace_start_up++;
        command |= FTRACE_ENABLE_CALLS;

        ftrace_startup_enable(command);

        mutex_unlock(&ftrace_start_lock);
}

static void ftrace_shutdown(int command)
{
        if (unlikely(ftrace_disabled))
                return;

        mutex_lock(&ftrace_start_lock);
        ftrace_start_up--;
        if (!ftrace_start_up)
                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(&ftrace_start_lock);
}

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

        if (unlikely(ftrace_disabled))
                return;

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

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

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

        if (unlikely(ftrace_disabled))
                return;

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

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

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

static int ftrace_update_code(struct module *mod)
{
        struct dyn_ftrace *p, *t;
        cycle_t start, stop;

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

        list_for_each_entry_safe(p, t, &ftrace_new_addrs, list) {

                /* If something went wrong, bail without enabling anything */
                if (unlikely(ftrace_disabled))
                        return -1;

                list_del_init(&p->list);

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

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

        return 0;
}

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 entries in %d pages\n",
                num_to_init, cnt + 1);

        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 {
        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 {
                        iter->idx = -1;
                }
        } 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_FILTER) &&
                     !(rec->flags & FTRACE_FL_FILTER)) ||

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

        return rec;
}

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

        if (*pos > 0) {
                if (iter->idx < 0)
                        return p;
                (*pos)--;
                iter->idx--;
        }

        p = t_next(m, p, pos);

        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;

        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->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;
        int not = 0;

        if (buff[0] == '!') {
                not = 1;
                buff++;
                len--;
        }

        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) {
                                if (not)
                                        rec->flags &= ~flag;
                                else
                                        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(&ftrace_start_lock);
        if (ftrace_start_up && ftrace_enabled)
                ftrace_run_update_code(FTRACE_ENABLE_CALLS);
        mutex_unlock(&ftrace_start_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 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,
};

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static DEFINE_MUTEX(graph_lock);

int ftrace_graph_count;
unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;

static void *
g_next(struct seq_file *m, void *v, loff_t *pos)
{
        unsigned long *array = m->private;
        int index = *pos;

        (*pos)++;

        if (index >= ftrace_graph_count)
                return NULL;

        return &array[index];
}

static void *g_start(struct seq_file *m, loff_t *pos)
{
        void *p = NULL;

        mutex_lock(&graph_lock);

        p = g_next(m, p, pos);

        return p;
}

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

static int g_show(struct seq_file *m, void *v)
{
        unsigned long *ptr = v;
        char str[KSYM_SYMBOL_LEN];

        if (!ptr)
                return 0;

        kallsyms_lookup(*ptr, NULL, NULL, NULL, str);

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

        return 0;
}

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

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

        if (unlikely(ftrace_disabled))
                return -ENODEV;

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

        if (file->f_mode & FMODE_READ) {
                ret = seq_open(file, &ftrace_graph_seq_ops);
                if (!ret) {
                        struct seq_file *m = file->private_data;
                        m->private = ftrace_graph_funcs;
                }
        } else
                file->private_data = ftrace_graph_funcs;
        mutex_unlock(&graph_lock);

        return ret;
}

static ssize_t
ftrace_graph_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 int
ftrace_set_func(unsigned long *array, int idx, char *buffer)
{
        char str[KSYM_SYMBOL_LEN];
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
        int found = 0;
        int i, j;

        if (ftrace_disabled)
                return -ENODEV;

        /* 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->flags & (FTRACE_FL_FAILED | FTRACE_FL_FREE))
                                continue;

                        kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
                        if (strcmp(str, buffer) == 0) {
                                found = 1;
                                for (j = 0; j < idx; j++)
                                        if (array[j] == rec->ip) {
                                                found = 0;
                                                break;
                                        }
                                if (found)
                                        array[idx] = rec->ip;
                                break;
                        }
                }
        }
        spin_unlock(&ftrace_lock);

        return found ? 0 : -EINVAL;
}

static ssize_t
ftrace_graph_write(struct file *file, const char __user *ubuf,
                   size_t cnt, loff_t *ppos)
{
        unsigned char buffer[FTRACE_BUFF_MAX+1];
        unsigned long *array;
        size_t read = 0;
        ssize_t ret;
        int index = 0;
        char ch;

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

        mutex_lock(&graph_lock);

        if (ftrace_graph_count >= FTRACE_GRAPH_MAX_FUNCS) {
                ret = -EBUSY;
                goto out;
        }

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

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

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

        if (isspace(ch)) {
                *ppos += read;
                ret = read;
                goto out;
        }

        while (cnt && !isspace(ch)) {
                if (index < FTRACE_BUFF_MAX)
                        buffer[index++] = ch;
                else {
                        ret = -EINVAL;
                        goto out;
                }
                ret = get_user(ch, ubuf++);
                if (ret)
                        goto out;
                read++;
                cnt--;
        }
        buffer[index] = 0;

        /* we allow only one at a time */
        ret = ftrace_set_func(array, ftrace_graph_count, buffer);
        if (ret)
                goto out;

        ftrace_graph_count++;

        file->f_pos += read;

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

        return ret;
}

static const struct file_operations ftrace_graph_fops = {
        .open = ftrace_graph_open,
        .read = ftrace_graph_read,
        .write = ftrace_graph_write,
};
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

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

        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");

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        entry = debugfs_create_file("set_graph_function", 0444, d_tracer,
                                    NULL,
                                    &ftrace_graph_fops);
        if (!entry)
                pr_warning("Could not create debugfs "
                           "'set_graph_function' entry\n");
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

        return 0;
}

static int ftrace_convert_nops(struct module *mod,
                               unsigned long *start,
                               unsigned long *end)
{
        unsigned long *p;
        unsigned long addr;
        unsigned long flags;

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

        /* disable interrupts to prevent kstop machine */
        local_irq_save(flags);
        ftrace_update_code(mod);
        local_irq_restore(flags);
        mutex_unlock(&ftrace_start_lock);

        return 0;
}

void ftrace_init_module(struct module *mod,
                        unsigned long *start, unsigned long *end)
{
        if (ftrace_disabled || start == end)
                return;
        ftrace_convert_nops(mod, 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(NULL,
                                  __start_mcount_loc,
                                  __stop_mcount_loc);

        return;
 failed:
        ftrace_disabled = 1;
}

#else

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

static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }
static inline void ftrace_startup_enable(int command) { }
/* Keep as macros so we do not need to define the commands */
# define ftrace_startup(command)        do { } while (0)
# define ftrace_shutdown(command)       do { } while (0)
# define ftrace_startup_sysctl()        do { } while (0)
# define ftrace_shutdown_sysctl()       do { } while (0)
#endif /* CONFIG_DYNAMIC_FTRACE */

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

        if (ftrace_pid_trace == ftrace_swapper_pid)
                r = sprintf(buf, "swapper tasks\n");
        else if (ftrace_pid_trace)
                r = sprintf(buf, "%u\n", pid_nr(ftrace_pid_trace));
        else
                r = sprintf(buf, "no pid\n");

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

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

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

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

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

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

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

        put_pid(pid);
}

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

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

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

        *pid = NULL;
}

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

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

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

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

        buf[cnt] = 0;

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

        mutex_lock(&ftrace_start_lock);
        if (val < 0) {
                /* disable pid tracing */
                if (!ftrace_pid_trace)
                        goto out;

                clear_ftrace_pid_task(&ftrace_pid_trace);

        } else {
                /* swapper task is special */
                if (!val) {
                        pid = ftrace_swapper_pid;
                        if (pid == ftrace_pid_trace)
                                goto out;
                } else {
                        pid = find_get_pid(val);

                        if (pid == ftrace_pid_trace) {
                                put_pid(pid);
                                goto out;
                        }
                }

                if (ftrace_pid_trace)
                        clear_ftrace_pid_task(&ftrace_pid_trace);

                if (!pid)
                        goto out;

                ftrace_pid_trace = pid;

                set_ftrace_pid_task(ftrace_pid_trace);
        }

        /* update the function call */
        ftrace_update_pid_func();
        ftrace_startup_enable(0);

 out:
        mutex_unlock(&ftrace_start_lock);

        return cnt;
}

static struct file_operations ftrace_pid_fops = {
        .read = ftrace_pid_read,
        .write = ftrace_pid_write,
};

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

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

        ftrace_init_dyn_debugfs(d_tracer);

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

fs_initcall(ftrace_init_debugfs);

/**
 * ftrace_kill - kill ftrace
 *
 * 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(void)
{
        ftrace_disabled = 1;
        ftrace_enabled = 0;
        clear_ftrace_function();
}

/**
 * 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(0);

        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(0);
        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;
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static atomic_t ftrace_graph_active;
static struct notifier_block ftrace_suspend_notifier;

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

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

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

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

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

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

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

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

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

        if (!ret_stack_list)
                return -ENOMEM;

        /* The cpu_boot init_task->ret_stack will never be freed */
        for_each_online_cpu(cpu)
                ftrace_graph_init_task(idle_task(cpu));

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

        kfree(ret_stack_list);
        return ret;
}

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

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

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

        mutex_lock(&ftrace_sysctl_lock);

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

        atomic_inc(&ftrace_graph_active);
        ret = start_graph_tracing();
        if (ret) {
                atomic_dec(&ftrace_graph_active);
                goto out;
        }

        ftrace_graph_return = retfunc;
        ftrace_graph_entry = entryfunc;

        ftrace_startup(FTRACE_START_FUNC_RET);

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

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

        atomic_dec(&ftrace_graph_active);
        ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
        ftrace_graph_entry = ftrace_graph_entry_stub;
        ftrace_shutdown(FTRACE_STOP_FUNC_RET);
        unregister_pm_notifier(&ftrace_suspend_notifier);

        mutex_unlock(&ftrace_sysctl_lock);
}

/* Allocate a return stack for newly created task */
void ftrace_graph_init_task(struct task_struct *t)
{
        if (atomic_read(&ftrace_graph_active)) {
                t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
                                * sizeof(struct ftrace_ret_stack),
                                GFP_KERNEL);
                if (!t->ret_stack)
                        return;
                t->curr_ret_stack = -1;
                atomic_set(&t->tracing_graph_pause, 0);
                atomic_set(&t->trace_overrun, 0);
        } else
                t->ret_stack = NULL;
}

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

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

        kfree(ret_stack);
}

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