// SPDX-License-Identifier: GPL-2.0
/*
 * ring buffer based function tracer
 *
 * Copyright (C) 2007-2012 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * Originally taken from the RT patch by:
 *    Arnaldo Carvalho de Melo <acme@redhat.com>
 *
 * Based on code from the latency_tracer, that is:
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 Nadia Yvette Chambers
 */
#include <linux/ring_buffer.h>
#include <generated/utsrelease.h>
#include <linux/stacktrace.h>
#include <linux/writeback.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/notifier.h>
#include <linux/irqflags.h>
#include <linux/debugfs.h>
#include <linux/tracefs.h>
#include <linux/pagemap.h>
#include <linux/hardirq.h>
#include <linux/linkage.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/splice.h>
#include <linux/kdebug.h>
#include <linux/string.h>
#include <linux/mount.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/nmi.h>
#include <linux/fs.h>
#include <linux/trace.h>
#include <linux/sched/clock.h>
#include <linux/sched/rt.h>

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

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

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

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

/* Pipe tracepoints to printk */
struct trace_iterator *tracepoint_print_iter;
int tracepoint_printk;
static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key);

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

static int
dummy_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
        return 0;
}

/*
 * To prevent the comm cache from being overwritten when no
 * tracing is active, only save the comm when a trace event
 * occurred.
 */
static DEFINE_PER_CPU(bool, trace_taskinfo_save);

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

cpumask_var_t __read_mostly     tracing_buffer_mask;

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

enum ftrace_dump_mode ftrace_dump_on_oops;

/* When set, tracing will stop when a WARN*() is hit */
int __disable_trace_on_warning;

#ifdef CONFIG_TRACE_EVAL_MAP_FILE
/* Map of enums to their values, for "eval_map" file */
struct trace_eval_map_head {
        struct module                   *mod;
        unsigned long                   length;
};

union trace_eval_map_item;

struct trace_eval_map_tail {
        /*
         * "end" is first and points to NULL as it must be different
         * than "mod" or "eval_string"
         */
        union trace_eval_map_item       *next;
        const char                      *end;   /* points to NULL */
};

static DEFINE_MUTEX(trace_eval_mutex);

/*
 * The trace_eval_maps are saved in an array with two extra elements,
 * one at the beginning, and one at the end. The beginning item contains
 * the count of the saved maps (head.length), and the module they
 * belong to if not built in (head.mod). The ending item contains a
 * pointer to the next array of saved eval_map items.
 */
union trace_eval_map_item {
        struct trace_eval_map           map;
        struct trace_eval_map_head      head;
        struct trace_eval_map_tail      tail;
};

static union trace_eval_map_item *trace_eval_maps;
#endif /* CONFIG_TRACE_EVAL_MAP_FILE */

static int tracing_set_tracer(struct trace_array *tr, const char *buf);
static void ftrace_trace_userstack(struct ring_buffer *buffer,
                                   unsigned long flags, int pc);

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

static bool allocate_snapshot;

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

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

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

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

static int __init stop_trace_on_warning(char *str)
{
        if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0))
                __disable_trace_on_warning = 1;
        return 1;
}
__setup("traceoff_on_warning", stop_trace_on_warning);

static int __init boot_alloc_snapshot(char *str)
{
        allocate_snapshot = true;
        /* We also need the main ring buffer expanded */
        ring_buffer_expanded = true;
        return 1;
}
__setup("alloc_snapshot", boot_alloc_snapshot);


static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;

static int __init set_trace_boot_options(char *str)
{
        strlcpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
        return 0;
}
__setup("trace_options=", set_trace_boot_options);

static char trace_boot_clock_buf[MAX_TRACER_SIZE] __initdata;
static char *trace_boot_clock __initdata;

static int __init set_trace_boot_clock(char *str)
{
        strlcpy(trace_boot_clock_buf, str, MAX_TRACER_SIZE);
        trace_boot_clock = trace_boot_clock_buf;
        return 0;
}
__setup("trace_clock=", set_trace_boot_clock);

static int __init set_tracepoint_printk(char *str)
{
        if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0))
                tracepoint_printk = 1;
        return 1;
}
__setup("tp_printk", set_tracepoint_printk);

unsigned long long ns2usecs(u64 nsec)
{
        nsec += 500;
        do_div(nsec, 1000);
        return nsec;
}

/* trace_flags holds trace_options default values */
#define TRACE_DEFAULT_FLAGS                                             \
        (FUNCTION_DEFAULT_FLAGS |                                       \
         TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |                  \
         TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO |                \
         TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |                 \
         TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS)

/* trace_options that are only supported by global_trace */
#define TOP_LEVEL_TRACE_FLAGS (TRACE_ITER_PRINTK |                      \
               TRACE_ITER_PRINTK_MSGONLY | TRACE_ITER_RECORD_CMD)

/* trace_flags that are default zero for instances */
#define ZEROED_TRACE_FLAGS \
        (TRACE_ITER_EVENT_FORK | TRACE_ITER_FUNC_FORK)

/*
 * The global_trace is the descriptor that holds the top-level tracing
 * buffers for the live tracing.
 */
static struct trace_array global_trace = {
        .trace_flags = TRACE_DEFAULT_FLAGS,
};

LIST_HEAD(ftrace_trace_arrays);

int trace_array_get(struct trace_array *this_tr)
{
        struct trace_array *tr;
        int ret = -ENODEV;

        mutex_lock(&trace_types_lock);
        list_for_each_entry(tr, &ftrace_trace_arrays, list) {
                if (tr == this_tr) {
                        tr->ref++;
                        ret = 0;
                        break;
                }
        }
        mutex_unlock(&trace_types_lock);

        return ret;
}

static void __trace_array_put(struct trace_array *this_tr)
{
        WARN_ON(!this_tr->ref);
        this_tr->ref--;
}

void trace_array_put(struct trace_array *this_tr)
{
        mutex_lock(&trace_types_lock);
        __trace_array_put(this_tr);
        mutex_unlock(&trace_types_lock);
}

int call_filter_check_discard(struct trace_event_call *call, void *rec,
                              struct ring_buffer *buffer,
                              struct ring_buffer_event *event)
{
        if (unlikely(call->flags & TRACE_EVENT_FL_FILTERED) &&
            !filter_match_preds(call->filter, rec)) {
                __trace_event_discard_commit(buffer, event);
                return 1;
        }

        return 0;
}

void trace_free_pid_list(struct trace_pid_list *pid_list)
{
        vfree(pid_list->pids);
        kfree(pid_list);
}

/**
 * trace_find_filtered_pid - check if a pid exists in a filtered_pid list
 * @filtered_pids: The list of pids to check
 * @search_pid: The PID to find in @filtered_pids
 *
 * Returns true if @search_pid is fonud in @filtered_pids, and false otherwis.
 */
bool
trace_find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_pid)
{
        /*
         * If pid_max changed after filtered_pids was created, we
         * by default ignore all pids greater than the previous pid_max.
         */
        if (search_pid >= filtered_pids->pid_max)
                return false;

        return test_bit(search_pid, filtered_pids->pids);
}

/**
 * trace_ignore_this_task - should a task be ignored for tracing
 * @filtered_pids: The list of pids to check
 * @task: The task that should be ignored if not filtered
 *
 * Checks if @task should be traced or not from @filtered_pids.
 * Returns true if @task should *NOT* be traced.
 * Returns false if @task should be traced.
 */
bool
trace_ignore_this_task(struct trace_pid_list *filtered_pids, struct task_struct *task)
{
        /*
         * Return false, because if filtered_pids does not exist,
         * all pids are good to trace.
         */
        if (!filtered_pids)
                return false;

        return !trace_find_filtered_pid(filtered_pids, task->pid);
}

/**
 * trace_filter_add_remove_task - Add or remove a task from a pid_list
 * @pid_list: The list to modify
 * @self: The current task for fork or NULL for exit
 * @task: The task to add or remove
 *
 * If adding a task, if @self is defined, the task is only added if @self
 * is also included in @pid_list. This happens on fork and tasks should
 * only be added when the parent is listed. If @self is NULL, then the
 * @task pid will be removed from the list, which would happen on exit
 * of a task.
 */
void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
                                  struct task_struct *self,
                                  struct task_struct *task)
{
        if (!pid_list)
                return;

        /* For forks, we only add if the forking task is listed */
        if (self) {
                if (!trace_find_filtered_pid(pid_list, self->pid))
                        return;
        }

        /* Sorry, but we don't support pid_max changing after setting */
        if (task->pid >= pid_list->pid_max)
                return;

        /* "self" is set for forks, and NULL for exits */
        if (self)
                set_bit(task->pid, pid_list->pids);
        else
                clear_bit(task->pid, pid_list->pids);
}

/**
 * trace_pid_next - Used for seq_file to get to the next pid of a pid_list
 * @pid_list: The pid list to show
 * @v: The last pid that was shown (+1 the actual pid to let zero be displayed)
 * @pos: The position of the file
 *
 * This is used by the seq_file "next" operation to iterate the pids
 * listed in a trace_pid_list structure.
 *
 * Returns the pid+1 as we want to display pid of zero, but NULL would
 * stop the iteration.
 */
void *trace_pid_next(struct trace_pid_list *pid_list, void *v, loff_t *pos)
{
        unsigned long pid = (unsigned long)v;

        (*pos)++;

        /* pid already is +1 of the actual prevous bit */
        pid = find_next_bit(pid_list->pids, pid_list->pid_max, pid);

        /* Return pid + 1 to allow zero to be represented */
        if (pid < pid_list->pid_max)
                return (void *)(pid + 1);

        return NULL;
}

/**
 * trace_pid_start - Used for seq_file to start reading pid lists
 * @pid_list: The pid list to show
 * @pos: The position of the file
 *
 * This is used by seq_file "start" operation to start the iteration
 * of listing pids.
 *
 * Returns the pid+1 as we want to display pid of zero, but NULL would
 * stop the iteration.
 */
void *trace_pid_start(struct trace_pid_list *pid_list, loff_t *pos)
{
        unsigned long pid;
        loff_t l = 0;

        pid = find_first_bit(pid_list->pids, pid_list->pid_max);
        if (pid >= pid_list->pid_max)
                return NULL;

        /* Return pid + 1 so that zero can be the exit value */
        for (pid++; pid && l < *pos;
             pid = (unsigned long)trace_pid_next(pid_list, (void *)pid, &l))
                ;
        return (void *)pid;
}

/**
 * trace_pid_show - show the current pid in seq_file processing
 * @m: The seq_file structure to write into
 * @v: A void pointer of the pid (+1) value to display
 *
 * Can be directly used by seq_file operations to display the current
 * pid value.
 */
int trace_pid_show(struct seq_file *m, void *v)
{
        unsigned long pid = (unsigned long)v - 1;

        seq_printf(m, "%lu\n", pid);
        return 0;
}

/* 128 should be much more than enough */
#define PID_BUF_SIZE            127

int trace_pid_write(struct trace_pid_list *filtered_pids,
                    struct trace_pid_list **new_pid_list,
                    const char __user *ubuf, size_t cnt)
{
        struct trace_pid_list *pid_list;
        struct trace_parser parser;
        unsigned long val;
        int nr_pids = 0;
        ssize_t read = 0;
        ssize_t ret = 0;
        loff_t pos;
        pid_t pid;

        if (trace_parser_get_init(&parser, PID_BUF_SIZE + 1))
                return -ENOMEM;

        /*
         * Always recreate a new array. The write is an all or nothing
         * operation. Always create a new array when adding new pids by
         * the user. If the operation fails, then the current list is
         * not modified.
         */
        pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
        if (!pid_list) {
                trace_parser_put(&parser);
                return -ENOMEM;
        }

        pid_list->pid_max = READ_ONCE(pid_max);

        /* Only truncating will shrink pid_max */
        if (filtered_pids && filtered_pids->pid_max > pid_list->pid_max)
                pid_list->pid_max = filtered_pids->pid_max;

        pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
        if (!pid_list->pids) {
                trace_parser_put(&parser);
                kfree(pid_list);
                return -ENOMEM;
        }

        if (filtered_pids) {
                /* copy the current bits to the new max */
                for_each_set_bit(pid, filtered_pids->pids,
                                 filtered_pids->pid_max) {
                        set_bit(pid, pid_list->pids);
                        nr_pids++;
                }
        }

        while (cnt > 0) {

                pos = 0;

                ret = trace_get_user(&parser, ubuf, cnt, &pos);
                if (ret < 0 || !trace_parser_loaded(&parser))
                        break;

                read += ret;
                ubuf += ret;
                cnt -= ret;

                ret = -EINVAL;
                if (kstrtoul(parser.buffer, 0, &val))
                        break;
                if (val >= pid_list->pid_max)
                        break;

                pid = (pid_t)val;

                set_bit(pid, pid_list->pids);
                nr_pids++;

                trace_parser_clear(&parser);
                ret = 0;
        }
        trace_parser_put(&parser);

        if (ret < 0) {
                trace_free_pid_list(pid_list);
                return ret;
        }

        if (!nr_pids) {
                /* Cleared the list of pids */
                trace_free_pid_list(pid_list);
                read = ret;
                pid_list = NULL;
        }

        *new_pid_list = pid_list;

        return read;
}

static u64 buffer_ftrace_now(struct trace_buffer *buf, int cpu)
{
        u64 ts;

        /* Early boot up does not have a buffer yet */
        if (!buf->buffer)
                return trace_clock_local();

        ts = ring_buffer_time_stamp(buf->buffer, cpu);
        ring_buffer_normalize_time_stamp(buf->buffer, cpu, &ts);

        return ts;
}

u64 ftrace_now(int cpu)
{
        return buffer_ftrace_now(&global_trace.trace_buffer, cpu);
}

/**
 * tracing_is_enabled - Show if global_trace has been disabled
 *
 * Shows if the global trace has been enabled or not. It uses the
 * mirror flag "buffer_disabled" to be used in fast paths such as for
 * the irqsoff tracer. But it may be inaccurate due to races. If you
 * need to know the accurate state, use tracing_is_on() which is a little
 * slower, but accurate.
 */
int tracing_is_enabled(void)
{
        /*
         * For quick access (irqsoff uses this in fast path), just
         * return the mirror variable of the state of the ring buffer.
         * It's a little racy, but we don't really care.
         */
        smp_rmb();
        return !global_trace.buffer_disabled;
}

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

static unsigned long            trace_buf_size = TRACE_BUF_SIZE_DEFAULT;

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

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

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

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

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

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

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

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

static inline void trace_access_lock_init(void)
{
        int cpu;

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

#else

static DEFINE_MUTEX(access_lock);

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

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

static inline void trace_access_lock_init(void)
{
}

#endif

#ifdef CONFIG_STACKTRACE
static void __ftrace_trace_stack(struct ring_buffer *buffer,
                                 unsigned long flags,
                                 int skip, int pc, struct pt_regs *regs);
static inline void ftrace_trace_stack(struct trace_array *tr,
                                      struct ring_buffer *buffer,
                                      unsigned long flags,
                                      int skip, int pc, struct pt_regs *regs);

#else
static inline void __ftrace_trace_stack(struct ring_buffer *buffer,
                                        unsigned long flags,
                                        int skip, int pc, struct pt_regs *regs)
{
}
static inline void ftrace_trace_stack(struct trace_array *tr,
                                      struct ring_buffer *buffer,
                                      unsigned long flags,
                                      int skip, int pc, struct pt_regs *regs)
{
}

#endif

static __always_inline void
trace_event_setup(struct ring_buffer_event *event,
                  int type, unsigned long flags, int pc)
{
        struct trace_entry *ent = ring_buffer_event_data(event);

        tracing_generic_entry_update(ent, type, flags, pc);
}

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

        event = ring_buffer_lock_reserve(buffer, len);
        if (event != NULL)
                trace_event_setup(event, type, flags, pc);

        return event;
}

void tracer_tracing_on(struct trace_array *tr)
{
        if (tr->trace_buffer.buffer)
                ring_buffer_record_on(tr->trace_buffer.buffer);
        /*
         * This flag is looked at when buffers haven't been allocated
         * yet, or by some tracers (like irqsoff), that just want to
         * know if the ring buffer has been disabled, but it can handle
         * races of where it gets disabled but we still do a record.
         * As the check is in the fast path of the tracers, it is more
         * important to be fast than accurate.
         */
        tr->buffer_disabled = 0;
        /* Make the flag seen by readers */
        smp_wmb();
}

/**
 * tracing_on - enable tracing buffers
 *
 * This function enables tracing buffers that may have been
 * disabled with tracing_off.
 */
void tracing_on(void)
{
        tracer_tracing_on(&global_trace);
}
EXPORT_SYMBOL_GPL(tracing_on);


static __always_inline void
__buffer_unlock_commit(struct ring_buffer *buffer, struct ring_buffer_event *event)
{
        __this_cpu_write(trace_taskinfo_save, true);

        /* If this is the temp buffer, we need to commit fully */
        if (this_cpu_read(trace_buffered_event) == event) {
                /* Length is in event->array[0] */
                ring_buffer_write(buffer, event->array[0], &event->array[1]);
                /* Release the temp buffer */
                this_cpu_dec(trace_buffered_event_cnt);
        } else
                ring_buffer_unlock_commit(buffer, event);
}

/**
 * __trace_puts - write a constant string into the trace buffer.
 * @ip:    The address of the caller
 * @str:   The constant string to write
 * @size:  The size of the string.
 */
int __trace_puts(unsigned long ip, const char *str, int size)
{
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        struct print_entry *entry;
        unsigned long irq_flags;
        int alloc;
        int pc;

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

        pc = preempt_count();

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

        alloc = sizeof(*entry) + size + 2; /* possible \n added */

        local_save_flags(irq_flags);
        buffer = global_trace.trace_buffer.buffer;
        event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, alloc, 
                                            irq_flags, pc);
        if (!event)
                return 0;

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

        memcpy(&entry->buf, str, size);

        /* Add a newline if necessary */
        if (entry->buf[size - 1] != '\n') {
                entry->buf[size] = '\n';
                entry->buf[size + 1] = '\0';
        } else
                entry->buf[size] = '\0';

        __buffer_unlock_commit(buffer, event);
        ftrace_trace_stack(&global_trace, buffer, irq_flags, 4, pc, NULL);

        return size;
}
EXPORT_SYMBOL_GPL(__trace_puts);

/**
 * __trace_bputs - write the pointer to a constant string into trace buffer
 * @ip:    The address of the caller
 * @str:   The constant string to write to the buffer to
 */
int __trace_bputs(unsigned long ip, const char *str)
{
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        struct bputs_entry *entry;
        unsigned long irq_flags;
        int size = sizeof(struct bputs_entry);
        int pc;

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

        pc = preempt_count();

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

        local_save_flags(irq_flags);
        buffer = global_trace.trace_buffer.buffer;
        event = __trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,
                                            irq_flags, pc);
        if (!event)
                return 0;

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

        __buffer_unlock_commit(buffer, event);
        ftrace_trace_stack(&global_trace, buffer, irq_flags, 4, pc, NULL);

        return 1;
}
EXPORT_SYMBOL_GPL(__trace_bputs);

#ifdef CONFIG_TRACER_SNAPSHOT
void tracing_snapshot_instance_cond(struct trace_array *tr, void *cond_data)
{
        struct tracer *tracer = tr->current_trace;
        unsigned long flags;

        if (in_nmi()) {
                internal_trace_puts("*** SNAPSHOT CALLED FROM NMI CONTEXT ***\n");
                internal_trace_puts("*** snapshot is being ignored        ***\n");
                return;
        }

        if (!tr->allocated_snapshot) {
                internal_trace_puts("*** SNAPSHOT NOT ALLOCATED ***\n");
                internal_trace_puts("*** stopping trace here!   ***\n");
                tracing_off();
                return;
        }

        /* Note, snapshot can not be used when the tracer uses it */
        if (tracer->use_max_tr) {
                internal_trace_puts("*** LATENCY TRACER ACTIVE ***\n");
                internal_trace_puts("*** Can not use snapshot (sorry) ***\n");
                return;
        }

        local_irq_save(flags);
        update_max_tr(tr, current, smp_processor_id(), cond_data);
        local_irq_restore(flags);
}

void tracing_snapshot_instance(struct trace_array *tr)
{
        tracing_snapshot_instance_cond(tr, NULL);
}

/**
 * tracing_snapshot - take a snapshot of the current buffer.
 *
 * This causes a swap between the snapshot buffer and the current live
 * tracing buffer. You can use this to take snapshots of the live
 * trace when some condition is triggered, but continue to trace.
 *
 * Note, make sure to allocate the snapshot with either
 * a tracing_snapshot_alloc(), or by doing it manually
 * with: echo 1 > /sys/kernel/debug/tracing/snapshot
 *
 * If the snapshot buffer is not allocated, it will stop tracing.
 * Basically making a permanent snapshot.
 */
void tracing_snapshot(void)
{
        struct trace_array *tr = &global_trace;

        tracing_snapshot_instance(tr);
}
EXPORT_SYMBOL_GPL(tracing_snapshot);

/**
 * tracing_snapshot_cond - conditionally take a snapshot of the current buffer.
 * @tr:         The tracing instance to snapshot
 * @cond_data:  The data to be tested conditionally, and possibly saved
 *
 * This is the same as tracing_snapshot() except that the snapshot is
 * conditional - the snapshot will only happen if the
 * cond_snapshot.update() implementation receiving the cond_data
 * returns true, which means that the trace array's cond_snapshot
 * update() operation used the cond_data to determine whether the
 * snapshot should be taken, and if it was, presumably saved it along
 * with the snapshot.
 */
void tracing_snapshot_cond(struct trace_array *tr, void *cond_data)
{
        tracing_snapshot_instance_cond(tr, cond_data);
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond);

/**
 * tracing_snapshot_cond_data - get the user data associated with a snapshot
 * @tr:         The tracing instance
 *
 * When the user enables a conditional snapshot using
 * tracing_snapshot_cond_enable(), the user-defined cond_data is saved
 * with the snapshot.  This accessor is used to retrieve it.
 *
 * Should not be called from cond_snapshot.update(), since it takes
 * the tr->max_lock lock, which the code calling
 * cond_snapshot.update() has already done.
 *
 * Returns the cond_data associated with the trace array's snapshot.
 */
void *tracing_cond_snapshot_data(struct trace_array *tr)
{
        void *cond_data = NULL;

        arch_spin_lock(&tr->max_lock);

        if (tr->cond_snapshot)
                cond_data = tr->cond_snapshot->cond_data;

        arch_spin_unlock(&tr->max_lock);

        return cond_data;
}
EXPORT_SYMBOL_GPL(tracing_cond_snapshot_data);

static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
                                        struct trace_buffer *size_buf, int cpu_id);
static void set_buffer_entries(struct trace_buffer *buf, unsigned long val);

int tracing_alloc_snapshot_instance(struct trace_array *tr)
{
        int ret;

        if (!tr->allocated_snapshot) {

                /* allocate spare buffer */
                ret = resize_buffer_duplicate_size(&tr->max_buffer,
                                   &tr->trace_buffer, RING_BUFFER_ALL_CPUS);
                if (ret < 0)
                        return ret;

                tr->allocated_snapshot = true;
        }

        return 0;
}

static void free_snapshot(struct trace_array *tr)
{
        /*
         * We don't free the ring buffer. instead, resize it because
         * The max_tr ring buffer has some state (e.g. ring->clock) and
         * we want preserve it.
         */
        ring_buffer_resize(tr->max_buffer.buffer, 1, RING_BUFFER_ALL_CPUS);
        set_buffer_entries(&tr->max_buffer, 1);
        tracing_reset_online_cpus(&tr->max_buffer);
        tr->allocated_snapshot = false;
}

/**
 * tracing_alloc_snapshot - allocate snapshot buffer.
 *
 * This only allocates the snapshot buffer if it isn't already
 * allocated - it doesn't also take a snapshot.
 *
 * This is meant to be used in cases where the snapshot buffer needs
 * to be set up for events that can't sleep but need to be able to
 * trigger a snapshot.
 */
int tracing_alloc_snapshot(void)
{
        struct trace_array *tr = &global_trace;
        int ret;

        ret = tracing_alloc_snapshot_instance(tr);
        WARN_ON(ret < 0);

        return ret;
}
EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);

/**
 * tracing_snapshot_alloc - allocate and take a snapshot of the current buffer.
 *
 * This is similar to tracing_snapshot(), but it will allocate the
 * snapshot buffer if it isn't already allocated. Use this only
 * where it is safe to sleep, as the allocation may sleep.
 *
 * This causes a swap between the snapshot buffer and the current live
 * tracing buffer. You can use this to take snapshots of the live
 * trace when some condition is triggered, but continue to trace.
 */
void tracing_snapshot_alloc(void)
{
        int ret;

        ret = tracing_alloc_snapshot();
        if (ret < 0)
                return;

        tracing_snapshot();
}
EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);

/**
 * tracing_snapshot_cond_enable - enable conditional snapshot for an instance
 * @tr:         The tracing instance
 * @cond_data:  User data to associate with the snapshot
 * @update:     Implementation of the cond_snapshot update function
 *
 * Check whether the conditional snapshot for the given instance has
 * already been enabled, or if the current tracer is already using a
 * snapshot; if so, return -EBUSY, else create a cond_snapshot and
 * save the cond_data and update function inside.
 *
 * Returns 0 if successful, error otherwise.
 */
int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data,
                                 cond_update_fn_t update)
{
        struct cond_snapshot *cond_snapshot;
        int ret = 0;

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

        cond_snapshot->cond_data = cond_data;
        cond_snapshot->update = update;

        mutex_lock(&trace_types_lock);

        ret = tracing_alloc_snapshot_instance(tr);
        if (ret)
                goto fail_unlock;

        if (tr->current_trace->use_max_tr) {
                ret = -EBUSY;
                goto fail_unlock;
        }

        /*
         * The cond_snapshot can only change to NULL without the
         * trace_types_lock. We don't care if we race with it going
         * to NULL, but we want to make sure that it's not set to
         * something other than NULL when we get here, which we can
         * do safely with only holding the trace_types_lock and not
         * having to take the max_lock.
         */
        if (tr->cond_snapshot) {
                ret = -EBUSY;
                goto fail_unlock;
        }

        arch_spin_lock(&tr->max_lock);
        tr->cond_snapshot = cond_snapshot;
        arch_spin_unlock(&tr->max_lock);

        mutex_unlock(&trace_types_lock);

        return ret;

 fail_unlock:
        mutex_unlock(&trace_types_lock);
        kfree(cond_snapshot);
        return ret;
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond_enable);

/**
 * tracing_snapshot_cond_disable - disable conditional snapshot for an instance
 * @tr:         The tracing instance
 *
 * Check whether the conditional snapshot for the given instance is
 * enabled; if so, free the cond_snapshot associated with it,
 * otherwise return -EINVAL.
 *
 * Returns 0 if successful, error otherwise.
 */
int tracing_snapshot_cond_disable(struct trace_array *tr)
{
        int ret = 0;

        arch_spin_lock(&tr->max_lock);

        if (!tr->cond_snapshot)
                ret = -EINVAL;
        else {
                kfree(tr->cond_snapshot);
                tr->cond_snapshot = NULL;
        }

        arch_spin_unlock(&tr->max_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond_disable);
#else
void tracing_snapshot(void)
{
        WARN_ONCE(1, "Snapshot feature not enabled, but internal snapshot used");
}
EXPORT_SYMBOL_GPL(tracing_snapshot);
void tracing_snapshot_cond(struct trace_array *tr, void *cond_data)
{
        WARN_ONCE(1, "Snapshot feature not enabled, but internal conditional snapshot used");
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond);
int tracing_alloc_snapshot(void)
{
        WARN_ONCE(1, "Snapshot feature not enabled, but snapshot allocation used");
        return -ENODEV;
}
EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);
void tracing_snapshot_alloc(void)
{
        /* Give warning */
        tracing_snapshot();
}
EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
void *tracing_cond_snapshot_data(struct trace_array *tr)
{
        return NULL;
}
EXPORT_SYMBOL_GPL(tracing_cond_snapshot_data);
int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data, cond_update_fn_t update)
{
        return -ENODEV;
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond_enable);
int tracing_snapshot_cond_disable(struct trace_array *tr)
{
        return false;
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond_disable);
#endif /* CONFIG_TRACER_SNAPSHOT */

void tracer_tracing_off(struct trace_array *tr)
{
        if (tr->trace_buffer.buffer)
                ring_buffer_record_off(tr->trace_buffer.buffer);
        /*
         * This flag is looked at when buffers haven't been allocated
         * yet, or by some tracers (like irqsoff), that just want to
         * know if the ring buffer has been disabled, but it can handle
         * races of where it gets disabled but we still do a record.
         * As the check is in the fast path of the tracers, it is more
         * important to be fast than accurate.
         */
        tr->buffer_disabled = 1;
        /* Make the flag seen by readers */
        smp_wmb();
}

/**
 * tracing_off - turn off tracing buffers
 *
 * This function stops the tracing buffers from recording data.
 * It does not disable any overhead the tracers themselves may
 * be causing. This function simply causes all recording to
 * the ring buffers to fail.
 */
void tracing_off(void)
{
        tracer_tracing_off(&global_trace);
}
EXPORT_SYMBOL_GPL(tracing_off);

void disable_trace_on_warning(void)
{
        if (__disable_trace_on_warning)
                tracing_off();
}

/**
 * tracer_tracing_is_on - show real state of ring buffer enabled
 * @tr : the trace array to know if ring buffer is enabled
 *
 * Shows real state of the ring buffer if it is enabled or not.
 */
bool tracer_tracing_is_on(struct trace_array *tr)
{
        if (tr->trace_buffer.buffer)
                return ring_buffer_record_is_on(tr->trace_buffer.buffer);
        return !tr->buffer_disabled;
}

/**
 * tracing_is_on - show state of ring buffers enabled
 */
int tracing_is_on(void)
{
        return tracer_tracing_is_on(&global_trace);
}
EXPORT_SYMBOL_GPL(tracing_is_on);

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

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

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

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

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

/*
 * TRACE_FLAGS is defined as a tuple matching bit masks with strings.
 * It uses C(a, b) where 'a' is the eval (enum) name and 'b' is the string that
 * matches it. By defining "C(a, b) b", TRACE_FLAGS becomes a list
 * of strings in the order that the evals (enum) were defined.
 */
#undef C
#define C(a, b) b

/* These must match the bit postions in trace_iterator_flags */
static const char *trace_options[] = {
        TRACE_FLAGS
        NULL
};

static struct {
        u64 (*func)(void);
        const char *name;
        int in_ns;              /* is this clock in nanoseconds? */
} trace_clocks[] = {
        { trace_clock_local,            "local",        1 },
        { trace_clock_global,           "global",       1 },
        { trace_clock_counter,          "counter",      0 },
        { trace_clock_jiffies,          "uptime",       0 },
        { trace_clock,                  "perf",         1 },
        { ktime_get_mono_fast_ns,       "mono",         1 },
        { ktime_get_raw_fast_ns,        "mono_raw",     1 },
        { ktime_get_boot_fast_ns,       "boot",         1 },
        ARCH_TRACE_CLOCKS
};

bool trace_clock_in_ns(struct trace_array *tr)
{
        if (trace_clocks[tr->clock_id].in_ns)
                return true;

        return false;
}

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

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

        parser->size = size;
        return 0;
}

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

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

        if (!*ppos)
                trace_parser_clear(parser);

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

        read++;
        cnt--;

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

                parser->idx = 0;

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

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

        /* We either got finished input or we have to wait for another call. */
        if (isspace(ch) || !ch) {
                parser->buffer[parser->idx] = 0;
                parser->cont = false;
        } else if (parser->idx < parser->size - 1) {
                parser->cont = true;
                parser->buffer[parser->idx++] = ch;
                /* Make sure the parsed string always terminates with '\0'. */
                parser->buffer[parser->idx] = 0;
        } else {
                ret = -EINVAL;
                goto out;
        }

        *ppos += read;
        ret = read;

out:
        return ret;
}

/* TODO add a seq_buf_to_buffer() */
static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
{
        int len;

        if (trace_seq_used(s) <= s->seq.readpos)
                return -EBUSY;

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

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

unsigned long __read_mostly     tracing_thresh;

#ifdef CONFIG_TRACER_MAX_TRACE
/*
 * Copy the new maximum trace into the separate maximum-trace
 * structure. (this way the maximum trace is permanently saved,
 * for later retrieval via /sys/kernel/tracing/tracing_max_latency)
 */
static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
        struct trace_buffer *trace_buf = &tr->trace_buffer;
        struct trace_buffer *max_buf = &tr->max_buffer;
        struct trace_array_cpu *data = per_cpu_ptr(trace_buf->data, cpu);
        struct trace_array_cpu *max_data = per_cpu_ptr(max_buf->data, cpu);

        max_buf->cpu = cpu;
        max_buf->time_start = data->preempt_timestamp;

        max_data->saved_latency = tr->max_latency;
        max_data->critical_start = data->critical_start;
        max_data->critical_end = data->critical_end;

        strncpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
        max_data->pid = tsk->pid;
        /*
         * If tsk == current, then use current_uid(), as that does not use
         * RCU. The irq tracer can be called out of RCU scope.
         */
        if (tsk == current)
                max_data->uid = current_uid();
        else
                max_data->uid = task_uid(tsk);

        max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
        max_data->policy = tsk->policy;
        max_data->rt_priority = tsk->rt_priority;

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

/**
 * update_max_tr - snapshot all trace buffers from global_trace to max_tr
 * @tr: tracer
 * @tsk: the task with the latency
 * @cpu: The cpu that initiated the trace.
 * @cond_data: User data associated with a conditional snapshot
 *
 * Flip the buffers between the @tr and the max_tr and record information
 * about which task was the cause of this latency.
 */
void
update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
              void *cond_data)
{
        if (tr->stop_count)
                return;

        WARN_ON_ONCE(!irqs_disabled());

        if (!tr->allocated_snapshot) {
                /* Only the nop tracer should hit this when disabling */
                WARN_ON_ONCE(tr->current_trace != &nop_trace);
                return;
        }

        arch_spin_lock(&tr->max_lock);

        /* Inherit the recordable setting from trace_buffer */
        if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer))
                ring_buffer_record_on(tr->max_buffer.buffer);
        else
                ring_buffer_record_off(tr->max_buffer.buffer);

#ifdef CONFIG_TRACER_SNAPSHOT
        if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data))
                goto out_unlock;
#endif
        swap(tr->trace_buffer.buffer, tr->max_buffer.buffer);

        __update_max_tr(tr, tsk, cpu);

 out_unlock:
        arch_spin_unlock(&tr->max_lock);
}

/**
 * update_max_tr_single - only copy one trace over, and reset the rest
 * @tr: tracer
 * @tsk: task with the latency
 * @cpu: the cpu of the buffer to copy.
 *
 * Flip the trace of a single CPU buffer between the @tr and the max_tr.
 */
void
update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
        int ret;

        if (tr->stop_count)
                return;

        WARN_ON_ONCE(!irqs_disabled());
        if (!tr->allocated_snapshot) {
                /* Only the nop tracer should hit this when disabling */
                WARN_ON_ONCE(tr->current_trace != &nop_trace);
                return;
        }

        arch_spin_lock(&tr->max_lock);

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

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

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

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

static int wait_on_pipe(struct trace_iterator *iter, int full)
{
        /* Iterators are static, they should be filled or empty */
        if (trace_buffer_iter(iter, iter->cpu_file))
                return 0;

        return ring_buffer_wait(iter->trace_buffer->buffer, iter->cpu_file,
                                full);
}

#ifdef CONFIG_FTRACE_STARTUP_TEST
static bool selftests_can_run;

struct trace_selftests {
        struct list_head                list;
        struct tracer                   *type;
};

static LIST_HEAD(postponed_selftests);

static int save_selftest(struct tracer *type)
{
        struct trace_selftests *selftest;

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

        selftest->type = type;
        list_add(&selftest->list, &postponed_selftests);
        return 0;
}

static int run_tracer_selftest(struct tracer *type)
{
        struct trace_array *tr = &global_trace;
        struct tracer *saved_tracer = tr->current_trace;
        int ret;

        if (!type->selftest || tracing_selftest_disabled)
                return 0;

        /*
         * If a tracer registers early in boot up (before scheduling is
         * initialized and such), then do not run its selftests yet.
         * Instead, run it a little later in the boot process.
         */
        if (!selftests_can_run)
                return save_selftest(type);

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

        tr->current_trace = type;

#ifdef CONFIG_TRACER_MAX_TRACE
        if (type->use_max_tr) {
                /* If we expanded the buffers, make sure the max is expanded too */
                if (ring_buffer_expanded)
                        ring_buffer_resize(tr->max_buffer.buffer, trace_buf_size,
                                           RING_BUFFER_ALL_CPUS);
                tr->allocated_snapshot = true;
        }
#endif

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

#ifdef CONFIG_TRACER_MAX_TRACE
        if (type->use_max_tr) {
                tr->allocated_snapshot = false;

                /* Shrink the max buffer again */
                if (ring_buffer_expanded)
                        ring_buffer_resize(tr->max_buffer.buffer, 1,
                                           RING_BUFFER_ALL_CPUS);
        }
#endif

        printk(KERN_CONT "PASSED\n");
        return 0;
}

static __init int init_trace_selftests(void)
{
        struct trace_selftests *p, *n;
        struct tracer *t, **last;
        int ret;

        selftests_can_run = true;

        mutex_lock(&trace_types_lock);

        if (list_empty(&postponed_selftests))
                goto out;

        pr_info("Running postponed tracer tests:\n");

        list_for_each_entry_safe(p, n, &postponed_selftests, list) {
                /* This loop can take minutes when sanitizers are enabled, so
                 * lets make sure we allow RCU processing.
                 */
                cond_resched();
                ret = run_tracer_selftest(p->type);
                /* If the test fails, then warn and remove from available_tracers */
                if (ret < 0) {
                        WARN(1, "tracer: %s failed selftest, disabling\n",
                             p->type->name);
                        last = &trace_types;
                        for (t = trace_types; t; t = t->next) {
                                if (t == p->type) {
                                        *last = t->next;
                                        break;
                                }
                                last = &t->next;
                        }
                }
                list_del(&p->list);
                kfree(p);
        }

 out:
        mutex_unlock(&trace_types_lock);

        return 0;
}
core_initcall(init_trace_selftests);
#else
static inline int run_tracer_selftest(struct tracer *type)
{
        return 0;
}
#endif /* CONFIG_FTRACE_STARTUP_TEST */

static void add_tracer_options(struct trace_array *tr, struct tracer *t);

static void __init apply_trace_boot_options(void);

/**
 * register_tracer - register a tracer with the ftrace system.
 * @type: the plugin for the tracer
 *
 * Register a new plugin tracer.
 */
int __init register_tracer(struct tracer *type)
{
        struct tracer *t;
        int ret = 0;

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

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

        mutex_lock(&trace_types_lock);

        tracing_selftest_running = true;

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

        if (!type->set_flag)
                type->set_flag = &dummy_set_flag;
        if (!type->flags) {
                /*allocate a dummy tracer_flags*/
                type->flags = kmalloc(sizeof(*type->flags), GFP_KERNEL);
                if (!type->flags) {
                        ret = -ENOMEM;
                        goto out;
                }
                type->flags->val = 0;
                type->flags->opts = dummy_tracer_opt;
        } else
                if (!type->flags->opts)
                        type->flags->opts = dummy_tracer_opt;

        /* store the tracer for __set_tracer_option */
        type->flags->trace = type;

        ret = run_tracer_selftest(type);
        if (ret < 0)
                goto out;

        type->next = trace_types;
        trace_types = type;
        add_tracer_options(&global_trace, type);

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

        if (ret || !default_bootup_tracer)
                goto out_unlock;

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

        printk(KERN_INFO "Starting tracer '%s'\n", type->name);
        /* Do we want this tracer to start on bootup? */
        tracing_set_tracer(&global_trace, type->name);
        default_bootup_tracer = NULL;

        apply_trace_boot_options();

        /* disable other selftests, since this will break it. */
        tracing_selftest_disabled = true;
#ifdef CONFIG_FTRACE_STARTUP_TEST
        printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
               type->name);
#endif

 out_unlock:
        return ret;
}

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

        if (!buffer)
                return;

        ring_buffer_record_disable(buffer);

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

        ring_buffer_record_enable(buffer);
}

void tracing_reset_online_cpus(struct trace_buffer *buf)
{
        struct ring_buffer *buffer = buf->buffer;
        int cpu;

        if (!buffer)
                return;

        ring_buffer_record_disable(buffer);

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

        buf->time_start = buffer_ftrace_now(buf, buf->cpu);

        for_each_online_cpu(cpu)
                ring_buffer_reset_cpu(buffer, cpu);

        ring_buffer_record_enable(buffer);
}

/* Must have trace_types_lock held */
void tracing_reset_all_online_cpus(void)
{
        struct trace_array *tr;

        list_for_each_entry(tr, &ftrace_trace_arrays, list) {
                if (!tr->clear_trace)
                        continue;
                tr->clear_trace = false;
                tracing_reset_online_cpus(&tr->trace_buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
                tracing_reset_online_cpus(&tr->max_buffer);
#endif
        }
}

static int *tgid_map;

#define SAVED_CMDLINES_DEFAULT 128
#define NO_CMDLINE_MAP UINT_MAX
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
struct saved_cmdlines_buffer {
        unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
        unsigned *map_cmdline_to_pid;
        unsigned cmdline_num;
        int cmdline_idx;
        char *saved_cmdlines;
};
static struct saved_cmdlines_buffer *savedcmd;

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

static inline char *get_saved_cmdlines(int idx)
{
        return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
}

static inline void set_cmdline(int idx, const char *cmdline)
{
        strncpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
}

static int allocate_cmdlines_buffer(unsigned int val,
                                    struct saved_cmdlines_buffer *s)
{
        s->map_cmdline_to_pid = kmalloc_array(val,
                                              sizeof(*s->map_cmdline_to_pid),
                                              GFP_KERNEL);
        if (!s->map_cmdline_to_pid)
                return -ENOMEM;

        s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL);
        if (!s->saved_cmdlines) {
                kfree(s->map_cmdline_to_pid);
                return -ENOMEM;
        }

        s->cmdline_idx = 0;
        s->cmdline_num = val;
        memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
               sizeof(s->map_pid_to_cmdline));
        memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
               val * sizeof(*s->map_cmdline_to_pid));

        return 0;
}

static int trace_create_savedcmd(void)
{
        int ret;

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

        ret = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT, savedcmd);
        if (ret < 0) {
                kfree(savedcmd);
                savedcmd = NULL;
                return -ENOMEM;
        }

        return 0;
}

int is_tracing_stopped(void)
{
        return global_trace.stop_count;
}

/**
 * tracing_start - quick start of the tracer
 *
 * If tracing is enabled but was stopped by tracing_stop,
 * this will start the tracer back up.
 */
void tracing_start(void)
{
        struct ring_buffer *buffer;
        unsigned long flags;

        if (tracing_disabled)
                return;

        raw_spin_lock_irqsave(&global_trace.start_lock, flags);
        if (--global_trace.stop_count) {

                if (global_trace.stop_count < 0) {
                        /* Someone screwed up their debugging */
                        WARN_ON_ONCE(1);
                        global_trace.stop_count = 0;
                }
                goto out;
        }

        /* Prevent the buffers from switching */
        arch_spin_lock(&global_trace.max_lock);

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

#ifdef CONFIG_TRACER_MAX_TRACE
        buffer = global_trace.max_buffer.buffer;
        if (buffer)
                ring_buffer_record_enable(buffer);
#endif

        arch_spin_unlock(&global_trace.max_lock);

 out:
        raw_spin_unlock_irqrestore(&global_trace.start_lock, flags);
}

static void tracing_start_tr(struct trace_array *tr)
{
        struct ring_buffer *buffer;
        unsigned long flags;

        if (tracing_disabled)
                return;

        /* If global, we need to also start the max tracer */
        if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
                return tracing_start();

        raw_spin_lock_irqsave(&tr->start_lock, flags);

        if (--tr->stop_count) {
                if (tr->stop_count < 0) {
                        /* Someone screwed up their debugging */
                        WARN_ON_ONCE(1);
                        tr->stop_count = 0;
                }
                goto out;
        }

        buffer = tr->trace_buffer.buffer;
        if (buffer)
                ring_buffer_record_enable(buffer);

 out:
        raw_spin_unlock_irqrestore(&tr->start_lock, flags);
}

/**
 * tracing_stop - quick stop of the tracer
 *
 * Light weight way to stop tracing. Use in conjunction with
 * tracing_start.
 */
void tracing_stop(void)
{
        struct ring_buffer *buffer;
        unsigned long flags;

        raw_spin_lock_irqsave(&global_trace.start_lock, flags);
        if (global_trace.stop_count++)
                goto out;

        /* Prevent the buffers from switching */
        arch_spin_lock(&global_trace.max_lock);

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

#ifdef CONFIG_TRACER_MAX_TRACE
        buffer = global_trace.max_buffer.buffer;
        if (buffer)
                ring_buffer_record_disable(buffer);
#endif

        arch_spin_unlock(&global_trace.max_lock);

 out:
        raw_spin_unlock_irqrestore(&global_trace.start_lock, flags);
}

static void tracing_stop_tr(struct trace_array *tr)
{
        struct ring_buffer *buffer;
        unsigned long flags;

        /* If global, we need to also stop the max tracer */
        if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
                return tracing_stop();

        raw_spin_lock_irqsave(&tr->start_lock, flags);
        if (tr->stop_count++)
                goto out;

        buffer = tr->trace_buffer.buffer;
        if (buffer)
                ring_buffer_record_disable(buffer);

 out:
        raw_spin_unlock_irqrestore(&tr->start_lock, flags);
}

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

        /* treat recording of idle task as a success */
        if (!tsk->pid)
                return 1;

        if (unlikely(tsk->pid > PID_MAX_DEFAULT))
                return 0;

        /*
         * It's not the end of the world if we don't get
         * the lock, but we also don't want to spin
         * nor do we want to disable interrupts,
         * so if we miss here, then better luck next time.
         */
        if (!arch_spin_trylock(&trace_cmdline_lock))
                return 0;

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

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

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

                savedcmd->cmdline_idx = idx;
        }

        set_cmdline(idx, tsk->comm);

        arch_spin_unlock(&trace_cmdline_lock);

        return 1;
}

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

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

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

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

        map = savedcmd->map_pid_to_cmdline[pid];
        if (map != NO_CMDLINE_MAP)
                strlcpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
        else
                strcpy(comm, "<...>");
}

void trace_find_cmdline(int pid, char comm[])
{
        preempt_disable();
        arch_spin_lock(&trace_cmdline_lock);

        __trace_find_cmdline(pid, comm);

        arch_spin_unlock(&trace_cmdline_lock);
        preempt_enable();
}

int trace_find_tgid(int pid)
{
        if (unlikely(!tgid_map || !pid || pid > PID_MAX_DEFAULT))
                return 0;

        return tgid_map[pid];
}

static int trace_save_tgid(struct task_struct *tsk)
{
        /* treat recording of idle task as a success */
        if (!tsk->pid)
                return 1;

        if (unlikely(!tgid_map || tsk->pid > PID_MAX_DEFAULT))
                return 0;

        tgid_map[tsk->pid] = tsk->tgid;
        return 1;
}

static bool tracing_record_taskinfo_skip(int flags)
{
        if (unlikely(!(flags & (TRACE_RECORD_CMDLINE | TRACE_RECORD_TGID))))
                return true;
        if (atomic_read(&trace_record_taskinfo_disabled) || !tracing_is_on())
                return true;
        if (!__this_cpu_read(trace_taskinfo_save))
                return true;
        return false;
}

/**
 * tracing_record_taskinfo - record the task info of a task
 *
 * @task:  task to record
 * @flags: TRACE_RECORD_CMDLINE for recording comm
 *         TRACE_RECORD_TGID for recording tgid
 */
void tracing_record_taskinfo(struct task_struct *task, int flags)
{
        bool done;

        if (tracing_record_taskinfo_skip(flags))
                return;

        /*
         * Record as much task information as possible. If some fail, continue
         * to try to record the others.
         */
        done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);

        /* If recording any information failed, retry again soon. */
        if (!done)
                return;

        __this_cpu_write(trace_taskinfo_save, false);
}

/**
 * tracing_record_taskinfo_sched_switch - record task info for sched_switch
 *
 * @prev: previous task during sched_switch
 * @next: next task during sched_switch
 * @flags: TRACE_RECORD_CMDLINE for recording comm
 *         TRACE_RECORD_TGID for recording tgid
 */
void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
                                          struct task_struct *next, int flags)
{
        bool done;

        if (tracing_record_taskinfo_skip(flags))
                return;

        /*
         * Record as much task information as possible. If some fail, continue
         * to try to record the others.
         */
        done  = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
        done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);

        /* If recording any information failed, retry again soon. */
        if (!done)
                return;

        __this_cpu_write(trace_taskinfo_save, false);
}

/* Helpers to record a specific task information */
void tracing_record_cmdline(struct task_struct *task)
{
        tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
}

void tracing_record_tgid(struct task_struct *task)
{
        tracing_record_taskinfo(task, TRACE_RECORD_TGID);
}

/*
 * Several functions return TRACE_TYPE_PARTIAL_LINE if the trace_seq
 * overflowed, and TRACE_TYPE_HANDLED otherwise. This helper function
 * simplifies those functions and keeps them in sync.
 */
enum print_line_t trace_handle_return(struct trace_seq *s)
{
        return trace_seq_has_overflowed(s) ?
                TRACE_TYPE_PARTIAL_LINE : TRACE_TYPE_HANDLED;
}
EXPORT_SYMBOL_GPL(trace_handle_return);

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

        entry->preempt_count            = pc & 0xff;
        entry->pid                      = (tsk) ? tsk->pid : 0;
        entry->type                     = type;
        entry->flags =
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
                (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
#else
                TRACE_FLAG_IRQS_NOSUPPORT |
#endif
                ((pc & NMI_MASK    ) ? TRACE_FLAG_NMI     : 0) |
                ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
                ((pc & SOFTIRQ_OFFSET) ? TRACE_FLAG_SOFTIRQ : 0) |
                (tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
                (test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0);
}
EXPORT_SYMBOL_GPL(tracing_generic_entry_update);

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

DEFINE_PER_CPU(struct ring_buffer_event *, trace_buffered_event);
DEFINE_PER_CPU(int, trace_buffered_event_cnt);
static int trace_buffered_event_ref;

/**
 * trace_buffered_event_enable - enable buffering events
 *
 * When events are being filtered, it is quicker to use a temporary
 * buffer to write the event data into if there's a likely chance
 * that it will not be committed. The discard of the ring buffer
 * is not as fast as committing, and is much slower than copying
 * a commit.
 *
 * When an event is to be filtered, allocate per cpu buffers to
 * write the event data into, and if the event is filtered and discarded
 * it is simply dropped, otherwise, the entire data is to be committed
 * in one shot.
 */
void trace_buffered_event_enable(void)
{
        struct ring_buffer_event *event;
        struct page *page;
        int cpu;

        WARN_ON_ONCE(!mutex_is_locked(&event_mutex));

        if (trace_buffered_event_ref++)
                return;

        for_each_tracing_cpu(cpu) {
                page = alloc_pages_node(cpu_to_node(cpu),
                                        GFP_KERNEL | __GFP_NORETRY, 0);
                if (!page)
                        goto failed;

                event = page_address(page);
                memset(event, 0, sizeof(*event));

                per_cpu(trace_buffered_event, cpu) = event;

                preempt_disable();
                if (cpu == smp_processor_id() &&
                    this_cpu_read(trace_buffered_event) !=
                    per_cpu(trace_buffered_event, cpu))
                        WARN_ON_ONCE(1);
                preempt_enable();
        }

        return;
 failed:
        trace_buffered_event_disable();
}

static void enable_trace_buffered_event(void *data)
{
        /* Probably not needed, but do it anyway */
        smp_rmb();
        this_cpu_dec(trace_buffered_event_cnt);
}

static void disable_trace_buffered_event(void *data)
{
        this_cpu_inc(trace_buffered_event_cnt);
}

/**
 * trace_buffered_event_disable - disable buffering events
 *
 * When a filter is removed, it is faster to not use the buffered
 * events, and to commit directly into the ring buffer. Free up
 * the temp buffers when there are no more users. This requires
 * special synchronization with current events.
 */
void trace_buffered_event_disable(void)
{
        int cpu;

        WARN_ON_ONCE(!mutex_is_locked(&event_mutex));

        if (WARN_ON_ONCE(!trace_buffered_event_ref))
                return;

        if (--trace_buffered_event_ref)
                return;

        preempt_disable();
        /* For each CPU, set the buffer as used. */
        smp_call_function_many(tracing_buffer_mask,
                               disable_trace_buffered_event, NULL, 1);
        preempt_enable();

        /* Wait for all current users to finish */
        synchronize_rcu();

        for_each_tracing_cpu(cpu) {
                free_page((unsigned long)per_cpu(trace_buffered_event, cpu));
                per_cpu(trace_buffered_event, cpu) = NULL;
        }
        /*
         * Make sure trace_buffered_event is NULL before clearing
         * trace_buffered_event_cnt.
         */
        smp_wmb();

        preempt_disable();
        /* Do the work on each cpu */
        smp_call_function_many(tracing_buffer_mask,
                               enable_trace_buffered_event, NULL, 1);
        preempt_enable();
}

static struct ring_buffer *temp_buffer;

struct ring_buffer_event *
trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
                          struct trace_event_file *trace_file,
                          int type, unsigned long len,
                          unsigned long flags, int pc)
{
        struct ring_buffer_event *entry;
        int val;

        *current_rb = trace_file->tr->trace_buffer.buffer;

        if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
             (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
            (entry = this_cpu_read(trace_buffered_event))) {
                /* Try to use the per cpu buffer first */
                val = this_cpu_inc_return(trace_buffered_event_cnt);
                if (val == 1) {
                        trace_event_setup(entry, type, flags, pc);
                        entry->array[0] = len;
                        return entry;
                }
                this_cpu_dec(trace_buffered_event_cnt);
        }

        entry = __trace_buffer_lock_reserve(*current_rb,
                                            type, len, flags, pc);
        /*
         * If tracing is off, but we have triggers enabled
         * we still need to look at the event data. Use the temp_buffer
         * to store the trace event for the tigger to use. It's recusive
         * safe and will not be recorded anywhere.
         */
        if (!entry && trace_file->flags & EVENT_FILE_FL_TRIGGER_COND) {
                *current_rb = temp_buffer;
                entry = __trace_buffer_lock_reserve(*current_rb,
                                                    type, len, flags, pc);
        }
        return entry;
}
EXPORT_SYMBOL_GPL(trace_event_buffer_lock_reserve);

static DEFINE_SPINLOCK(tracepoint_iter_lock);
static DEFINE_MUTEX(tracepoint_printk_mutex);

static void output_printk(struct trace_event_buffer *fbuffer)
{
        struct trace_event_call *event_call;
        struct trace_event *event;
        unsigned long flags;
        struct trace_iterator *iter = tracepoint_print_iter;

        /* We should never get here if iter is NULL */
        if (WARN_ON_ONCE(!iter))
                return;

        event_call = fbuffer->trace_file->event_call;
        if (!event_call || !event_call->event.funcs ||
            !event_call->event.funcs->trace)
                return;

        event = &fbuffer->trace_file->event_call->event;

        spin_lock_irqsave(&tracepoint_iter_lock, flags);
        trace_seq_init(&iter->seq);
        iter->ent = fbuffer->entry;
        event_call->event.funcs->trace(iter, 0, event);
        trace_seq_putc(&iter->seq, 0);
        printk("%s", iter->seq.buffer);

        spin_unlock_irqrestore(&tracepoint_iter_lock, flags);
}

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

        mutex_lock(&tracepoint_printk_mutex);
        save_tracepoint_printk = tracepoint_printk;

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

        /*
         * This will force exiting early, as tracepoint_printk
         * is always zero when tracepoint_printk_iter is not allocated
         */
        if (!tracepoint_print_iter)
                tracepoint_printk = 0;

        if (save_tracepoint_printk == tracepoint_printk)
                goto out;

        if (tracepoint_printk)
                static_key_enable(&tracepoint_printk_key.key);
        else
                static_key_disable(&tracepoint_printk_key.key);

 out:
        mutex_unlock(&tracepoint_printk_mutex);

        return ret;
}

void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
{
        if (static_key_false(&tracepoint_printk_key.key))
                output_printk(fbuffer);

        event_trigger_unlock_commit(fbuffer->trace_file, fbuffer->buffer,
                                    fbuffer->event, fbuffer->entry,
                                    fbuffer->flags, fbuffer->pc);
}
EXPORT_SYMBOL_GPL(trace_event_buffer_commit);

/*
 * Skip 3:
 *
 *   trace_buffer_unlock_commit_regs()
 *   trace_event_buffer_commit()
 *   trace_event_raw_event_xxx()
 */
# define STACK_SKIP 3

void trace_buffer_unlock_commit_regs(struct trace_array *tr,
                                     struct ring_buffer *buffer,
                                     struct ring_buffer_event *event,
                                     unsigned long flags, int pc,
                                     struct pt_regs *regs)
{
        __buffer_unlock_commit(buffer, event);

        /*
         * If regs is not set, then skip the necessary functions.
         * Note, we can still get here via blktrace, wakeup tracer
         * and mmiotrace, but that's ok if they lose a function or
         * two. They are not that meaningful.
         */
        ftrace_trace_stack(tr, buffer, flags, regs ? 0 : STACK_SKIP, pc, regs);
        ftrace_trace_userstack(buffer, flags, pc);
}

/*
 * Similar to trace_buffer_unlock_commit_regs() but do not dump stack.
 */
void
trace_buffer_unlock_commit_nostack(struct ring_buffer *buffer,
                                   struct ring_buffer_event *event)
{
        __buffer_unlock_commit(buffer, event);
}

static void
trace_process_export(struct trace_export *export,
               struct ring_buffer_event *event)
{
        struct trace_entry *entry;
        unsigned int size = 0;

        entry = ring_buffer_event_data(event);
        size = ring_buffer_event_length(event);
        export->write(export, entry, size);
}

static DEFINE_MUTEX(ftrace_export_lock);

static struct trace_export __rcu *ftrace_exports_list __read_mostly;

static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);

static inline void ftrace_exports_enable(void)
{
        static_branch_enable(&ftrace_exports_enabled);
}

static inline void ftrace_exports_disable(void)
{
        static_branch_disable(&ftrace_exports_enabled);
}

static void ftrace_exports(struct ring_buffer_event *event)
{
        struct trace_export *export;

        preempt_disable_notrace();

        export = rcu_dereference_raw_notrace(ftrace_exports_list);
        while (export) {
                trace_process_export(export, event);
                export = rcu_dereference_raw_notrace(export->next);
        }

        preempt_enable_notrace();
}

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

static inline int
rm_trace_export(struct trace_export **list, struct trace_export *export)
{
        struct trace_export **p;

        for (p = list; *p != NULL; p = &(*p)->next)
                if (*p == export)
                        break;

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

        rcu_assign_pointer(*p, (*p)->next);

        return 0;
}

static inline void
add_ftrace_export(struct trace_export **list, struct trace_export *export)
{
        if (*list == NULL)
                ftrace_exports_enable();

        add_trace_export(list, export);
}

static inline int
rm_ftrace_export(struct trace_export **list, struct trace_export *export)
{
        int ret;

        ret = rm_trace_export(list, export);
        if (*list == NULL)
                ftrace_exports_disable();

        return ret;
}

int register_ftrace_export(struct trace_export *export)
{
        if (WARN_ON_ONCE(!export->write))
                return -1;

        mutex_lock(&ftrace_export_lock);

        add_ftrace_export(&ftrace_exports_list, export);

        mutex_unlock(&ftrace_export_lock);

        return 0;
}
EXPORT_SYMBOL_GPL(register_ftrace_export);

int unregister_ftrace_export(struct trace_export *export)
{
        int ret;

        mutex_lock(&ftrace_export_lock);

        ret = rm_ftrace_export(&ftrace_exports_list, export);

        mutex_unlock(&ftrace_export_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(unregister_ftrace_export);

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

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

        if (!call_filter_check_discard(call, entry, buffer, event)) {
                if (static_branch_unlikely(&ftrace_exports_enabled))
                        ftrace_exports(event);
                __buffer_unlock_commit(buffer, event);
        }
}

#ifdef CONFIG_STACKTRACE

/* Allow 4 levels of nesting: normal, softirq, irq, NMI */
#define FTRACE_KSTACK_NESTING   4

#define FTRACE_KSTACK_ENTRIES   (PAGE_SIZE / FTRACE_KSTACK_NESTING)

struct ftrace_stack {
        unsigned long           calls[FTRACE_KSTACK_ENTRIES];
};


struct ftrace_stacks {
        struct ftrace_stack     stacks[FTRACE_KSTACK_NESTING];
};

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

static void __ftrace_trace_stack(struct ring_buffer *buffer,
                                 unsigned long flags,
                                 int skip, int pc, struct pt_regs *regs)
{
        struct trace_event_call *call = &event_kernel_stack;
        struct ring_buffer_event *event;
        unsigned int size, nr_entries;
        struct ftrace_stack *fstack;
        struct stack_entry *entry;
        int stackidx;

        /*
         * Add one, for this function and the call to save_stack_trace()
         * If regs is set, then these functions will not be in the way.
         */
#ifndef CONFIG_UNWINDER_ORC
        if (!regs)
                skip++;
#endif

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

        stackidx = __this_cpu_inc_return(ftrace_stack_reserve) - 1;

        /* This should never happen. If it does, yell once and skip */
        if (WARN_ON_ONCE(stackidx > FTRACE_KSTACK_NESTING))
                goto out;

        /*
         * The above __this_cpu_inc_return() is 'atomic' cpu local. An
         * interrupt will either see the value pre increment or post
         * increment. If the interrupt happens pre increment it will have
         * restored the counter when it returns.  We just need a barrier to
         * keep gcc from moving things around.
         */
        barrier();

        fstack = this_cpu_ptr(ftrace_stacks.stacks) + stackidx;
        size = ARRAY_SIZE(fstack->calls);

        if (regs) {
                nr_entries = stack_trace_save_regs(regs, fstack->calls,
                                                   size, skip);
        } else {
                nr_entries = stack_trace_save(fstack->calls, size, skip);
        }

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

        memcpy(&entry->caller, fstack->calls, size);
        entry->size = nr_entries;

        if (!call_filter_check_discard(call, entry, buffer, event))
                __buffer_unlock_commit(buffer, event);

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

}

static inline void ftrace_trace_stack(struct trace_array *tr,
                                      struct ring_buffer *buffer,
                                      unsigned long flags,
                                      int skip, int pc, struct pt_regs *regs)
{
        if (!(tr->trace_flags & TRACE_ITER_STACKTRACE))
                return;

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

void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
                   int pc)
{
        struct ring_buffer *buffer = tr->trace_buffer.buffer;

        if (rcu_is_watching()) {
                __ftrace_trace_stack(buffer, flags, skip, pc, NULL);
                return;
        }

        /*
         * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
         * but if the above rcu_is_watching() failed, then the NMI
         * triggered someplace critical, and rcu_irq_enter() should
         * not be called from NMI.
         */
        if (unlikely(in_nmi()))
                return;

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

/**
 * trace_dump_stack - record a stack back trace in the trace buffer
 * @skip: Number of functions to skip (helper handlers)
 */
void trace_dump_stack(int skip)
{
        unsigned long flags;

        if (tracing_disabled || tracing_selftest_running)
                return;

        local_save_flags(flags);

#ifndef CONFIG_UNWINDER_ORC
        /* Skip 1 to skip this function. */
        skip++;
#endif
        __ftrace_trace_stack(global_trace.trace_buffer.buffer,
                             flags, skip, preempt_count(), NULL);
}
EXPORT_SYMBOL_GPL(trace_dump_stack);

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
static DEFINE_PER_CPU(int, user_stack_count);

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

        if (!(global_trace.trace_flags & TRACE_ITER_USERSTACKTRACE))
                return;

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

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

        __this_cpu_inc(user_stack_count);

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

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

        stack_trace_save_user(entry->caller, FTRACE_STACK_ENTRIES);
        if (!call_filter_check_discard(call, entry, buffer, event))
                __buffer_unlock_commit(buffer, event);

 out_drop_count:
        __this_cpu_dec(user_stack_count);
 out:
        preempt_enable();
}
#else /* CONFIG_USER_STACKTRACE_SUPPORT */
static void ftrace_trace_userstack(struct ring_buffer *buffer,
                                   unsigned long flags, int pc)
{
}
#endif /* !CONFIG_USER_STACKTRACE_SUPPORT */

#endif /* CONFIG_STACKTRACE */

/* created for use with alloc_percpu */
struct trace_buffer_struct {
        int nesting;
        char buffer[4][TRACE_BUF_SIZE];
};

static struct trace_buffer_struct *trace_percpu_buffer;

/*
 * Thise allows for lockless recording.  If we're nested too deeply, then
 * this returns NULL.
 */
static char *get_trace_buf(void)
{
        struct trace_buffer_struct *buffer = this_cpu_ptr(trace_percpu_buffer);

        if (!buffer || buffer->nesting >= 4)
                return NULL;

        buffer->nesting++;

        /* Interrupts must see nesting incremented before we use the buffer */
        barrier();
        return &buffer->buffer[buffer->nesting][0];
}

static void put_trace_buf(void)
{
        /* Don't let the decrement of nesting leak before this */
        barrier();
        this_cpu_dec(trace_percpu_buffer->nesting);
}

static int alloc_percpu_trace_buffer(void)
{

        struct trace_buffer_struct *buffers;

        buffers = alloc_percpu(struct trace_buffer_struct);
        if (WARN(!buffers, "Could not allocate percpu trace_printk buffer"))
                return -ENOMEM;

        trace_percpu_buffer = buffers;
        return 0;
}

static int buffers_allocated;

void trace_printk_init_buffers(void)
{
        if (buffers_allocated)
                return;

        if (alloc_percpu_trace_buffer())
                return;

        /* trace_printk() is for debug use only. Don't use it in production. */

        pr_warn("\n");
        pr_warn("**********************************************************\n");
        pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
        pr_warn("**                                                      **\n");
        pr_warn("** trace_printk() being used. Allocating extra memory.  **\n");
        pr_warn("**                                                      **\n");
        pr_warn("** This means that this is a DEBUG kernel and it is     **\n");
        pr_warn("** unsafe for production use.                           **\n");
        pr_warn("**                                                      **\n");
        pr_warn("** If you see this message and you are not debugging    **\n");
        pr_warn("** the kernel, report this immediately to your vendor!  **\n");
        pr_warn("**                                                      **\n");
        pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
        pr_warn("**********************************************************\n");

        /* Expand the buffers to set size */
        tracing_update_buffers();

        buffers_allocated = 1;

        /*
         * trace_printk_init_buffers() can be called by modules.
         * If that happens, then we need to start cmdline recording
         * directly here. If the global_trace.buffer is already
         * allocated here, then this was called by module code.
         */
        if (global_trace.trace_buffer.buffer)
                tracing_start_cmdline_record();
}
EXPORT_SYMBOL_GPL(trace_printk_init_buffers);

void trace_printk_start_comm(void)
{
        /* Start tracing comms if trace printk is set */
        if (!buffers_allocated)
                return;
        tracing_start_cmdline_record();
}

static void trace_printk_start_stop_comm(int enabled)
{
        if (!buffers_allocated)
                return;

        if (enabled)
                tracing_start_cmdline_record();
        else
                tracing_stop_cmdline_record();
}

/**
 * trace_vbprintk - write binary msg to tracing buffer
 * @ip:    The address of the caller
 * @fmt:   The string format to write to the buffer
 * @args:  Arguments for @fmt
 */
int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
{
        struct trace_event_call *call = &event_bprint;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        struct trace_array *tr = &global_trace;
        struct bprint_entry *entry;
        unsigned long flags;
        char *tbuffer;
        int len = 0, size, pc;

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

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

        pc = preempt_count();
        preempt_disable_notrace();

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

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

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

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

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

out:
        put_trace_buf();

out_nobuffer:
        preempt_enable_notrace();
        unpause_graph_tracing();

        return len;
}
EXPORT_SYMBOL_GPL(trace_vbprintk);

__printf(3, 0)
static int
__trace_array_vprintk(struct ring_buffer *buffer,
                      unsigned long ip, const char *fmt, va_list args)
{
        struct trace_event_call *call = &event_print;
        struct ring_buffer_event *event;
        int len = 0, size, pc;
        struct print_entry *entry;
        unsigned long flags;
        char *tbuffer;

        if (tracing_disabled || tracing_selftest_running)
                return 0;

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

        pc = preempt_count();
        preempt_disable_notrace();


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

        len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);

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

        memcpy(&entry->buf, tbuffer, len + 1);
        if (!call_filter_check_discard(call, entry, buffer, event)) {
                __buffer_unlock_commit(buffer, event);
                ftrace_trace_stack(&global_trace, buffer, flags, 6, pc, NULL);
        }

out:
        put_trace_buf();

out_nobuffer:
        preempt_enable_notrace();
        unpause_graph_tracing();

        return len;
}

__printf(3, 0)
int trace_array_vprintk(struct trace_array *tr,
                        unsigned long ip, const char *fmt, va_list args)
{
        return __trace_array_vprintk(tr->trace_buffer.buffer, ip, fmt, args);
}

__printf(3, 0)
int trace_array_printk(struct trace_array *tr,
                       unsigned long ip, const char *fmt, ...)
{
        int ret;
        va_list ap;

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

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

__printf(3, 4)
int trace_array_printk_buf(struct ring_buffer *buffer,
                           unsigned long ip, const char *fmt, ...)
{
        int ret;
        va_list ap;

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

        va_start(ap, fmt);
        ret = __trace_array_vprintk(buffer, ip, fmt, ap);
        va_end(ap);
        return ret;
}

__printf(2, 0)
int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
{
        return trace_array_vprintk(&global_trace, ip, fmt, args);
}
EXPORT_SYMBOL_GPL(trace_vprintk);

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

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

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

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

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

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

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

                return ent;
        }

        for_each_tracing_cpu(cpu) {

                if (ring_buffer_empty_cpu(buffer, cpu))
                        continue;

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

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

        iter->ent_size = next_size;

        if (ent_cpu)
                *ent_cpu = next_cpu;

        if (ent_ts)
                *ent_ts = next_ts;

        if (missing_events)
                *missing_events = next_lost;

        return next;
}

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

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

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

        return iter->ent ? iter : NULL;
}

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

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

        WARN_ON_ONCE(iter->leftover);

        (*pos)++;

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

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

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

        iter->pos = *pos;

        return ent;
}

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

        per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = 0;

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

        ring_buffer_iter_reset(buf_iter);

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

        per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = entries;
}

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

        /*
         * copy the tracer to avoid using a global lock all around.
         * iter->trace is a copy of current_trace, the pointer to the
         * name may be used instead of a strcmp(), as iter->trace->name
         * will point to the same string as current_trace->name.
         */
        mutex_lock(&trace_types_lock);
        if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name))
                *iter->trace = *tr->current_trace;
        mutex_unlock(&trace_types_lock);

#ifdef CONFIG_TRACER_MAX_TRACE
        if (iter->snapshot && iter->trace->use_max_tr)
                return ERR_PTR(-EBUSY);
#endif

        if (!iter->snapshot)
                atomic_inc(&trace_record_taskinfo_disabled);

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

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

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

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

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

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

#ifdef CONFIG_TRACER_MAX_TRACE
        if (iter->snapshot && iter->trace->use_max_tr)
                return;
#endif

        if (!iter->snapshot)
                atomic_dec(&trace_record_taskinfo_disabled);

        trace_access_unlock(iter->cpu_file);
        trace_event_read_unlock();
}

static void
get_total_entries_cpu(struct trace_buffer *buf, unsigned long *total,
                      unsigned long *entries, int cpu)
{
        unsigned long count;

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

static void
get_total_entries(struct trace_buffer *buf,
                  unsigned long *total, unsigned long *entries)
{
        unsigned long t, e;
        int cpu;

        *total = 0;
        *entries = 0;

        for_each_tracing_cpu(cpu) {
                get_total_entries_cpu(buf, &t, &e, cpu);
                *total += t;
                *entries += e;
        }
}

unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu)
{
        unsigned long total, entries;

        if (!tr)
                tr = &global_trace;

        get_total_entries_cpu(&tr->trace_buffer, &total, &entries, cpu);

        return entries;
}

unsigned long trace_total_entries(struct trace_array *tr)
{
        unsigned long total, entries;

        if (!tr)
                tr = &global_trace;

        get_total_entries(&tr->trace_buffer, &total, &entries);

        return entries;
}

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

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

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

static void print_func_help_header(struct trace_buffer *buf, struct seq_file *m,
                                   unsigned int flags)
{
        bool tgid = flags & TRACE_ITER_RECORD_TGID;

        print_event_info(buf, m);

        seq_printf(m, "#           TASK-PID   %s  CPU#   TIMESTAMP  FUNCTION\n", tgid ? "TGID     " : "");
        seq_printf(m, "#              | |     %s    |       |         |\n",      tgid ? "  |      " : "");
}

static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file *m,
                                       unsigned int flags)
{
        bool tgid = flags & TRACE_ITER_RECORD_TGID;
        const char *space = "          ";
        int prec = tgid ? 10 : 2;

        print_event_info(buf, m);

        seq_printf(m, "#                          %.*s  _-----=> irqs-off\n", prec, space);
        seq_printf(m, "#                          %.*s / _----=> need-resched\n", prec, space);
        seq_printf(m, "#                          %.*s| / _---=> hardirq/softirq\n", prec, space);
        seq_printf(m, "#                          %.*s|| / _--=> preempt-depth\n", prec, space);
        seq_printf(m, "#                          %.*s||| /     delay\n", prec, space);
        seq_printf(m, "#           TASK-PID %.*sCPU#  ||||    TIMESTAMP  FUNCTION\n", prec, "   TGID   ");
        seq_printf(m, "#              | |   %.*s  |   ||||       |         |\n", prec, "     |    ");
}

void
print_trace_header(struct seq_file *m, struct trace_iterator *iter)
{
        unsigned long sym_flags = (global_trace.trace_flags & TRACE_ITER_SYM_MASK);
        struct trace_buffer *buf = iter->trace_buffer;
        struct trace_array_cpu *data = per_cpu_ptr(buf->data, buf->cpu);
        struct tracer *type = iter->trace;
        unsigned long entries;
        unsigned long total;
        const char *name = "preemption";

        name = type->name;

        get_total_entries(buf, &total, &entries);

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

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

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

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

        if (!(tr->trace_flags & TRACE_ITER_ANNOTATE))
                return;

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

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

        if (per_cpu_ptr(iter->trace_buffer->data, iter->cpu)->skipped_entries)
                return;

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

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

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

        entry = iter->ent;

        test_cpu_buff_start(iter);

        event = ftrace_find_event(entry->type);

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

        if (trace_seq_has_overflowed(s))
                return TRACE_TYPE_PARTIAL_LINE;

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

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

        return trace_handle_return(s);
}

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

        entry = iter->ent;

        if (tr->trace_flags & TRACE_ITER_CONTEXT_INFO)
                trace_seq_printf(s, "%d %d %llu ",
                                 entry->pid, iter->cpu, iter->ts);

        if (trace_seq_has_overflowed(s))
                return TRACE_TYPE_PARTIAL_LINE;

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

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

        return trace_handle_return(s);
}

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

        entry = iter->ent;

        if (tr->trace_flags & TRACE_ITER_CONTEXT_INFO) {
                SEQ_PUT_HEX_FIELD(s, entry->pid);
                SEQ_PUT_HEX_FIELD(s, iter->cpu);
                SEQ_PUT_HEX_FIELD(s, iter->ts);
                if (trace_seq_has_overflowed(s))
                        return TRACE_TYPE_PARTIAL_LINE;
        }

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

        SEQ_PUT_FIELD(s, newline);

        return trace_handle_return(s);
}

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

        entry = iter->ent;

        if (tr->trace_flags & TRACE_ITER_CONTEXT_INFO) {
                SEQ_PUT_FIELD(s, entry->pid);
                SEQ_PUT_FIELD(s, iter->cpu);
                SEQ_PUT_FIELD(s, iter->ts);
                if (trace_seq_has_overflowed(s))
                        return TRACE_TYPE_PARTIAL_LINE;
        }

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

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

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

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

        return 1;
}

/*  Called with trace_event_read_lock() held. */
enum print_line_t print_trace_line(struct trace_iterator *iter)
{
        struct trace_array *tr = iter->tr;
        unsigned long trace_flags = tr->trace_flags;
        enum print_line_t ret;

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

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

        if (iter->ent->type == TRACE_BPUTS &&
                        trace_flags & TRACE_ITER_PRINTK &&
                        trace_flags & TRACE_ITER_PRINTK_MSGONLY)
                return trace_print_bputs_msg_only(iter);

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

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

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

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

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

        return print_trace_fmt(iter);
}

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

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

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

        if (!(tr->trace_flags & TRACE_ITER_VERBOSE))
                print_lat_help_header(m);
}

void trace_default_header(struct seq_file *m)
{
        struct trace_iterator *iter = m->private;
        struct trace_array *tr = iter->tr;
        unsigned long trace_flags = tr->trace_flags;

        if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
                return;

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

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

#ifdef CONFIG_TRACER_MAX_TRACE
static void show_snapshot_main_help(struct seq_file *m)
{
        seq_puts(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n"
                    "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n"
                    "#                      Takes a snapshot of the main buffer.\n"
                    "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)\n"
                    "#                      (Doesn't have to be '2' works with any number that\n"
                    "#                       is not a '0' or '1')\n");
}

static void show_snapshot_percpu_help(struct seq_file *m)
{
        seq_puts(m, "# echo 0 > snapshot : Invalid for per_cpu snapshot file.\n");
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
        seq_puts(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n"
                    "#                      Takes a snapshot of the main buffer for this cpu.\n");
#else
        seq_puts(m, "# echo 1 > snapshot : Not supported with this kernel.\n"
                    "#                     Must use main snapshot file to allocate.\n");
#endif
        seq_puts(m, "# echo 2 > snapshot : Clears this cpu's snapshot buffer (but does not allocate)\n"
                    "#                      (Doesn't have to be '2' works with any number that\n"
                    "#                       is not a '0' or '1')\n");
}

static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter)
{
        if (iter->tr->allocated_snapshot)
                seq_puts(m, "#\n# * Snapshot is allocated *\n#\n");
        else
                seq_puts(m, "#\n# * Snapshot is freed *\n#\n");

        seq_puts(m, "# Snapshot commands:\n");
        if (iter->cpu_file == RING_BUFFER_ALL_CPUS)
                show_snapshot_main_help(m);
        else
                show_snapshot_percpu_help(m);
}
#else
/* Should never be called */
static inline void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) { }
#endif

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

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

        } else if (iter->leftover) {