kernel/trace/trace.c

/*
 * 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/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);

#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_pid_filter_add_remove - 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)
		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) {
		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;

		parser.buffer[parser.idx] = 0;

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

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
static void tracing_snapshot_instance(struct trace_array *tr)
{
	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());
	local_irq_restore(flags);
}

/**
 * trace_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);

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);

static int alloc_snapshot(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 = alloc_snapshot(tr);
	WARN_ON(ret < 0);

	return ret;
}
EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);

/**
 * trace_snapshot_alloc - allocate and take a snapshot of the current buffer.
 *
 * This is similar to trace_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);
#else
void tracing_snapshot(void)
{
	WARN_ONCE(1, "Snapshot feature not enabled, but internal snapshot used");
}
EXPORT_SYMBOL_GPL(tracing_snapshot);
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);
#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.
 */
int 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
};

/*
 * 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--;
		}

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

		parser->idx = 0;
	}

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

	/* We either got finished input or we have to wait for another call. */
	if (isspace(ch)) {
		parser->buffer[parser->idx] = 0;
		parser->cont = false;
	} else if (parser->idx < parser->size - 1) {
		parser->cont = true;
		parser->buffer[parser->idx++] = ch;
	} 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/debug/tracing/latency_trace)
 */
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;

	memcpy(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.
 *
 * 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)
{
	struct ring_buffer *buf;

	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);

	buf = tr->trace_buffer.buffer;
	tr->trace_buffer.buffer = tr->max_buffer.buffer;
	tr->max_buffer.buffer = buf;

	__update_max_tr(tr, tsk, cpu);
	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, bool 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) {
		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_sched();
	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_sched();

	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)
{
	memcpy(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(val * sizeof(*s->map_cmdline_to_pid),
					GFP_KERNEL);
	if (!s->map_cmdline_to_pid)
		return -ENOMEM;

	s->saved_cmdlines = kmalloc(val * TASK_COMM_LEN, 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 long flags,
			     int pc)
{
	struct task_struct *tsk = current;

	entry->preempt_count		= pc & 0xff;
	entry->pid			= (tsk) ? tsk->pid : 0;
	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_sched();

	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 ((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);

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 following callers:
	 *   trace_buffer_unlock_commit_regs
	 *   event_trigger_unlock_commit
	 *   trace_event_buffer_commit
	 *   trace_event_raw_event_sched_switch
	 * 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 that meaningful.
	 */
	ftrace_trace_stack(tr, buffer, flags, regs ? 0 : 4, 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(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);
}

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

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

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

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

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

	/*
	 * Add two, for this function and the call to save_stack_trace()
	 * If regs is set, then these functions will not be in the way.
	 */
	if (!regs)
		trace.skip += 2;

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

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

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

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

	size *= sizeof(unsigned long);

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

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

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

	entry->size = trace.nr_entries;

	if (!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;

	/*
	 * It is possible that a function is being traced in a
	 * location that RCU is not watching. A call to
	 * rcu_irq_enter() will make sure that it is, but there's
	 * a few internal rcu functions that could be traced
	 * where that wont work either. In those cases, we just
	 * do nothing.
	 */
	if (unlikely(rcu_irq_enter_disabled()))
		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);

	/*
	 * Skip 3 more, seems to get us at the caller of
	 * this function.
	 */
	skip += 3;
	__ftrace_trace_stack(global_trace.trace_buffer.buffer,
			     flags, skip, preempt_count(), NULL);
}

static DEFINE_PER_CPU(int, user_stack_count);

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

	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));

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

	save_stack_trace_user(&trace);
	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();
}

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

#endif /* CONFIG_STACKTRACE */

/* created for use with alloc_percpu */
struct trace_buffer_struct {
	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();
}

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
 *
 */
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);

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;
}

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);
}

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;
}

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;
}

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

	*total = 0;
	*entries = 0;

	for_each_tracing_cpu(cpu) {
		count = ring_buffer_entries_cpu(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 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