ftrace.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Infrastructure for profiling code inserted by 'gcc -pg'.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2004-2008 Ingo Molnar <mingo@redhat.com>
 *
 * Originally ported from the -rt patch by:
 *   Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
 *
 * Based on code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 Nadia Yvette Chambers
 */

#include <linux/stop_machine.h>
#include <linux/clocksource.h>
#include <linux/sched/task.h>
#include <linux/kallsyms.h>
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/tracefs.h>
#include <linux/hardirq.h>
#include <linux/kthread.h>
#include <linux/uaccess.h>
#include <linux/bsearch.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/sort.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/rcupdate.h>
#include <linux/kprobes.h>

#include <trace/events/sched.h>

#include <asm/sections.h>
#include <asm/setup.h>

#include "ftrace_internal.h"
#include "trace_output.h"
#include "trace_stat.h"

/* Flags that do not get reset */
#define FTRACE_NOCLEAR_FLAGS	(FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED | \
				 FTRACE_FL_MODIFIED)

#define FTRACE_INVALID_FUNCTION		"__ftrace_invalid_address__"

#define FTRACE_WARN_ON(cond)			\
	({					\
		int ___r = cond;		\
		if (WARN_ON(___r))		\
			ftrace_kill();		\
		___r;				\
	})

#define FTRACE_WARN_ON_ONCE(cond)		\
	({					\
		int ___r = cond;		\
		if (WARN_ON_ONCE(___r))		\
			ftrace_kill();		\
		___r;				\
	})

/* hash bits for specific function selection */
#define FTRACE_HASH_DEFAULT_BITS 10
#define FTRACE_HASH_MAX_BITS 12

#ifdef CONFIG_DYNAMIC_FTRACE
#define INIT_OPS_HASH(opsname)	\
	.func_hash		= &opsname.local_hash,			\
	.local_hash.regex_lock	= __MUTEX_INITIALIZER(opsname.local_hash.regex_lock), \
	.subop_list		= LIST_HEAD_INIT(opsname.subop_list),
#else
#define INIT_OPS_HASH(opsname)
#endif

enum {
	FTRACE_MODIFY_ENABLE_FL		= (1 << 0),
	FTRACE_MODIFY_MAY_SLEEP_FL	= (1 << 1),
};

struct ftrace_ops ftrace_list_end __read_mostly = {
	.func		= ftrace_stub,
	.flags		= FTRACE_OPS_FL_STUB,
	INIT_OPS_HASH(ftrace_list_end)
};

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

/* Current function tracing op */
struct ftrace_ops *function_trace_op __read_mostly = &ftrace_list_end;
/* What to set function_trace_op to */
static struct ftrace_ops *set_function_trace_op;

bool ftrace_pids_enabled(struct ftrace_ops *ops)
{
	struct trace_array *tr;

	if (!(ops->flags & FTRACE_OPS_FL_PID) || !ops->private)
		return false;

	tr = ops->private;

	return tr->function_pids != NULL || tr->function_no_pids != NULL;
}

static void ftrace_update_trampoline(struct ftrace_ops *ops);

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

DEFINE_MUTEX(ftrace_lock);

struct ftrace_ops __rcu *ftrace_ops_list __read_mostly = (struct ftrace_ops __rcu *)&ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
struct ftrace_ops global_ops;

/* Defined by vmlinux.lds.h see the comment above arch_ftrace_ops_list_func for details */
void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
			  struct ftrace_ops *op, struct ftrace_regs *fregs);

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
/*
 * Stub used to invoke the list ops without requiring a separate trampoline.
 */
const struct ftrace_ops ftrace_list_ops = {
	.func	= ftrace_ops_list_func,
	.flags	= FTRACE_OPS_FL_STUB,
};

static void ftrace_ops_nop_func(unsigned long ip, unsigned long parent_ip,
				struct ftrace_ops *op,
				struct ftrace_regs *fregs)
{
	/* do nothing */
}

/*
 * Stub used when a call site is disabled. May be called transiently by threads
 * which have made it into ftrace_caller but haven't yet recovered the ops at
 * the point the call site is disabled.
 */
const struct ftrace_ops ftrace_nop_ops = {
	.func	= ftrace_ops_nop_func,
	.flags  = FTRACE_OPS_FL_STUB,
};
#endif

static inline void ftrace_ops_init(struct ftrace_ops *ops)
{
#ifdef CONFIG_DYNAMIC_FTRACE
	if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED)) {
		mutex_init(&ops->local_hash.regex_lock);
		INIT_LIST_HEAD(&ops->subop_list);
		ops->func_hash = &ops->local_hash;
		ops->flags |= FTRACE_OPS_FL_INITIALIZED;
	}
#endif
}

/* Call this function for when a callback filters on set_ftrace_pid */
static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
			    struct ftrace_ops *op, struct ftrace_regs *fregs)
{
	struct trace_array *tr = op->private;
	int pid;

	if (tr) {
		pid = this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid);
		if (pid == FTRACE_PID_IGNORE)
			return;
		if (pid != FTRACE_PID_TRACE &&
		    pid != current->pid)
			return;
	}

	op->saved_func(ip, parent_ip, op, fregs);
}

void ftrace_sync_ipi(void *data)
{
	/* Probably not needed, but do it anyway */
	smp_rmb();
}

static ftrace_func_t ftrace_ops_get_list_func(struct ftrace_ops *ops)
{
	/*
	 * If this is a dynamic or RCU ops, or we force list func,
	 * then it needs to call the list anyway.
	 */
	if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_RCU) ||
	    FTRACE_FORCE_LIST_FUNC)
		return ftrace_ops_list_func;

	return ftrace_ops_get_func(ops);
}

static void update_ftrace_function(void)
{
	ftrace_func_t func;

	/*
	 * Prepare the ftrace_ops that the arch callback will use.
	 * If there's only one ftrace_ops registered, the ftrace_ops_list
	 * will point to the ops we want.
	 */
	set_function_trace_op = rcu_dereference_protected(ftrace_ops_list,
						lockdep_is_held(&ftrace_lock));

	/* If there's no ftrace_ops registered, just call the stub function */
	if (set_function_trace_op == &ftrace_list_end) {
		func = ftrace_stub;

	/*
	 * If we are at the end of the list and this ops is
	 * recursion safe and not dynamic and the arch supports passing ops,
	 * then have the mcount trampoline call the function directly.
	 */
	} else if (rcu_dereference_protected(ftrace_ops_list->next,
			lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) {
		func = ftrace_ops_get_list_func(ftrace_ops_list);

	} else {
		/* Just use the default ftrace_ops */
		set_function_trace_op = &ftrace_list_end;
		func = ftrace_ops_list_func;
	}

	/* If there's no change, then do nothing more here */
	if (ftrace_trace_function == func)
		return;

	/*
	 * If we are using the list function, it doesn't care
	 * about the function_trace_ops.
	 */
	if (func == ftrace_ops_list_func) {
		ftrace_trace_function = func;
		/*
		 * Don't even bother setting function_trace_ops,
		 * it would be racy to do so anyway.
		 */
		return;
	}

#ifndef CONFIG_DYNAMIC_FTRACE
	/*
	 * For static tracing, we need to be a bit more careful.
	 * The function change takes affect immediately. Thus,
	 * we need to coordinate the setting of the function_trace_ops
	 * with the setting of the ftrace_trace_function.
	 *
	 * Set the function to the list ops, which will call the
	 * function we want, albeit indirectly, but it handles the
	 * ftrace_ops and doesn't depend on function_trace_op.
	 */
	ftrace_trace_function = ftrace_ops_list_func;
	/*
	 * Make sure all CPUs see this. Yes this is slow, but static
	 * tracing is slow and nasty to have enabled.
	 */
	synchronize_rcu_tasks_rude();
	/* Now all cpus are using the list ops. */
	function_trace_op = set_function_trace_op;
	/* Make sure the function_trace_op is visible on all CPUs */
	smp_wmb();
	/* Nasty way to force a rmb on all cpus */
	smp_call_function(ftrace_sync_ipi, NULL, 1);
	/* OK, we are all set to update the ftrace_trace_function now! */
#endif /* !CONFIG_DYNAMIC_FTRACE */

	ftrace_trace_function = func;
}

static void add_ftrace_ops(struct ftrace_ops __rcu **list,
			   struct ftrace_ops *ops)
{
	rcu_assign_pointer(ops->next, *list);

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

static int remove_ftrace_ops(struct ftrace_ops __rcu **list,
			     struct ftrace_ops *ops)
{
	struct ftrace_ops **p;

	/*
	 * If we are removing the last function, then simply point
	 * to the ftrace_stub.
	 */
	if (rcu_dereference_protected(*list,
			lockdep_is_held(&ftrace_lock)) == ops &&
	    rcu_dereference_protected(ops->next,
			lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) {
		rcu_assign_pointer(*list, &ftrace_list_end);
		return 0;
	}

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

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

	*p = (*p)->next;
	return 0;
}

static void ftrace_update_trampoline(struct ftrace_ops *ops);

int __register_ftrace_function(struct ftrace_ops *ops)
{
	if (ops->flags & FTRACE_OPS_FL_DELETED)
		return -EINVAL;

	if (WARN_ON(ops->flags & FTRACE_OPS_FL_ENABLED))
		return -EBUSY;

#ifndef CONFIG_DYNAMIC_FTRACE_WITH_REGS
	/*
	 * If the ftrace_ops specifies SAVE_REGS, then it only can be used
	 * if the arch supports it, or SAVE_REGS_IF_SUPPORTED is also set.
	 * Setting SAVE_REGS_IF_SUPPORTED makes SAVE_REGS irrelevant.
	 */
	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS &&
	    !(ops->flags & FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED))
		return -EINVAL;

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED)
		ops->flags |= FTRACE_OPS_FL_SAVE_REGS;
#endif
	if (!ftrace_enabled && (ops->flags & FTRACE_OPS_FL_PERMANENT))
		return -EBUSY;

	if (!is_kernel_core_data((unsigned long)ops))
		ops->flags |= FTRACE_OPS_FL_DYNAMIC;

	add_ftrace_ops(&ftrace_ops_list, ops);

	/* Always save the function, and reset at unregistering */
	ops->saved_func = ops->func;

	if (ftrace_pids_enabled(ops))
		ops->func = ftrace_pid_func;

	ftrace_update_trampoline(ops);

	if (ftrace_enabled)
		update_ftrace_function();

	return 0;
}

int __unregister_ftrace_function(struct ftrace_ops *ops)
{
	int ret;

	if (WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED)))
		return -EBUSY;

	ret = remove_ftrace_ops(&ftrace_ops_list, ops);

	if (ret < 0)
		return ret;

	if (ftrace_enabled)
		update_ftrace_function();

	ops->func = ops->saved_func;

	return 0;
}

static void ftrace_update_pid_func(void)
{
	struct ftrace_ops *op;

	/* Only do something if we are tracing something */
	if (ftrace_trace_function == ftrace_stub)
		return;

	do_for_each_ftrace_op(op, ftrace_ops_list) {
		if (op->flags & FTRACE_OPS_FL_PID) {
			op->func = ftrace_pids_enabled(op) ?
				ftrace_pid_func : op->saved_func;
			ftrace_update_trampoline(op);
		}
	} while_for_each_ftrace_op(op);

	fgraph_update_pid_func();

	update_ftrace_function();
}

#ifdef CONFIG_FUNCTION_PROFILER
struct ftrace_profile {
	struct hlist_node		node;
	unsigned long			ip;
	unsigned long			counter;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	unsigned long long		time;
	unsigned long long		time_squared;
#endif
};

struct ftrace_profile_page {
	struct ftrace_profile_page	*next;
	unsigned long			index;
	struct ftrace_profile		records[];
};

struct ftrace_profile_stat {
	atomic_t			disabled;
	struct hlist_head		*hash;
	struct ftrace_profile_page	*pages;
	struct ftrace_profile_page	*start;
	struct tracer_stat		stat;
};

#define PROFILE_RECORDS_SIZE						\
	(PAGE_SIZE - offsetof(struct ftrace_profile_page, records))

#define PROFILES_PER_PAGE					\
	(PROFILE_RECORDS_SIZE / sizeof(struct ftrace_profile))

static int ftrace_profile_enabled __read_mostly;

/* ftrace_profile_lock - synchronize the enable and disable of the profiler */
static DEFINE_MUTEX(ftrace_profile_lock);

static DEFINE_PER_CPU(struct ftrace_profile_stat, ftrace_profile_stats);

#define FTRACE_PROFILE_HASH_BITS 10
#define FTRACE_PROFILE_HASH_SIZE (1 << FTRACE_PROFILE_HASH_BITS)

static void *
function_stat_next(void *v, int idx)
{
	struct ftrace_profile *rec = v;
	struct ftrace_profile_page *pg;

	pg = (struct ftrace_profile_page *)((unsigned long)rec & PAGE_MASK);

 again:
	if (idx != 0)
		rec++;

	if ((void *)rec >= (void *)&pg->records[pg->index]) {
		pg = pg->next;
		if (!pg)
			return NULL;
		rec = &pg->records[0];
		if (!rec->counter)
			goto again;
	}

	return rec;
}

static void *function_stat_start(struct tracer_stat *trace)
{
	struct ftrace_profile_stat *stat =
		container_of(trace, struct ftrace_profile_stat, stat);

	if (!stat || !stat->start)
		return NULL;

	return function_stat_next(&stat->start->records[0], 0);
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* function graph compares on total time */
static int function_stat_cmp(const void *p1, const void *p2)
{
	const struct ftrace_profile *a = p1;
	const struct ftrace_profile *b = p2;

	if (a->time < b->time)
		return -1;
	if (a->time > b->time)
		return 1;
	else
		return 0;
}
#else
/* not function graph compares against hits */
static int function_stat_cmp(const void *p1, const void *p2)
{
	const struct ftrace_profile *a = p1;
	const struct ftrace_profile *b = p2;

	if (a->counter < b->counter)
		return -1;
	if (a->counter > b->counter)
		return 1;
	else
		return 0;
}
#endif

static int function_stat_headers(struct seq_file *m)
{
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	seq_puts(m, "  Function                               "
		 "Hit    Time            Avg             s^2\n"
		    "  --------                               "
		 "---    ----            ---             ---\n");
#else
	seq_puts(m, "  Function                               Hit\n"
		    "  --------                               ---\n");
#endif
	return 0;
}

static int function_stat_show(struct seq_file *m, void *v)
{
	struct ftrace_profile *rec = v;
	char str[KSYM_SYMBOL_LEN];
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	static struct trace_seq s;
	unsigned long long avg;
	unsigned long long stddev;
	unsigned long long stddev_denom;
#endif
	guard(mutex)(&ftrace_profile_lock);

	/* we raced with function_profile_reset() */
	if (unlikely(rec->counter == 0))
		return -EBUSY;

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	avg = div64_ul(rec->time, rec->counter);
	if (tracing_thresh && (avg < tracing_thresh))
		return 0;
#endif

	kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
	seq_printf(m, "  %-30.30s  %10lu", str, rec->counter);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	seq_puts(m, "    ");

	/*
	 * Variance formula:
	 * s^2 = 1 / (n * (n-1)) * (n * \Sum (x_i)^2 - (\Sum x_i)^2)
	 * Maybe Welford's method is better here?
	 * Divide only by 1000 for ns^2 -> us^2 conversion.
	 * trace_print_graph_duration will divide by 1000 again.
	 */
	stddev = 0;
	stddev_denom = rec->counter * (rec->counter - 1) * 1000;
	if (stddev_denom) {
		stddev = rec->counter * rec->time_squared -
			 rec->time * rec->time;
		stddev = div64_ul(stddev, stddev_denom);
	}

	trace_seq_init(&s);
	trace_print_graph_duration(rec->time, &s);
	trace_seq_puts(&s, "    ");
	trace_print_graph_duration(avg, &s);
	trace_seq_puts(&s, "    ");
	trace_print_graph_duration(stddev, &s);
	trace_print_seq(m, &s);
#endif
	seq_putc(m, '\n');

	return 0;
}

static void ftrace_profile_reset(struct ftrace_profile_stat *stat)
{
	struct ftrace_profile_page *pg;

	pg = stat->pages = stat->start;

	while (pg) {
		memset(pg->records, 0, PROFILE_RECORDS_SIZE);
		pg->index = 0;
		pg = pg->next;
	}

	memset(stat->hash, 0,
	       FTRACE_PROFILE_HASH_SIZE * sizeof(struct hlist_head));
}

static int ftrace_profile_pages_init(struct ftrace_profile_stat *stat)
{
	struct ftrace_profile_page *pg;
	int functions;
	int pages;
	int i;

	/* If we already allocated, do nothing */
	if (stat->pages)
		return 0;

	stat->pages = (void *)get_zeroed_page(GFP_KERNEL);
	if (!stat->pages)
		return -ENOMEM;

#ifdef CONFIG_DYNAMIC_FTRACE
	functions = ftrace_update_tot_cnt;
#else
	/*
	 * We do not know the number of functions that exist because
	 * dynamic tracing is what counts them. With past experience
	 * we have around 20K functions. That should be more than enough.
	 * It is highly unlikely we will execute every function in
	 * the kernel.
	 */
	functions = 20000;
#endif

	pg = stat->start = stat->pages;

	pages = DIV_ROUND_UP(functions, PROFILES_PER_PAGE);

	for (i = 1; i < pages; i++) {
		pg->next = (void *)get_zeroed_page(GFP_KERNEL);
		if (!pg->next)
			goto out_free;
		pg = pg->next;
	}

	return 0;

 out_free:
	pg = stat->start;
	while (pg) {
		unsigned long tmp = (unsigned long)pg;

		pg = pg->next;
		free_page(tmp);
	}

	stat->pages = NULL;
	stat->start = NULL;

	return -ENOMEM;
}

static int ftrace_profile_init_cpu(int cpu)
{
	struct ftrace_profile_stat *stat;
	int size;

	stat = &per_cpu(ftrace_profile_stats, cpu);

	if (stat->hash) {
		/* If the profile is already created, simply reset it */
		ftrace_profile_reset(stat);
		return 0;
	}

	/*
	 * We are profiling all functions, but usually only a few thousand
	 * functions are hit. We'll make a hash of 1024 items.
	 */
	size = FTRACE_PROFILE_HASH_SIZE;

	stat->hash = kcalloc(size, sizeof(struct hlist_head), GFP_KERNEL);

	if (!stat->hash)
		return -ENOMEM;

	/* Preallocate the function profiling pages */
	if (ftrace_profile_pages_init(stat) < 0) {
		kfree(stat->hash);
		stat->hash = NULL;
		return -ENOMEM;
	}

	return 0;
}

static int ftrace_profile_init(void)
{
	int cpu;
	int ret = 0;

	for_each_possible_cpu(cpu) {
		ret = ftrace_profile_init_cpu(cpu);
		if (ret)
			break;
	}

	return ret;
}

/* interrupts must be disabled */
static struct ftrace_profile *
ftrace_find_profiled_func(struct ftrace_profile_stat *stat, unsigned long ip)
{
	struct ftrace_profile *rec;
	struct hlist_head *hhd;
	unsigned long key;

	key = hash_long(ip, FTRACE_PROFILE_HASH_BITS);
	hhd = &stat->hash[key];

	if (hlist_empty(hhd))
		return NULL;

	hlist_for_each_entry_rcu_notrace(rec, hhd, node) {
		if (rec->ip == ip)
			return rec;
	}

	return NULL;
}

static void ftrace_add_profile(struct ftrace_profile_stat *stat,
			       struct ftrace_profile *rec)
{
	unsigned long key;

	key = hash_long(rec->ip, FTRACE_PROFILE_HASH_BITS);
	hlist_add_head_rcu(&rec->node, &stat->hash[key]);
}

/*
 * The memory is already allocated, this simply finds a new record to use.
 */
static struct ftrace_profile *
ftrace_profile_alloc(struct ftrace_profile_stat *stat, unsigned long ip)
{
	struct ftrace_profile *rec = NULL;

	/* prevent recursion (from NMIs) */
	if (atomic_inc_return(&stat->disabled) != 1)
		goto out;

	/*
	 * Try to find the function again since an NMI
	 * could have added it
	 */
	rec = ftrace_find_profiled_func(stat, ip);
	if (rec)
		goto out;

	if (stat->pages->index == PROFILES_PER_PAGE) {
		if (!stat->pages->next)
			goto out;
		stat->pages = stat->pages->next;
	}

	rec = &stat->pages->records[stat->pages->index++];
	rec->ip = ip;
	ftrace_add_profile(stat, rec);

 out:
	atomic_dec(&stat->disabled);

	return rec;
}

static void
function_profile_call(unsigned long ip, unsigned long parent_ip,
		      struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
	struct ftrace_profile_stat *stat;
	struct ftrace_profile *rec;

	if (!ftrace_profile_enabled)
		return;

	guard(preempt_notrace)();

	stat = this_cpu_ptr(&ftrace_profile_stats);
	if (!stat->hash || !ftrace_profile_enabled)
		return;

	rec = ftrace_find_profiled_func(stat, ip);
	if (!rec) {
		rec = ftrace_profile_alloc(stat, ip);
		if (!rec)
			return;
	}

	rec->counter++;
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static bool fgraph_graph_time = true;

void ftrace_graph_graph_time_control(bool enable)
{
	fgraph_graph_time = enable;
}

struct profile_fgraph_data {
	unsigned long long		calltime;
	unsigned long long		subtime;
	unsigned long long		sleeptime;
};

static int profile_graph_entry(struct ftrace_graph_ent *trace,
			       struct fgraph_ops *gops,
			       struct ftrace_regs *fregs)
{
	struct profile_fgraph_data *profile_data;

	function_profile_call(trace->func, 0, NULL, NULL);

	/* If function graph is shutting down, ret_stack can be NULL */
	if (!current->ret_stack)
		return 0;

	profile_data = fgraph_reserve_data(gops->idx, sizeof(*profile_data));
	if (!profile_data)
		return 0;

	profile_data->subtime = 0;
	profile_data->sleeptime = current->ftrace_sleeptime;
	profile_data->calltime = trace_clock_local();

	return 1;
}

static void profile_graph_return(struct ftrace_graph_ret *trace,
				 struct fgraph_ops *gops,
				 struct ftrace_regs *fregs)
{
	struct profile_fgraph_data *profile_data;
	struct ftrace_profile_stat *stat;
	unsigned long long calltime;
	unsigned long long rettime = trace_clock_local();
	struct ftrace_profile *rec;
	int size;

	guard(preempt_notrace)();

	stat = this_cpu_ptr(&ftrace_profile_stats);
	if (!stat->hash || !ftrace_profile_enabled)
		return;

	profile_data = fgraph_retrieve_data(gops->idx, &size);

	/* If the calltime was zero'd ignore it */
	if (!profile_data || !profile_data->calltime)
		return;

	calltime = rettime - profile_data->calltime;

	if (!fgraph_sleep_time) {
		if (current->ftrace_sleeptime)
			calltime -= current->ftrace_sleeptime - profile_data->sleeptime;
	}

	if (!fgraph_graph_time) {
		struct profile_fgraph_data *parent_data;

		/* Append this call time to the parent time to subtract */
		parent_data = fgraph_retrieve_parent_data(gops->idx, &size, 1);
		if (parent_data)
			parent_data->subtime += calltime;

		if (profile_data->subtime && profile_data->subtime < calltime)
			calltime -= profile_data->subtime;
		else
			calltime = 0;
	}

	rec = ftrace_find_profiled_func(stat, trace->func);
	if (rec) {
		rec->time += calltime;
		rec->time_squared += calltime * calltime;
	}
}

static struct fgraph_ops fprofiler_ops = {
	.entryfunc = &profile_graph_entry,
	.retfunc = &profile_graph_return,
};

static int register_ftrace_profiler(void)
{
	ftrace_ops_set_global_filter(&fprofiler_ops.ops);
	return register_ftrace_graph(&fprofiler_ops);
}

static void unregister_ftrace_profiler(void)
{
	unregister_ftrace_graph(&fprofiler_ops);
}
#else
static struct ftrace_ops ftrace_profile_ops __read_mostly = {
	.func		= function_profile_call,
};

static int register_ftrace_profiler(void)
{
	ftrace_ops_set_global_filter(&ftrace_profile_ops);
	return register_ftrace_function(&ftrace_profile_ops);
}

static void unregister_ftrace_profiler(void)
{
	unregister_ftrace_function(&ftrace_profile_ops);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

static ssize_t
ftrace_profile_write(struct file *filp, const char __user *ubuf,
		     size_t cnt, loff_t *ppos)
{
	unsigned long val;
	int ret;

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

	val = !!val;

	guard(mutex)(&ftrace_profile_lock);
	if (ftrace_profile_enabled ^ val) {
		if (val) {
			ret = ftrace_profile_init();
			if (ret < 0)
				return ret;

			ret = register_ftrace_profiler();
			if (ret < 0)
				return ret;
			ftrace_profile_enabled = 1;
		} else {
			ftrace_profile_enabled = 0;
			/*
			 * unregister_ftrace_profiler calls stop_machine
			 * so this acts like an synchronize_rcu.
			 */
			unregister_ftrace_profiler();
		}
	}

	*ppos += cnt;

	return cnt;
}

static ssize_t
ftrace_profile_read(struct file *filp, char __user *ubuf,
		     size_t cnt, loff_t *ppos)
{
	char buf[64];		/* big enough to hold a number */
	int r;

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

static const struct file_operations ftrace_profile_fops = {
	.open		= tracing_open_generic,
	.read		= ftrace_profile_read,
	.write		= ftrace_profile_write,
	.llseek		= default_llseek,
};

/* used to initialize the real stat files */
static struct tracer_stat function_stats __initdata = {
	.name		= "functions",
	.stat_start	= function_stat_start,
	.stat_next	= function_stat_next,
	.stat_cmp	= function_stat_cmp,
	.stat_headers	= function_stat_headers,
	.stat_show	= function_stat_show
};

static __init void ftrace_profile_tracefs(struct dentry *d_tracer)
{
	struct ftrace_profile_stat *stat;
	char *name;
	int ret;
	int cpu;

	for_each_possible_cpu(cpu) {
		stat = &per_cpu(ftrace_profile_stats, cpu);