[linux-2.6-block.git] / kernel / trace / trace_event_perf.c

/*
 * trace event based perf event profiling/tracing
 *
 * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
 * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
 */

#include <linux/module.h>
#include <linux/kprobes.h>
#include "trace.h"

DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);

EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);

static char *perf_trace_buf;
static char *perf_trace_buf_nmi;

/*
 * Force it to be aligned to unsigned long to avoid misaligned accesses
 * suprises
 */
typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
	perf_trace_t;

/* Count the events in use (per event id, not per instance) */
static int	total_ref_count;

static int perf_trace_event_enable(struct ftrace_event_call *event)
{
	char *buf;
	int ret = -ENOMEM;

	if (event->perf_refcount++ > 0)
		return 0;

	if (!total_ref_count) {
		buf = (char *)alloc_percpu(perf_trace_t);
		if (!buf)
			goto fail_buf;

		rcu_assign_pointer(perf_trace_buf, buf);

		buf = (char *)alloc_percpu(perf_trace_t);
		if (!buf)
			goto fail_buf_nmi;

		rcu_assign_pointer(perf_trace_buf_nmi, buf);
	}

	ret = event->perf_event_enable(event);
	if (!ret) {
		total_ref_count++;
		return 0;
	}

fail_buf_nmi:
	if (!total_ref_count) {
		free_percpu(perf_trace_buf_nmi);
		free_percpu(perf_trace_buf);
		perf_trace_buf_nmi = NULL;
		perf_trace_buf = NULL;
	}
fail_buf:
	event->perf_refcount--;

	return ret;
}

int perf_trace_enable(int event_id)
{
	struct ftrace_event_call *event;
	int ret = -EINVAL;

	mutex_lock(&event_mutex);
	list_for_each_entry(event, &ftrace_events, list) {
		if (event->id == event_id && event->perf_event_enable &&
		    try_module_get(event->mod)) {
			ret = perf_trace_event_enable(event);
			break;
		}
	}
	mutex_unlock(&event_mutex);

	return ret;
}

static void perf_trace_event_disable(struct ftrace_event_call *event)
{
	char *buf, *nmi_buf;

	if (--event->perf_refcount > 0)
		return;

	event->perf_event_disable(event);

	if (!--total_ref_count) {
		buf = perf_trace_buf;
		rcu_assign_pointer(perf_trace_buf, NULL);

		nmi_buf = perf_trace_buf_nmi;
		rcu_assign_pointer(perf_trace_buf_nmi, NULL);

		/*
		 * Ensure every events in profiling have finished before
		 * releasing the buffers
		 */
		synchronize_sched();

		free_percpu(buf);
		free_percpu(nmi_buf);
	}
}

void perf_trace_disable(int event_id)
{
	struct ftrace_event_call *event;

	mutex_lock(&event_mutex);
	list_for_each_entry(event, &ftrace_events, list) {
		if (event->id == event_id) {
			perf_trace_event_disable(event);
			module_put(event->mod);
			break;
		}
	}
	mutex_unlock(&event_mutex);
}

__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
				       int *rctxp, unsigned long *irq_flags)
{
	struct trace_entry *entry;
	char *trace_buf, *raw_data;
	int pc, cpu;

	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));

	pc = preempt_count();

	/* Protect the per cpu buffer, begin the rcu read side */
	local_irq_save(*irq_flags);

	*rctxp = perf_swevent_get_recursion_context();
	if (*rctxp < 0)
		goto err_recursion;

	cpu = smp_processor_id();

	if (in_nmi())
		trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
	else
		trace_buf = rcu_dereference_sched(perf_trace_buf);

	if (!trace_buf)
		goto err;

	raw_data = per_cpu_ptr(trace_buf, cpu);

	/* zero the dead bytes from align to not leak stack to user */
	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));

	entry = (struct trace_entry *)raw_data;
	tracing_generic_entry_update(entry, *irq_flags, pc);
	entry->type = type;

	return raw_data;
err:
	perf_swevent_put_recursion_context(*rctxp);
err_recursion:
	local_irq_restore(*irq_flags);
	return NULL;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
Commit	Line	Data
	1	/*
	2	* trace event based perf event profiling/tracing
	3	*
	4	* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
	5	* Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
	6	*/
	7
	8	#include <linux/module.h>
	9	#include <linux/kprobes.h>
	10	#include "trace.h"
	11
	12	DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
	13	EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);
	14
	15	EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
	16
	17	static char *perf_trace_buf;
	18	static char *perf_trace_buf_nmi;
	19
	20	/*
	21	* Force it to be aligned to unsigned long to avoid misaligned accesses
	22	* suprises
	23	*/
	24	typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
	25	perf_trace_t;
	26
	27	/* Count the events in use (per event id, not per instance) */
	28	static int total_ref_count;
	29
	30	static int perf_trace_event_enable(struct ftrace_event_call *event)
	31	{
	32	char *buf;
	33	int ret = -ENOMEM;
	34
	35	if (event->perf_refcount++ > 0)
	36	return 0;
	37
	38	if (!total_ref_count) {
	39	buf = (char *)alloc_percpu(perf_trace_t);
	40	if (!buf)
	41	goto fail_buf;
	42
	43	rcu_assign_pointer(perf_trace_buf, buf);
	44
	45	buf = (char *)alloc_percpu(perf_trace_t);
	46	if (!buf)
	47	goto fail_buf_nmi;
	48
	49	rcu_assign_pointer(perf_trace_buf_nmi, buf);
	50	}
	51
	52	ret = event->perf_event_enable(event);
	53	if (!ret) {
	54	total_ref_count++;
	55	return 0;
	56	}
	57
	58	fail_buf_nmi:
	59	if (!total_ref_count) {
	60	free_percpu(perf_trace_buf_nmi);
	61	free_percpu(perf_trace_buf);
	62	perf_trace_buf_nmi = NULL;
	63	perf_trace_buf = NULL;
	64	}
	65	fail_buf:
	66	event->perf_refcount--;
	67
	68	return ret;
	69	}
	70
	71	int perf_trace_enable(int event_id)
	72	{
	73	struct ftrace_event_call *event;
	74	int ret = -EINVAL;
	75
	76	mutex_lock(&event_mutex);
	77	list_for_each_entry(event, &ftrace_events, list) {
	78	if (event->id == event_id && event->perf_event_enable &&
	79	try_module_get(event->mod)) {
	80	ret = perf_trace_event_enable(event);
	81	break;
	82	}
	83	}
	84	mutex_unlock(&event_mutex);
	85
	86	return ret;
	87	}
	88
	89	static void perf_trace_event_disable(struct ftrace_event_call *event)
	90	{
	91	char buf, nmi_buf;
	92
	93	if (--event->perf_refcount > 0)
	94	return;
	95
	96	event->perf_event_disable(event);
	97
	98	if (!--total_ref_count) {
	99	buf = perf_trace_buf;
	100	rcu_assign_pointer(perf_trace_buf, NULL);
	101
	102	nmi_buf = perf_trace_buf_nmi;
	103	rcu_assign_pointer(perf_trace_buf_nmi, NULL);
	104
	105	/*
	106	* Ensure every events in profiling have finished before
	107	* releasing the buffers
	108	*/
	109	synchronize_sched();
	110
	111	free_percpu(buf);
	112	free_percpu(nmi_buf);
	113	}
	114	}
	115
	116	void perf_trace_disable(int event_id)
	117	{
	118	struct ftrace_event_call *event;
	119
	120	mutex_lock(&event_mutex);
	121	list_for_each_entry(event, &ftrace_events, list) {
	122	if (event->id == event_id) {
	123	perf_trace_event_disable(event);
	124	module_put(event->mod);
	125	break;
	126	}
	127	}
	128	mutex_unlock(&event_mutex);
	129	}
	130
	131	__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
	132	int rctxp, unsigned long irq_flags)
	133	{
	134	struct trace_entry *entry;
	135	char trace_buf, raw_data;
	136	int pc, cpu;
	137
	138	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
	139
	140	pc = preempt_count();
	141
	142	/* Protect the per cpu buffer, begin the rcu read side */
	143	local_irq_save(*irq_flags);
	144
	145	*rctxp = perf_swevent_get_recursion_context();
	146	if (*rctxp < 0)
	147	goto err_recursion;
	148
	149	cpu = smp_processor_id();
	150
	151	if (in_nmi())
	152	trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
	153	else
	154	trace_buf = rcu_dereference_sched(perf_trace_buf);
	155
	156	if (!trace_buf)
	157	goto err;
	158
	159	raw_data = per_cpu_ptr(trace_buf, cpu);
	160
	161	/* zero the dead bytes from align to not leak stack to user */
	162	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
	163
	164	entry = (struct trace_entry *)raw_data;
	165	tracing_generic_entry_update(entry, *irq_flags, pc);
	166	entry->type = type;
	167
	168	return raw_data;
	169	err:
	170	perf_swevent_put_recursion_context(*rctxp);
	171	err_recursion:
	172	local_irq_restore(*irq_flags);
	173	return NULL;
	174	}
	175	EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);