[lttng-ust.git] / liblttng-ust / lttng-context-procname.c

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * LTTng UST procname context.
 */

#define _LGPL_SOURCE
#include <stddef.h>
#include <lttng/ust-events.h>
#include <lttng/ust-tracer.h>
#include <lttng/ringbuffer-context.h>
#include <urcu/tls-compat.h>
#include <assert.h>
#include "compat.h"
#include "lttng-tracer-core.h"

#include "context-internal.h"

/* Maximum number of nesting levels for the procname cache. */
#define PROCNAME_NESTING_MAX	2

/*
 * We cache the result to ensure we don't trigger a system call for
 * each event.
 * Upon exec, procname changes, but exec takes care of throwing away
 * this cached version.
 * The procname can also change by calling prctl(). The procname should
 * be set for a thread before the first event is logged within this
 * thread.
 */
typedef char procname_array[PROCNAME_NESTING_MAX][17];

static DEFINE_URCU_TLS(procname_array, cached_procname);

static DEFINE_URCU_TLS(int, procname_nesting);

static inline
const char *wrapper_getprocname(void)
{
	int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));

	if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
		return "<unknown>";
	if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
		CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
		/* Increment nesting before updating cache. */
		cmm_barrier();
		lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN);
		URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_PROCNAME_LEN - 1] = '\0';
		/* Decrement nesting after updating cache. */
		cmm_barrier();
		CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
	}
	return URCU_TLS(cached_procname)[nesting];
}

/* Reset should not be called from a signal handler. */
void lttng_ust_context_procname_reset(void)
{
	CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
	CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
}

static
size_t procname_get_size(struct lttng_ust_ctx_field *field __attribute__((unused)),
		size_t offset __attribute__((unused)))
{
	return LTTNG_UST_ABI_PROCNAME_LEN;
}

static
void procname_record(struct lttng_ust_ctx_field *field __attribute__((unused)),
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_ust_channel_buffer *chan)
{
	const char *procname;

	procname = wrapper_getprocname();
	chan->ops->event_write(ctx, procname, LTTNG_UST_ABI_PROCNAME_LEN, 1);
}

static
void procname_get_value(struct lttng_ust_ctx_field *field __attribute__((unused)),
		struct lttng_ust_ctx_value *value)
{
	value->u.str = wrapper_getprocname();
}

int lttng_add_procname_to_ctx(struct lttng_ust_ctx **ctx)
{
	struct lttng_ust_ctx_field *field;
	struct lttng_ust_type_common *type;
	int ret;

	type = lttng_ust_create_type_array_text(LTTNG_UST_ABI_PROCNAME_LEN);
	if (!type)
		return -ENOMEM;
	field = lttng_append_context(ctx);
	if (!field) {
		ret = -ENOMEM;
		goto error_context;
	}
	if (lttng_find_context(*ctx, "procname")) {
		ret = -EEXIST;
		goto error_find_context;
	}
	field->event_field->name = strdup("procname");
	if (!field->event_field->name) {
		ret = -ENOMEM;
		goto error_name;
	}
	field->event_field->type = type;
	field->get_size = procname_get_size;
	field->record = procname_record;
	field->get_value = procname_get_value;
	lttng_context_update(*ctx);
	return 0;

error_name:
error_find_context:
	lttng_remove_context_field(ctx, field);
error_context:
	lttng_ust_destroy_type(type);
	return ret;
}

/*
 * Force a read (imply TLS fixup for dlopen) of TLS variables.
 */
void lttng_fixup_procname_tls(void)
{
	asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));
}
Commit	Line	Data
	1	/*
	2	* SPDX-License-Identifier: LGPL-2.1-only
	3	*
	4	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	5	*
	6	* LTTng UST procname context.
	7	*/
	8
	9	#define _LGPL_SOURCE
	10	#include <stddef.h>
	11	#include <lttng/ust-events.h>
	12	#include <lttng/ust-tracer.h>
	13	#include <lttng/ringbuffer-context.h>
	14	#include <urcu/tls-compat.h>
	15	#include <assert.h>
	16	#include "compat.h"
	17	#include "lttng-tracer-core.h"
	18
	19	#include "context-internal.h"
	20
	21	/* Maximum number of nesting levels for the procname cache. */
	22	#define PROCNAME_NESTING_MAX 2
	23
	24	/*
	25	* We cache the result to ensure we don't trigger a system call for
	26	* each event.
	27	* Upon exec, procname changes, but exec takes care of throwing away
	28	* this cached version.
	29	* The procname can also change by calling prctl(). The procname should
	30	* be set for a thread before the first event is logged within this
	31	* thread.
	32	*/
	33	typedef char procname_array[PROCNAME_NESTING_MAX][17];
	34
	35	static DEFINE_URCU_TLS(procname_array, cached_procname);
	36
	37	static DEFINE_URCU_TLS(int, procname_nesting);
	38
	39	static inline
	40	const char *wrapper_getprocname(void)
	41	{
	42	int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
	43
	44	if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
	45	return "<unknown>";
	46	if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
	47	CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
	48	/* Increment nesting before updating cache. */
	49	cmm_barrier();
	50	lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN);
	51	URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_PROCNAME_LEN - 1] = '\0';
	52	/* Decrement nesting after updating cache. */
	53	cmm_barrier();
	54	CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
	55	}
	56	return URCU_TLS(cached_procname)[nesting];
	57	}
	58
	59	/* Reset should not be called from a signal handler. */
	60	void lttng_ust_context_procname_reset(void)
	61	{
	62	CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
	63	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
	64	CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
	65	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
	66	}
	67
	68	static
	69	size_t procname_get_size(struct lttng_ust_ctx_field *field __attribute__((unused)),
	70	size_t offset __attribute__((unused)))
	71	{
	72	return LTTNG_UST_ABI_PROCNAME_LEN;
	73	}
	74
	75	static
	76	void procname_record(struct lttng_ust_ctx_field *field __attribute__((unused)),
	77	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	78	struct lttng_ust_channel_buffer *chan)
	79	{
	80	const char *procname;
	81
	82	procname = wrapper_getprocname();
	83	chan->ops->event_write(ctx, procname, LTTNG_UST_ABI_PROCNAME_LEN, 1);
	84	}
	85
	86	static
	87	void procname_get_value(struct lttng_ust_ctx_field *field __attribute__((unused)),
	88	struct lttng_ust_ctx_value *value)
	89	{
	90	value->u.str = wrapper_getprocname();
	91	}
	92
	93	int lttng_add_procname_to_ctx(struct lttng_ust_ctx **ctx)
	94	{
	95	struct lttng_ust_ctx_field *field;
	96	struct lttng_ust_type_common *type;
	97	int ret;
	98
	99	type = lttng_ust_create_type_array_text(LTTNG_UST_ABI_PROCNAME_LEN);
	100	if (!type)
	101	return -ENOMEM;
	102	field = lttng_append_context(ctx);
	103	if (!field) {
	104	ret = -ENOMEM;
	105	goto error_context;
	106	}
	107	if (lttng_find_context(*ctx, "procname")) {
	108	ret = -EEXIST;
	109	goto error_find_context;
	110	}
	111	field->event_field->name = strdup("procname");
	112	if (!field->event_field->name) {
	113	ret = -ENOMEM;
	114	goto error_name;
	115	}
	116	field->event_field->type = type;
	117	field->get_size = procname_get_size;
	118	field->record = procname_record;
	119	field->get_value = procname_get_value;
	120	lttng_context_update(*ctx);
	121	return 0;
	122
	123	error_name:
	124	error_find_context:
	125	lttng_remove_context_field(ctx, field);
	126	error_context:
	127	lttng_ust_destroy_type(type);
	128	return ret;
	129	}
	130
	131	/*
	132	* Force a read (imply TLS fixup for dlopen) of TLS variables.
	133	*/
	134	void lttng_fixup_procname_tls(void)
	135	{
	136	asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));
	137	}