[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-config.h>
#include <urcu/tls-compat.h>
#include <assert.h>
#include "compat.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
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_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_ctx_field *field, size_t offset)
{
	return LTTNG_UST_ABI_PROCNAME_LEN;
}

static
void procname_record(struct lttng_ctx_field *field,
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_channel *chan)
{
	char *procname;

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

static
void procname_get_value(struct lttng_ctx_field *field,
		struct lttng_ctx_value *value)
{
	value->u.str = wrapper_getprocname();
}

static const struct lttng_type procname_array_elem_type =
	__type_integer(char, BYTE_ORDER, 10, UTF8);

int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
{
	struct lttng_ctx_field *field;

	field = lttng_append_context(ctx);
	if (!field)
		return -ENOMEM;
	if (lttng_find_context(*ctx, "procname")) {
		lttng_remove_context_field(ctx, field);
		return -EEXIST;
	}
	field->event_field.name = "procname";
	field->event_field.type.atype = atype_array_nestable;
	field->event_field.type.u.array_nestable.elem_type =
		&procname_array_elem_type;
	field->event_field.type.u.array_nestable.length = LTTNG_UST_ABI_PROCNAME_LEN;
	field->get_size = procname_get_size;
	field->record = procname_record;
	field->get_value = procname_get_value;
	lttng_context_update(*ctx);
	return 0;
}

/*
 * 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-config.h>
	14	#include <urcu/tls-compat.h>
	15	#include <assert.h>
	16	#include "compat.h"
	17
	18	/* Maximum number of nesting levels for the procname cache. */
	19	#define PROCNAME_NESTING_MAX 2
	20
	21	/*
	22	* We cache the result to ensure we don't trigger a system call for
	23	* each event.
	24	* Upon exec, procname changes, but exec takes care of throwing away
	25	* this cached version.
	26	* The procname can also change by calling prctl(). The procname should
	27	* be set for a thread before the first event is logged within this
	28	* thread.
	29	*/
	30	typedef char procname_array[PROCNAME_NESTING_MAX][17];
	31
	32	static DEFINE_URCU_TLS(procname_array, cached_procname);
	33
	34	static DEFINE_URCU_TLS(int, procname_nesting);
	35
	36	static inline
	37	char *wrapper_getprocname(void)
	38	{
	39	int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
	40
	41	if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
	42	return "<unknown>";
	43	if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
	44	CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
	45	/* Increment nesting before updating cache. */
	46	cmm_barrier();
	47	lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN);
	48	URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_PROCNAME_LEN - 1] = '\0';
	49	/* Decrement nesting after updating cache. */
	50	cmm_barrier();
	51	CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
	52	}
	53	return URCU_TLS(cached_procname)[nesting];
	54	}
	55
	56	/* Reset should not be called from a signal handler. */
	57	void lttng_context_procname_reset(void)
	58	{
	59	CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
	60	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
	61	CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
	62	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
	63	}
	64
	65	static
	66	size_t procname_get_size(struct lttng_ctx_field *field, size_t offset)
	67	{
	68	return LTTNG_UST_ABI_PROCNAME_LEN;
	69	}
	70
	71	static
	72	void procname_record(struct lttng_ctx_field *field,
	73	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	74	struct lttng_channel *chan)
	75	{
	76	char *procname;
	77
	78	procname = wrapper_getprocname();
	79	chan->ops->event_write(ctx, procname, LTTNG_UST_ABI_PROCNAME_LEN);
	80	}
	81
	82	static
	83	void procname_get_value(struct lttng_ctx_field *field,
	84	struct lttng_ctx_value *value)
	85	{
	86	value->u.str = wrapper_getprocname();
	87	}
	88
	89	static const struct lttng_type procname_array_elem_type =
	90	__type_integer(char, BYTE_ORDER, 10, UTF8);
	91
	92	int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
	93	{
	94	struct lttng_ctx_field *field;
	95
	96	field = lttng_append_context(ctx);
	97	if (!field)
	98	return -ENOMEM;
	99	if (lttng_find_context(*ctx, "procname")) {
	100	lttng_remove_context_field(ctx, field);
	101	return -EEXIST;
	102	}
	103	field->event_field.name = "procname";
	104	field->event_field.type.atype = atype_array_nestable;
	105	field->event_field.type.u.array_nestable.elem_type =
	106	&procname_array_elem_type;
	107	field->event_field.type.u.array_nestable.length = LTTNG_UST_ABI_PROCNAME_LEN;
	108	field->get_size = procname_get_size;
	109	field->record = procname_record;
	110	field->get_value = procname_get_value;
	111	lttng_context_update(*ctx);
	112	return 0;
	113	}
	114
	115	/*
	116	* Force a read (imply TLS fixup for dlopen) of TLS variables.
	117	*/
	118	void lttng_fixup_procname_tls(void)
	119	{
	120	asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));
	121	}