[lttng-ust.git] / liblttng-ust / lttng-context-ipc-ns.c

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
 *
 * LTTng UST ipc namespace context.
 */

#define _LGPL_SOURCE
#include <stddef.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <lttng/ust-events.h>
#include <lttng/ust-tracer.h>
#include <lttng/ringbuffer-config.h>
#include <lttng/ust-tid.h>
#include <urcu/tls-compat.h>
#include "lttng-tracer-core.h"
#include "ns.h"

/*
 * We cache the result to ensure we don't stat(2) the proc filesystem on
 * each event.
 */
static DEFINE_URCU_TLS_INIT(ino_t, cached_ipc_ns, NS_INO_UNINITIALIZED);

static
ino_t get_ipc_ns(void)
{
	struct stat sb;
	ino_t ipc_ns;

	ipc_ns = CMM_LOAD_SHARED(URCU_TLS(cached_ipc_ns));

	/*
	 * If the cache is populated, do nothing and return the
	 * cached inode number.
	 */
	if (caa_likely(ipc_ns != NS_INO_UNINITIALIZED))
		return ipc_ns;

	/*
	 * At this point we have to populate the cache, set the initial
	 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
	 * number from the proc filesystem, this is the value we will
	 * cache.
	 */
	ipc_ns = NS_INO_UNAVAILABLE;

	/*
	 * /proc/thread-self was introduced in kernel v3.17
	 */
	if (stat("/proc/thread-self/ns/ipc", &sb) == 0) {
		ipc_ns = sb.st_ino;
	} else {
		char proc_ns_path[LTTNG_PROC_NS_PATH_MAX];

		if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX,
				"/proc/self/task/%d/ns/ipc",
				lttng_gettid()) >= 0) {

			if (stat(proc_ns_path, &sb) == 0) {
				ipc_ns = sb.st_ino;
			}
		}
	}

	/*
	 * And finally, store the inode number in the cache.
	 */
	CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), ipc_ns);

	return ipc_ns;
}

/*
 * The ipc namespace can change for 3 reasons
 *  * clone(2) called with CLONE_NEWIPC
 *  * setns(2) called with the fd of a different ipc ns
 *  * unshare(2) called with CLONE_NEWIPC
 */
void lttng_context_ipc_ns_reset(void)
{
	CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), NS_INO_UNINITIALIZED);
}

static
size_t ipc_ns_get_size(struct lttng_ctx_field *field, size_t offset)
{
	size_t size = 0;

	size += lib_ring_buffer_align(offset, lttng_alignof(ino_t));
	size += sizeof(ino_t);
	return size;
}

static
void ipc_ns_record(struct lttng_ctx_field *field,
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_channel *chan)
{
	ino_t ipc_ns;

	ipc_ns = get_ipc_ns();
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(ipc_ns));
	chan->ops->event_write(ctx, &ipc_ns, sizeof(ipc_ns));
}

static
void ipc_ns_get_value(struct lttng_ctx_field *field,
		struct lttng_ctx_value *value)
{
	value->u.s64 = get_ipc_ns();
}

int lttng_add_ipc_ns_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, "ipc_ns")) {
		lttng_remove_context_field(ctx, field);
		return -EEXIST;
	}
	field->event_field.name = "ipc_ns";
	field->event_field.type.atype = atype_integer;
	field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT;
	field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT;
	field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t);
	field->event_field.type.u.integer.reverse_byte_order = 0;
	field->event_field.type.u.integer.base = 10;
	field->event_field.type.u.integer.encoding = lttng_encode_none;
	field->get_size = ipc_ns_get_size;
	field->record = ipc_ns_record;
	field->get_value = ipc_ns_get_value;
	lttng_context_update(*ctx);
	return 0;
}

/*
 *  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 *   */
void lttng_fixup_ipc_ns_tls(void)
{
	asm volatile ("" : : "m" (URCU_TLS(cached_ipc_ns)));
}
Commit	Line	Data
735bef47	1	/*
c0c0989a	2	* SPDX-License-Identifier: LGPL-2.1-only
735bef47 MJ	3	*
735bef47 MJ	4	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
c0c0989a	5	* Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
735bef47	6	*
c0c0989a	7	* LTTng UST ipc namespace context.
735bef47 MJ	8	*/
	9
	10	#define _LGPL_SOURCE
b4051ad8	11	#include <stddef.h>
735bef47 MJ	12	#include <sys/types.h>
	13	#include <sys/stat.h>
	14	#include <unistd.h>
	15	#include <lttng/ust-events.h>
	16	#include <lttng/ust-tracer.h>
	17	#include <lttng/ringbuffer-config.h>
	18	#include <lttng/ust-tid.h>
	19	#include <urcu/tls-compat.h>
	20	#include "lttng-tracer-core.h"
	21	#include "ns.h"
	22
735bef47 MJ	23	/*
	24	* We cache the result to ensure we don't stat(2) the proc filesystem on
	25	* each event.
	26	*/
a251a209	27	static DEFINE_URCU_TLS_INIT(ino_t, cached_ipc_ns, NS_INO_UNINITIALIZED);
735bef47 MJ	28
	29	static
	30	ino_t get_ipc_ns(void)
	31	{
	32	struct stat sb;
	33	ino_t ipc_ns;
	34
	35	ipc_ns = CMM_LOAD_SHARED(URCU_TLS(cached_ipc_ns));
	36
	37	/*
	38	* If the cache is populated, do nothing and return the
	39	* cached inode number.
	40	*/
	41	if (caa_likely(ipc_ns != NS_INO_UNINITIALIZED))
	42	return ipc_ns;
	43
	44	/*
	45	* At this point we have to populate the cache, set the initial
	46	* value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
	47	* number from the proc filesystem, this is the value we will
	48	* cache.
	49	*/
	50	ipc_ns = NS_INO_UNAVAILABLE;
	51
	52	/*
	53	* /proc/thread-self was introduced in kernel v3.17
	54	*/
	55	if (stat("/proc/thread-self/ns/ipc", &sb) == 0) {
	56	ipc_ns = sb.st_ino;
	57	} else {
	58	char proc_ns_path[LTTNG_PROC_NS_PATH_MAX];
	59
	60	if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX,
	61	"/proc/self/task/%d/ns/ipc",
	62	lttng_gettid()) >= 0) {
	63
	64	if (stat(proc_ns_path, &sb) == 0) {
	65	ipc_ns = sb.st_ino;
	66	}
	67	}
	68	}
	69
	70	/*
	71	* And finally, store the inode number in the cache.
	72	*/
	73	CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), ipc_ns);
	74
	75	return ipc_ns;
	76	}
	77
	78	/*
	79	* The ipc namespace can change for 3 reasons
	80	* * clone(2) called with CLONE_NEWIPC
	81	* * setns(2) called with the fd of a different ipc ns
	82	* * unshare(2) called with CLONE_NEWIPC
	83	*/
	84	void lttng_context_ipc_ns_reset(void)
	85	{
	86	CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), NS_INO_UNINITIALIZED);
	87	}
	88
	89	static
	90	size_t ipc_ns_get_size(struct lttng_ctx_field *field, size_t offset)
	91	{
92	size_t size = 0;
93
94	size += lib_ring_buffer_align(offset, lttng_alignof(ino_t));
95	size += sizeof(ino_t);
96	return size;
97	}
98
99	static
100	void ipc_ns_record(struct lttng_ctx_field *field,
101	struct lttng_ust_lib_ring_buffer_ctx *ctx,
102	struct lttng_channel *chan)
103	{
104	ino_t ipc_ns;
105
106	ipc_ns = get_ipc_ns();
107	lib_ring_buffer_align_ctx(ctx, lttng_alignof(ipc_ns));
108	chan->ops->event_write(ctx, &ipc_ns, sizeof(ipc_ns));
109	}
110
111	static
112	void ipc_ns_get_value(struct lttng_ctx_field *field,
113	struct lttng_ctx_value *value)
114	{
115	value->u.s64 = get_ipc_ns();
116	}
117
118	int lttng_add_ipc_ns_to_ctx(struct lttng_ctx **ctx)
119	{
120	struct lttng_ctx_field *field;
121
122	field = lttng_append_context(ctx);
123	if (!field)
124	return -ENOMEM;
125	if (lttng_find_context(*ctx, "ipc_ns")) {
126	lttng_remove_context_field(ctx, field);
127	return -EEXIST;
128	}
129	field->event_field.name = "ipc_ns";
130	field->event_field.type.atype = atype_integer;
218deb69 MD	131	field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT;
	132	field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT;
	133	field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t);
	134	field->event_field.type.u.integer.reverse_byte_order = 0;
	135	field->event_field.type.u.integer.base = 10;
	136	field->event_field.type.u.integer.encoding = lttng_encode_none;
735bef47 MJ	137	field->get_size = ipc_ns_get_size;
	138	field->record = ipc_ns_record;
	139	field->get_value = ipc_ns_get_value;
	140	lttng_context_update(*ctx);
	141	return 0;
	142	}
	143
	144	/*
	145	* * Force a read (imply TLS fixup for dlopen) of TLS variables.
	146	* */
	147	void lttng_fixup_ipc_ns_tls(void)
	148	{
	149	asm volatile ("" : : "m" (URCU_TLS(cached_ipc_ns)));
	150	}