2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
7 * LTTng UST cgroup namespace context.
13 #include <sys/types.h>
16 #include <lttng/ust-events.h>
17 #include <lttng/ust-tracer.h>
19 #include <urcu/tls-compat.h>
20 #include <lttng/ringbuffer-context.h>
22 #include "context-internal.h"
23 #include "lttng-tracer-core.h"
28 * We cache the result to ensure we don't stat(2) the proc filesystem on
31 static DEFINE_URCU_TLS_INIT(ino_t
, cached_cgroup_ns
, NS_INO_UNINITIALIZED
);
34 ino_t
get_cgroup_ns(void)
39 cgroup_ns
= CMM_LOAD_SHARED(URCU_TLS(cached_cgroup_ns
));
42 * If the cache is populated, do nothing and return the
43 * cached inode number.
45 if (caa_likely(cgroup_ns
!= NS_INO_UNINITIALIZED
))
49 * At this point we have to populate the cache, set the initial
50 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
51 * number from the proc filesystem, this is the value we will
54 cgroup_ns
= NS_INO_UNAVAILABLE
;
57 * /proc/thread-self was introduced in kernel v3.17
59 if (stat("/proc/thread-self/ns/cgroup", &sb
) == 0) {
60 cgroup_ns
= sb
.st_ino
;
62 char proc_ns_path
[LTTNG_PROC_NS_PATH_MAX
];
64 if (snprintf(proc_ns_path
, LTTNG_PROC_NS_PATH_MAX
,
65 "/proc/self/task/%d/ns/cgroup",
66 lttng_gettid()) >= 0) {
68 if (stat(proc_ns_path
, &sb
) == 0) {
69 cgroup_ns
= sb
.st_ino
;
75 * And finally, store the inode number in the cache.
77 CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns
), cgroup_ns
);
83 * The cgroup namespace can change for 3 reasons
84 * * clone(2) called with CLONE_NEWCGROUP
85 * * setns(2) called with the fd of a different cgroup ns
86 * * unshare(2) called with CLONE_NEWCGROUP
88 void lttng_context_cgroup_ns_reset(void)
90 CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns
), NS_INO_UNINITIALIZED
);
94 size_t cgroup_ns_get_size(void *priv
__attribute__((unused
)),
99 size
+= lttng_ust_lib_ring_buffer_align(offset
, lttng_ust_rb_alignof(ino_t
));
100 size
+= sizeof(ino_t
);
105 void cgroup_ns_record(void *priv
__attribute__((unused
)),
106 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
107 struct lttng_ust_channel_buffer
*chan
)
111 cgroup_ns
= get_cgroup_ns();
112 chan
->ops
->event_write(ctx
, &cgroup_ns
, sizeof(cgroup_ns
),
113 lttng_ust_rb_alignof(cgroup_ns
));
117 void cgroup_ns_get_value(void *priv
__attribute__((unused
)),
118 struct lttng_ust_ctx_value
*value
)
120 value
->u
.s64
= get_cgroup_ns();
123 static const struct lttng_ust_ctx_field
*ctx_field
= lttng_ust_static_ctx_field(
124 lttng_ust_static_event_field("cgroup_ns",
125 lttng_ust_static_type_integer(sizeof(ino_t
) * CHAR_BIT
,
126 lttng_ust_rb_alignof(ino_t
) * CHAR_BIT
,
127 lttng_ust_is_signed_type(ino_t
),
135 int lttng_add_cgroup_ns_to_ctx(struct lttng_ust_ctx
**ctx
)
139 if (lttng_find_context(*ctx
, ctx_field
->event_field
->name
)) {
141 goto error_find_context
;
143 ret
= lttng_ust_context_append(ctx
, ctx_field
);
153 * * Force a read (imply TLS fixup for dlopen) of TLS variables.
155 void lttng_fixup_cgroup_ns_tls(void)
157 asm volatile ("" : : "m" (URCU_TLS(cached_cgroup_ns
)));