2 * lttng-context-cgroup-ns.c
4 * LTTng UST cgroup namespace context.
6 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * 2019 Michael Jeanson <mjeanson@efficios.com>
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; only
12 * version 2.1 of the License.
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 #include <sys/types.h>
28 #include <lttng/ust-events.h>
29 #include <lttng/ust-tracer.h>
30 #include <lttng/ringbuffer-config.h>
31 #include <lttng/ust-tid.h>
32 #include <urcu/tls-compat.h>
33 #include "lttng-tracer-core.h"
38 * We cache the result to ensure we don't stat(2) the proc filesystem on
42 static DEFINE_URCU_TLS(ino_t
, cached_cgroup_ns
) = NS_INO_UNINITIALIZED
;
44 static DEFINE_URCU_TLS_INIT(ino_t
, cached_cgroup_ns
, NS_INO_UNINITIALIZED
);
48 ino_t
get_cgroup_ns(void)
53 cgroup_ns
= CMM_LOAD_SHARED(URCU_TLS(cached_cgroup_ns
));
56 * If the cache is populated, do nothing and return the
57 * cached inode number.
59 if (caa_likely(cgroup_ns
!= NS_INO_UNINITIALIZED
))
63 * At this point we have to populate the cache, set the initial
64 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
65 * number from the proc filesystem, this is the value we will
68 cgroup_ns
= NS_INO_UNAVAILABLE
;
71 * /proc/thread-self was introduced in kernel v3.17
73 if (stat("/proc/thread-self/ns/cgroup", &sb
) == 0) {
74 cgroup_ns
= sb
.st_ino
;
76 char proc_ns_path
[LTTNG_PROC_NS_PATH_MAX
];
78 if (snprintf(proc_ns_path
, LTTNG_PROC_NS_PATH_MAX
,
79 "/proc/self/task/%d/ns/cgroup",
80 lttng_gettid()) >= 0) {
82 if (stat(proc_ns_path
, &sb
) == 0) {
83 cgroup_ns
= sb
.st_ino
;
89 * And finally, store the inode number in the cache.
91 CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns
), cgroup_ns
);
97 * The cgroup namespace can change for 3 reasons
98 * * clone(2) called with CLONE_NEWCGROUP
99 * * setns(2) called with the fd of a different cgroup ns
100 * * unshare(2) called with CLONE_NEWCGROUP
102 void lttng_context_cgroup_ns_reset(void)
104 CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns
), NS_INO_UNINITIALIZED
);
108 size_t cgroup_ns_get_size(struct lttng_ctx_field
*field
, size_t offset
)
112 size
+= lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
113 size
+= sizeof(ino_t
);
118 void cgroup_ns_record(struct lttng_ctx_field
*field
,
119 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
120 struct lttng_channel
*chan
)
124 cgroup_ns
= get_cgroup_ns();
125 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(cgroup_ns
));
126 chan
->ops
->event_write(ctx
, &cgroup_ns
, sizeof(cgroup_ns
));
130 void cgroup_ns_get_value(struct lttng_ctx_field
*field
,
131 struct lttng_ctx_value
*value
)
133 value
->u
.s64
= get_cgroup_ns();
136 int lttng_add_cgroup_ns_to_ctx(struct lttng_ctx
**ctx
)
138 struct lttng_ctx_field
*field
;
140 field
= lttng_append_context(ctx
);
143 if (lttng_find_context(*ctx
, "cgroup_ns")) {
144 lttng_remove_context_field(ctx
, field
);
147 field
->event_field
.name
= "cgroup_ns";
148 field
->event_field
.type
.atype
= atype_integer
;
149 field
->event_field
.type
.u
.basic
.integer
.size
= sizeof(ino_t
) * CHAR_BIT
;
150 field
->event_field
.type
.u
.basic
.integer
.alignment
= lttng_alignof(ino_t
) * CHAR_BIT
;
151 field
->event_field
.type
.u
.basic
.integer
.signedness
= lttng_is_signed_type(ino_t
);
152 field
->event_field
.type
.u
.basic
.integer
.reverse_byte_order
= 0;
153 field
->event_field
.type
.u
.basic
.integer
.base
= 10;
154 field
->event_field
.type
.u
.basic
.integer
.encoding
= lttng_encode_none
;
155 field
->get_size
= cgroup_ns_get_size
;
156 field
->record
= cgroup_ns_record
;
157 field
->get_value
= cgroup_ns_get_value
;
158 lttng_context_update(*ctx
);
163 * * Force a read (imply TLS fixup for dlopen) of TLS variables.
165 void lttng_fixup_cgroup_ns_tls(void)
167 asm volatile ("" : : "m" (URCU_TLS(cached_cgroup_ns
)));