2 * lttng-context-pid-ns.c
4 * LTTng UST pid 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>
35 * We cache the result to ensure we don't stat(2) the proc filesystem on
36 * each event. The PID namespace is global to the process.
38 static ino_t cached_pid_ns
= NS_INO_UNINITIALIZED
;
41 ino_t
get_pid_ns(void)
46 pid_ns
= CMM_LOAD_SHARED(cached_pid_ns
);
49 * If the cache is populated, do nothing and return the
50 * cached inode number.
52 if (caa_likely(pid_ns
!= NS_INO_UNINITIALIZED
))
56 * At this point we have to populate the cache, set the initial
57 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
58 * number from the proc filesystem, this is the value we will
61 pid_ns
= NS_INO_UNAVAILABLE
;
63 if (stat("/proc/self/ns/pid", &sb
) == 0) {
68 * And finally, store the inode number in the cache.
70 CMM_STORE_SHARED(cached_pid_ns
, pid_ns
);
76 * A process's PID namespace membership is determined when the process is
77 * created and cannot be changed thereafter.
79 * The pid namespace can change only on clone(2) / fork(2) :
80 * - clone(2) with the CLONE_NEWPID flag
81 * - clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWPID flag
82 * - clone(2) / fork(2) after a call to setns(2) with a PID namespace fd
84 void lttng_context_pid_ns_reset(void)
86 CMM_STORE_SHARED(cached_pid_ns
, NS_INO_UNINITIALIZED
);
90 size_t pid_ns_get_size(struct lttng_ctx_field
*field
, size_t offset
)
94 size
+= lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
95 size
+= sizeof(ino_t
);
100 void pid_ns_record(struct lttng_ctx_field
*field
,
101 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
102 struct lttng_channel
*chan
)
106 pid_ns
= get_pid_ns();
107 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(pid_ns
));
108 chan
->ops
->event_write(ctx
, &pid_ns
, sizeof(pid_ns
));
112 void pid_ns_get_value(struct lttng_ctx_field
*field
,
113 struct lttng_ctx_value
*value
)
115 value
->u
.s64
= get_pid_ns();
118 int lttng_add_pid_ns_to_ctx(struct lttng_ctx
**ctx
)
120 struct lttng_ctx_field
*field
;
122 field
= lttng_append_context(ctx
);
125 if (lttng_find_context(*ctx
, "pid_ns")) {
126 lttng_remove_context_field(ctx
, field
);
129 field
->event_field
.name
= "pid_ns";
130 field
->event_field
.type
.atype
= atype_integer
;
131 field
->event_field
.type
.u
.basic
.integer
.size
= sizeof(ino_t
) * CHAR_BIT
;
132 field
->event_field
.type
.u
.basic
.integer
.alignment
= lttng_alignof(ino_t
) * CHAR_BIT
;
133 field
->event_field
.type
.u
.basic
.integer
.signedness
= lttng_is_signed_type(ino_t
);
134 field
->event_field
.type
.u
.basic
.integer
.reverse_byte_order
= 0;
135 field
->event_field
.type
.u
.basic
.integer
.base
= 10;
136 field
->event_field
.type
.u
.basic
.integer
.encoding
= lttng_encode_none
;
137 field
->get_size
= pid_ns_get_size
;
138 field
->record
= pid_ns_record
;
139 field
->get_value
= pid_ns_get_value
;
140 lttng_context_update(*ctx
);