2 * lttng-context-user-ns.c
4 * LTTng UST user 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 user namespace is global to the process.
38 static ino_t cached_user_ns
= NS_INO_UNINITIALIZED
;
41 ino_t
get_user_ns(void)
46 user_ns
= CMM_LOAD_SHARED(cached_user_ns
);
49 * If the cache is populated, do nothing and return the
50 * cached inode number.
52 if (caa_likely(user_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 user_ns
= NS_INO_UNAVAILABLE
;
63 if (stat("/proc/self/ns/user", &sb
) == 0) {
68 * And finally, store the inode number in the cache.
70 CMM_STORE_SHARED(cached_user_ns
, user_ns
);
76 * The user namespace can change for 3 reasons
77 * * clone(2) called with CLONE_NEWUSER
78 * * setns(2) called with the fd of a different user ns
79 * * unshare(2) called with CLONE_NEWUSER
81 void lttng_context_user_ns_reset(void)
83 CMM_STORE_SHARED(cached_user_ns
, NS_INO_UNINITIALIZED
);
87 size_t user_ns_get_size(struct lttng_ctx_field
*field
, size_t offset
)
91 size
+= lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
92 size
+= sizeof(ino_t
);
97 void user_ns_record(struct lttng_ctx_field
*field
,
98 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
99 struct lttng_channel
*chan
)
103 user_ns
= get_user_ns();
104 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(user_ns
));
105 chan
->ops
->event_write(ctx
, &user_ns
, sizeof(user_ns
));
109 void user_ns_get_value(struct lttng_ctx_field
*field
,
110 struct lttng_ctx_value
*value
)
112 value
->u
.s64
= get_user_ns();
115 int lttng_add_user_ns_to_ctx(struct lttng_ctx
**ctx
)
117 struct lttng_ctx_field
*field
;
119 field
= lttng_append_context(ctx
);
122 if (lttng_find_context(*ctx
, "user_ns")) {
123 lttng_remove_context_field(ctx
, field
);
126 field
->event_field
.name
= "user_ns";
127 field
->event_field
.type
.atype
= atype_integer
;
128 field
->event_field
.type
.u
.basic
.integer
.size
= sizeof(ino_t
) * CHAR_BIT
;
129 field
->event_field
.type
.u
.basic
.integer
.alignment
= lttng_alignof(ino_t
) * CHAR_BIT
;
130 field
->event_field
.type
.u
.basic
.integer
.signedness
= lttng_is_signed_type(ino_t
);
131 field
->event_field
.type
.u
.basic
.integer
.reverse_byte_order
= 0;
132 field
->event_field
.type
.u
.basic
.integer
.base
= 10;
133 field
->event_field
.type
.u
.basic
.integer
.encoding
= lttng_encode_none
;
134 field
->get_size
= user_ns_get_size
;
135 field
->record
= user_ns_record
;
136 field
->get_value
= user_ns_get_value
;
137 lttng_context_update(*ctx
);