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 mnt namespace context.
12 #include <sys/types.h>
15 #include <lttng/ust-events.h>
16 #include <lttng/ust-tracer.h>
17 #include <lttng/ringbuffer-config.h>
19 #include "context-internal.h"
23 * We cache the result to ensure we don't stat(2) the proc filesystem on
24 * each event. The mount namespace is global to the process.
26 static ino_t cached_mnt_ns
= NS_INO_UNINITIALIZED
;
29 ino_t
get_mnt_ns(void)
34 mnt_ns
= CMM_LOAD_SHARED(cached_mnt_ns
);
37 * If the cache is populated, do nothing and return the
38 * cached inode number.
40 if (caa_likely(mnt_ns
!= NS_INO_UNINITIALIZED
))
44 * At this point we have to populate the cache, set the initial
45 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
46 * number from the proc filesystem, this is the value we will
49 mnt_ns
= NS_INO_UNAVAILABLE
;
51 if (stat("/proc/self/ns/mnt", &sb
) == 0) {
56 * And finally, store the inode number in the cache.
58 CMM_STORE_SHARED(cached_mnt_ns
, mnt_ns
);
64 * The mnt namespace can change for 3 reasons
65 * * clone(2) called with CLONE_NEWNS
66 * * setns(2) called with the fd of a different mnt ns
67 * * unshare(2) called with CLONE_NEWNS
69 void lttng_context_mnt_ns_reset(void)
71 CMM_STORE_SHARED(cached_mnt_ns
, NS_INO_UNINITIALIZED
);
75 size_t mnt_ns_get_size(struct lttng_ctx_field
*field
, size_t offset
)
79 size
+= lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
80 size
+= sizeof(ino_t
);
85 void mnt_ns_record(struct lttng_ctx_field
*field
,
86 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
87 struct lttng_channel
*chan
)
91 mnt_ns
= get_mnt_ns();
92 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(mnt_ns
));
93 chan
->ops
->event_write(ctx
, &mnt_ns
, sizeof(mnt_ns
));
97 void mnt_ns_get_value(struct lttng_ctx_field
*field
,
98 struct lttng_ctx_value
*value
)
100 value
->u
.s64
= get_mnt_ns();
103 int lttng_add_mnt_ns_to_ctx(struct lttng_ctx
**ctx
)
105 struct lttng_ctx_field
*field
;
107 field
= lttng_append_context(ctx
);
110 if (lttng_find_context(*ctx
, "mnt_ns")) {
111 lttng_remove_context_field(ctx
, field
);
114 field
->event_field
.name
= "mnt_ns";
115 field
->event_field
.type
.atype
= atype_integer
;
116 field
->event_field
.type
.u
.integer
.size
= sizeof(ino_t
) * CHAR_BIT
;
117 field
->event_field
.type
.u
.integer
.alignment
= lttng_alignof(ino_t
) * CHAR_BIT
;
118 field
->event_field
.type
.u
.integer
.signedness
= lttng_is_signed_type(ino_t
);
119 field
->event_field
.type
.u
.integer
.reverse_byte_order
= 0;
120 field
->event_field
.type
.u
.integer
.base
= 10;
121 field
->event_field
.type
.u
.integer
.encoding
= lttng_encode_none
;
122 field
->get_size
= mnt_ns_get_size
;
123 field
->record
= mnt_ns_record
;
124 field
->get_value
= mnt_ns_get_value
;
125 lttng_context_update(*ctx
);