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 uts namespace context.
13 #include <sys/types.h>
16 #include <lttng/ust-events.h>
17 #include <lttng/ust-tracer.h>
18 #include <lttng/ringbuffer-context.h>
20 #include <urcu/tls-compat.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_uts_ns
, NS_INO_UNINITIALIZED
);
34 ino_t
get_uts_ns(void)
39 uts_ns
= CMM_LOAD_SHARED(URCU_TLS(cached_uts_ns
));
42 * If the cache is populated, do nothing and return the
43 * cached inode number.
45 if (caa_likely(uts_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 uts_ns
= NS_INO_UNAVAILABLE
;
57 * /proc/thread-self was introduced in kernel v3.17
59 if (stat("/proc/thread-self/ns/uts", &sb
) == 0) {
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/uts",
66 lttng_gettid()) >= 0) {
68 if (stat(proc_ns_path
, &sb
) == 0) {
75 * And finally, store the inode number in the cache.
77 CMM_STORE_SHARED(URCU_TLS(cached_uts_ns
), uts_ns
);
83 * The uts namespace can change for 3 reasons
84 * * clone(2) called with CLONE_NEWUTS
85 * * setns(2) called with the fd of a different uts ns
86 * * unshare(2) called with CLONE_NEWUTS
88 void lttng_context_uts_ns_reset(void)
90 CMM_STORE_SHARED(URCU_TLS(cached_uts_ns
), NS_INO_UNINITIALIZED
);
94 size_t uts_ns_get_size(struct lttng_ust_ctx_field
*field
, size_t offset
)
98 size
+= lttng_ust_lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
99 size
+= sizeof(ino_t
);
104 void uts_ns_record(struct lttng_ust_ctx_field
*field
,
105 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
106 struct lttng_ust_channel_buffer
*chan
)
110 uts_ns
= get_uts_ns();
111 lttng_ust_lib_ring_buffer_align_ctx(ctx
, lttng_alignof(uts_ns
));
112 chan
->ops
->event_write(ctx
, &uts_ns
, sizeof(uts_ns
));
116 void uts_ns_get_value(struct lttng_ust_ctx_field
*field
,
117 struct lttng_ust_ctx_value
*value
)
119 value
->u
.s64
= get_uts_ns();
122 int lttng_add_uts_ns_to_ctx(struct lttng_ust_ctx
**ctx
)
124 struct lttng_ust_ctx_field
*field
;
125 struct lttng_ust_type_common
*type
;
128 type
= lttng_ust_create_type_integer(sizeof(ino_t
) * CHAR_BIT
,
129 lttng_alignof(ino_t
) * CHAR_BIT
,
130 lttng_ust_is_signed_type(ino_t
),
134 field
= lttng_append_context(ctx
);
139 if (lttng_find_context(*ctx
, "uts_ns")) {
141 goto error_find_context
;
143 field
->event_field
->name
= strdup("uts_ns");
144 if (!field
->event_field
->name
) {
148 field
->event_field
->type
= type
;
149 field
->get_size
= uts_ns_get_size
;
150 field
->record
= uts_ns_record
;
151 field
->get_value
= uts_ns_get_value
;
152 lttng_context_update(*ctx
);
157 lttng_remove_context_field(ctx
, field
);
159 lttng_ust_destroy_type(type
);
164 * * Force a read (imply TLS fixup for dlopen) of TLS variables.
166 void lttng_fixup_uts_ns_tls(void)
168 asm volatile ("" : : "m" (URCU_TLS(cached_uts_ns
)));