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.
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 <urcu/tls-compat.h>
20 #include "lttng-tracer-core.h"
25 * We cache the result to ensure we don't stat(2) the proc filesystem on
28 static DEFINE_URCU_TLS_INIT(ino_t
, cached_uts_ns
, NS_INO_UNINITIALIZED
);
31 ino_t
get_uts_ns(void)
36 uts_ns
= CMM_LOAD_SHARED(URCU_TLS(cached_uts_ns
));
39 * If the cache is populated, do nothing and return the
40 * cached inode number.
42 if (caa_likely(uts_ns
!= NS_INO_UNINITIALIZED
))
46 * At this point we have to populate the cache, set the initial
47 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
48 * number from the proc filesystem, this is the value we will
51 uts_ns
= NS_INO_UNAVAILABLE
;
54 * /proc/thread-self was introduced in kernel v3.17
56 if (stat("/proc/thread-self/ns/uts", &sb
) == 0) {
59 char proc_ns_path
[LTTNG_PROC_NS_PATH_MAX
];
61 if (snprintf(proc_ns_path
, LTTNG_PROC_NS_PATH_MAX
,
62 "/proc/self/task/%d/ns/uts",
63 lttng_gettid()) >= 0) {
65 if (stat(proc_ns_path
, &sb
) == 0) {
72 * And finally, store the inode number in the cache.
74 CMM_STORE_SHARED(URCU_TLS(cached_uts_ns
), uts_ns
);
80 * The uts namespace can change for 3 reasons
81 * * clone(2) called with CLONE_NEWUTS
82 * * setns(2) called with the fd of a different uts ns
83 * * unshare(2) called with CLONE_NEWUTS
85 void lttng_context_uts_ns_reset(void)
87 CMM_STORE_SHARED(URCU_TLS(cached_uts_ns
), NS_INO_UNINITIALIZED
);
91 size_t uts_ns_get_size(struct lttng_ctx_field
*field
, size_t offset
)
95 size
+= lib_ring_buffer_align(offset
, lttng_alignof(ino_t
));
96 size
+= sizeof(ino_t
);
101 void uts_ns_record(struct lttng_ctx_field
*field
,
102 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
103 struct lttng_channel
*chan
)
107 uts_ns
= get_uts_ns();
108 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(uts_ns
));
109 chan
->ops
->event_write(ctx
, &uts_ns
, sizeof(uts_ns
));
113 void uts_ns_get_value(struct lttng_ctx_field
*field
,
114 struct lttng_ctx_value
*value
)
116 value
->u
.s64
= get_uts_ns();
119 int lttng_add_uts_ns_to_ctx(struct lttng_ctx
**ctx
)
121 struct lttng_ctx_field
*field
;
123 field
= lttng_append_context(ctx
);
126 if (lttng_find_context(*ctx
, "uts_ns")) {
127 lttng_remove_context_field(ctx
, field
);
130 field
->event_field
.name
= "uts_ns";
131 field
->event_field
.type
.atype
= atype_integer
;
132 field
->event_field
.type
.u
.integer
.size
= sizeof(ino_t
) * CHAR_BIT
;
133 field
->event_field
.type
.u
.integer
.alignment
= lttng_alignof(ino_t
) * CHAR_BIT
;
134 field
->event_field
.type
.u
.integer
.signedness
= lttng_is_signed_type(ino_t
);
135 field
->event_field
.type
.u
.integer
.reverse_byte_order
= 0;
136 field
->event_field
.type
.u
.integer
.base
= 10;
137 field
->event_field
.type
.u
.integer
.encoding
= lttng_encode_none
;
138 field
->get_size
= uts_ns_get_size
;
139 field
->record
= uts_ns_record
;
140 field
->get_value
= uts_ns_get_value
;
141 lttng_context_update(*ctx
);
146 * * Force a read (imply TLS fixup for dlopen) of TLS variables.
148 void lttng_fixup_uts_ns_tls(void)
150 asm volatile ("" : : "m" (URCU_TLS(cached_uts_ns
)));