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735bef47 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
735bef47 MJ |
3 | * |
4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
c0c0989a | 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
735bef47 | 6 | * |
c0c0989a | 7 | * LTTng UST uts namespace context. |
735bef47 MJ |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
9af5d97a | 11 | #include <limits.h> |
b4051ad8 | 12 | #include <stddef.h> |
735bef47 MJ |
13 | #include <sys/types.h> |
14 | #include <sys/stat.h> | |
15 | #include <unistd.h> | |
16 | #include <lttng/ust-events.h> | |
17 | #include <lttng/ust-tracer.h> | |
0b4b8811 | 18 | #include <lttng/ust-ringbuffer-context.h> |
9d315d6d | 19 | #include "common/compat/tid.h" |
735bef47 | 20 | #include <urcu/tls-compat.h> |
fc80554e MJ |
21 | |
22 | #include "context-internal.h" | |
735bef47 | 23 | #include "lttng-tracer-core.h" |
c5e8ef85 | 24 | #include "common/ns.h" |
735bef47 MJ |
25 | |
26 | ||
27 | /* | |
28 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
29 | * each event. | |
30 | */ | |
a251a209 | 31 | static DEFINE_URCU_TLS_INIT(ino_t, cached_uts_ns, NS_INO_UNINITIALIZED); |
735bef47 MJ |
32 | |
33 | static | |
34 | ino_t get_uts_ns(void) | |
35 | { | |
36 | struct stat sb; | |
37 | ino_t uts_ns; | |
38 | ||
39 | uts_ns = CMM_LOAD_SHARED(URCU_TLS(cached_uts_ns)); | |
40 | ||
41 | /* | |
42 | * If the cache is populated, do nothing and return the | |
43 | * cached inode number. | |
44 | */ | |
45 | if (caa_likely(uts_ns != NS_INO_UNINITIALIZED)) | |
46 | return uts_ns; | |
47 | ||
48 | /* | |
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 | |
52 | * cache. | |
53 | */ | |
54 | uts_ns = NS_INO_UNAVAILABLE; | |
55 | ||
56 | /* | |
57 | * /proc/thread-self was introduced in kernel v3.17 | |
58 | */ | |
59 | if (stat("/proc/thread-self/ns/uts", &sb) == 0) { | |
60 | uts_ns = sb.st_ino; | |
61 | } else { | |
62 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
63 | ||
64 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
65 | "/proc/self/task/%d/ns/uts", | |
66 | lttng_gettid()) >= 0) { | |
67 | ||
68 | if (stat(proc_ns_path, &sb) == 0) { | |
69 | uts_ns = sb.st_ino; | |
70 | } | |
71 | } | |
72 | } | |
73 | ||
74 | /* | |
75 | * And finally, store the inode number in the cache. | |
76 | */ | |
77 | CMM_STORE_SHARED(URCU_TLS(cached_uts_ns), uts_ns); | |
78 | ||
79 | return uts_ns; | |
80 | } | |
81 | ||
82 | /* | |
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 | |
87 | */ | |
88 | void lttng_context_uts_ns_reset(void) | |
89 | { | |
90 | CMM_STORE_SHARED(URCU_TLS(cached_uts_ns), NS_INO_UNINITIALIZED); | |
91 | } | |
92 | ||
93 | static | |
4e48b5d2 | 94 | size_t uts_ns_get_size(void *priv __attribute__((unused)), |
b2e37d27 | 95 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
2208d8b5 | 96 | size_t offset) |
735bef47 MJ |
97 | { |
98 | size_t size = 0; | |
99 | ||
b5457df5 | 100 | size += lttng_ust_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
735bef47 MJ |
101 | size += sizeof(ino_t); |
102 | return size; | |
103 | } | |
104 | ||
105 | static | |
4e48b5d2 | 106 | void uts_ns_record(void *priv __attribute__((unused)), |
b2e37d27 MD |
107 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
108 | struct lttng_ust_ring_buffer_ctx *ctx, | |
109 | struct lttng_ust_channel_buffer *chan) | |
735bef47 MJ |
110 | { |
111 | ino_t uts_ns; | |
112 | ||
113 | uts_ns = get_uts_ns(); | |
8936b6c0 | 114 | chan->ops->event_write(ctx, &uts_ns, sizeof(uts_ns), lttng_ust_rb_alignof(uts_ns)); |
735bef47 MJ |
115 | } |
116 | ||
117 | static | |
4e48b5d2 | 118 | void uts_ns_get_value(void *priv __attribute__((unused)), |
b2e37d27 | 119 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
daacdbfc | 120 | struct lttng_ust_ctx_value *value) |
735bef47 | 121 | { |
b2e37d27 | 122 | value->u.u64 = get_uts_ns(); |
735bef47 MJ |
123 | } |
124 | ||
4e48b5d2 MD |
125 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
126 | lttng_ust_static_event_field("uts_ns", | |
127 | lttng_ust_static_type_integer(sizeof(ino_t) * CHAR_BIT, | |
128 | lttng_ust_rb_alignof(ino_t) * CHAR_BIT, | |
129 | lttng_ust_is_signed_type(ino_t), | |
baa8acf3 | 130 | LTTNG_UST_BYTE_ORDER, 10), |
4e48b5d2 MD |
131 | false, false), |
132 | uts_ns_get_size, | |
133 | uts_ns_record, | |
134 | uts_ns_get_value, | |
135 | NULL, NULL); | |
136 | ||
daacdbfc | 137 | int lttng_add_uts_ns_to_ctx(struct lttng_ust_ctx **ctx) |
735bef47 | 138 | { |
a084756d MD |
139 | int ret; |
140 | ||
4e48b5d2 | 141 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
142 | ret = -EEXIST; |
143 | goto error_find_context; | |
144 | } | |
4e48b5d2 MD |
145 | ret = lttng_ust_context_append(ctx, ctx_field); |
146 | if (ret) | |
147 | return ret; | |
735bef47 | 148 | return 0; |
a084756d | 149 | |
a084756d | 150 | error_find_context: |
a084756d | 151 | return ret; |
735bef47 MJ |
152 | } |
153 | ||
154 | /* | |
a9fd951a MJ |
155 | * Force a read (imply TLS allocation for dlopen) of TLS variables. |
156 | */ | |
c246521d | 157 | void lttng_ust_uts_ns_init_thread(int flags) |
735bef47 | 158 | { |
742ac92a | 159 | __asm__ __volatile__ ("" : : "m" (URCU_TLS(cached_uts_ns))); |
c246521d NL |
160 | if (flags & LTTNG_UST_INIT_THREAD_CONTEXT_CACHE) |
161 | (void)get_uts_ns(); | |
735bef47 | 162 | } |