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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 ipc 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> | |
ae4b659d | 18 | #include <ust-tid.h> |
735bef47 | 19 | #include <urcu/tls-compat.h> |
0466ac28 | 20 | #include <lttng/ringbuffer-context.h> |
fc80554e MJ |
21 | |
22 | #include "context-internal.h" | |
735bef47 MJ |
23 | #include "lttng-tracer-core.h" |
24 | #include "ns.h" | |
25 | ||
735bef47 MJ |
26 | /* |
27 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
28 | * each event. | |
29 | */ | |
a251a209 | 30 | static DEFINE_URCU_TLS_INIT(ino_t, cached_ipc_ns, NS_INO_UNINITIALIZED); |
735bef47 MJ |
31 | |
32 | static | |
33 | ino_t get_ipc_ns(void) | |
34 | { | |
35 | struct stat sb; | |
36 | ino_t ipc_ns; | |
37 | ||
38 | ipc_ns = CMM_LOAD_SHARED(URCU_TLS(cached_ipc_ns)); | |
39 | ||
40 | /* | |
41 | * If the cache is populated, do nothing and return the | |
42 | * cached inode number. | |
43 | */ | |
44 | if (caa_likely(ipc_ns != NS_INO_UNINITIALIZED)) | |
45 | return ipc_ns; | |
46 | ||
47 | /* | |
48 | * At this point we have to populate the cache, set the initial | |
49 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
50 | * number from the proc filesystem, this is the value we will | |
51 | * cache. | |
52 | */ | |
53 | ipc_ns = NS_INO_UNAVAILABLE; | |
54 | ||
55 | /* | |
56 | * /proc/thread-self was introduced in kernel v3.17 | |
57 | */ | |
58 | if (stat("/proc/thread-self/ns/ipc", &sb) == 0) { | |
59 | ipc_ns = sb.st_ino; | |
60 | } else { | |
61 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
62 | ||
63 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
64 | "/proc/self/task/%d/ns/ipc", | |
65 | lttng_gettid()) >= 0) { | |
66 | ||
67 | if (stat(proc_ns_path, &sb) == 0) { | |
68 | ipc_ns = sb.st_ino; | |
69 | } | |
70 | } | |
71 | } | |
72 | ||
73 | /* | |
74 | * And finally, store the inode number in the cache. | |
75 | */ | |
76 | CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), ipc_ns); | |
77 | ||
78 | return ipc_ns; | |
79 | } | |
80 | ||
81 | /* | |
82 | * The ipc namespace can change for 3 reasons | |
83 | * * clone(2) called with CLONE_NEWIPC | |
84 | * * setns(2) called with the fd of a different ipc ns | |
85 | * * unshare(2) called with CLONE_NEWIPC | |
86 | */ | |
87 | void lttng_context_ipc_ns_reset(void) | |
88 | { | |
89 | CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), NS_INO_UNINITIALIZED); | |
90 | } | |
91 | ||
92 | static | |
4e48b5d2 | 93 | size_t ipc_ns_get_size(void *priv __attribute__((unused)), |
2208d8b5 | 94 | size_t offset) |
735bef47 MJ |
95 | { |
96 | size_t size = 0; | |
97 | ||
dc325c1d | 98 | size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
735bef47 MJ |
99 | size += sizeof(ino_t); |
100 | return size; | |
101 | } | |
102 | ||
103 | static | |
4e48b5d2 | 104 | void ipc_ns_record(void *priv __attribute__((unused)), |
735bef47 | 105 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
e7bc0ef6 | 106 | struct lttng_ust_channel_buffer *chan) |
735bef47 MJ |
107 | { |
108 | ino_t ipc_ns; | |
109 | ||
110 | ipc_ns = get_ipc_ns(); | |
8936b6c0 | 111 | chan->ops->event_write(ctx, &ipc_ns, sizeof(ipc_ns), lttng_ust_rb_alignof(ipc_ns)); |
735bef47 MJ |
112 | } |
113 | ||
114 | static | |
4e48b5d2 | 115 | void ipc_ns_get_value(void *priv __attribute__((unused)), |
daacdbfc | 116 | struct lttng_ust_ctx_value *value) |
735bef47 MJ |
117 | { |
118 | value->u.s64 = get_ipc_ns(); | |
119 | } | |
120 | ||
4e48b5d2 MD |
121 | const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
122 | lttng_ust_static_event_field("ipc_ns", | |
123 | lttng_ust_static_type_integer(sizeof(ino_t) * CHAR_BIT, | |
124 | lttng_ust_rb_alignof(ino_t) * CHAR_BIT, | |
125 | lttng_ust_is_signed_type(ino_t), | |
126 | BYTE_ORDER, 10), | |
127 | false, false), | |
128 | ipc_ns_get_size, | |
129 | ipc_ns_record, | |
130 | ipc_ns_get_value, | |
131 | NULL, NULL); | |
132 | ||
daacdbfc | 133 | int lttng_add_ipc_ns_to_ctx(struct lttng_ust_ctx **ctx) |
735bef47 | 134 | { |
a084756d MD |
135 | int ret; |
136 | ||
4e48b5d2 | 137 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
138 | ret = -EEXIST; |
139 | goto error_find_context; | |
140 | } | |
4e48b5d2 MD |
141 | ret = lttng_ust_context_append(ctx, ctx_field); |
142 | if (ret) | |
143 | return ret; | |
735bef47 | 144 | return 0; |
a084756d | 145 | |
a084756d | 146 | error_find_context: |
a084756d | 147 | return ret; |
735bef47 MJ |
148 | } |
149 | ||
150 | /* | |
151 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
152 | * */ | |
153 | void lttng_fixup_ipc_ns_tls(void) | |
154 | { | |
155 | asm volatile ("" : : "m" (URCU_TLS(cached_ipc_ns))); | |
156 | } |