Fix: pass private data to context callbacks
[lttng-ust.git] / liblttng-ust / lttng-context-ipc-ns.c
CommitLineData
735bef47 1/*
c0c0989a 2 * SPDX-License-Identifier: LGPL-2.1-only
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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.
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8 */
9
10#define _LGPL_SOURCE
9af5d97a 11#include <limits.h>
b4051ad8 12#include <stddef.h>
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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>
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21
22#include "context-internal.h"
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23#include "lttng-tracer-core.h"
24#include "ns.h"
25
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26/*
27 * We cache the result to ensure we don't stat(2) the proc filesystem on
28 * each event.
29 */
a251a209 30static DEFINE_URCU_TLS_INIT(ino_t, cached_ipc_ns, NS_INO_UNINITIALIZED);
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31
32static
33ino_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 */
87void lttng_context_ipc_ns_reset(void)
88{
89 CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), NS_INO_UNINITIALIZED);
90}
91
92static
4e48b5d2 93size_t ipc_ns_get_size(void *priv __attribute__((unused)),
2208d8b5 94 size_t offset)
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95{
96 size_t size = 0;
97
dc325c1d 98 size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t));
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99 size += sizeof(ino_t);
100 return size;
101}
102
103static
4e48b5d2 104void 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)
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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));
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112}
113
114static
4e48b5d2 115void ipc_ns_get_value(void *priv __attribute__((unused)),
daacdbfc 116 struct lttng_ust_ctx_value *value)
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117{
118 value->u.s64 = get_ipc_ns();
119}
120
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121const 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 133int lttng_add_ipc_ns_to_ctx(struct lttng_ust_ctx **ctx)
735bef47 134{
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135 int ret;
136
4e48b5d2 137 if (lttng_find_context(*ctx, ctx_field->event_field->name)) {
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138 ret = -EEXIST;
139 goto error_find_context;
140 }
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141 ret = lttng_ust_context_append(ctx, ctx_field);
142 if (ret)
143 return ret;
735bef47 144 return 0;
a084756d 145
a084756d 146error_find_context:
a084756d 147 return ret;
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148}
149
150/*
151 * * Force a read (imply TLS fixup for dlopen) of TLS variables.
152 * */
153void lttng_fixup_ipc_ns_tls(void)
154{
155 asm volatile ("" : : "m" (URCU_TLS(cached_ipc_ns)));
156}
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