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cefef7a7 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
cefef7a7 MJ |
3 | * |
4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
c0c0989a | 5 | * Copyright (C) 2020 Michael Jeanson <mjeanson@efficios.com> |
cefef7a7 | 6 | * |
c0c0989a | 7 | * LTTng UST time namespace context. |
cefef7a7 MJ |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
9af5d97a | 11 | #include <limits.h> |
cefef7a7 MJ |
12 | #include <stddef.h> |
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" |
cefef7a7 MJ |
20 | #include <urcu/tls-compat.h> |
21 | #include "lttng-tracer-core.h" | |
c5e8ef85 | 22 | #include "common/ns.h" |
5287fad0 | 23 | #include "context-internal.h" |
cefef7a7 MJ |
24 | |
25 | ||
26 | /* | |
27 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
28 | * each event. | |
29 | */ | |
30 | static DEFINE_URCU_TLS_INIT(ino_t, cached_time_ns, NS_INO_UNINITIALIZED); | |
31 | ||
32 | static | |
33 | ino_t get_time_ns(void) | |
34 | { | |
35 | struct stat sb; | |
36 | ino_t time_ns; | |
37 | ||
38 | time_ns = CMM_LOAD_SHARED(URCU_TLS(cached_time_ns)); | |
39 | ||
40 | /* | |
41 | * If the cache is populated, do nothing and return the | |
42 | * cached inode number. | |
43 | */ | |
44 | if (caa_likely(time_ns != NS_INO_UNINITIALIZED)) | |
45 | return time_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 | time_ns = NS_INO_UNAVAILABLE; | |
54 | ||
55 | /* | |
56 | * /proc/thread-self was introduced in kernel v3.17 | |
57 | */ | |
58 | if (stat("/proc/thread-self/ns/time", &sb) == 0) { | |
59 | time_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/time", | |
65 | lttng_gettid()) >= 0) { | |
66 | ||
67 | if (stat(proc_ns_path, &sb) == 0) { | |
68 | time_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_time_ns), time_ns); | |
77 | ||
78 | return time_ns; | |
79 | } | |
80 | ||
81 | /* | |
82 | * The time namespace can change for 2 reasons | |
83 | * * setns(2) called with the fd of a different time ns | |
84 | * * clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWTIME flag | |
85 | */ | |
86 | void lttng_context_time_ns_reset(void) | |
87 | { | |
88 | CMM_STORE_SHARED(URCU_TLS(cached_time_ns), NS_INO_UNINITIALIZED); | |
89 | } | |
90 | ||
91 | static | |
4e48b5d2 | 92 | size_t time_ns_get_size(void *priv __attribute__((unused)), |
b2e37d27 | 93 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
2208d8b5 | 94 | size_t offset) |
cefef7a7 MJ |
95 | { |
96 | size_t size = 0; | |
97 | ||
b5457df5 | 98 | size += lttng_ust_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
cefef7a7 MJ |
99 | size += sizeof(ino_t); |
100 | return size; | |
101 | } | |
102 | ||
103 | static | |
4e48b5d2 | 104 | void time_ns_record(void *priv __attribute__((unused)), |
b2e37d27 MD |
105 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
106 | struct lttng_ust_ring_buffer_ctx *ctx, | |
107 | struct lttng_ust_channel_buffer *chan) | |
cefef7a7 MJ |
108 | { |
109 | ino_t time_ns; | |
110 | ||
111 | time_ns = get_time_ns(); | |
8936b6c0 | 112 | chan->ops->event_write(ctx, &time_ns, sizeof(time_ns), lttng_ust_rb_alignof(time_ns)); |
cefef7a7 MJ |
113 | } |
114 | ||
115 | static | |
4e48b5d2 | 116 | void time_ns_get_value(void *priv __attribute__((unused)), |
b2e37d27 | 117 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
daacdbfc | 118 | struct lttng_ust_ctx_value *value) |
cefef7a7 | 119 | { |
b2e37d27 | 120 | value->u.u64 = get_time_ns(); |
cefef7a7 MJ |
121 | } |
122 | ||
4e48b5d2 MD |
123 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
124 | lttng_ust_static_event_field("time_ns", | |
125 | lttng_ust_static_type_integer(sizeof(ino_t) * CHAR_BIT, | |
126 | lttng_ust_rb_alignof(ino_t) * CHAR_BIT, | |
127 | lttng_ust_is_signed_type(ino_t), | |
baa8acf3 | 128 | LTTNG_UST_BYTE_ORDER, 10), |
4e48b5d2 MD |
129 | false, false), |
130 | time_ns_get_size, | |
131 | time_ns_record, | |
132 | time_ns_get_value, | |
133 | NULL, NULL); | |
134 | ||
daacdbfc | 135 | int lttng_add_time_ns_to_ctx(struct lttng_ust_ctx **ctx) |
cefef7a7 | 136 | { |
a084756d MD |
137 | int ret; |
138 | ||
4e48b5d2 | 139 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
140 | ret = -EEXIST; |
141 | goto error_find_context; | |
142 | } | |
4e48b5d2 MD |
143 | ret = lttng_ust_context_append(ctx, ctx_field); |
144 | if (ret) | |
145 | return ret; | |
cefef7a7 | 146 | return 0; |
a084756d | 147 | |
a084756d | 148 | error_find_context: |
a084756d | 149 | return ret; |
cefef7a7 MJ |
150 | } |
151 | ||
152 | /* | |
a9fd951a MJ |
153 | * Force a read (imply TLS allocation for dlopen) of TLS variables. |
154 | */ | |
155 | void lttng_time_ns_alloc_tls(void) | |
cefef7a7 MJ |
156 | { |
157 | asm volatile ("" : : "m" (URCU_TLS(cached_time_ns))); | |
158 | } |