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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> | |
0466ac28 | 18 | #include <lttng/ringbuffer-context.h> |
ae4b659d | 19 | #include <ust-tid.h> |
cefef7a7 MJ |
20 | #include <urcu/tls-compat.h> |
21 | #include "lttng-tracer-core.h" | |
22 | #include "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 | |
2208d8b5 MJ |
92 | size_t time_ns_get_size(struct lttng_ust_ctx_field *field __attribute__((unused)), |
93 | size_t offset) | |
cefef7a7 MJ |
94 | { |
95 | size_t size = 0; | |
96 | ||
dc325c1d | 97 | size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
cefef7a7 MJ |
98 | size += sizeof(ino_t); |
99 | return size; | |
100 | } | |
101 | ||
102 | static | |
2208d8b5 | 103 | void time_ns_record(struct lttng_ust_ctx_field *field __attribute__((unused)), |
cefef7a7 | 104 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
e7bc0ef6 | 105 | struct lttng_ust_channel_buffer *chan) |
cefef7a7 MJ |
106 | { |
107 | ino_t time_ns; | |
108 | ||
109 | time_ns = get_time_ns(); | |
8936b6c0 | 110 | chan->ops->event_write(ctx, &time_ns, sizeof(time_ns), lttng_ust_rb_alignof(time_ns)); |
cefef7a7 MJ |
111 | } |
112 | ||
113 | static | |
2208d8b5 | 114 | void time_ns_get_value(struct lttng_ust_ctx_field *field __attribute__((unused)), |
daacdbfc | 115 | struct lttng_ust_ctx_value *value) |
cefef7a7 MJ |
116 | { |
117 | value->u.s64 = get_time_ns(); | |
118 | } | |
119 | ||
daacdbfc | 120 | int lttng_add_time_ns_to_ctx(struct lttng_ust_ctx **ctx) |
cefef7a7 | 121 | { |
daacdbfc | 122 | struct lttng_ust_ctx_field *field; |
a084756d MD |
123 | struct lttng_ust_type_common *type; |
124 | int ret; | |
125 | ||
126 | type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT, | |
dc325c1d | 127 | lttng_ust_rb_alignof(ino_t) * CHAR_BIT, |
eae3c729 | 128 | lttng_ust_is_signed_type(ino_t), |
a084756d MD |
129 | BYTE_ORDER, 10); |
130 | if (!type) | |
cefef7a7 | 131 | return -ENOMEM; |
a084756d MD |
132 | field = lttng_append_context(ctx); |
133 | if (!field) { | |
134 | ret = -ENOMEM; | |
135 | goto error_context; | |
136 | } | |
cefef7a7 | 137 | if (lttng_find_context(*ctx, "time_ns")) { |
a084756d MD |
138 | ret = -EEXIST; |
139 | goto error_find_context; | |
140 | } | |
141 | field->event_field->name = strdup("time_ns"); | |
142 | if (!field->event_field->name) { | |
143 | ret = -ENOMEM; | |
144 | goto error_name; | |
cefef7a7 | 145 | } |
a084756d | 146 | field->event_field->type = type; |
cefef7a7 MJ |
147 | field->get_size = time_ns_get_size; |
148 | field->record = time_ns_record; | |
149 | field->get_value = time_ns_get_value; | |
150 | lttng_context_update(*ctx); | |
151 | return 0; | |
a084756d MD |
152 | |
153 | error_name: | |
154 | error_find_context: | |
155 | lttng_remove_context_field(ctx, field); | |
156 | error_context: | |
157 | lttng_ust_destroy_type(type); | |
158 | return ret; | |
cefef7a7 MJ |
159 | } |
160 | ||
161 | /* | |
162 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
163 | * */ | |
164 | void lttng_fixup_time_ns_tls(void) | |
165 | { | |
166 | asm volatile ("" : : "m" (URCU_TLS(cached_time_ns))); | |
167 | } |