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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 | |
11 | #include <stddef.h> | |
12 | #include <sys/types.h> | |
13 | #include <sys/stat.h> | |
14 | #include <unistd.h> | |
15 | #include <lttng/ust-events.h> | |
16 | #include <lttng/ust-tracer.h> | |
0466ac28 | 17 | #include <lttng/ringbuffer-context.h> |
ae4b659d | 18 | #include <ust-tid.h> |
cefef7a7 MJ |
19 | #include <urcu/tls-compat.h> |
20 | #include "lttng-tracer-core.h" | |
21 | #include "ns.h" | |
5287fad0 | 22 | #include "context-internal.h" |
cefef7a7 MJ |
23 | |
24 | ||
25 | /* | |
26 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
27 | * each event. | |
28 | */ | |
29 | static DEFINE_URCU_TLS_INIT(ino_t, cached_time_ns, NS_INO_UNINITIALIZED); | |
30 | ||
31 | static | |
32 | ino_t get_time_ns(void) | |
33 | { | |
34 | struct stat sb; | |
35 | ino_t time_ns; | |
36 | ||
37 | time_ns = CMM_LOAD_SHARED(URCU_TLS(cached_time_ns)); | |
38 | ||
39 | /* | |
40 | * If the cache is populated, do nothing and return the | |
41 | * cached inode number. | |
42 | */ | |
43 | if (caa_likely(time_ns != NS_INO_UNINITIALIZED)) | |
44 | return time_ns; | |
45 | ||
46 | /* | |
47 | * At this point we have to populate the cache, set the initial | |
48 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
49 | * number from the proc filesystem, this is the value we will | |
50 | * cache. | |
51 | */ | |
52 | time_ns = NS_INO_UNAVAILABLE; | |
53 | ||
54 | /* | |
55 | * /proc/thread-self was introduced in kernel v3.17 | |
56 | */ | |
57 | if (stat("/proc/thread-self/ns/time", &sb) == 0) { | |
58 | time_ns = sb.st_ino; | |
59 | } else { | |
60 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
61 | ||
62 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
63 | "/proc/self/task/%d/ns/time", | |
64 | lttng_gettid()) >= 0) { | |
65 | ||
66 | if (stat(proc_ns_path, &sb) == 0) { | |
67 | time_ns = sb.st_ino; | |
68 | } | |
69 | } | |
70 | } | |
71 | ||
72 | /* | |
73 | * And finally, store the inode number in the cache. | |
74 | */ | |
75 | CMM_STORE_SHARED(URCU_TLS(cached_time_ns), time_ns); | |
76 | ||
77 | return time_ns; | |
78 | } | |
79 | ||
80 | /* | |
81 | * The time namespace can change for 2 reasons | |
82 | * * setns(2) called with the fd of a different time ns | |
83 | * * clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWTIME flag | |
84 | */ | |
85 | void lttng_context_time_ns_reset(void) | |
86 | { | |
87 | CMM_STORE_SHARED(URCU_TLS(cached_time_ns), NS_INO_UNINITIALIZED); | |
88 | } | |
89 | ||
90 | static | |
daacdbfc | 91 | size_t time_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
cefef7a7 MJ |
92 | { |
93 | size_t size = 0; | |
94 | ||
95 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
96 | size += sizeof(ino_t); | |
97 | return size; | |
98 | } | |
99 | ||
100 | static | |
daacdbfc | 101 | void time_ns_record(struct lttng_ust_ctx_field *field, |
cefef7a7 MJ |
102 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
103 | struct lttng_channel *chan) | |
104 | { | |
105 | ino_t time_ns; | |
106 | ||
107 | time_ns = get_time_ns(); | |
108 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(time_ns)); | |
109 | chan->ops->event_write(ctx, &time_ns, sizeof(time_ns)); | |
110 | } | |
111 | ||
112 | static | |
daacdbfc MD |
113 | void time_ns_get_value(struct lttng_ust_ctx_field *field, |
114 | struct lttng_ust_ctx_value *value) | |
cefef7a7 MJ |
115 | { |
116 | value->u.s64 = get_time_ns(); | |
117 | } | |
118 | ||
daacdbfc | 119 | int lttng_add_time_ns_to_ctx(struct lttng_ust_ctx **ctx) |
cefef7a7 | 120 | { |
daacdbfc | 121 | struct lttng_ust_ctx_field *field; |
a084756d MD |
122 | struct lttng_ust_type_common *type; |
123 | int ret; | |
124 | ||
125 | type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT, | |
126 | lttng_alignof(ino_t) * CHAR_BIT, | |
127 | lttng_is_signed_type(ino_t), | |
128 | BYTE_ORDER, 10); | |
129 | if (!type) | |
cefef7a7 | 130 | return -ENOMEM; |
a084756d MD |
131 | field = lttng_append_context(ctx); |
132 | if (!field) { | |
133 | ret = -ENOMEM; | |
134 | goto error_context; | |
135 | } | |
cefef7a7 | 136 | if (lttng_find_context(*ctx, "time_ns")) { |
a084756d MD |
137 | ret = -EEXIST; |
138 | goto error_find_context; | |
139 | } | |
140 | field->event_field->name = strdup("time_ns"); | |
141 | if (!field->event_field->name) { | |
142 | ret = -ENOMEM; | |
143 | goto error_name; | |
cefef7a7 | 144 | } |
a084756d | 145 | field->event_field->type = type; |
cefef7a7 MJ |
146 | field->get_size = time_ns_get_size; |
147 | field->record = time_ns_record; | |
148 | field->get_value = time_ns_get_value; | |
149 | lttng_context_update(*ctx); | |
150 | return 0; | |
a084756d MD |
151 | |
152 | error_name: | |
153 | error_find_context: | |
154 | lttng_remove_context_field(ctx, field); | |
155 | error_context: | |
156 | lttng_ust_destroy_type(type); | |
157 | return ret; | |
cefef7a7 MJ |
158 | } |
159 | ||
160 | /* | |
161 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
162 | * */ | |
163 | void lttng_fixup_time_ns_tls(void) | |
164 | { | |
165 | asm volatile ("" : : "m" (URCU_TLS(cached_time_ns))); | |
166 | } |