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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 pid 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> | |
0466ac28 | 18 | #include <lttng/ringbuffer-context.h> |
735bef47 | 19 | |
fc80554e | 20 | #include "context-internal.h" |
735bef47 MJ |
21 | #include "ns.h" |
22 | ||
23 | /* | |
24 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
25 | * each event. The PID namespace is global to the process. | |
26 | */ | |
27 | static ino_t cached_pid_ns = NS_INO_UNINITIALIZED; | |
28 | ||
29 | static | |
30 | ino_t get_pid_ns(void) | |
31 | { | |
32 | struct stat sb; | |
33 | ino_t pid_ns; | |
34 | ||
35 | pid_ns = CMM_LOAD_SHARED(cached_pid_ns); | |
36 | ||
37 | /* | |
38 | * If the cache is populated, do nothing and return the | |
39 | * cached inode number. | |
40 | */ | |
41 | if (caa_likely(pid_ns != NS_INO_UNINITIALIZED)) | |
42 | return pid_ns; | |
43 | ||
44 | /* | |
45 | * At this point we have to populate the cache, set the initial | |
46 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
47 | * number from the proc filesystem, this is the value we will | |
48 | * cache. | |
49 | */ | |
50 | pid_ns = NS_INO_UNAVAILABLE; | |
51 | ||
52 | if (stat("/proc/self/ns/pid", &sb) == 0) { | |
53 | pid_ns = sb.st_ino; | |
54 | } | |
55 | ||
56 | /* | |
57 | * And finally, store the inode number in the cache. | |
58 | */ | |
59 | CMM_STORE_SHARED(cached_pid_ns, pid_ns); | |
60 | ||
61 | return pid_ns; | |
62 | } | |
63 | ||
64 | /* | |
65 | * A process's PID namespace membership is determined when the process is | |
66 | * created and cannot be changed thereafter. | |
67 | * | |
68 | * The pid namespace can change only on clone(2) / fork(2) : | |
69 | * - clone(2) with the CLONE_NEWPID flag | |
70 | * - clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWPID flag | |
71 | * - clone(2) / fork(2) after a call to setns(2) with a PID namespace fd | |
72 | */ | |
73 | void lttng_context_pid_ns_reset(void) | |
74 | { | |
75 | CMM_STORE_SHARED(cached_pid_ns, NS_INO_UNINITIALIZED); | |
76 | } | |
77 | ||
78 | static | |
4e48b5d2 | 79 | size_t pid_ns_get_size(void *priv __attribute__((unused)), |
2208d8b5 | 80 | size_t offset) |
735bef47 MJ |
81 | { |
82 | size_t size = 0; | |
83 | ||
dc325c1d | 84 | size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
735bef47 MJ |
85 | size += sizeof(ino_t); |
86 | return size; | |
87 | } | |
88 | ||
89 | static | |
4e48b5d2 | 90 | void pid_ns_record(void *priv __attribute__((unused)), |
735bef47 | 91 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
e7bc0ef6 | 92 | struct lttng_ust_channel_buffer *chan) |
735bef47 MJ |
93 | { |
94 | ino_t pid_ns; | |
95 | ||
96 | pid_ns = get_pid_ns(); | |
8936b6c0 | 97 | chan->ops->event_write(ctx, &pid_ns, sizeof(pid_ns), lttng_ust_rb_alignof(pid_ns)); |
735bef47 MJ |
98 | } |
99 | ||
100 | static | |
4e48b5d2 | 101 | void pid_ns_get_value(void *priv __attribute__((unused)), |
daacdbfc | 102 | struct lttng_ust_ctx_value *value) |
735bef47 MJ |
103 | { |
104 | value->u.s64 = get_pid_ns(); | |
105 | } | |
106 | ||
4e48b5d2 MD |
107 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
108 | lttng_ust_static_event_field("pid_ns", | |
109 | lttng_ust_static_type_integer(sizeof(ino_t) * CHAR_BIT, | |
110 | lttng_ust_rb_alignof(ino_t) * CHAR_BIT, | |
111 | lttng_ust_is_signed_type(ino_t), | |
112 | BYTE_ORDER, 10), | |
113 | false, false), | |
114 | pid_ns_get_size, | |
115 | pid_ns_record, | |
116 | pid_ns_get_value, | |
117 | NULL, NULL); | |
118 | ||
daacdbfc | 119 | int lttng_add_pid_ns_to_ctx(struct lttng_ust_ctx **ctx) |
735bef47 | 120 | { |
a084756d MD |
121 | int ret; |
122 | ||
4e48b5d2 | 123 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
a084756d MD |
124 | ret = -EEXIST; |
125 | goto error_find_context; | |
126 | } | |
4e48b5d2 MD |
127 | ret = lttng_ust_context_append(ctx, ctx_field); |
128 | if (ret) | |
129 | return ret; | |
735bef47 | 130 | return 0; |
a084756d | 131 | |
a084756d | 132 | error_find_context: |
a084756d | 133 | return ret; |
735bef47 | 134 | } |