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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 user 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> | |
0b4b8811 | 18 | #include <lttng/ust-ringbuffer-context.h> |
735bef47 | 19 | |
fc80554e | 20 | #include "context-internal.h" |
c5e8ef85 | 21 | #include "common/ns.h" |
735bef47 MJ |
22 | |
23 | /* | |
24 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
25 | * each event. The user namespace is global to the process. | |
26 | */ | |
27 | static ino_t cached_user_ns = NS_INO_UNINITIALIZED; | |
28 | ||
29 | static | |
30 | ino_t get_user_ns(void) | |
31 | { | |
32 | struct stat sb; | |
33 | ino_t user_ns; | |
34 | ||
35 | user_ns = CMM_LOAD_SHARED(cached_user_ns); | |
36 | ||
37 | /* | |
38 | * If the cache is populated, do nothing and return the | |
39 | * cached inode number. | |
40 | */ | |
41 | if (caa_likely(user_ns != NS_INO_UNINITIALIZED)) | |
42 | return user_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 | user_ns = NS_INO_UNAVAILABLE; | |
51 | ||
52 | if (stat("/proc/self/ns/user", &sb) == 0) { | |
53 | user_ns = sb.st_ino; | |
54 | } | |
55 | ||
56 | /* | |
57 | * And finally, store the inode number in the cache. | |
58 | */ | |
59 | CMM_STORE_SHARED(cached_user_ns, user_ns); | |
60 | ||
61 | return user_ns; | |
62 | } | |
63 | ||
64 | /* | |
65 | * The user namespace can change for 3 reasons | |
66 | * * clone(2) called with CLONE_NEWUSER | |
67 | * * setns(2) called with the fd of a different user ns | |
68 | * * unshare(2) called with CLONE_NEWUSER | |
69 | */ | |
70 | void lttng_context_user_ns_reset(void) | |
71 | { | |
72 | CMM_STORE_SHARED(cached_user_ns, NS_INO_UNINITIALIZED); | |
73 | } | |
74 | ||
75 | static | |
4e48b5d2 | 76 | size_t user_ns_get_size(void *priv __attribute__((unused)), |
b2e37d27 | 77 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
2208d8b5 | 78 | size_t offset) |
735bef47 MJ |
79 | { |
80 | size_t size = 0; | |
81 | ||
b5457df5 | 82 | size += lttng_ust_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t)); |
735bef47 MJ |
83 | size += sizeof(ino_t); |
84 | return size; | |
85 | } | |
86 | ||
87 | static | |
4e48b5d2 | 88 | void user_ns_record(void *priv __attribute__((unused)), |
b2e37d27 MD |
89 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
90 | struct lttng_ust_ring_buffer_ctx *ctx, | |
91 | struct lttng_ust_channel_buffer *chan) | |
735bef47 MJ |
92 | { |
93 | ino_t user_ns; | |
94 | ||
95 | user_ns = get_user_ns(); | |
8936b6c0 | 96 | chan->ops->event_write(ctx, &user_ns, sizeof(user_ns), lttng_ust_rb_alignof(user_ns)); |
735bef47 MJ |
97 | } |
98 | ||
99 | static | |
4e48b5d2 | 100 | void user_ns_get_value(void *priv __attribute__((unused)), |
b2e37d27 | 101 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
daacdbfc | 102 | struct lttng_ust_ctx_value *value) |
735bef47 | 103 | { |
b2e37d27 | 104 | value->u.u64 = get_user_ns(); |
735bef47 MJ |
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("user_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), | |
baa8acf3 | 112 | LTTNG_UST_BYTE_ORDER, 10), |
4e48b5d2 MD |
113 | false, false), |
114 | user_ns_get_size, | |
115 | user_ns_record, | |
116 | user_ns_get_value, | |
117 | NULL, NULL); | |
118 | ||
daacdbfc | 119 | int lttng_add_user_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 | } |