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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 cgroup 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> | |
ae4b659d | 18 | #include <ust-tid.h> |
735bef47 | 19 | #include <urcu/tls-compat.h> |
0466ac28 | 20 | #include <lttng/ringbuffer-context.h> |
fc80554e MJ |
21 | |
22 | #include "context-internal.h" | |
735bef47 MJ |
23 | #include "lttng-tracer-core.h" |
24 | #include "ns.h" | |
25 | ||
26 | ||
27 | /* | |
28 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
29 | * each event. | |
30 | */ | |
a251a209 | 31 | static DEFINE_URCU_TLS_INIT(ino_t, cached_cgroup_ns, NS_INO_UNINITIALIZED); |
735bef47 MJ |
32 | |
33 | static | |
34 | ino_t get_cgroup_ns(void) | |
35 | { | |
36 | struct stat sb; | |
37 | ino_t cgroup_ns; | |
38 | ||
39 | cgroup_ns = CMM_LOAD_SHARED(URCU_TLS(cached_cgroup_ns)); | |
40 | ||
41 | /* | |
42 | * If the cache is populated, do nothing and return the | |
43 | * cached inode number. | |
44 | */ | |
45 | if (caa_likely(cgroup_ns != NS_INO_UNINITIALIZED)) | |
46 | return cgroup_ns; | |
47 | ||
48 | /* | |
49 | * At this point we have to populate the cache, set the initial | |
50 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
51 | * number from the proc filesystem, this is the value we will | |
52 | * cache. | |
53 | */ | |
54 | cgroup_ns = NS_INO_UNAVAILABLE; | |
55 | ||
56 | /* | |
57 | * /proc/thread-self was introduced in kernel v3.17 | |
58 | */ | |
59 | if (stat("/proc/thread-self/ns/cgroup", &sb) == 0) { | |
60 | cgroup_ns = sb.st_ino; | |
61 | } else { | |
62 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
63 | ||
64 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
65 | "/proc/self/task/%d/ns/cgroup", | |
66 | lttng_gettid()) >= 0) { | |
67 | ||
68 | if (stat(proc_ns_path, &sb) == 0) { | |
69 | cgroup_ns = sb.st_ino; | |
70 | } | |
71 | } | |
72 | } | |
73 | ||
74 | /* | |
75 | * And finally, store the inode number in the cache. | |
76 | */ | |
77 | CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns), cgroup_ns); | |
78 | ||
79 | return cgroup_ns; | |
80 | } | |
81 | ||
82 | /* | |
83 | * The cgroup namespace can change for 3 reasons | |
84 | * * clone(2) called with CLONE_NEWCGROUP | |
85 | * * setns(2) called with the fd of a different cgroup ns | |
86 | * * unshare(2) called with CLONE_NEWCGROUP | |
87 | */ | |
88 | void lttng_context_cgroup_ns_reset(void) | |
89 | { | |
90 | CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns), NS_INO_UNINITIALIZED); | |
91 | } | |
92 | ||
93 | static | |
daacdbfc | 94 | size_t cgroup_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
735bef47 MJ |
95 | { |
96 | size_t size = 0; | |
97 | ||
98 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
99 | size += sizeof(ino_t); | |
100 | return size; | |
101 | } | |
102 | ||
103 | static | |
daacdbfc | 104 | void cgroup_ns_record(struct lttng_ust_ctx_field *field, |
735bef47 | 105 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
e7bc0ef6 | 106 | struct lttng_ust_channel_buffer *chan) |
735bef47 MJ |
107 | { |
108 | ino_t cgroup_ns; | |
109 | ||
110 | cgroup_ns = get_cgroup_ns(); | |
111 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(cgroup_ns)); | |
112 | chan->ops->event_write(ctx, &cgroup_ns, sizeof(cgroup_ns)); | |
113 | } | |
114 | ||
115 | static | |
daacdbfc MD |
116 | void cgroup_ns_get_value(struct lttng_ust_ctx_field *field, |
117 | struct lttng_ust_ctx_value *value) | |
735bef47 MJ |
118 | { |
119 | value->u.s64 = get_cgroup_ns(); | |
120 | } | |
121 | ||
daacdbfc | 122 | int lttng_add_cgroup_ns_to_ctx(struct lttng_ust_ctx **ctx) |
735bef47 | 123 | { |
daacdbfc | 124 | struct lttng_ust_ctx_field *field; |
a084756d MD |
125 | struct lttng_ust_type_common *type; |
126 | int ret; | |
127 | ||
128 | type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT, | |
129 | lttng_alignof(ino_t) * CHAR_BIT, | |
eae3c729 | 130 | lttng_ust_is_signed_type(ino_t), |
a084756d MD |
131 | BYTE_ORDER, 10); |
132 | if (!type) | |
735bef47 | 133 | return -ENOMEM; |
a084756d MD |
134 | field = lttng_append_context(ctx); |
135 | if (!field) { | |
136 | ret = -ENOMEM; | |
137 | goto error_context; | |
138 | } | |
735bef47 | 139 | if (lttng_find_context(*ctx, "cgroup_ns")) { |
a084756d MD |
140 | ret = -EEXIST; |
141 | goto error_find_context; | |
142 | } | |
143 | field->event_field->name = strdup("cgroup_ns"); | |
144 | if (!field->event_field->name) { | |
145 | ret = -ENOMEM; | |
146 | goto error_name; | |
735bef47 | 147 | } |
a084756d | 148 | field->event_field->type = type; |
735bef47 MJ |
149 | field->get_size = cgroup_ns_get_size; |
150 | field->record = cgroup_ns_record; | |
151 | field->get_value = cgroup_ns_get_value; | |
152 | lttng_context_update(*ctx); | |
153 | return 0; | |
a084756d MD |
154 | |
155 | error_name: | |
156 | error_find_context: | |
157 | lttng_remove_context_field(ctx, field); | |
158 | error_context: | |
159 | lttng_ust_destroy_type(type); | |
160 | return ret; | |
735bef47 MJ |
161 | } |
162 | ||
163 | /* | |
164 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
165 | * */ | |
166 | void lttng_fixup_cgroup_ns_tls(void) | |
167 | { | |
168 | asm volatile ("" : : "m" (URCU_TLS(cached_cgroup_ns))); | |
169 | } |