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735bef47 MJ |
1 | /* |
2 | * lttng-context-pid-ns.c | |
3 | * | |
4 | * LTTng UST pid namespace context. | |
5 | * | |
6 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * 2019 Michael Jeanson <mjeanson@efficios.com> | |
8 | * | |
9 | * This library is free software; you can redistribute it and/or | |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; only | |
12 | * version 2.1 of the License. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
22 | */ | |
23 | ||
24 | #define _LGPL_SOURCE | |
25 | #include <sys/types.h> | |
26 | #include <sys/stat.h> | |
27 | #include <unistd.h> | |
28 | #include <lttng/ust-events.h> | |
29 | #include <lttng/ust-tracer.h> | |
30 | #include <lttng/ringbuffer-config.h> | |
31 | ||
32 | #include "ns.h" | |
33 | ||
34 | /* | |
35 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
36 | * each event. The PID namespace is global to the process. | |
37 | */ | |
38 | static ino_t cached_pid_ns = NS_INO_UNINITIALIZED; | |
39 | ||
40 | static | |
41 | ino_t get_pid_ns(void) | |
42 | { | |
43 | struct stat sb; | |
44 | ino_t pid_ns; | |
45 | ||
46 | pid_ns = CMM_LOAD_SHARED(cached_pid_ns); | |
47 | ||
48 | /* | |
49 | * If the cache is populated, do nothing and return the | |
50 | * cached inode number. | |
51 | */ | |
52 | if (caa_likely(pid_ns != NS_INO_UNINITIALIZED)) | |
53 | return pid_ns; | |
54 | ||
55 | /* | |
56 | * At this point we have to populate the cache, set the initial | |
57 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
58 | * number from the proc filesystem, this is the value we will | |
59 | * cache. | |
60 | */ | |
61 | pid_ns = NS_INO_UNAVAILABLE; | |
62 | ||
63 | if (stat("/proc/self/ns/pid", &sb) == 0) { | |
64 | pid_ns = sb.st_ino; | |
65 | } | |
66 | ||
67 | /* | |
68 | * And finally, store the inode number in the cache. | |
69 | */ | |
70 | CMM_STORE_SHARED(cached_pid_ns, pid_ns); | |
71 | ||
72 | return pid_ns; | |
73 | } | |
74 | ||
75 | /* | |
76 | * A process's PID namespace membership is determined when the process is | |
77 | * created and cannot be changed thereafter. | |
78 | * | |
79 | * The pid namespace can change only on clone(2) / fork(2) : | |
80 | * - clone(2) with the CLONE_NEWPID flag | |
81 | * - clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWPID flag | |
82 | * - clone(2) / fork(2) after a call to setns(2) with a PID namespace fd | |
83 | */ | |
84 | void lttng_context_pid_ns_reset(void) | |
85 | { | |
86 | CMM_STORE_SHARED(cached_pid_ns, NS_INO_UNINITIALIZED); | |
87 | } | |
88 | ||
89 | static | |
90 | size_t pid_ns_get_size(struct lttng_ctx_field *field, size_t offset) | |
91 | { | |
92 | size_t size = 0; | |
93 | ||
94 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
95 | size += sizeof(ino_t); | |
96 | return size; | |
97 | } | |
98 | ||
99 | static | |
100 | void pid_ns_record(struct lttng_ctx_field *field, | |
101 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
102 | struct lttng_channel *chan) | |
103 | { | |
104 | ino_t pid_ns; | |
105 | ||
106 | pid_ns = get_pid_ns(); | |
107 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid_ns)); | |
108 | chan->ops->event_write(ctx, &pid_ns, sizeof(pid_ns)); | |
109 | } | |
110 | ||
111 | static | |
112 | void pid_ns_get_value(struct lttng_ctx_field *field, | |
113 | struct lttng_ctx_value *value) | |
114 | { | |
115 | value->u.s64 = get_pid_ns(); | |
116 | } | |
117 | ||
118 | int lttng_add_pid_ns_to_ctx(struct lttng_ctx **ctx) | |
119 | { | |
120 | struct lttng_ctx_field *field; | |
121 | ||
122 | field = lttng_append_context(ctx); | |
123 | if (!field) | |
124 | return -ENOMEM; | |
125 | if (lttng_find_context(*ctx, "pid_ns")) { | |
126 | lttng_remove_context_field(ctx, field); | |
127 | return -EEXIST; | |
128 | } | |
129 | field->event_field.name = "pid_ns"; | |
130 | field->event_field.type.atype = atype_integer; | |
131 | field->event_field.type.u.basic.integer.size = sizeof(ino_t) * CHAR_BIT; | |
132 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT; | |
133 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(ino_t); | |
134 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
135 | field->event_field.type.u.basic.integer.base = 10; | |
136 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
137 | field->get_size = pid_ns_get_size; | |
138 | field->record = pid_ns_record; | |
139 | field->get_value = pid_ns_get_value; | |
140 | lttng_context_update(*ctx); | |
141 | return 0; | |
142 | } |