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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 mnt namespace context. |
735bef47 MJ |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
b4051ad8 | 11 | #include <stddef.h> |
735bef47 MJ |
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> | |
17 | #include <lttng/ringbuffer-config.h> | |
18 | ||
fc80554e | 19 | #include "context-internal.h" |
735bef47 MJ |
20 | #include "ns.h" |
21 | ||
22 | /* | |
23 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
24 | * each event. The mount namespace is global to the process. | |
25 | */ | |
26 | static ino_t cached_mnt_ns = NS_INO_UNINITIALIZED; | |
27 | ||
28 | static | |
29 | ino_t get_mnt_ns(void) | |
30 | { | |
31 | struct stat sb; | |
32 | ino_t mnt_ns; | |
33 | ||
34 | mnt_ns = CMM_LOAD_SHARED(cached_mnt_ns); | |
35 | ||
36 | /* | |
37 | * If the cache is populated, do nothing and return the | |
38 | * cached inode number. | |
39 | */ | |
40 | if (caa_likely(mnt_ns != NS_INO_UNINITIALIZED)) | |
41 | return mnt_ns; | |
42 | ||
43 | /* | |
44 | * At this point we have to populate the cache, set the initial | |
45 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
46 | * number from the proc filesystem, this is the value we will | |
47 | * cache. | |
48 | */ | |
49 | mnt_ns = NS_INO_UNAVAILABLE; | |
50 | ||
51 | if (stat("/proc/self/ns/mnt", &sb) == 0) { | |
52 | mnt_ns = sb.st_ino; | |
53 | } | |
54 | ||
55 | /* | |
56 | * And finally, store the inode number in the cache. | |
57 | */ | |
58 | CMM_STORE_SHARED(cached_mnt_ns, mnt_ns); | |
59 | ||
60 | return mnt_ns; | |
61 | } | |
62 | ||
63 | /* | |
64 | * The mnt namespace can change for 3 reasons | |
65 | * * clone(2) called with CLONE_NEWNS | |
66 | * * setns(2) called with the fd of a different mnt ns | |
67 | * * unshare(2) called with CLONE_NEWNS | |
68 | */ | |
69 | void lttng_context_mnt_ns_reset(void) | |
70 | { | |
71 | CMM_STORE_SHARED(cached_mnt_ns, NS_INO_UNINITIALIZED); | |
72 | } | |
73 | ||
74 | static | |
75 | size_t mnt_ns_get_size(struct lttng_ctx_field *field, size_t offset) | |
76 | { | |
77 | size_t size = 0; | |
78 | ||
79 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
80 | size += sizeof(ino_t); | |
81 | return size; | |
82 | } | |
83 | ||
84 | static | |
85 | void mnt_ns_record(struct lttng_ctx_field *field, | |
86 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
87 | struct lttng_channel *chan) | |
88 | { | |
89 | ino_t mnt_ns; | |
90 | ||
91 | mnt_ns = get_mnt_ns(); | |
92 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns)); | |
93 | chan->ops->event_write(ctx, &mnt_ns, sizeof(mnt_ns)); | |
94 | } | |
95 | ||
96 | static | |
97 | void mnt_ns_get_value(struct lttng_ctx_field *field, | |
98 | struct lttng_ctx_value *value) | |
99 | { | |
100 | value->u.s64 = get_mnt_ns(); | |
101 | } | |
102 | ||
103 | int lttng_add_mnt_ns_to_ctx(struct lttng_ctx **ctx) | |
104 | { | |
105 | struct lttng_ctx_field *field; | |
106 | ||
107 | field = lttng_append_context(ctx); | |
108 | if (!field) | |
109 | return -ENOMEM; | |
110 | if (lttng_find_context(*ctx, "mnt_ns")) { | |
111 | lttng_remove_context_field(ctx, field); | |
112 | return -EEXIST; | |
113 | } | |
114 | field->event_field.name = "mnt_ns"; | |
115 | field->event_field.type.atype = atype_integer; | |
218deb69 MD |
116 | field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT; |
117 | field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT; | |
118 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t); | |
119 | field->event_field.type.u.integer.reverse_byte_order = 0; | |
120 | field->event_field.type.u.integer.base = 10; | |
121 | field->event_field.type.u.integer.encoding = lttng_encode_none; | |
735bef47 MJ |
122 | field->get_size = mnt_ns_get_size; |
123 | field->record = mnt_ns_record; | |
124 | field->get_value = mnt_ns_get_value; | |
125 | lttng_context_update(*ctx); | |
126 | return 0; | |
127 | } |