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