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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 ipc 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> | |
ae4b659d | 18 | #include <ust-tid.h> |
735bef47 | 19 | #include <urcu/tls-compat.h> |
fc80554e MJ |
20 | |
21 | #include "context-internal.h" | |
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22 | #include "lttng-tracer-core.h" |
23 | #include "ns.h" | |
24 | ||
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25 | /* |
26 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
27 | * each event. | |
28 | */ | |
a251a209 | 29 | static DEFINE_URCU_TLS_INIT(ino_t, cached_ipc_ns, NS_INO_UNINITIALIZED); |
735bef47 MJ |
30 | |
31 | static | |
32 | ino_t get_ipc_ns(void) | |
33 | { | |
34 | struct stat sb; | |
35 | ino_t ipc_ns; | |
36 | ||
37 | ipc_ns = CMM_LOAD_SHARED(URCU_TLS(cached_ipc_ns)); | |
38 | ||
39 | /* | |
40 | * If the cache is populated, do nothing and return the | |
41 | * cached inode number. | |
42 | */ | |
43 | if (caa_likely(ipc_ns != NS_INO_UNINITIALIZED)) | |
44 | return ipc_ns; | |
45 | ||
46 | /* | |
47 | * At this point we have to populate the cache, set the initial | |
48 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
49 | * number from the proc filesystem, this is the value we will | |
50 | * cache. | |
51 | */ | |
52 | ipc_ns = NS_INO_UNAVAILABLE; | |
53 | ||
54 | /* | |
55 | * /proc/thread-self was introduced in kernel v3.17 | |
56 | */ | |
57 | if (stat("/proc/thread-self/ns/ipc", &sb) == 0) { | |
58 | ipc_ns = sb.st_ino; | |
59 | } else { | |
60 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
61 | ||
62 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
63 | "/proc/self/task/%d/ns/ipc", | |
64 | lttng_gettid()) >= 0) { | |
65 | ||
66 | if (stat(proc_ns_path, &sb) == 0) { | |
67 | ipc_ns = sb.st_ino; | |
68 | } | |
69 | } | |
70 | } | |
71 | ||
72 | /* | |
73 | * And finally, store the inode number in the cache. | |
74 | */ | |
75 | CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), ipc_ns); | |
76 | ||
77 | return ipc_ns; | |
78 | } | |
79 | ||
80 | /* | |
81 | * The ipc namespace can change for 3 reasons | |
82 | * * clone(2) called with CLONE_NEWIPC | |
83 | * * setns(2) called with the fd of a different ipc ns | |
84 | * * unshare(2) called with CLONE_NEWIPC | |
85 | */ | |
86 | void lttng_context_ipc_ns_reset(void) | |
87 | { | |
88 | CMM_STORE_SHARED(URCU_TLS(cached_ipc_ns), NS_INO_UNINITIALIZED); | |
89 | } | |
90 | ||
91 | static | |
92 | size_t ipc_ns_get_size(struct lttng_ctx_field *field, size_t offset) | |
93 | { | |
94 | size_t size = 0; | |
95 | ||
96 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
97 | size += sizeof(ino_t); | |
98 | return size; | |
99 | } | |
100 | ||
101 | static | |
102 | void ipc_ns_record(struct lttng_ctx_field *field, | |
103 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
104 | struct lttng_channel *chan) | |
105 | { | |
106 | ino_t ipc_ns; | |
107 | ||
108 | ipc_ns = get_ipc_ns(); | |
109 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(ipc_ns)); | |
110 | chan->ops->event_write(ctx, &ipc_ns, sizeof(ipc_ns)); | |
111 | } | |
112 | ||
113 | static | |
114 | void ipc_ns_get_value(struct lttng_ctx_field *field, | |
115 | struct lttng_ctx_value *value) | |
116 | { | |
117 | value->u.s64 = get_ipc_ns(); | |
118 | } | |
119 | ||
120 | int lttng_add_ipc_ns_to_ctx(struct lttng_ctx **ctx) | |
121 | { | |
122 | struct lttng_ctx_field *field; | |
123 | ||
124 | field = lttng_append_context(ctx); | |
125 | if (!field) | |
126 | return -ENOMEM; | |
127 | if (lttng_find_context(*ctx, "ipc_ns")) { | |
128 | lttng_remove_context_field(ctx, field); | |
129 | return -EEXIST; | |
130 | } | |
131 | field->event_field.name = "ipc_ns"; | |
132 | field->event_field.type.atype = atype_integer; | |
218deb69 MD |
133 | field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT; |
134 | field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT; | |
135 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t); | |
136 | field->event_field.type.u.integer.reverse_byte_order = 0; | |
137 | field->event_field.type.u.integer.base = 10; | |
138 | field->event_field.type.u.integer.encoding = lttng_encode_none; | |
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139 | field->get_size = ipc_ns_get_size; |
140 | field->record = ipc_ns_record; | |
141 | field->get_value = ipc_ns_get_value; | |
142 | lttng_context_update(*ctx); | |
143 | return 0; | |
144 | } | |
145 | ||
146 | /* | |
147 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
148 | * */ | |
149 | void lttng_fixup_ipc_ns_tls(void) | |
150 | { | |
151 | asm volatile ("" : : "m" (URCU_TLS(cached_ipc_ns))); | |
152 | } |