Commit | Line | Data |
---|---|---|
735bef47 MJ |
1 | /* |
2 | * lttng-context-uts-ns.c | |
3 | * | |
4 | * LTTng UST uts 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 | |
b4051ad8 | 25 | #include <stddef.h> |
735bef47 MJ |
26 | #include <sys/types.h> |
27 | #include <sys/stat.h> | |
28 | #include <unistd.h> | |
29 | #include <lttng/ust-events.h> | |
30 | #include <lttng/ust-tracer.h> | |
31 | #include <lttng/ringbuffer-config.h> | |
32 | #include <lttng/ust-tid.h> | |
33 | #include <urcu/tls-compat.h> | |
34 | #include "lttng-tracer-core.h" | |
35 | #include "ns.h" | |
36 | ||
37 | ||
38 | /* | |
39 | * We cache the result to ensure we don't stat(2) the proc filesystem on | |
40 | * each event. | |
41 | */ | |
42 | static DEFINE_URCU_TLS(ino_t, cached_uts_ns) = NS_INO_UNINITIALIZED; | |
43 | ||
44 | static | |
45 | ino_t get_uts_ns(void) | |
46 | { | |
47 | struct stat sb; | |
48 | ino_t uts_ns; | |
49 | ||
50 | uts_ns = CMM_LOAD_SHARED(URCU_TLS(cached_uts_ns)); | |
51 | ||
52 | /* | |
53 | * If the cache is populated, do nothing and return the | |
54 | * cached inode number. | |
55 | */ | |
56 | if (caa_likely(uts_ns != NS_INO_UNINITIALIZED)) | |
57 | return uts_ns; | |
58 | ||
59 | /* | |
60 | * At this point we have to populate the cache, set the initial | |
61 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode | |
62 | * number from the proc filesystem, this is the value we will | |
63 | * cache. | |
64 | */ | |
65 | uts_ns = NS_INO_UNAVAILABLE; | |
66 | ||
67 | /* | |
68 | * /proc/thread-self was introduced in kernel v3.17 | |
69 | */ | |
70 | if (stat("/proc/thread-self/ns/uts", &sb) == 0) { | |
71 | uts_ns = sb.st_ino; | |
72 | } else { | |
73 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; | |
74 | ||
75 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, | |
76 | "/proc/self/task/%d/ns/uts", | |
77 | lttng_gettid()) >= 0) { | |
78 | ||
79 | if (stat(proc_ns_path, &sb) == 0) { | |
80 | uts_ns = sb.st_ino; | |
81 | } | |
82 | } | |
83 | } | |
84 | ||
85 | /* | |
86 | * And finally, store the inode number in the cache. | |
87 | */ | |
88 | CMM_STORE_SHARED(URCU_TLS(cached_uts_ns), uts_ns); | |
89 | ||
90 | return uts_ns; | |
91 | } | |
92 | ||
93 | /* | |
94 | * The uts namespace can change for 3 reasons | |
95 | * * clone(2) called with CLONE_NEWUTS | |
96 | * * setns(2) called with the fd of a different uts ns | |
97 | * * unshare(2) called with CLONE_NEWUTS | |
98 | */ | |
99 | void lttng_context_uts_ns_reset(void) | |
100 | { | |
101 | CMM_STORE_SHARED(URCU_TLS(cached_uts_ns), NS_INO_UNINITIALIZED); | |
102 | } | |
103 | ||
104 | static | |
105 | size_t uts_ns_get_size(struct lttng_ctx_field *field, size_t offset) | |
106 | { | |
107 | size_t size = 0; | |
108 | ||
109 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); | |
110 | size += sizeof(ino_t); | |
111 | return size; | |
112 | } | |
113 | ||
114 | static | |
115 | void uts_ns_record(struct lttng_ctx_field *field, | |
116 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
117 | struct lttng_channel *chan) | |
118 | { | |
119 | ino_t uts_ns; | |
120 | ||
121 | uts_ns = get_uts_ns(); | |
122 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(uts_ns)); | |
123 | chan->ops->event_write(ctx, &uts_ns, sizeof(uts_ns)); | |
124 | } | |
125 | ||
126 | static | |
127 | void uts_ns_get_value(struct lttng_ctx_field *field, | |
128 | struct lttng_ctx_value *value) | |
129 | { | |
130 | value->u.s64 = get_uts_ns(); | |
131 | } | |
132 | ||
133 | int lttng_add_uts_ns_to_ctx(struct lttng_ctx **ctx) | |
134 | { | |
135 | struct lttng_ctx_field *field; | |
136 | ||
137 | field = lttng_append_context(ctx); | |
138 | if (!field) | |
139 | return -ENOMEM; | |
140 | if (lttng_find_context(*ctx, "uts_ns")) { | |
141 | lttng_remove_context_field(ctx, field); | |
142 | return -EEXIST; | |
143 | } | |
144 | field->event_field.name = "uts_ns"; | |
145 | field->event_field.type.atype = atype_integer; | |
146 | field->event_field.type.u.basic.integer.size = sizeof(ino_t) * CHAR_BIT; | |
147 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT; | |
148 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(ino_t); | |
149 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
150 | field->event_field.type.u.basic.integer.base = 10; | |
151 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
152 | field->get_size = uts_ns_get_size; | |
153 | field->record = uts_ns_record; | |
154 | field->get_value = uts_ns_get_value; | |
155 | lttng_context_update(*ctx); | |
156 | return 0; | |
157 | } | |
158 | ||
159 | /* | |
160 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
161 | * */ | |
162 | void lttng_fixup_uts_ns_tls(void) | |
163 | { | |
164 | asm volatile ("" : : "m" (URCU_TLS(cached_uts_ns))); | |
165 | } |