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fca2f191 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
fca2f191 MJ |
3 | * |
4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
c0c0989a | 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
fca2f191 | 6 | * |
c0c0989a | 7 | * LTTng UST namespaced effective group ID context. |
fca2f191 MJ |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
b4051ad8 | 11 | #include <stddef.h> |
fca2f191 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> | |
fc80554e MJ |
18 | |
19 | #include "context-internal.h" | |
fca2f191 MJ |
20 | #include "creds.h" |
21 | ||
22 | ||
23 | /* | |
24 | * At the kernel level, user IDs and group IDs are a per-thread attribute. | |
25 | * However, POSIX requires that all threads in a process share the same | |
26 | * credentials. The NPTL threading implementation handles the POSIX | |
27 | * requirements by providing wrapper functions for the various system calls | |
28 | * that change process UIDs and GIDs. These wrapper functions (including those | |
29 | * for setreuid() and setregid()) employ a signal-based technique to ensure | |
30 | * that when one thread changes credentials, all of the other threads in the | |
31 | * process also change their credentials. | |
32 | */ | |
33 | ||
34 | /* | |
35 | * We cache the result to ensure we don't trigger a system call for | |
36 | * each event. User / group IDs are global to the process. | |
37 | */ | |
38 | static gid_t cached_vegid = INVALID_GID; | |
39 | ||
40 | static | |
41 | gid_t get_vegid(void) | |
42 | { | |
43 | gid_t vegid; | |
44 | ||
45 | vegid = CMM_LOAD_SHARED(cached_vegid); | |
46 | ||
47 | if (caa_unlikely(vegid == INVALID_GID)) { | |
48 | vegid = getegid(); | |
49 | CMM_STORE_SHARED(cached_vegid, vegid); | |
50 | } | |
51 | ||
52 | return vegid; | |
53 | } | |
54 | ||
55 | /* | |
56 | * The vegid can change on setuid, setreuid, setresuid and seteuid. | |
57 | */ | |
58 | void lttng_context_vegid_reset(void) | |
59 | { | |
60 | CMM_STORE_SHARED(cached_vegid, INVALID_GID); | |
61 | } | |
62 | ||
63 | static | |
64 | size_t vegid_get_size(struct lttng_ctx_field *field, size_t offset) | |
65 | { | |
66 | size_t size = 0; | |
67 | ||
68 | size += lib_ring_buffer_align(offset, lttng_alignof(gid_t)); | |
69 | size += sizeof(gid_t); | |
70 | return size; | |
71 | } | |
72 | ||
73 | static | |
74 | void vegid_record(struct lttng_ctx_field *field, | |
75 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
76 | struct lttng_channel *chan) | |
77 | { | |
78 | gid_t vegid; | |
79 | ||
80 | vegid = get_vegid(); | |
81 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(vegid)); | |
82 | chan->ops->event_write(ctx, &vegid, sizeof(vegid)); | |
83 | } | |
84 | ||
85 | static | |
86 | void vegid_get_value(struct lttng_ctx_field *field, | |
87 | struct lttng_ctx_value *value) | |
88 | { | |
89 | value->u.s64 = get_vegid(); | |
90 | } | |
91 | ||
92 | int lttng_add_vegid_to_ctx(struct lttng_ctx **ctx) | |
93 | { | |
94 | struct lttng_ctx_field *field; | |
95 | ||
96 | field = lttng_append_context(ctx); | |
97 | if (!field) | |
98 | return -ENOMEM; | |
99 | if (lttng_find_context(*ctx, "vegid")) { | |
100 | lttng_remove_context_field(ctx, field); | |
101 | return -EEXIST; | |
102 | } | |
103 | field->event_field.name = "vegid"; | |
104 | field->event_field.type.atype = atype_integer; | |
218deb69 MD |
105 | field->event_field.type.u.integer.size = sizeof(gid_t) * CHAR_BIT; |
106 | field->event_field.type.u.integer.alignment = lttng_alignof(gid_t) * CHAR_BIT; | |
107 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(gid_t); | |
108 | field->event_field.type.u.integer.reverse_byte_order = 0; | |
109 | field->event_field.type.u.integer.base = 10; | |
110 | field->event_field.type.u.integer.encoding = lttng_encode_none; | |
fca2f191 MJ |
111 | field->get_size = vegid_get_size; |
112 | field->record = vegid_record; | |
113 | field->get_value = vegid_get_value; | |
114 | lttng_context_update(*ctx); | |
115 | return 0; | |
116 | } |