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