2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
7 * LTTng UST namespaced saved set-user ID context.
12 #include <sys/types.h>
15 #include <lttng/ust-events.h>
16 #include <lttng/ust-tracer.h>
17 #include <lttng/ringbuffer-config.h>
19 #include "context-internal.h"
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.
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.
38 static uid_t cached_vsuid
= INVALID_UID
;
45 vsuid
= CMM_LOAD_SHARED(cached_vsuid
);
47 if (caa_unlikely(vsuid
== INVALID_UID
)) {
48 uid_t uid
, euid
, suid
;
50 if (getresuid(&uid
, &euid
, &suid
) == 0) {
52 CMM_STORE_SHARED(cached_vsuid
, vsuid
);
60 * The vsuid can change on setuid, setreuid and setresuid.
62 void lttng_context_vsuid_reset(void)
64 CMM_STORE_SHARED(cached_vsuid
, INVALID_UID
);
68 size_t vsuid_get_size(struct lttng_ctx_field
*field
, size_t offset
)
72 size
+= lib_ring_buffer_align(offset
, lttng_alignof(uid_t
));
73 size
+= sizeof(uid_t
);
78 void vsuid_record(struct lttng_ctx_field
*field
,
79 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
80 struct lttng_channel
*chan
)
85 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(vsuid
));
86 chan
->ops
->event_write(ctx
, &vsuid
, sizeof(vsuid
));
90 void vsuid_get_value(struct lttng_ctx_field
*field
,
91 struct lttng_ctx_value
*value
)
93 value
->u
.s64
= get_vsuid();
96 int lttng_add_vsuid_to_ctx(struct lttng_ctx
**ctx
)
98 struct lttng_ctx_field
*field
;
100 field
= lttng_append_context(ctx
);
103 if (lttng_find_context(*ctx
, "vsuid")) {
104 lttng_remove_context_field(ctx
, field
);
107 field
->event_field
.name
= "vsuid";
108 field
->event_field
.type
.atype
= atype_integer
;
109 field
->event_field
.type
.u
.integer
.size
= sizeof(uid_t
) * CHAR_BIT
;
110 field
->event_field
.type
.u
.integer
.alignment
= lttng_alignof(uid_t
) * CHAR_BIT
;
111 field
->event_field
.type
.u
.integer
.signedness
= lttng_is_signed_type(uid_t
);
112 field
->event_field
.type
.u
.integer
.reverse_byte_order
= 0;
113 field
->event_field
.type
.u
.integer
.base
= 10;
114 field
->event_field
.type
.u
.integer
.encoding
= lttng_encode_none
;
115 field
->get_size
= vsuid_get_size
;
116 field
->record
= vsuid_record
;
117 field
->get_value
= vsuid_get_value
;
118 lttng_context_update(*ctx
);