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 effective user ID context.
13 #include <sys/types.h>
16 #include <lttng/ust-events.h>
17 #include <lttng/ust-tracer.h>
18 #include <lttng/ust-ringbuffer-context.h>
20 #include "context-internal.h"
21 #include "common/creds.h"
25 * At the kernel level, user IDs and group IDs are a per-thread attribute.
26 * However, POSIX requires that all threads in a process share the same
27 * credentials. The NPTL threading implementation handles the POSIX
28 * requirements by providing wrapper functions for the various system calls
29 * that change process UIDs and GIDs. These wrapper functions (including those
30 * for setreuid() and setregid()) employ a signal-based technique to ensure
31 * that when one thread changes credentials, all of the other threads in the
32 * process also change their credentials.
36 * We cache the result to ensure we don't trigger a system call for
37 * each event. User / group IDs are global to the process.
39 static uid_t cached_veuid
= INVALID_UID
;
46 veuid
= CMM_LOAD_SHARED(cached_veuid
);
48 if (caa_unlikely(veuid
== INVALID_UID
)) {
50 CMM_STORE_SHARED(cached_veuid
, veuid
);
57 * The veuid can change on setuid, setreuid, setresuid and seteuid.
59 void lttng_context_veuid_reset(void)
61 CMM_STORE_SHARED(cached_veuid
, INVALID_UID
);
65 size_t veuid_get_size(void *priv
__attribute__((unused
)),
70 size
+= lttng_ust_ring_buffer_align(offset
, lttng_ust_rb_alignof(uid_t
));
71 size
+= sizeof(uid_t
);
76 void veuid_record(void *priv
__attribute__((unused
)),
77 struct lttng_ust_ring_buffer_ctx
*ctx
,
78 struct lttng_ust_channel_buffer
*chan
)
83 chan
->ops
->event_write(ctx
, &veuid
, sizeof(veuid
), lttng_ust_rb_alignof(veuid
));
87 void veuid_get_value(void *priv
__attribute__((unused
)),
88 struct lttng_ust_ctx_value
*value
)
90 value
->u
.s64
= get_veuid();
93 static const struct lttng_ust_ctx_field
*ctx_field
= lttng_ust_static_ctx_field(
94 lttng_ust_static_event_field("veuid",
95 lttng_ust_static_type_integer(sizeof(uid_t
) * CHAR_BIT
,
96 lttng_ust_rb_alignof(uid_t
) * CHAR_BIT
,
97 lttng_ust_is_signed_type(uid_t
),
105 int lttng_add_veuid_to_ctx(struct lttng_ust_ctx
**ctx
)
109 if (lttng_find_context(*ctx
, ctx_field
->event_field
->name
)) {
111 goto error_find_context
;
113 ret
= lttng_ust_context_append(ctx
, ctx_field
);