2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * LTTng UST procname context.
11 #include <lttng/ust-events.h>
12 #include <lttng/ust-tracer.h>
13 #include <lttng/ringbuffer-context.h>
14 #include <urcu/tls-compat.h>
18 #include "context-internal.h"
20 /* Maximum number of nesting levels for the procname cache. */
21 #define PROCNAME_NESTING_MAX 2
24 * We cache the result to ensure we don't trigger a system call for
26 * Upon exec, procname changes, but exec takes care of throwing away
27 * this cached version.
28 * The procname can also change by calling prctl(). The procname should
29 * be set for a thread before the first event is logged within this
32 typedef char procname_array
[PROCNAME_NESTING_MAX
][17];
34 static DEFINE_URCU_TLS(procname_array
, cached_procname
);
36 static DEFINE_URCU_TLS(int, procname_nesting
);
39 char *wrapper_getprocname(void)
41 int nesting
= CMM_LOAD_SHARED(URCU_TLS(procname_nesting
));
43 if (caa_unlikely(nesting
>= PROCNAME_NESTING_MAX
))
45 if (caa_unlikely(!URCU_TLS(cached_procname
)[nesting
][0])) {
46 CMM_STORE_SHARED(URCU_TLS(procname_nesting
), nesting
+ 1);
47 /* Increment nesting before updating cache. */
49 lttng_pthread_getname_np(URCU_TLS(cached_procname
)[nesting
], LTTNG_UST_ABI_PROCNAME_LEN
);
50 URCU_TLS(cached_procname
)[nesting
][LTTNG_UST_ABI_PROCNAME_LEN
- 1] = '\0';
51 /* Decrement nesting after updating cache. */
53 CMM_STORE_SHARED(URCU_TLS(procname_nesting
), nesting
);
55 return URCU_TLS(cached_procname
)[nesting
];
58 /* Reset should not be called from a signal handler. */
59 void lttng_ust_context_procname_reset(void)
61 CMM_STORE_SHARED(URCU_TLS(cached_procname
)[1][0], '\0');
62 CMM_STORE_SHARED(URCU_TLS(procname_nesting
), 1);
63 CMM_STORE_SHARED(URCU_TLS(cached_procname
)[0][0], '\0');
64 CMM_STORE_SHARED(URCU_TLS(procname_nesting
), 0);
68 size_t procname_get_size(struct lttng_ust_ctx_field
*field
, size_t offset
)
70 return LTTNG_UST_ABI_PROCNAME_LEN
;
74 void procname_record(struct lttng_ust_ctx_field
*field
,
75 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
76 struct lttng_ust_channel_buffer
*chan
)
80 procname
= wrapper_getprocname();
81 chan
->ops
->event_write(ctx
, procname
, LTTNG_UST_ABI_PROCNAME_LEN
, 1);
85 void procname_get_value(struct lttng_ust_ctx_field
*field
,
86 struct lttng_ust_ctx_value
*value
)
88 value
->u
.str
= wrapper_getprocname();
91 int lttng_add_procname_to_ctx(struct lttng_ust_ctx
**ctx
)
93 struct lttng_ust_ctx_field
*field
;
94 struct lttng_ust_type_common
*type
;
97 type
= lttng_ust_create_type_array_text(LTTNG_UST_ABI_PROCNAME_LEN
);
100 field
= lttng_append_context(ctx
);
105 if (lttng_find_context(*ctx
, "procname")) {
107 goto error_find_context
;
109 field
->event_field
->name
= strdup("procname");
110 if (!field
->event_field
->name
) {
114 field
->event_field
->type
= type
;
115 field
->get_size
= procname_get_size
;
116 field
->record
= procname_record
;
117 field
->get_value
= procname_get_value
;
118 lttng_context_update(*ctx
);
123 lttng_remove_context_field(ctx
, field
);
125 lttng_ust_destroy_type(type
);
130 * Force a read (imply TLS fixup for dlopen) of TLS variables.
132 void lttng_fixup_procname_tls(void)
134 asm volatile ("" : : "m" (URCU_TLS(cached_procname
)[0]));