Fix: pass private data to context callbacks
[lttng-ust.git] / liblttng-ust / lttng-context-procname.c
CommitLineData
4847e9bb 1/*
c0c0989a 2 * SPDX-License-Identifier: LGPL-2.1-only
4847e9bb 3 *
009745db 4 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
e92f3e28 5 *
c0c0989a 6 * LTTng UST procname context.
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7 */
8
3fbec7dc 9#define _LGPL_SOURCE
b4051ad8 10#include <stddef.h>
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11#include <lttng/ust-events.h>
12#include <lttng/ust-tracer.h>
0466ac28 13#include <lttng/ringbuffer-context.h>
8c90a710 14#include <urcu/tls-compat.h>
4847e9bb 15#include <assert.h>
08114193 16#include "compat.h"
4b4a1337 17#include "lttng-tracer-core.h"
4847e9bb 18
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19#include "context-internal.h"
20
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21/* Maximum number of nesting levels for the procname cache. */
22#define PROCNAME_NESTING_MAX 2
23
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24/*
25 * We cache the result to ensure we don't trigger a system call for
26 * each event.
27 * Upon exec, procname changes, but exec takes care of throwing away
28 * this cached version.
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29 * The procname can also change by calling prctl(). The procname should
30 * be set for a thread before the first event is logged within this
31 * thread.
4847e9bb 32 */
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33typedef char procname_array[PROCNAME_NESTING_MAX][17];
34
16adecf1 35static DEFINE_URCU_TLS(procname_array, cached_procname);
4847e9bb 36
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37static DEFINE_URCU_TLS(int, procname_nesting);
38
4847e9bb 39static inline
74c3f8e2 40const char *wrapper_getprocname(void)
4847e9bb 41{
2c44512a 42 int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
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43
44 if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
45 return "<unknown>";
46 if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
47 CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
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48 /* Increment nesting before updating cache. */
49 cmm_barrier();
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50 lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN);
51 URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_PROCNAME_LEN - 1] = '\0';
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52 /* Decrement nesting after updating cache. */
53 cmm_barrier();
74011e88 54 CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
4847e9bb 55 }
74011e88 56 return URCU_TLS(cached_procname)[nesting];
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57}
58
2c44512a 59/* Reset should not be called from a signal handler. */
0af0bdb2 60void lttng_ust_context_procname_reset(void)
4847e9bb 61{
2c44512a 62 CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
74011e88 63 CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
2c44512a 64 CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
74011e88 65 CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
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66}
67
68static
4e48b5d2 69size_t procname_get_size(void *priv __attribute__((unused)),
2208d8b5 70 size_t offset __attribute__((unused)))
4847e9bb 71{
0db3d6ee 72 return LTTNG_UST_ABI_PROCNAME_LEN;
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73}
74
75static
4e48b5d2 76void procname_record(void *priv __attribute__((unused)),
4cfec15c 77 struct lttng_ust_lib_ring_buffer_ctx *ctx,
e7bc0ef6 78 struct lttng_ust_channel_buffer *chan)
4847e9bb 79{
74c3f8e2 80 const char *procname;
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81
82 procname = wrapper_getprocname();
8936b6c0 83 chan->ops->event_write(ctx, procname, LTTNG_UST_ABI_PROCNAME_LEN, 1);
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84}
85
77aa5901 86static
4e48b5d2 87void procname_get_value(void *priv __attribute__((unused)),
daacdbfc 88 struct lttng_ust_ctx_value *value)
77aa5901 89{
6e9ac4ae 90 value->u.str = wrapper_getprocname();
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91}
92
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93static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field(
94 lttng_ust_static_event_field("procname",
95 lttng_ust_static_type_array_text(LTTNG_UST_ABI_PROCNAME_LEN),
96 false, false),
97 procname_get_size,
98 procname_record,
99 procname_get_value,
100 NULL, NULL);
101
daacdbfc 102int lttng_add_procname_to_ctx(struct lttng_ust_ctx **ctx)
4847e9bb 103{
a084756d 104 int ret;
4847e9bb 105
4e48b5d2 106 if (lttng_find_context(*ctx, ctx_field->event_field->name)) {
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107 ret = -EEXIST;
108 goto error_find_context;
109 }
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110 ret = lttng_ust_context_append(ctx, ctx_field);
111 if (ret)
112 return ret;
4847e9bb 113 return 0;
a084756d 114
a084756d 115error_find_context:
a084756d 116 return ret;
4847e9bb 117}
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118
119/*
120 * Force a read (imply TLS fixup for dlopen) of TLS variables.
121 */
122void lttng_fixup_procname_tls(void)
123{
8c90a710 124 asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));
009745db 125}
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