| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * |
| 6 | * LTTng UST procname context. |
| 7 | */ |
| 8 | |
| 9 | #define _LGPL_SOURCE |
| 10 | #include <stddef.h> |
| 11 | #include <lttng/ust-events.h> |
| 12 | #include <lttng/ust-tracer.h> |
| 13 | #include <lttng/ust-ringbuffer-context.h> |
| 14 | #include <urcu/tls-compat.h> |
| 15 | #include <assert.h> |
| 16 | #include "common/compat/pthread.h" |
| 17 | #include "lttng-tracer-core.h" |
| 18 | |
| 19 | #include "context-internal.h" |
| 20 | |
| 21 | /* Maximum number of nesting levels for the procname cache. */ |
| 22 | #define PROCNAME_NESTING_MAX 2 |
| 23 | |
| 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. |
| 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. |
| 32 | */ |
| 33 | typedef char procname_array[PROCNAME_NESTING_MAX][LTTNG_UST_CONTEXT_PROCNAME_LEN]; |
| 34 | |
| 35 | static DEFINE_URCU_TLS(procname_array, cached_procname); |
| 36 | |
| 37 | static DEFINE_URCU_TLS(int, procname_nesting); |
| 38 | |
| 39 | static inline |
| 40 | const char *wrapper_getprocname(void) |
| 41 | { |
| 42 | int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting)); |
| 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); |
| 48 | /* Increment nesting before updating cache. */ |
| 49 | cmm_barrier(); |
| 50 | lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_CONTEXT_PROCNAME_LEN); |
| 51 | URCU_TLS(cached_procname)[nesting][LTTNG_UST_CONTEXT_PROCNAME_LEN - 1] = '\0'; |
| 52 | /* Decrement nesting after updating cache. */ |
| 53 | cmm_barrier(); |
| 54 | CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting); |
| 55 | } |
| 56 | return URCU_TLS(cached_procname)[nesting]; |
| 57 | } |
| 58 | |
| 59 | /* Reset should not be called from a signal handler. */ |
| 60 | void lttng_ust_context_procname_reset(void) |
| 61 | { |
| 62 | CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0'); |
| 63 | CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1); |
| 64 | CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0'); |
| 65 | CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0); |
| 66 | } |
| 67 | |
| 68 | static |
| 69 | size_t procname_get_size(void *priv __attribute__((unused)), |
| 70 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
| 71 | size_t offset __attribute__((unused))) |
| 72 | { |
| 73 | return LTTNG_UST_CONTEXT_PROCNAME_LEN; |
| 74 | } |
| 75 | |
| 76 | static |
| 77 | void procname_record(void *priv __attribute__((unused)), |
| 78 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
| 79 | struct lttng_ust_ring_buffer_ctx *ctx, |
| 80 | struct lttng_ust_channel_buffer *chan) |
| 81 | { |
| 82 | const char *procname; |
| 83 | |
| 84 | procname = wrapper_getprocname(); |
| 85 | chan->ops->event_write(ctx, procname, LTTNG_UST_CONTEXT_PROCNAME_LEN, 1); |
| 86 | } |
| 87 | |
| 88 | static |
| 89 | void procname_get_value(void *priv __attribute__((unused)), |
| 90 | struct lttng_ust_probe_ctx *probe_ctx __attribute__((unused)), |
| 91 | struct lttng_ust_ctx_value *value) |
| 92 | { |
| 93 | value->u.str = wrapper_getprocname(); |
| 94 | } |
| 95 | |
| 96 | static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( |
| 97 | lttng_ust_static_event_field("procname", |
| 98 | lttng_ust_static_type_array_text(LTTNG_UST_CONTEXT_PROCNAME_LEN), |
| 99 | false, false), |
| 100 | procname_get_size, |
| 101 | procname_record, |
| 102 | procname_get_value, |
| 103 | NULL, NULL); |
| 104 | |
| 105 | int lttng_add_procname_to_ctx(struct lttng_ust_ctx **ctx) |
| 106 | { |
| 107 | int ret; |
| 108 | |
| 109 | if (lttng_find_context(*ctx, ctx_field->event_field->name)) { |
| 110 | ret = -EEXIST; |
| 111 | goto error_find_context; |
| 112 | } |
| 113 | ret = lttng_ust_context_append(ctx, ctx_field); |
| 114 | if (ret) |
| 115 | return ret; |
| 116 | return 0; |
| 117 | |
| 118 | error_find_context: |
| 119 | return ret; |
| 120 | } |
| 121 | |
| 122 | /* |
| 123 | * Force a read (imply TLS allocation for dlopen) of TLS variables. |
| 124 | */ |
| 125 | void lttng_ust_procname_init_thread(int flags) |
| 126 | { |
| 127 | __asm__ __volatile__ ("" : : "m" (URCU_TLS(cached_procname)[0])); |
| 128 | if (flags & LTTNG_UST_INIT_THREAD_CONTEXT_CACHE) |
| 129 | (void)wrapper_getprocname(); |
| 130 | } |