| 1 | /* |
| 2 | * lttng-context-procname.c |
| 3 | * |
| 4 | * LTTng UST procname context. |
| 5 | * |
| 6 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * |
| 8 | * This library is free software; you can redistribute it and/or |
| 9 | * modify it under the terms of the GNU Lesser General Public |
| 10 | * License as published by the Free Software Foundation; only |
| 11 | * version 2.1 of the License. |
| 12 | * |
| 13 | * This library is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 16 | * Lesser General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU Lesser General Public |
| 19 | * License along with this library; if not, write to the Free Software |
| 20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 21 | */ |
| 22 | |
| 23 | #define _LGPL_SOURCE |
| 24 | #include <lttng/ust-events.h> |
| 25 | #include <lttng/ust-tracer.h> |
| 26 | #include <lttng/ringbuffer-config.h> |
| 27 | #include <urcu/tls-compat.h> |
| 28 | #include <assert.h> |
| 29 | #include "compat.h" |
| 30 | |
| 31 | /* |
| 32 | * We cache the result to ensure we don't trigger a system call for |
| 33 | * each event. |
| 34 | * Upon exec, procname changes, but exec takes care of throwing away |
| 35 | * this cached version. |
| 36 | * The procname can also change by calling prctl(). The procname should |
| 37 | * be set for a thread before the first event is logged within this |
| 38 | * thread. |
| 39 | */ |
| 40 | typedef char procname_array[17]; |
| 41 | static DEFINE_URCU_TLS(procname_array, cached_procname); |
| 42 | |
| 43 | static inline |
| 44 | char *wrapper_getprocname(void) |
| 45 | { |
| 46 | if (caa_unlikely(!URCU_TLS(cached_procname)[0])) { |
| 47 | lttng_ust_getprocname(URCU_TLS(cached_procname)); |
| 48 | URCU_TLS(cached_procname)[LTTNG_UST_PROCNAME_LEN - 1] = '\0'; |
| 49 | } |
| 50 | return URCU_TLS(cached_procname); |
| 51 | } |
| 52 | |
| 53 | void lttng_context_procname_reset(void) |
| 54 | { |
| 55 | URCU_TLS(cached_procname)[0] = '\0'; |
| 56 | } |
| 57 | |
| 58 | static |
| 59 | size_t procname_get_size(struct lttng_ctx_field *field, size_t offset) |
| 60 | { |
| 61 | size_t size = 0; |
| 62 | |
| 63 | size += LTTNG_UST_PROCNAME_LEN; |
| 64 | return size; |
| 65 | } |
| 66 | |
| 67 | static |
| 68 | void procname_record(struct lttng_ctx_field *field, |
| 69 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
| 70 | struct lttng_channel *chan) |
| 71 | { |
| 72 | char *procname; |
| 73 | |
| 74 | procname = wrapper_getprocname(); |
| 75 | chan->ops->event_write(ctx, procname, LTTNG_UST_PROCNAME_LEN); |
| 76 | } |
| 77 | |
| 78 | static |
| 79 | void procname_get_value(struct lttng_ctx_field *field, |
| 80 | struct lttng_ctx_value *value) |
| 81 | { |
| 82 | char *procname; |
| 83 | |
| 84 | procname = wrapper_getprocname(); |
| 85 | value->u.str = procname; |
| 86 | } |
| 87 | |
| 88 | int lttng_add_procname_to_ctx(struct lttng_ctx **ctx) |
| 89 | { |
| 90 | struct lttng_ctx_field *field; |
| 91 | |
| 92 | field = lttng_append_context(ctx); |
| 93 | if (!field) |
| 94 | return -ENOMEM; |
| 95 | if (lttng_find_context(*ctx, "procname")) { |
| 96 | lttng_remove_context_field(ctx, field); |
| 97 | return -EEXIST; |
| 98 | } |
| 99 | field->event_field.name = "procname"; |
| 100 | field->event_field.type.atype = atype_array; |
| 101 | field->event_field.type.u.array.elem_type.atype = atype_integer; |
| 102 | field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT; |
| 103 | field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT; |
| 104 | field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char); |
| 105 | field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0; |
| 106 | field->event_field.type.u.array.elem_type.u.basic.integer.base = 10; |
| 107 | field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8; |
| 108 | field->event_field.type.u.array.length = LTTNG_UST_PROCNAME_LEN; |
| 109 | field->get_size = procname_get_size; |
| 110 | field->record = procname_record; |
| 111 | field->get_value = procname_get_value; |
| 112 | lttng_context_update(*ctx); |
| 113 | return 0; |
| 114 | } |
| 115 | |
| 116 | /* |
| 117 | * Force a read (imply TLS fixup for dlopen) of TLS variables. |
| 118 | */ |
| 119 | void lttng_fixup_procname_tls(void) |
| 120 | { |
| 121 | asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0])); |
| 122 | } |