1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#include <errno.h> 18#include <fcntl.h> 19#include <stdio.h> 20#include <stdlib.h> 21#include <string.h> 22 23#include "private/bionic_lock.h" 24#include "private/bionic_systrace.h" 25#include "private/CachedProperty.h" 26 27#include <cutils/trace.h> // For ATRACE_TAG_BIONIC. 28 29#define WRITE_OFFSET 32 30 31static Lock g_lock; 32static CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags"); 33static uint64_t g_tags; 34static int g_trace_marker_fd = -1; 35 36static bool should_trace() { 37 g_lock.lock(); 38 if (g_debug_atrace_tags_enableflags.DidChange()) { 39 g_tags = strtoull(g_debug_atrace_tags_enableflags.Get(), nullptr, 0); 40 } 41 g_lock.unlock(); 42 return ((g_tags & ATRACE_TAG_BIONIC) != 0); 43} 44 45static int get_trace_marker_fd() { 46 g_lock.lock(); 47 if (g_trace_marker_fd == -1) { 48 g_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_CLOEXEC | O_WRONLY); 49 } 50 g_lock.unlock(); 51 return g_trace_marker_fd; 52} 53 54void bionic_trace_begin(const char* message) { 55 if (!should_trace()) { 56 return; 57 } 58 59 int trace_marker_fd = get_trace_marker_fd(); 60 if (trace_marker_fd == -1) { 61 return; 62 } 63 64 // If bionic tracing has been enabled, then write the message to the 65 // kernel trace_marker. 66 int length = strlen(message); 67 char buf[length + WRITE_OFFSET]; 68 size_t len = snprintf(buf, length + WRITE_OFFSET, "B|%d|%s", getpid(), message); 69 70 // Tracing may stop just after checking property and before writing the message. 71 // So the write is acceptable to fail. See b/20666100. 72 TEMP_FAILURE_RETRY(write(trace_marker_fd, buf, len)); 73} 74 75void bionic_trace_end() { 76 if (!should_trace()) { 77 return; 78 } 79 80 int trace_marker_fd = get_trace_marker_fd(); 81 if (trace_marker_fd == -1) { 82 return; 83 } 84 85 TEMP_FAILURE_RETRY(write(trace_marker_fd, "E", 1)); 86} 87 88ScopedTrace::ScopedTrace(const char* message) : called_end_(false) { 89 bionic_trace_begin(message); 90} 91 92ScopedTrace::~ScopedTrace() { 93 End(); 94} 95 96void ScopedTrace::End() { 97 if (!called_end_) { 98 bionic_trace_end(); 99 called_end_ = true; 100 } 101} 102