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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "private/bionic_systrace.h"
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <async_safe/log.h>
#include <cutils/trace.h> // For ATRACE_TAG_BIONIC.
#include "private/CachedProperty.h"
#include "private/bionic_lock.h"
#define WRITE_OFFSET 32
static Lock g_lock;
bool should_trace(const uint64_t enable_tags) {
static uint64_t tags_val;
static CachedProperty tags_prop(kTraceTagsProp);
g_lock.lock();
if (tags_prop.DidChange()) {
tags_val = strtoull(tags_prop.Get(), nullptr, 0);
}
g_lock.unlock();
return tags_val & enable_tags;
}
int get_trace_marker_fd() {
static int opened_trace_marker_fd = -1;
g_lock.lock();
if (opened_trace_marker_fd == -1) {
opened_trace_marker_fd = open("/sys/kernel/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
if (opened_trace_marker_fd == -1) {
opened_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
}
}
g_lock.unlock();
return opened_trace_marker_fd;
}
// event could be 'B' for begin or 'E' for end.
void output_trace(const char* message, const char event) {
int trace_marker_fd = get_trace_marker_fd();
if (trace_marker_fd == -1) {
return;
}
// If bionic tracing has been enabled, then write the message to the
// kernel trace_marker.
int length = strlen(message);
char buf[length + WRITE_OFFSET];
size_t len =
async_safe_format_buffer(buf, length + WRITE_OFFSET, "%c|%d|%s", event, getpid(), message);
// Tracing may stop just after checking property and before writing the message.
// So the write is acceptable to fail. See b/20666100.
TEMP_FAILURE_RETRY(write(trace_marker_fd, buf, len));
}
void bionic_trace_begin(const char* message) {
if (!should_trace()) {
return;
}
output_trace(message);
}
void bionic_trace_end() {
if (!should_trace()) {
return;
}
int trace_marker_fd = get_trace_marker_fd();
if (trace_marker_fd == -1) {
return;
}
TEMP_FAILURE_RETRY(write(trace_marker_fd, "E|", 2));
}
ScopedTrace::ScopedTrace(const char* message) : called_end_(false) {
bionic_trace_begin(message);
}
ScopedTrace::~ScopedTrace() {
End();
}
void ScopedTrace::End() {
if (!called_end_) {
bionic_trace_end();
called_end_ = true;
}
}
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