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