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
31 static Lock g_lock;
32 static int g_trace_marker_fd = -1;
33
should_trace()34 static bool should_trace() {
35 static CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags");
36 static uint64_t g_tags;
37
38 g_lock.lock();
39 if (g_debug_atrace_tags_enableflags.DidChange()) {
40 g_tags = strtoull(g_debug_atrace_tags_enableflags.Get(), nullptr, 0);
41 }
42 g_lock.unlock();
43 return ((g_tags & ATRACE_TAG_BIONIC) != 0);
44 }
45
get_trace_marker_fd()46 static int get_trace_marker_fd() {
47 g_lock.lock();
48 if (g_trace_marker_fd == -1) {
49 g_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
50 }
51 g_lock.unlock();
52 return g_trace_marker_fd;
53 }
54
bionic_trace_begin(const char * message)55 void bionic_trace_begin(const char* message) {
56 if (!should_trace()) {
57 return;
58 }
59
60 int trace_marker_fd = get_trace_marker_fd();
61 if (trace_marker_fd == -1) {
62 return;
63 }
64
65 // If bionic tracing has been enabled, then write the message to the
66 // kernel trace_marker.
67 int length = strlen(message);
68 char buf[length + WRITE_OFFSET];
69 size_t len = snprintf(buf, length + WRITE_OFFSET, "B|%d|%s", getpid(), message);
70
71 // Tracing may stop just after checking property and before writing the message.
72 // So the write is acceptable to fail. See b/20666100.
73 TEMP_FAILURE_RETRY(write(trace_marker_fd, buf, len));
74 }
75
bionic_trace_end()76 void bionic_trace_end() {
77 if (!should_trace()) {
78 return;
79 }
80
81 int trace_marker_fd = get_trace_marker_fd();
82 if (trace_marker_fd == -1) {
83 return;
84 }
85
86 TEMP_FAILURE_RETRY(write(trace_marker_fd, "E", 1));
87 }
88
ScopedTrace(const char * message)89 ScopedTrace::ScopedTrace(const char* message) : called_end_(false) {
90 bionic_trace_begin(message);
91 }
92
~ScopedTrace()93 ScopedTrace::~ScopedTrace() {
94 End();
95 }
96
End()97 void ScopedTrace::End() {
98 if (!called_end_) {
99 bionic_trace_end();
100 called_end_ = true;
101 }
102 }
103