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 <async_safe/log.h>
28 #include <cutils/trace.h> // For ATRACE_TAG_BIONIC.
29
30 #define WRITE_OFFSET 32
31
32 static Lock g_lock;
33 static CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags");
34 static uint64_t g_tags;
35 static int g_trace_marker_fd = -1;
36
should_trace()37 static bool should_trace() {
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/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
50 if (g_trace_marker_fd == -1) {
51 g_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
52 }
53 }
54 g_lock.unlock();
55 return g_trace_marker_fd;
56 }
57
bionic_trace_begin(const char * message)58 void bionic_trace_begin(const char* message) {
59 if (!should_trace()) {
60 return;
61 }
62
63 int trace_marker_fd = get_trace_marker_fd();
64 if (trace_marker_fd == -1) {
65 return;
66 }
67
68 // If bionic tracing has been enabled, then write the message to the
69 // kernel trace_marker.
70 int length = strlen(message);
71 char buf[length + WRITE_OFFSET];
72 size_t len = async_safe_format_buffer(buf, length + WRITE_OFFSET, "B|%d|%s", getpid(), message);
73
74 // Tracing may stop just after checking property and before writing the message.
75 // So the write is acceptable to fail. See b/20666100.
76 TEMP_FAILURE_RETRY(write(trace_marker_fd, buf, len));
77 }
78
bionic_trace_end()79 void bionic_trace_end() {
80 if (!should_trace()) {
81 return;
82 }
83
84 int trace_marker_fd = get_trace_marker_fd();
85 if (trace_marker_fd == -1) {
86 return;
87 }
88
89 TEMP_FAILURE_RETRY(write(trace_marker_fd, "E|", 2));
90 }
91
ScopedTrace(const char * message)92 ScopedTrace::ScopedTrace(const char* message) : called_end_(false) {
93 bionic_trace_begin(message);
94 }
95
~ScopedTrace()96 ScopedTrace::~ScopedTrace() {
97 End();
98 }
99
End()100 void ScopedTrace::End() {
101 if (!called_end_) {
102 bionic_trace_end();
103 called_end_ = true;
104 }
105 }
106