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 CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags");
33 static uint64_t g_tags;
34 static int g_trace_marker_fd = -1;
35
should_trace()36 static 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
get_trace_marker_fd()45 static 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
bionic_trace_begin(const char * message)54 void 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
bionic_trace_end()75 void 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|", 2));
86 }
87
ScopedTrace(const char * message)88 ScopedTrace::ScopedTrace(const char* message) : called_end_(false) {
89 bionic_trace_begin(message);
90 }
91
~ScopedTrace()92 ScopedTrace::~ScopedTrace() {
93 End();
94 }
95
End()96 void ScopedTrace::End() {
97 if (!called_end_) {
98 bionic_trace_end();
99 called_end_ = true;
100 }
101 }
102