1/*
2 * Copyright (C) 2012 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#define LOG_TAG "cutils-trace"
18
19#include <errno.h>
20#include <fcntl.h>
21#include <limits.h>
22#include <pthread.h>
23#include <stdatomic.h>
24#include <stdbool.h>
25#include <stdlib.h>
26#include <string.h>
27#include <sys/types.h>
28
29#include <cutils/compiler.h>
30#include <cutils/properties.h>
31#include <cutils/trace.h>
32#include <log/log.h>
33#include <log/log_properties.h>
34
35/**
36 * Maximum size of a message that can be logged to the trace buffer.
37 * Note this message includes a tag, the pid, and the string given as the name.
38 * Names should be kept short to get the most use of the trace buffer.
39 */
40#define ATRACE_MESSAGE_LENGTH 1024
41
42atomic_bool             atrace_is_ready      = ATOMIC_VAR_INIT(false);
43int                     atrace_marker_fd     = -1;
44uint64_t                atrace_enabled_tags  = ATRACE_TAG_NOT_READY;
45static bool             atrace_is_debuggable = false;
46static atomic_bool      atrace_is_enabled    = ATOMIC_VAR_INIT(true);
47static pthread_once_t   atrace_once_control  = PTHREAD_ONCE_INIT;
48static pthread_mutex_t  atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;
49
50// Set whether this process is debuggable, which determines whether
51// application-level tracing is allowed when the ro.debuggable system property
52// is not set to '1'.
53void atrace_set_debuggable(bool debuggable)
54{
55    atrace_is_debuggable = debuggable;
56    atrace_update_tags();
57}
58
59// Set whether tracing is enabled in this process.  This is used to prevent
60// the Zygote process from tracing.
61void atrace_set_tracing_enabled(bool enabled)
62{
63    atomic_store_explicit(&atrace_is_enabled, enabled, memory_order_release);
64    atrace_update_tags();
65}
66
67// Check whether the given command line matches one of the comma-separated
68// values listed in the app_cmdlines property.
69static bool atrace_is_cmdline_match(const char* cmdline)
70{
71    int count = property_get_int32("debug.atrace.app_number", 0);
72
73    char buf[PROPERTY_KEY_MAX];
74    char value[PROPERTY_VALUE_MAX];
75
76    for (int i = 0; i < count; i++) {
77        snprintf(buf, sizeof(buf), "debug.atrace.app_%d", i);
78        property_get(buf, value, "");
79        if (strcmp(value, cmdline) == 0) {
80            return true;
81        }
82    }
83
84    return false;
85}
86
87// Determine whether application-level tracing is enabled for this process.
88static bool atrace_is_app_tracing_enabled()
89{
90    bool sys_debuggable = __android_log_is_debuggable();
91    bool result = false;
92
93    if (sys_debuggable || atrace_is_debuggable) {
94        // Check whether tracing is enabled for this process.
95        FILE * file = fopen("/proc/self/cmdline", "re");
96        if (file) {
97            char cmdline[4096];
98            if (fgets(cmdline, sizeof(cmdline), file)) {
99                result = atrace_is_cmdline_match(cmdline);
100            } else {
101                ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
102            }
103            fclose(file);
104        } else {
105            ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
106                    errno);
107        }
108    }
109
110    return result;
111}
112
113// Read the sysprop and return the value tags should be set to
114static uint64_t atrace_get_property()
115{
116    char value[PROPERTY_VALUE_MAX];
117    char *endptr;
118    uint64_t tags;
119
120    property_get("debug.atrace.tags.enableflags", value, "0");
121    errno = 0;
122    tags = strtoull(value, &endptr, 0);
123    if (value[0] == '\0' || *endptr != '\0') {
124        ALOGE("Error parsing trace property: Not a number: %s", value);
125        return 0;
126    } else if (errno == ERANGE || tags == ULLONG_MAX) {
127        ALOGE("Error parsing trace property: Number too large: %s", value);
128        return 0;
129    }
130
131    // Only set the "app" tag if this process was selected for app-level debug
132    // tracing.
133    if (atrace_is_app_tracing_enabled()) {
134        tags |= ATRACE_TAG_APP;
135    } else {
136        tags &= ~ATRACE_TAG_APP;
137    }
138
139    return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
140}
141
142// Update tags if tracing is ready. Useful as a sysprop change callback.
143void atrace_update_tags()
144{
145    uint64_t tags;
146    if (CC_UNLIKELY(atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
147        if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
148            tags = atrace_get_property();
149            pthread_mutex_lock(&atrace_tags_mutex);
150            atrace_enabled_tags = tags;
151            pthread_mutex_unlock(&atrace_tags_mutex);
152        } else {
153            // Tracing is disabled for this process, so we simply don't
154            // initialize the tags.
155            pthread_mutex_lock(&atrace_tags_mutex);
156            atrace_enabled_tags = ATRACE_TAG_NOT_READY;
157            pthread_mutex_unlock(&atrace_tags_mutex);
158        }
159    }
160}
161
162static void atrace_init_once()
163{
164    atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
165    if (atrace_marker_fd == -1) {
166        ALOGE("Error opening trace file: %s (%d)", strerror(errno), errno);
167        atrace_enabled_tags = 0;
168        goto done;
169    }
170
171    atrace_enabled_tags = atrace_get_property();
172
173done:
174    atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
175}
176
177void atrace_setup()
178{
179    pthread_once(&atrace_once_control, atrace_init_once);
180}
181
182void atrace_begin_body(const char* name)
183{
184    char buf[ATRACE_MESSAGE_LENGTH];
185
186    int len = snprintf(buf, sizeof(buf), "B|%d|%s", getpid(), name);
187    if (len >= (int) sizeof(buf)) {
188        ALOGW("Truncated name in %s: %s\n", __FUNCTION__, name);
189        len = sizeof(buf) - 1;
190    }
191    write(atrace_marker_fd, buf, len);
192}
193
194void atrace_end_body()
195{
196    char c = 'E';
197    write(atrace_marker_fd, &c, 1);
198}
199
200#define WRITE_MSG(format_begin, format_end, pid, name, value) { \
201    char buf[ATRACE_MESSAGE_LENGTH]; \
202    int len = snprintf(buf, sizeof(buf), format_begin "%s" format_end, pid, \
203        name, value); \
204    if (len >= (int) sizeof(buf)) { \
205        /* Given the sizeof(buf), and all of the current format buffers, \
206         * it is impossible for name_len to be < 0 if len >= sizeof(buf). */ \
207        int name_len = strlen(name) - (len - sizeof(buf)) - 1; \
208        /* Truncate the name to make the message fit. */ \
209        ALOGW("Truncated name in %s: %s\n", __FUNCTION__, name); \
210        len = snprintf(buf, sizeof(buf), format_begin "%.*s" format_end, pid, \
211            name_len, name, value); \
212    } \
213    write(atrace_marker_fd, buf, len); \
214}
215
216void atrace_async_begin_body(const char* name, int32_t cookie)
217{
218    WRITE_MSG("S|%d|", "|%" PRId32, getpid(), name, cookie);
219}
220
221void atrace_async_end_body(const char* name, int32_t cookie)
222{
223    WRITE_MSG("F|%d|", "|%" PRId32, getpid(), name, cookie);
224}
225
226void atrace_int_body(const char* name, int32_t value)
227{
228    WRITE_MSG("C|%d|", "|%" PRId32, getpid(), name, value);
229}
230
231void atrace_int64_body(const char* name, int64_t value)
232{
233    WRITE_MSG("C|%d|", "|%" PRId64, getpid(), name, value);
234}
235