trace-dev.c revision 23ed4c242a01052696dde84babd7631a7ec5a691 
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#include <cutils/compiler.h>
29#include <cutils/properties.h>
30#include <cutils/trace.h>
31
32#include <android/log.h>
33
34/**
35 * Maximum size of a message that can be logged to the trace buffer.
36 * Note this message includes a tag, the pid, and the string given as the name.
37 * Names should be kept short to get the most use of the trace buffer.
38 */
39#define ATRACE_MESSAGE_LENGTH 1024
40
41atomic_bool             atrace_is_ready      = ATOMIC_VAR_INIT(false);
42int                     atrace_marker_fd     = -1;
43uint64_t                atrace_enabled_tags  = ATRACE_TAG_NOT_READY;
44static bool             atrace_is_debuggable = false;
45static atomic_bool      atrace_is_enabled    = ATOMIC_VAR_INIT(true);
46static pthread_once_t   atrace_once_control  = PTHREAD_ONCE_INIT;
47static pthread_mutex_t  atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;
48
49// Set whether this process is debuggable, which determines whether
50// application-level tracing is allowed when the ro.debuggable system property
51// is not set to '1'.
52void atrace_set_debuggable(bool debuggable)
53{
54    atrace_is_debuggable = debuggable;
55    atrace_update_tags();
56}
57
58// Set whether tracing is enabled in this process.  This is used to prevent
59// the Zygote process from tracing.
60void atrace_set_tracing_enabled(bool enabled)
61{
62    atomic_store_explicit(&atrace_is_enabled, enabled, memory_order_release);
63    atrace_update_tags();
64}
65
66// Check whether the given command line matches one of the comma-separated
67// values listed in the app_cmdlines property.
68static bool atrace_is_cmdline_match(const char* cmdline)
69{
70    int count = property_get_int32("debug.atrace.app_number", 0);
71
72    char buf[PROPERTY_KEY_MAX];
73    char value[PROPERTY_VALUE_MAX];
74
75    for (int i = 0; i < count; i++) {
76        snprintf(buf, sizeof(buf), "debug.atrace.app_%d", i);
77        property_get(buf, value, "");
78        if (strcmp(value, cmdline) == 0) {
79            return true;
80        }
81    }
82
83    return false;
84}
85
86// Determine whether application-level tracing is enabled for this process.
87static bool atrace_is_app_tracing_enabled()
88{
89    bool sys_debuggable = false;
90    char value[PROPERTY_VALUE_MAX];
91    bool result = false;
92
93    // Check whether the system is debuggable.
94    property_get("ro.debuggable", value, "0");
95    if (value[0] == '1') {
96        sys_debuggable = true;
97    }
98
99    if (sys_debuggable || atrace_is_debuggable) {
100        // Check whether tracing is enabled for this process.
101        FILE * file = fopen("/proc/self/cmdline", "re");
102        if (file) {
103            char cmdline[4096];
104            if (fgets(cmdline, sizeof(cmdline), file)) {
105                result = atrace_is_cmdline_match(cmdline);
106            } else {
107                ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
108            }
109            fclose(file);
110        } else {
111            ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
112                    errno);
113        }
114    }
115
116    return result;
117}
118
119// Read the sysprop and return the value tags should be set to
120static uint64_t atrace_get_property()
121{
122    char value[PROPERTY_VALUE_MAX];
123    char *endptr;
124    uint64_t tags;
125
126    property_get("debug.atrace.tags.enableflags", value, "0");
127    errno = 0;
128    tags = strtoull(value, &endptr, 0);
129    if (value[0] == '\0' || *endptr != '\0') {
130        ALOGE("Error parsing trace property: Not a number: %s", value);
131        return 0;
132    } else if (errno == ERANGE || tags == ULLONG_MAX) {
133        ALOGE("Error parsing trace property: Number too large: %s", value);
134        return 0;
135    }
136
137    // Only set the "app" tag if this process was selected for app-level debug
138    // tracing.
139    if (atrace_is_app_tracing_enabled()) {
140        tags |= ATRACE_TAG_APP;
141    } else {
142        tags &= ~ATRACE_TAG_APP;
143    }
144
145    return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
146}
147
148// Update tags if tracing is ready. Useful as a sysprop change callback.
149void atrace_update_tags()
150{
151    uint64_t tags;
152    if (CC_UNLIKELY(atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
153        if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
154            tags = atrace_get_property();
155            pthread_mutex_lock(&atrace_tags_mutex);
156            atrace_enabled_tags = tags;
157            pthread_mutex_unlock(&atrace_tags_mutex);
158        } else {
159            // Tracing is disabled for this process, so we simply don't
160            // initialize the tags.
161            pthread_mutex_lock(&atrace_tags_mutex);
162            atrace_enabled_tags = ATRACE_TAG_NOT_READY;
163            pthread_mutex_unlock(&atrace_tags_mutex);
164        }
165    }
166}
167
168static void atrace_init_once()
169{
170    atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
171    if (atrace_marker_fd == -1) {
172        ALOGE("Error opening trace file: %s (%d)", strerror(errno), errno);
173        atrace_enabled_tags = 0;
174        goto done;
175    }
176
177    atrace_enabled_tags = atrace_get_property();
178
179done:
180    atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
181}
182
183void atrace_setup()
184{
185    pthread_once(&atrace_once_control, atrace_init_once);
186}
187
188void atrace_begin_body(const char* name)
189{
190    char buf[ATRACE_MESSAGE_LENGTH];
191
192    int len = snprintf(buf, sizeof(buf), "B|%d|%s", getpid(), name);
193    if (len >= (int) sizeof(buf)) {
194        ALOGW("Truncated name in %s: %s\n", __FUNCTION__, name);
195        len = sizeof(buf) - 1;
196    }
197    write(atrace_marker_fd, buf, len);
198}
199
200void atrace_end_body()
201{
202    char c = 'E';
203    write(atrace_marker_fd, &c, 1);
204}
205
206#define WRITE_MSG(format_begin, format_end, pid, name, value) { \
207    char buf[ATRACE_MESSAGE_LENGTH]; \
208    int len = snprintf(buf, sizeof(buf), format_begin "%s" format_end, pid, \
209        name, value); \
210    if (len >= (int) sizeof(buf)) { \
211        /* Given the sizeof(buf), and all of the current format buffers, \
212         * it is impossible for name_len to be < 0 if len >= sizeof(buf). */ \
213        int name_len = strlen(name) - (len - sizeof(buf)) - 1; \
214        /* Truncate the name to make the message fit. */ \
215        ALOGW("Truncated name in %s: %s\n", __FUNCTION__, name); \
216        len = snprintf(buf, sizeof(buf), format_begin "%.*s" format_end, pid, \
217            name_len, name, value); \
218    } \
219    write(atrace_marker_fd, buf, len); \
220}
221
222void atrace_async_begin_body(const char* name, int32_t cookie)
223{
224    WRITE_MSG("S|%d|", "|%" PRId32, getpid(), name, cookie);
225}
226
227void atrace_async_end_body(const char* name, int32_t cookie)
228{
229    WRITE_MSG("F|%d|", "|%" PRId32, getpid(), name, cookie);
230}
231
232void atrace_int_body(const char* name, int32_t value)
233{
234    WRITE_MSG("C|%d|", "|%" PRId32, getpid(), name, value);
235}
236
237void atrace_int64_body(const char* name, int64_t value)
238{
239    WRITE_MSG("C|%d|", "|%" PRId64, getpid(), name, value);
240}
241