trace-dev.c revision dee1ef48a97e5412b3bd1d7e5a3e2b81f3741dc4 
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#include <errno.h>
18#include <fcntl.h>
19#include <limits.h>
20#include <pthread.h>
21#include <stdatomic.h>
22#include <stdbool.h>
23#include <stdlib.h>
24#include <string.h>
25#include <sys/types.h>
26#include <cutils/compiler.h>
27#include <cutils/properties.h>
28#include <cutils/trace.h>
29
30#define LOG_TAG "cutils-trace"
31#include <log/log.h>
32
33/**
34 * Maximum size of a message that can be logged to the trace buffer.
35 * Note this message includes a tag, the pid, and the string given as the name.
36 * Names should be kept short to get the most use of the trace buffer.
37 */
38#define ATRACE_MESSAGE_LENGTH 1024
39
40atomic_bool             atrace_is_ready      = ATOMIC_VAR_INIT(false);
41int                     atrace_marker_fd     = -1;
42uint64_t                atrace_enabled_tags  = ATRACE_TAG_NOT_READY;
43static bool             atrace_is_debuggable = false;
44static atomic_bool      atrace_is_enabled    = ATOMIC_VAR_INIT(true);
45static pthread_once_t   atrace_once_control  = PTHREAD_ONCE_INIT;
46static pthread_mutex_t  atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;
47
48// Set whether this process is debuggable, which determines whether
49// application-level tracing is allowed when the ro.debuggable system property
50// is not set to '1'.
51void atrace_set_debuggable(bool debuggable)
52{
53    atrace_is_debuggable = debuggable;
54    atrace_update_tags();
55}
56
57// Set whether tracing is enabled in this process.  This is used to prevent
58// the Zygote process from tracing.
59void atrace_set_tracing_enabled(bool enabled)
60{
61    atomic_store_explicit(&atrace_is_enabled, enabled, memory_order_release);
62    atrace_update_tags();
63}
64
65// Check whether the given command line matches one of the comma-separated
66// values listed in the app_cmdlines property.
67static bool atrace_is_cmdline_match(const char* cmdline)
68{
69    char value[PROPERTY_VALUE_MAX];
70    char* start = value;
71
72    property_get("debug.atrace.app_cmdlines", value, "");
73
74    while (start != NULL) {
75        char* end = strchr(start, ',');
76
77        if (end != NULL) {
78            *end = '\0';
79            end++;
80        }
81
82        if (strcmp(cmdline, start) == 0) {
83            return true;
84        }
85
86        start = end;
87    }
88
89    return false;
90}
91
92// Determine whether application-level tracing is enabled for this process.
93static bool atrace_is_app_tracing_enabled()
94{
95    bool sys_debuggable = false;
96    char value[PROPERTY_VALUE_MAX];
97    bool result = false;
98
99    // Check whether the system is debuggable.
100    property_get("ro.debuggable", value, "0");
101    if (value[0] == '1') {
102        sys_debuggable = true;
103    }
104
105    if (sys_debuggable || atrace_is_debuggable) {
106        // Check whether tracing is enabled for this process.
107        FILE * file = fopen("/proc/self/cmdline", "re");
108        if (file) {
109            char cmdline[4096];
110            if (fgets(cmdline, sizeof(cmdline), file)) {
111                result = atrace_is_cmdline_match(cmdline);
112            } else {
113                ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
114            }
115            fclose(file);
116        } else {
117            ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
118                    errno);
119        }
120    }
121
122    return result;
123}
124
125// Read the sysprop and return the value tags should be set to
126static uint64_t atrace_get_property()
127{
128    char value[PROPERTY_VALUE_MAX];
129    char *endptr;
130    uint64_t tags;
131
132    property_get("debug.atrace.tags.enableflags", value, "0");
133    errno = 0;
134    tags = strtoull(value, &endptr, 0);
135    if (value[0] == '\0' || *endptr != '\0') {
136        ALOGE("Error parsing trace property: Not a number: %s", value);
137        return 0;
138    } else if (errno == ERANGE || tags == ULLONG_MAX) {
139        ALOGE("Error parsing trace property: Number too large: %s", value);
140        return 0;
141    }
142
143    // Only set the "app" tag if this process was selected for app-level debug
144    // tracing.
145    if (atrace_is_app_tracing_enabled()) {
146        tags |= ATRACE_TAG_APP;
147    } else {
148        tags &= ~ATRACE_TAG_APP;
149    }
150
151    return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
152}
153
154// Update tags if tracing is ready. Useful as a sysprop change callback.
155void atrace_update_tags()
156{
157    uint64_t tags;
158    if (CC_UNLIKELY(atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
159        if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
160            tags = atrace_get_property();
161            pthread_mutex_lock(&atrace_tags_mutex);
162            atrace_enabled_tags = tags;
163            pthread_mutex_unlock(&atrace_tags_mutex);
164        } else {
165            // Tracing is disabled for this process, so we simply don't
166            // initialize the tags.
167            pthread_mutex_lock(&atrace_tags_mutex);
168            atrace_enabled_tags = ATRACE_TAG_NOT_READY;
169            pthread_mutex_unlock(&atrace_tags_mutex);
170        }
171    }
172}
173
174static void atrace_init_once()
175{
176    atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
177    if (atrace_marker_fd == -1) {
178        ALOGE("Error opening trace file: %s (%d)", strerror(errno), errno);
179        atrace_enabled_tags = 0;
180        goto done;
181    }
182
183    atrace_enabled_tags = atrace_get_property();
184
185done:
186    atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
187}
188
189void atrace_setup()
190{
191    pthread_once(&atrace_once_control, atrace_init_once);
192}
193
194void atrace_begin_body(const char* name)
195{
196    char buf[ATRACE_MESSAGE_LENGTH];
197    size_t len;
198
199    len = snprintf(buf, ATRACE_MESSAGE_LENGTH, "B|%d|%s", getpid(), name);
200    write(atrace_marker_fd, buf, len);
201}
202
203
204void atrace_async_begin_body(const char* name, int32_t cookie)
205{
206    char buf[ATRACE_MESSAGE_LENGTH];
207    size_t len;
208
209    len = snprintf(buf, ATRACE_MESSAGE_LENGTH, "S|%d|%s|%" PRId32,
210            getpid(), name, cookie);
211    write(atrace_marker_fd, buf, len);
212}
213
214void atrace_async_end_body(const char* name, int32_t cookie)
215{
216    char buf[ATRACE_MESSAGE_LENGTH];
217    size_t len;
218
219    len = snprintf(buf, ATRACE_MESSAGE_LENGTH, "F|%d|%s|%" PRId32,
220            getpid(), name, cookie);
221    write(atrace_marker_fd, buf, len);
222}
223
224void atrace_int_body(const char* name, int32_t value)
225{
226    char buf[ATRACE_MESSAGE_LENGTH];
227    size_t len;
228
229    len = snprintf(buf, ATRACE_MESSAGE_LENGTH, "C|%d|%s|%" PRId32,
230            getpid(), name, value);
231    write(atrace_marker_fd, buf, len);
232}
233
234void atrace_int64_body(const char* name, int64_t value)
235{
236    char buf[ATRACE_MESSAGE_LENGTH];
237    size_t len;
238
239    len = snprintf(buf, ATRACE_MESSAGE_LENGTH, "C|%d|%s|%" PRId64,
240            getpid(), name, value);
241    write(atrace_marker_fd, buf, len);
242}
243