1/*
2 * Copyright (C) 2017 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#ifndef __TRACE_DEV_INC
18#define __TRACE_DEV_INC
19
20#define LOG_TAG "cutils-trace"
21
22#include <errno.h>
23#include <fcntl.h>
24#include <fnmatch.h>
25#include <limits.h>
26#include <pthread.h>
27#include <stdatomic.h>
28#include <stdlib.h>
29#include <string.h>
30#include <sys/types.h>
31
32#include <cutils/compiler.h>
33#include <cutils/properties.h>
34#include <cutils/trace.h>
35#include <log/log.h>
36#include <log/log_properties.h>
37
38#if defined(__BIONIC__)
39#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
40#include <sys/_system_properties.h>
41#endif
42
43/**
44 * Maximum size of a message that can be logged to the trace buffer.
45 * Note this message includes a tag, the pid, and the string given as the name.
46 * Names should be kept short to get the most use of the trace buffer.
47 */
48#define ATRACE_MESSAGE_LENGTH 1024
49
50constexpr uint32_t kSeqNoNotInit = static_cast<uint32_t>(-1);
51
52atomic_bool              atrace_is_ready      = ATOMIC_VAR_INIT(false);
53int                      atrace_marker_fd     = -1;
54uint64_t                 atrace_enabled_tags  = ATRACE_TAG_NOT_READY;
55static atomic_bool       atrace_is_enabled    = ATOMIC_VAR_INIT(true);
56static pthread_mutex_t   atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;
57
58/**
59 * Sequence number of debug.atrace.tags.enableflags the last time the enabled
60 * tags were reloaded.
61 **/
62static _Atomic(uint32_t) last_sequence_number = ATOMIC_VAR_INIT(kSeqNoNotInit);
63
64#if defined(__BIONIC__)
65// All zero prop_info that has a sequence number of 0. This is easier than
66// depending on implementation details of the property implementation.
67//
68// prop_info is static_assert-ed to be 96 bytes, which cannot change due to
69// ABI compatibility.
70alignas(uint64_t) static char empty_pi[96];
71static const prop_info* atrace_property_info = reinterpret_cast<const prop_info*>(empty_pi);
72#endif
73
74/**
75 * This is called when the sequence number of debug.atrace.tags.enableflags
76 * changes and we need to reload the enabled tags.
77 **/
78static void atrace_seq_number_changed(uint32_t prev_seq_no, uint32_t seq_no);
79
80void atrace_init() {
81#if defined(__BIONIC__)
82    uint32_t seq_no = __system_property_serial(atrace_property_info);  // Acquire semantics.
83#else
84    uint32_t seq_no = 0;
85#endif
86    uint32_t prev_seq_no = atomic_load_explicit(&last_sequence_number, memory_order_relaxed);
87    if (CC_UNLIKELY(seq_no != prev_seq_no)) {
88        atrace_seq_number_changed(prev_seq_no, seq_no);
89    }
90}
91
92uint64_t atrace_get_enabled_tags()
93{
94    atrace_init();
95    return atrace_enabled_tags;
96}
97
98// Check whether the given command line matches one of the comma-separated
99// values listed in the app_cmdlines property.
100static bool atrace_is_cmdline_match(const char* cmdline)
101{
102    int count = property_get_int32("debug.atrace.app_number", 0);
103
104    char buf[PROPERTY_KEY_MAX];
105    char value[PROPERTY_VALUE_MAX];
106
107    for (int i = 0; i < count; i++) {
108        snprintf(buf, sizeof(buf), "debug.atrace.app_%d", i);
109        property_get(buf, value, "");
110        if (fnmatch(value, cmdline, FNM_NOESCAPE) == 0) {
111            return true;
112        }
113    }
114
115    return false;
116}
117
118// Determine whether application-level tracing is enabled for this process.
119static bool atrace_is_app_tracing_enabled()
120{
121    bool result = false;
122
123    // Check whether tracing is enabled for this process.
124    FILE * file = fopen("/proc/self/cmdline", "re");
125    if (file) {
126        char cmdline[4096];
127        if (fgets(cmdline, sizeof(cmdline), file)) {
128            result = atrace_is_cmdline_match(cmdline);
129        } else {
130            ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
131        }
132        fclose(file);
133    } else {
134        ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
135                errno);
136    }
137
138    return result;
139}
140
141// Read the sysprop and return the value tags should be set to
142static uint64_t atrace_get_property()
143{
144    char value[PROPERTY_VALUE_MAX];
145    char *endptr;
146    uint64_t tags;
147
148    property_get("debug.atrace.tags.enableflags", value, "0");
149    errno = 0;
150    tags = strtoull(value, &endptr, 0);
151    if (value[0] == '\0' || *endptr != '\0') {
152        ALOGE("Error parsing trace property: Not a number: %s", value);
153        return 0;
154    } else if (errno == ERANGE || tags == ULLONG_MAX) {
155        ALOGE("Error parsing trace property: Number too large: %s", value);
156        return 0;
157    }
158
159    // Only set the "app" tag if this process was selected for app-level debug
160    // tracing.
161    if (atrace_is_app_tracing_enabled()) {
162        tags |= ATRACE_TAG_APP;
163    } else {
164        tags &= ~ATRACE_TAG_APP;
165    }
166
167    return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
168}
169
170// Update tags if tracing is ready. Useful as a sysprop change callback.
171void atrace_update_tags()
172{
173    uint64_t tags;
174    if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
175        tags = atrace_get_property();
176        pthread_mutex_lock(&atrace_tags_mutex);
177        atrace_enabled_tags = tags;
178        pthread_mutex_unlock(&atrace_tags_mutex);
179    } else {
180        // Tracing is disabled for this process, so we simply don't
181        // initialize the tags.
182        pthread_mutex_lock(&atrace_tags_mutex);
183        atrace_enabled_tags = ATRACE_TAG_NOT_READY;
184        pthread_mutex_unlock(&atrace_tags_mutex);
185    }
186}
187
188#define WRITE_MSG(format_begin, format_end, track_name, name, value) { \
189    char buf[ATRACE_MESSAGE_LENGTH] __attribute__((uninitialized));     \
190    const char* track_name_sep = track_name[0] != '\0' ? "|" : ""; \
191    int pid = getpid(); \
192    int len = snprintf(buf, sizeof(buf), format_begin "%s%s%s" format_end, pid, \
193        track_name, track_name_sep, name, value); \
194    if (len >= (int) sizeof(buf)) { \
195        int name_len = strlen(name) - (len - sizeof(buf)) - 1; \
196        /* Truncate the name to make the message fit. */ \
197        if (name_len > 0) { \
198            len = snprintf(buf, sizeof(buf), format_begin "%s%s%.*s" format_end, pid, \
199                track_name, track_name_sep, name_len, name, value); \
200        } else { \
201            int track_name_len = 0; \
202            if (track_name[0] != '\0') { \
203                track_name_len = strlen(track_name) - (len - strlen(name) - sizeof(buf)) - 2; \
204            } \
205            if (track_name_len <= 0) { \
206                /* Data is still too long. Drop it. */ \
207                len = 0; \
208            } else { \
209                /* Truncate the trackName and name to make the message fit */ \
210                len = snprintf(buf, sizeof(buf), format_begin "%.*s|%.1s" format_end, pid, \
211                    track_name_len, track_name, name, value); \
212            } \
213        } \
214    } \
215    if (len > 0) { \
216        write(atrace_marker_fd, buf, len); \
217    } \
218}
219
220#endif  // __TRACE_DEV_INC
221