1 /*
2 * Copyright 2008, 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 "DEBUG"
18
19 #include "utility.h"
20
21 #include <errno.h>
22 #include <signal.h>
23 #include <string.h>
24 #include <unistd.h>
25 #include <sys/ptrace.h>
26 #include <sys/wait.h>
27
28 #include <string>
29
30 #include <android-base/stringprintf.h>
31 #include <backtrace/Backtrace.h>
32 #include <log/log.h>
33
34 constexpr int SLEEP_TIME_USEC = 50000; // 0.05 seconds
35 constexpr int MAX_TOTAL_SLEEP_USEC = 10000000; // 10 seconds
36
37 // Whitelist output desired in the logcat output.
is_allowed_in_logcat(enum logtype ltype)38 bool is_allowed_in_logcat(enum logtype ltype) {
39 if ((ltype == HEADER)
40 || (ltype == REGISTERS)
41 || (ltype == BACKTRACE)) {
42 return true;
43 }
44 return false;
45 }
46
_LOG(log_t * log,enum logtype ltype,const char * fmt,...)47 void _LOG(log_t* log, enum logtype ltype, const char* fmt, ...) {
48 bool write_to_tombstone = (log->tfd != -1);
49 bool write_to_logcat = is_allowed_in_logcat(ltype)
50 && log->crashed_tid != -1
51 && log->current_tid != -1
52 && (log->crashed_tid == log->current_tid);
53
54 char buf[512];
55 va_list ap;
56 va_start(ap, fmt);
57 vsnprintf(buf, sizeof(buf), fmt, ap);
58 va_end(ap);
59
60 size_t len = strlen(buf);
61 if (len <= 0) {
62 return;
63 }
64
65 if (write_to_tombstone) {
66 TEMP_FAILURE_RETRY(write(log->tfd, buf, len));
67 }
68
69 if (write_to_logcat) {
70 __android_log_buf_write(LOG_ID_CRASH, ANDROID_LOG_FATAL, LOG_TAG, buf);
71 if (log->amfd_data != nullptr) {
72 *log->amfd_data += buf;
73 }
74 }
75 }
76
wait_for_signal(pid_t tid,int * total_sleep_time_usec)77 int wait_for_signal(pid_t tid, int* total_sleep_time_usec) {
78 while (true) {
79 int status;
80 pid_t n = TEMP_FAILURE_RETRY(waitpid(tid, &status, __WALL | WNOHANG));
81 if (n == -1) {
82 ALOGE("waitpid failed: tid %d, %s", tid, strerror(errno));
83 return -1;
84 } else if (n == tid) {
85 if (WIFSTOPPED(status)) {
86 return WSTOPSIG(status);
87 } else {
88 ALOGE("unexpected waitpid response: n=%d, status=%08x\n", n, status);
89 // This is the only circumstance under which we can allow a detach
90 // to fail with ESRCH, which indicates the tid has exited.
91 return -1;
92 }
93 }
94
95 if (*total_sleep_time_usec > MAX_TOTAL_SLEEP_USEC) {
96 ALOGE("timed out waiting for stop signal: tid=%d", tid);
97 return -1;
98 }
99
100 usleep(SLEEP_TIME_USEC);
101 *total_sleep_time_usec += SLEEP_TIME_USEC;
102 }
103 }
104
105 #define MEMORY_BYTES_TO_DUMP 256
106 #define MEMORY_BYTES_PER_LINE 16
107
dump_memory(log_t * log,Backtrace * backtrace,uintptr_t addr,const char * fmt,...)108 void dump_memory(log_t* log, Backtrace* backtrace, uintptr_t addr, const char* fmt, ...) {
109 std::string log_msg;
110 va_list ap;
111 va_start(ap, fmt);
112 android::base::StringAppendV(&log_msg, fmt, ap);
113 va_end(ap);
114
115 // Align the address to sizeof(long) and start 32 bytes before the address.
116 addr &= ~(sizeof(long) - 1);
117 if (addr >= 4128) {
118 addr -= 32;
119 }
120
121 // Don't bother if the address looks too low, or looks too high.
122 if (addr < 4096 ||
123 #if defined(__LP64__)
124 addr > 0x4000000000000000UL - MEMORY_BYTES_TO_DUMP) {
125 #else
126 addr > 0xffff0000 - MEMORY_BYTES_TO_DUMP) {
127 #endif
128 return;
129 }
130
131 _LOG(log, logtype::MEMORY, "\n%s\n", log_msg.c_str());
132
133 // Dump 256 bytes
134 uintptr_t data[MEMORY_BYTES_TO_DUMP/sizeof(uintptr_t)];
135 memset(data, 0, MEMORY_BYTES_TO_DUMP);
136 size_t bytes = backtrace->Read(addr, reinterpret_cast<uint8_t*>(data), sizeof(data));
137 if (bytes % sizeof(uintptr_t) != 0) {
138 // This should never happen, but just in case.
139 ALOGE("Bytes read %zu, is not a multiple of %zu", bytes, sizeof(uintptr_t));
140 bytes &= ~(sizeof(uintptr_t) - 1);
141 }
142
143 uintptr_t start = 0;
144 bool skip_2nd_read = false;
145 if (bytes == 0) {
146 // In this case, we might want to try another read at the beginning of
147 // the next page only if it's within the amount of memory we would have
148 // read.
149 size_t page_size = sysconf(_SC_PAGE_SIZE);
150 start = ((addr + (page_size - 1)) & ~(page_size - 1)) - addr;
151 if (start == 0 || start >= MEMORY_BYTES_TO_DUMP) {
152 skip_2nd_read = true;
153 }
154 }
155
156 if (bytes < MEMORY_BYTES_TO_DUMP && !skip_2nd_read) {
157 // Try to do one more read. This could happen if a read crosses a map,
158 // but the maps do not have any break between them. Or it could happen
159 // if reading from an unreadable map, but the read would cross back
160 // into a readable map. Only requires one extra read because a map has
161 // to contain at least one page, and the total number of bytes to dump
162 // is smaller than a page.
163 size_t bytes2 = backtrace->Read(addr + start + bytes, reinterpret_cast<uint8_t*>(data) + bytes,
164 sizeof(data) - bytes - start);
165 bytes += bytes2;
166 if (bytes2 > 0 && bytes % sizeof(uintptr_t) != 0) {
167 // This should never happen, but we'll try and continue any way.
168 ALOGE("Bytes after second read %zu, is not a multiple of %zu", bytes, sizeof(uintptr_t));
169 bytes &= ~(sizeof(uintptr_t) - 1);
170 }
171 }
172
173 // Dump the code around memory as:
174 // addr contents ascii
175 // 0000000000008d34 ef000000e8bd0090 e1b00000512fff1e ............../Q
176 // 0000000000008d44 ea00b1f9e92d0090 e3a070fcef000000 ......-..p......
177 // On 32-bit machines, there are still 16 bytes per line but addresses and
178 // words are of course presented differently.
179 uintptr_t* data_ptr = data;
180 size_t current = 0;
181 size_t total_bytes = start + bytes;
182 for (size_t line = 0; line < MEMORY_BYTES_TO_DUMP / MEMORY_BYTES_PER_LINE; line++) {
183 std::string logline;
184 android::base::StringAppendF(&logline, " %" PRIPTR, addr);
185
186 addr += MEMORY_BYTES_PER_LINE;
187 std::string ascii;
188 for (size_t i = 0; i < MEMORY_BYTES_PER_LINE / sizeof(uintptr_t); i++) {
189 if (current >= start && current + sizeof(uintptr_t) <= total_bytes) {
190 android::base::StringAppendF(&logline, " %" PRIPTR, *data_ptr);
191
192 // Fill out the ascii string from the data.
193 uint8_t* ptr = reinterpret_cast<uint8_t*>(data_ptr);
194 for (size_t val = 0; val < sizeof(uintptr_t); val++, ptr++) {
195 if (*ptr >= 0x20 && *ptr < 0x7f) {
196 ascii += *ptr;
197 } else {
198 ascii += '.';
199 }
200 }
201 data_ptr++;
202 } else {
203 logline += ' ' + std::string(sizeof(uintptr_t) * 2, '-');
204 ascii += std::string(sizeof(uintptr_t), '.');
205 }
206 current += sizeof(uintptr_t);
207 }
208 _LOG(log, logtype::MEMORY, "%s %s\n", logline.c_str(), ascii.c_str());
209 }
210 }
211