1 /* 2 * Copyright 2006, 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 <stdio.h> 18 #include <errno.h> 19 #include <signal.h> 20 #include <pthread.h> 21 #include <stdarg.h> 22 #include <fcntl.h> 23 #include <sys/types.h> 24 #include <dirent.h> 25 #include <time.h> 26 27 #include <sys/ptrace.h> 28 #include <sys/wait.h> 29 #include <elf.h> 30 #include <sys/stat.h> 31 #include <sys/poll.h> 32 33 #include <log/logger.h> 34 35 #include <cutils/sockets.h> 36 #include <cutils/properties.h> 37 #include <cutils/debugger.h> 38 39 #include <linux/input.h> 40 41 #include <private/android_filesystem_config.h> 42 43 #include "backtrace.h" 44 #include "getevent.h" 45 #include "tombstone.h" 46 #include "utility.h" 47 48 struct debugger_request_t { 49 debugger_action_t action; 50 pid_t pid, tid; 51 uid_t uid, gid; 52 uintptr_t abort_msg_address; 53 int32_t original_si_code; 54 }; 55 56 static void wait_for_user_action(const debugger_request_t &request) { 57 // Find out the name of the process that crashed. 58 char path[64]; 59 snprintf(path, sizeof(path), "/proc/%d/exe", request.pid); 60 61 char exe[PATH_MAX]; 62 int count; 63 if ((count = readlink(path, exe, sizeof(exe) - 1)) == -1) { 64 ALOGE("readlink('%s') failed: %s", path, strerror(errno)); 65 strlcpy(exe, "unknown", sizeof(exe)); 66 } else { 67 exe[count] = '\0'; 68 } 69 70 // Explain how to attach the debugger. 71 ALOGI("********************************************************\n" 72 "* Process %d has been suspended while crashing.\n" 73 "* To attach gdbserver for a gdb connection on port 5039\n" 74 "* and start gdbclient:\n" 75 "*\n" 76 "* gdbclient %s :5039 %d\n" 77 "*\n" 78 "* Wait for gdb to start, then press the VOLUME DOWN key\n" 79 "* to let the process continue crashing.\n" 80 "********************************************************", 81 request.pid, exe, request.tid); 82 83 // Wait for VOLUME DOWN. 84 if (init_getevent() == 0) { 85 while (true) { 86 input_event e; 87 if (get_event(&e, -1) == 0) { 88 if (e.type == EV_KEY && e.code == KEY_VOLUMEDOWN && e.value == 0) { 89 break; 90 } 91 } 92 } 93 uninit_getevent(); 94 } 95 96 ALOGI("debuggerd resuming process %d", request.pid); 97 } 98 99 static int get_process_info(pid_t tid, pid_t* out_pid, uid_t* out_uid, uid_t* out_gid) { 100 char path[64]; 101 snprintf(path, sizeof(path), "/proc/%d/status", tid); 102 103 FILE* fp = fopen(path, "r"); 104 if (!fp) { 105 return -1; 106 } 107 108 int fields = 0; 109 char line[1024]; 110 while (fgets(line, sizeof(line), fp)) { 111 size_t len = strlen(line); 112 if (len > 6 && !memcmp(line, "Tgid:\t", 6)) { 113 *out_pid = atoi(line + 6); 114 fields |= 1; 115 } else if (len > 5 && !memcmp(line, "Uid:\t", 5)) { 116 *out_uid = atoi(line + 5); 117 fields |= 2; 118 } else if (len > 5 && !memcmp(line, "Gid:\t", 5)) { 119 *out_gid = atoi(line + 5); 120 fields |= 4; 121 } 122 } 123 fclose(fp); 124 return fields == 7 ? 0 : -1; 125 } 126 127 static int read_request(int fd, debugger_request_t* out_request) { 128 ucred cr; 129 socklen_t len = sizeof(cr); 130 int status = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &len); 131 if (status != 0) { 132 ALOGE("cannot get credentials"); 133 return -1; 134 } 135 136 ALOGV("reading tid"); 137 fcntl(fd, F_SETFL, O_NONBLOCK); 138 139 pollfd pollfds[1]; 140 pollfds[0].fd = fd; 141 pollfds[0].events = POLLIN; 142 pollfds[0].revents = 0; 143 status = TEMP_FAILURE_RETRY(poll(pollfds, 1, 3000)); 144 if (status != 1) { 145 ALOGE("timed out reading tid (from pid=%d uid=%d)\n", cr.pid, cr.uid); 146 return -1; 147 } 148 149 debugger_msg_t msg; 150 memset(&msg, 0, sizeof(msg)); 151 status = TEMP_FAILURE_RETRY(read(fd, &msg, sizeof(msg))); 152 if (status < 0) { 153 ALOGE("read failure? %s (pid=%d uid=%d)\n", strerror(errno), cr.pid, cr.uid); 154 return -1; 155 } 156 if (status != sizeof(debugger_msg_t)) { 157 ALOGE("invalid crash request of size %d (from pid=%d uid=%d)\n", status, cr.pid, cr.uid); 158 return -1; 159 } 160 161 out_request->action = msg.action; 162 out_request->tid = msg.tid; 163 out_request->pid = cr.pid; 164 out_request->uid = cr.uid; 165 out_request->gid = cr.gid; 166 out_request->abort_msg_address = msg.abort_msg_address; 167 out_request->original_si_code = msg.original_si_code; 168 169 if (msg.action == DEBUGGER_ACTION_CRASH) { 170 // Ensure that the tid reported by the crashing process is valid. 171 char buf[64]; 172 struct stat s; 173 snprintf(buf, sizeof buf, "/proc/%d/task/%d", out_request->pid, out_request->tid); 174 if (stat(buf, &s)) { 175 ALOGE("tid %d does not exist in pid %d. ignoring debug request\n", 176 out_request->tid, out_request->pid); 177 return -1; 178 } 179 } else if (cr.uid == 0 180 || (cr.uid == AID_SYSTEM && msg.action == DEBUGGER_ACTION_DUMP_BACKTRACE)) { 181 // Only root or system can ask us to attach to any process and dump it explicitly. 182 // However, system is only allowed to collect backtraces but cannot dump tombstones. 183 status = get_process_info(out_request->tid, &out_request->pid, 184 &out_request->uid, &out_request->gid); 185 if (status < 0) { 186 ALOGE("tid %d does not exist. ignoring explicit dump request\n", out_request->tid); 187 return -1; 188 } 189 } else { 190 // No one else is allowed to dump arbitrary processes. 191 return -1; 192 } 193 return 0; 194 } 195 196 static bool should_attach_gdb(debugger_request_t* request) { 197 if (request->action == DEBUGGER_ACTION_CRASH) { 198 char value[PROPERTY_VALUE_MAX]; 199 property_get("debug.db.uid", value, "-1"); 200 int debug_uid = atoi(value); 201 return debug_uid >= 0 && request->uid <= (uid_t)debug_uid; 202 } 203 return false; 204 } 205 206 static void handle_request(int fd) { 207 ALOGV("handle_request(%d)\n", fd); 208 209 debugger_request_t request; 210 memset(&request, 0, sizeof(request)); 211 int status = read_request(fd, &request); 212 if (!status) { 213 ALOGV("BOOM: pid=%d uid=%d gid=%d tid=%d\n", 214 request.pid, request.uid, request.gid, request.tid); 215 216 // At this point, the thread that made the request is blocked in 217 // a read() call. If the thread has crashed, then this gives us 218 // time to PTRACE_ATTACH to it before it has a chance to really fault. 219 // 220 // The PTRACE_ATTACH sends a SIGSTOP to the target process, but it 221 // won't necessarily have stopped by the time ptrace() returns. (We 222 // currently assume it does.) We write to the file descriptor to 223 // ensure that it can run as soon as we call PTRACE_CONT below. 224 // See details in bionic/libc/linker/debugger.c, in function 225 // debugger_signal_handler(). 226 if (ptrace(PTRACE_ATTACH, request.tid, 0, 0)) { 227 ALOGE("ptrace attach failed: %s\n", strerror(errno)); 228 } else { 229 bool detach_failed = false; 230 bool tid_unresponsive = false; 231 bool attach_gdb = should_attach_gdb(&request); 232 if (TEMP_FAILURE_RETRY(write(fd, "\0", 1)) != 1) { 233 ALOGE("failed responding to client: %s\n", strerror(errno)); 234 } else { 235 char* tombstone_path = NULL; 236 237 if (request.action == DEBUGGER_ACTION_CRASH) { 238 close(fd); 239 fd = -1; 240 } 241 242 int total_sleep_time_usec = 0; 243 for (;;) { 244 int signal = wait_for_sigstop(request.tid, &total_sleep_time_usec, &detach_failed); 245 if (signal == -1) { 246 tid_unresponsive = true; 247 break; 248 } 249 250 switch (signal) { 251 case SIGSTOP: 252 if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) { 253 ALOGV("stopped -- dumping to tombstone\n"); 254 tombstone_path = engrave_tombstone(request.pid, request.tid, 255 signal, request.original_si_code, 256 request.abort_msg_address, true, 257 &detach_failed, &total_sleep_time_usec); 258 } else if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE) { 259 ALOGV("stopped -- dumping to fd\n"); 260 dump_backtrace(fd, -1, request.pid, request.tid, &detach_failed, 261 &total_sleep_time_usec); 262 } else { 263 ALOGV("stopped -- continuing\n"); 264 status = ptrace(PTRACE_CONT, request.tid, 0, 0); 265 if (status) { 266 ALOGE("ptrace continue failed: %s\n", strerror(errno)); 267 } 268 continue; // loop again 269 } 270 break; 271 272 case SIGABRT: 273 case SIGBUS: 274 case SIGFPE: 275 case SIGILL: 276 case SIGPIPE: 277 case SIGSEGV: 278 #ifdef SIGSTKFLT 279 case SIGSTKFLT: 280 #endif 281 case SIGTRAP: 282 ALOGV("stopped -- fatal signal\n"); 283 // Send a SIGSTOP to the process to make all of 284 // the non-signaled threads stop moving. Without 285 // this we get a lot of "ptrace detach failed: 286 // No such process". 287 kill(request.pid, SIGSTOP); 288 // don't dump sibling threads when attaching to GDB because it 289 // makes the process less reliable, apparently... 290 tombstone_path = engrave_tombstone(request.pid, request.tid, 291 signal, request.original_si_code, 292 request.abort_msg_address, !attach_gdb, 293 &detach_failed, &total_sleep_time_usec); 294 break; 295 296 default: 297 ALOGE("process stopped due to unexpected signal %d\n", signal); 298 break; 299 } 300 break; 301 } 302 303 if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) { 304 if (tombstone_path) { 305 write(fd, tombstone_path, strlen(tombstone_path)); 306 } 307 close(fd); 308 fd = -1; 309 } 310 free(tombstone_path); 311 } 312 313 if (!tid_unresponsive) { 314 ALOGV("detaching"); 315 if (attach_gdb) { 316 // stop the process so we can debug 317 kill(request.pid, SIGSTOP); 318 } 319 if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) { 320 ALOGE("ptrace detach from %d failed: %s", request.tid, strerror(errno)); 321 detach_failed = true; 322 } else if (attach_gdb) { 323 // if debug.db.uid is set, its value indicates if we should wait 324 // for user action for the crashing process. 325 // in this case, we log a message and turn the debug LED on 326 // waiting for a gdb connection (for instance) 327 wait_for_user_action(request); 328 } 329 } 330 331 // resume stopped process (so it can crash in peace). 332 kill(request.pid, SIGCONT); 333 334 // If we didn't successfully detach, we're still the parent, and the 335 // actual parent won't receive a death notification via wait(2). At this point 336 // there's not much we can do about that. 337 if (detach_failed) { 338 ALOGE("debuggerd committing suicide to free the zombie!\n"); 339 kill(getpid(), SIGKILL); 340 } 341 } 342 343 } 344 if (fd >= 0) { 345 close(fd); 346 } 347 } 348 349 static int do_server() { 350 // debuggerd crashes can't be reported to debuggerd. 351 // Reset all of the crash handlers. 352 signal(SIGABRT, SIG_DFL); 353 signal(SIGBUS, SIG_DFL); 354 signal(SIGFPE, SIG_DFL); 355 signal(SIGILL, SIG_DFL); 356 signal(SIGSEGV, SIG_DFL); 357 #ifdef SIGSTKFLT 358 signal(SIGSTKFLT, SIG_DFL); 359 #endif 360 signal(SIGTRAP, SIG_DFL); 361 362 // Ignore failed writes to closed sockets 363 signal(SIGPIPE, SIG_IGN); 364 365 int logsocket = socket_local_client("logd", ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_DGRAM); 366 if (logsocket < 0) { 367 logsocket = -1; 368 } else { 369 fcntl(logsocket, F_SETFD, FD_CLOEXEC); 370 } 371 372 struct sigaction act; 373 act.sa_handler = SIG_DFL; 374 sigemptyset(&act.sa_mask); 375 sigaddset(&act.sa_mask,SIGCHLD); 376 act.sa_flags = SA_NOCLDWAIT; 377 sigaction(SIGCHLD, &act, 0); 378 379 int s = socket_local_server(DEBUGGER_SOCKET_NAME, ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM); 380 if (s < 0) 381 return 1; 382 fcntl(s, F_SETFD, FD_CLOEXEC); 383 384 ALOGI("debuggerd: " __DATE__ " " __TIME__ "\n"); 385 386 for (;;) { 387 sockaddr addr; 388 socklen_t alen = sizeof(addr); 389 390 ALOGV("waiting for connection\n"); 391 int fd = accept(s, &addr, &alen); 392 if (fd < 0) { 393 ALOGV("accept failed: %s\n", strerror(errno)); 394 continue; 395 } 396 397 fcntl(fd, F_SETFD, FD_CLOEXEC); 398 399 handle_request(fd); 400 } 401 return 0; 402 } 403 404 static int do_explicit_dump(pid_t tid, bool dump_backtrace) { 405 fprintf(stdout, "Sending request to dump task %d.\n", tid); 406 407 if (dump_backtrace) { 408 fflush(stdout); 409 if (dump_backtrace_to_file(tid, fileno(stdout)) < 0) { 410 fputs("Error dumping backtrace.\n", stderr); 411 return 1; 412 } 413 } else { 414 char tombstone_path[PATH_MAX]; 415 if (dump_tombstone(tid, tombstone_path, sizeof(tombstone_path)) < 0) { 416 fputs("Error dumping tombstone.\n", stderr); 417 return 1; 418 } 419 fprintf(stderr, "Tombstone written to: %s\n", tombstone_path); 420 } 421 return 0; 422 } 423 424 static void usage() { 425 fputs("Usage: -b [<tid>]\n" 426 " -b dump backtrace to console, otherwise dump full tombstone file\n" 427 "\n" 428 "If tid specified, sends a request to debuggerd to dump that task.\n" 429 "Otherwise, starts the debuggerd server.\n", stderr); 430 } 431 432 int main(int argc, char** argv) { 433 if (argc == 1) { 434 return do_server(); 435 } 436 437 bool dump_backtrace = false; 438 bool have_tid = false; 439 pid_t tid = 0; 440 for (int i = 1; i < argc; i++) { 441 if (!strcmp(argv[i], "-b")) { 442 dump_backtrace = true; 443 } else if (!have_tid) { 444 tid = atoi(argv[i]); 445 have_tid = true; 446 } else { 447 usage(); 448 return 1; 449 } 450 } 451 if (!have_tid) { 452 usage(); 453 return 1; 454 } 455 return do_explicit_dump(tid, dump_backtrace); 456 } 457
