1 /* system/debuggerd/debuggerd.c
2 **
3 ** Copyright 2006, The Android Open Source Project
4 **
5 ** Licensed under the Apache License, Version 2.0 (the "License");
6 ** you may not use this file except in compliance with the License.
7 ** You may obtain a copy of the License at
8 **
9 ** http://www.apache.org/licenses/LICENSE-2.0
10 **
11 ** Unless required by applicable law or agreed to in writing, software
12 ** distributed under the License is distributed on an "AS IS" BASIS,
13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 ** See the License for the specific language governing permissions and
15 ** limitations under the License.
16 */
17
18 #include <stdio.h>
19 #include <errno.h>
20 #include <signal.h>
21 #include <pthread.h>
22 #include <stdarg.h>
23 #include <fcntl.h>
24 #include <sys/types.h>
25 #include <dirent.h>
26 #include <time.h>
27
28 #include <sys/ptrace.h>
29 #include <sys/wait.h>
30 #include <sys/exec_elf.h>
31 #include <sys/stat.h>
32 #include <sys/poll.h>
33
34 #include <cutils/sockets.h>
35 #include <cutils/logd.h>
36 #include <cutils/logger.h>
37 #include <cutils/properties.h>
38 #include <cutils/debugger.h>
39
40 #include <corkscrew/backtrace.h>
41
42 #include <linux/input.h>
43
44 #include <private/android_filesystem_config.h>
45
46 #include "backtrace.h"
47 #include "getevent.h"
48 #include "tombstone.h"
49 #include "utility.h"
50
51 typedef struct {
52 debugger_action_t action;
53 pid_t pid, tid;
54 uid_t uid, gid;
55 uintptr_t abort_msg_address;
56 } debugger_request_t;
57
58 static int
write_string(const char * file,const char * string)59 write_string(const char* file, const char* string)
60 {
61 int len;
62 int fd;
63 ssize_t amt;
64 fd = open(file, O_RDWR);
65 len = strlen(string);
66 if (fd < 0)
67 return -errno;
68 amt = write(fd, string, len);
69 close(fd);
70 return amt >= 0 ? 0 : -errno;
71 }
72
73 static
init_debug_led(void)74 void init_debug_led(void)
75 {
76 // trout leds
77 write_string("/sys/class/leds/red/brightness", "0");
78 write_string("/sys/class/leds/green/brightness", "0");
79 write_string("/sys/class/leds/blue/brightness", "0");
80 write_string("/sys/class/leds/red/device/blink", "0");
81 // sardine leds
82 write_string("/sys/class/leds/left/cadence", "0,0");
83 }
84
85 static
enable_debug_led(void)86 void enable_debug_led(void)
87 {
88 // trout leds
89 write_string("/sys/class/leds/red/brightness", "255");
90 // sardine leds
91 write_string("/sys/class/leds/left/cadence", "1,0");
92 }
93
94 static
disable_debug_led(void)95 void disable_debug_led(void)
96 {
97 // trout leds
98 write_string("/sys/class/leds/red/brightness", "0");
99 // sardine leds
100 write_string("/sys/class/leds/left/cadence", "0,0");
101 }
102
wait_for_user_action(pid_t pid)103 static void wait_for_user_action(pid_t pid) {
104 /* First log a helpful message */
105 LOG( "********************************************************\n"
106 "* Process %d has been suspended while crashing. To\n"
107 "* attach gdbserver for a gdb connection on port 5039\n"
108 "* and start gdbclient:\n"
109 "*\n"
110 "* gdbclient app_process :5039 %d\n"
111 "*\n"
112 "* Wait for gdb to start, then press HOME or VOLUME DOWN key\n"
113 "* to let the process continue crashing.\n"
114 "********************************************************\n",
115 pid, pid);
116
117 /* wait for HOME or VOLUME DOWN key */
118 if (init_getevent() == 0) {
119 int ms = 1200 / 10;
120 int dit = 1;
121 int dah = 3*dit;
122 int _ = -dit;
123 int ___ = 3*_;
124 int _______ = 7*_;
125 const signed char codes[] = {
126 dit,_,dit,_,dit,___,dah,_,dah,_,dah,___,dit,_,dit,_,dit,_______
127 };
128 size_t s = 0;
129 struct input_event e;
130 bool done = false;
131 init_debug_led();
132 enable_debug_led();
133 do {
134 int timeout = abs((int)(codes[s])) * ms;
135 int res = get_event(&e, timeout);
136 if (res == 0) {
137 if (e.type == EV_KEY
138 && (e.code == KEY_HOME || e.code == KEY_VOLUMEDOWN)
139 && e.value == 0) {
140 done = true;
141 }
142 } else if (res == 1) {
143 if (++s >= sizeof(codes)/sizeof(*codes))
144 s = 0;
145 if (codes[s] > 0) {
146 enable_debug_led();
147 } else {
148 disable_debug_led();
149 }
150 }
151 } while (!done);
152 uninit_getevent();
153 }
154
155 /* don't forget to turn debug led off */
156 disable_debug_led();
157 LOG("debuggerd resuming process %d", pid);
158 }
159
get_process_info(pid_t tid,pid_t * out_pid,uid_t * out_uid,uid_t * out_gid)160 static int get_process_info(pid_t tid, pid_t* out_pid, uid_t* out_uid, uid_t* out_gid) {
161 char path[64];
162 snprintf(path, sizeof(path), "/proc/%d/status", tid);
163
164 FILE* fp = fopen(path, "r");
165 if (!fp) {
166 return -1;
167 }
168
169 int fields = 0;
170 char line[1024];
171 while (fgets(line, sizeof(line), fp)) {
172 size_t len = strlen(line);
173 if (len > 6 && !memcmp(line, "Tgid:\t", 6)) {
174 *out_pid = atoi(line + 6);
175 fields |= 1;
176 } else if (len > 5 && !memcmp(line, "Uid:\t", 5)) {
177 *out_uid = atoi(line + 5);
178 fields |= 2;
179 } else if (len > 5 && !memcmp(line, "Gid:\t", 5)) {
180 *out_gid = atoi(line + 5);
181 fields |= 4;
182 }
183 }
184 fclose(fp);
185 return fields == 7 ? 0 : -1;
186 }
187
read_request(int fd,debugger_request_t * out_request)188 static int read_request(int fd, debugger_request_t* out_request) {
189 struct ucred cr;
190 int len = sizeof(cr);
191 int status = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &len);
192 if (status != 0) {
193 LOG("cannot get credentials\n");
194 return -1;
195 }
196
197 XLOG("reading tid\n");
198 fcntl(fd, F_SETFL, O_NONBLOCK);
199
200 struct pollfd pollfds[1];
201 pollfds[0].fd = fd;
202 pollfds[0].events = POLLIN;
203 pollfds[0].revents = 0;
204 status = TEMP_FAILURE_RETRY(poll(pollfds, 1, 3000));
205 if (status != 1) {
206 LOG("timed out reading tid (from pid=%d uid=%d)\n", cr.pid, cr.uid);
207 return -1;
208 }
209
210 debugger_msg_t msg;
211 memset(&msg, 0, sizeof(msg));
212 status = TEMP_FAILURE_RETRY(read(fd, &msg, sizeof(msg)));
213 if (status < 0) {
214 LOG("read failure? %s (pid=%d uid=%d)\n",
215 strerror(errno), cr.pid, cr.uid);
216 return -1;
217 }
218 if (status == sizeof(debugger_msg_t)) {
219 XLOG("crash request of size %d abort_msg_address=%#08x\n", status, msg.abort_msg_address);
220 } else {
221 LOG("invalid crash request of size %d (from pid=%d uid=%d)\n",
222 status, cr.pid, cr.uid);
223 return -1;
224 }
225
226 out_request->action = msg.action;
227 out_request->tid = msg.tid;
228 out_request->pid = cr.pid;
229 out_request->uid = cr.uid;
230 out_request->gid = cr.gid;
231 out_request->abort_msg_address = msg.abort_msg_address;
232
233 if (msg.action == DEBUGGER_ACTION_CRASH) {
234 /* Ensure that the tid reported by the crashing process is valid. */
235 char buf[64];
236 struct stat s;
237 snprintf(buf, sizeof buf, "/proc/%d/task/%d", out_request->pid, out_request->tid);
238 if(stat(buf, &s)) {
239 LOG("tid %d does not exist in pid %d. ignoring debug request\n",
240 out_request->tid, out_request->pid);
241 return -1;
242 }
243 } else if (cr.uid == 0
244 || (cr.uid == AID_SYSTEM && msg.action == DEBUGGER_ACTION_DUMP_BACKTRACE)) {
245 /* Only root or system can ask us to attach to any process and dump it explicitly.
246 * However, system is only allowed to collect backtraces but cannot dump tombstones. */
247 status = get_process_info(out_request->tid, &out_request->pid,
248 &out_request->uid, &out_request->gid);
249 if (status < 0) {
250 LOG("tid %d does not exist. ignoring explicit dump request\n",
251 out_request->tid);
252 return -1;
253 }
254 } else {
255 /* No one else is allowed to dump arbitrary processes. */
256 return -1;
257 }
258 return 0;
259 }
260
should_attach_gdb(debugger_request_t * request)261 static bool should_attach_gdb(debugger_request_t* request) {
262 if (request->action == DEBUGGER_ACTION_CRASH) {
263 char value[PROPERTY_VALUE_MAX];
264 property_get("debug.db.uid", value, "-1");
265 int debug_uid = atoi(value);
266 return debug_uid >= 0 && request->uid <= (uid_t)debug_uid;
267 }
268 return false;
269 }
270
handle_request(int fd)271 static void handle_request(int fd) {
272 XLOG("handle_request(%d)\n", fd);
273
274 debugger_request_t request;
275 memset(&request, 0, sizeof(request));
276 int status = read_request(fd, &request);
277 if (!status) {
278 XLOG("BOOM: pid=%d uid=%d gid=%d tid=%d\n",
279 request.pid, request.uid, request.gid, request.tid);
280
281 /* At this point, the thread that made the request is blocked in
282 * a read() call. If the thread has crashed, then this gives us
283 * time to PTRACE_ATTACH to it before it has a chance to really fault.
284 *
285 * The PTRACE_ATTACH sends a SIGSTOP to the target process, but it
286 * won't necessarily have stopped by the time ptrace() returns. (We
287 * currently assume it does.) We write to the file descriptor to
288 * ensure that it can run as soon as we call PTRACE_CONT below.
289 * See details in bionic/libc/linker/debugger.c, in function
290 * debugger_signal_handler().
291 */
292 if (ptrace(PTRACE_ATTACH, request.tid, 0, 0)) {
293 LOG("ptrace attach failed: %s\n", strerror(errno));
294 } else {
295 bool detach_failed = false;
296 bool attach_gdb = should_attach_gdb(&request);
297 if (TEMP_FAILURE_RETRY(write(fd, "\0", 1)) != 1) {
298 LOG("failed responding to client: %s\n", strerror(errno));
299 } else {
300 char* tombstone_path = NULL;
301
302 if (request.action == DEBUGGER_ACTION_CRASH) {
303 close(fd);
304 fd = -1;
305 }
306
307 int total_sleep_time_usec = 0;
308 for (;;) {
309 int signal = wait_for_signal(request.tid, &total_sleep_time_usec);
310 if (signal < 0) {
311 break;
312 }
313
314 switch (signal) {
315 case SIGSTOP:
316 if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
317 XLOG("stopped -- dumping to tombstone\n");
318 tombstone_path = engrave_tombstone(request.pid, request.tid,
319 signal, request.abort_msg_address, true, true, &detach_failed,
320 &total_sleep_time_usec);
321 } else if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE) {
322 XLOG("stopped -- dumping to fd\n");
323 dump_backtrace(fd, -1,
324 request.pid, request.tid, &detach_failed,
325 &total_sleep_time_usec);
326 } else {
327 XLOG("stopped -- continuing\n");
328 status = ptrace(PTRACE_CONT, request.tid, 0, 0);
329 if (status) {
330 LOG("ptrace continue failed: %s\n", strerror(errno));
331 }
332 continue; /* loop again */
333 }
334 break;
335
336 case SIGILL:
337 case SIGABRT:
338 case SIGBUS:
339 case SIGFPE:
340 case SIGSEGV:
341 case SIGPIPE:
342 #ifdef SIGSTKFLT
343 case SIGSTKFLT:
344 #endif
345 {
346 XLOG("stopped -- fatal signal\n");
347 /*
348 * Send a SIGSTOP to the process to make all of
349 * the non-signaled threads stop moving. Without
350 * this we get a lot of "ptrace detach failed:
351 * No such process".
352 */
353 kill(request.pid, SIGSTOP);
354 /* don't dump sibling threads when attaching to GDB because it
355 * makes the process less reliable, apparently... */
356 tombstone_path = engrave_tombstone(request.pid, request.tid,
357 signal, request.abort_msg_address, !attach_gdb, false,
358 &detach_failed, &total_sleep_time_usec);
359 break;
360 }
361
362 default:
363 XLOG("stopped -- unexpected signal\n");
364 LOG("process stopped due to unexpected signal %d\n", signal);
365 break;
366 }
367 break;
368 }
369
370 if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
371 if (tombstone_path) {
372 write(fd, tombstone_path, strlen(tombstone_path));
373 }
374 close(fd);
375 fd = -1;
376 }
377 free(tombstone_path);
378 }
379
380 XLOG("detaching\n");
381 if (attach_gdb) {
382 /* stop the process so we can debug */
383 kill(request.pid, SIGSTOP);
384
385 /* detach so we can attach gdbserver */
386 if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) {
387 LOG("ptrace detach from %d failed: %s\n", request.tid, strerror(errno));
388 detach_failed = true;
389 }
390
391 /*
392 * if debug.db.uid is set, its value indicates if we should wait
393 * for user action for the crashing process.
394 * in this case, we log a message and turn the debug LED on
395 * waiting for a gdb connection (for instance)
396 */
397 wait_for_user_action(request.pid);
398 } else {
399 /* just detach */
400 if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) {
401 LOG("ptrace detach from %d failed: %s\n", request.tid, strerror(errno));
402 detach_failed = true;
403 }
404 }
405
406 /* resume stopped process (so it can crash in peace). */
407 kill(request.pid, SIGCONT);
408
409 /* If we didn't successfully detach, we're still the parent, and the
410 * actual parent won't receive a death notification via wait(2). At this point
411 * there's not much we can do about that. */
412 if (detach_failed) {
413 LOG("debuggerd committing suicide to free the zombie!\n");
414 kill(getpid(), SIGKILL);
415 }
416 }
417
418 }
419 if (fd >= 0) {
420 close(fd);
421 }
422 }
423
do_server()424 static int do_server() {
425 int s;
426 struct sigaction act;
427 int logsocket = -1;
428
429 /*
430 * debuggerd crashes can't be reported to debuggerd. Reset all of the
431 * crash handlers.
432 */
433 signal(SIGILL, SIG_DFL);
434 signal(SIGABRT, SIG_DFL);
435 signal(SIGBUS, SIG_DFL);
436 signal(SIGFPE, SIG_DFL);
437 signal(SIGSEGV, SIG_DFL);
438 signal(SIGPIPE, SIG_DFL);
439 #ifdef SIGSTKFLT
440 signal(SIGSTKFLT, SIG_DFL);
441 #endif
442
443 logsocket = socket_local_client("logd",
444 ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_DGRAM);
445 if(logsocket < 0) {
446 logsocket = -1;
447 } else {
448 fcntl(logsocket, F_SETFD, FD_CLOEXEC);
449 }
450
451 act.sa_handler = SIG_DFL;
452 sigemptyset(&act.sa_mask);
453 sigaddset(&act.sa_mask,SIGCHLD);
454 act.sa_flags = SA_NOCLDWAIT;
455 sigaction(SIGCHLD, &act, 0);
456
457 s = socket_local_server(DEBUGGER_SOCKET_NAME,
458 ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM);
459 if(s < 0) return 1;
460 fcntl(s, F_SETFD, FD_CLOEXEC);
461
462 LOG("debuggerd: " __DATE__ " " __TIME__ "\n");
463
464 for(;;) {
465 struct sockaddr addr;
466 socklen_t alen;
467 int fd;
468
469 alen = sizeof(addr);
470 XLOG("waiting for connection\n");
471 fd = accept(s, &addr, &alen);
472 if(fd < 0) {
473 XLOG("accept failed: %s\n", strerror(errno));
474 continue;
475 }
476
477 fcntl(fd, F_SETFD, FD_CLOEXEC);
478
479 handle_request(fd);
480 }
481 return 0;
482 }
483
do_explicit_dump(pid_t tid,bool dump_backtrace)484 static int do_explicit_dump(pid_t tid, bool dump_backtrace) {
485 fprintf(stdout, "Sending request to dump task %d.\n", tid);
486
487 if (dump_backtrace) {
488 fflush(stdout);
489 if (dump_backtrace_to_file(tid, fileno(stdout)) < 0) {
490 fputs("Error dumping backtrace.\n", stderr);
491 return 1;
492 }
493 } else {
494 char tombstone_path[PATH_MAX];
495 if (dump_tombstone(tid, tombstone_path, sizeof(tombstone_path)) < 0) {
496 fputs("Error dumping tombstone.\n", stderr);
497 return 1;
498 }
499 fprintf(stderr, "Tombstone written to: %s\n", tombstone_path);
500 }
501 return 0;
502 }
503
usage()504 static void usage() {
505 fputs("Usage: -b [<tid>]\n"
506 " -b dump backtrace to console, otherwise dump full tombstone file\n"
507 "\n"
508 "If tid specified, sends a request to debuggerd to dump that task.\n"
509 "Otherwise, starts the debuggerd server.\n", stderr);
510 }
511
main(int argc,char ** argv)512 int main(int argc, char** argv) {
513 if (argc == 1) {
514 return do_server();
515 }
516
517 bool dump_backtrace = false;
518 bool have_tid = false;
519 pid_t tid = 0;
520 for (int i = 1; i < argc; i++) {
521 if (!strcmp(argv[i], "-b")) {
522 dump_backtrace = true;
523 } else if (!have_tid) {
524 tid = atoi(argv[i]);
525 have_tid = true;
526 } else {
527 usage();
528 return 1;
529 }
530 }
531 if (!have_tid) {
532 usage();
533 return 1;
534 }
535 return do_explicit_dump(tid, dump_backtrace);
536 }
537