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
wait_for_user_action(const debugger_request_t & request)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
get_process_info(pid_t tid,pid_t * out_pid,uid_t * out_uid,uid_t * out_gid)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
read_request(int fd,debugger_request_t * out_request)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
should_attach_gdb(debugger_request_t * request)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
handle_request(int fd)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
do_server()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
do_explicit_dump(pid_t tid,bool dump_backtrace)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
usage()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
main(int argc,char ** argv)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