1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "linker.h"
30
31 #include <errno.h>
32 #include <signal.h>
33 #include <stdio.h>
34 #include <stdlib.h>
35 #include <sys/mman.h>
36 #include <sys/prctl.h>
37 #include <sys/socket.h>
38 #include <sys/un.h>
39 #include <unistd.h>
40
41 extern "C" int tgkill(int tgid, int tid, int sig);
42
43 #define DEBUGGER_SOCKET_NAME "android:debuggerd"
44
45 enum debugger_action_t {
46 // dump a crash
47 DEBUGGER_ACTION_CRASH,
48 // dump a tombstone file
49 DEBUGGER_ACTION_DUMP_TOMBSTONE,
50 // dump a backtrace only back to the socket
51 DEBUGGER_ACTION_DUMP_BACKTRACE,
52 };
53
54 /* message sent over the socket */
55 struct debugger_msg_t {
56 // version 1 included:
57 debugger_action_t action;
58 pid_t tid;
59
60 // version 2 added:
61 uintptr_t abort_msg_address;
62 };
63
64 // see man(2) prctl, specifically the section about PR_GET_NAME
65 #define MAX_TASK_NAME_LEN (16)
66
socket_abstract_client(const char * name,int type)67 static int socket_abstract_client(const char* name, int type) {
68 sockaddr_un addr;
69
70 // Test with length +1 for the *initial* '\0'.
71 size_t namelen = strlen(name);
72 if ((namelen + 1) > sizeof(addr.sun_path)) {
73 errno = EINVAL;
74 return -1;
75 }
76
77 /* This is used for abstract socket namespace, we need
78 * an initial '\0' at the start of the Unix socket path.
79 *
80 * Note: The path in this case is *not* supposed to be
81 * '\0'-terminated. ("man 7 unix" for the gory details.)
82 */
83 memset(&addr, 0, sizeof(addr));
84 addr.sun_family = AF_LOCAL;
85 addr.sun_path[0] = 0;
86 memcpy(addr.sun_path + 1, name, namelen);
87
88 socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
89
90 int s = socket(AF_LOCAL, type, 0);
91 if (s == -1) {
92 return -1;
93 }
94
95 int err = TEMP_FAILURE_RETRY(connect(s, (sockaddr*) &addr, alen));
96 if (err == -1) {
97 close(s);
98 s = -1;
99 }
100
101 return s;
102 }
103
104 /*
105 * Writes a summary of the signal to the log file. We do this so that, if
106 * for some reason we're not able to contact debuggerd, there is still some
107 * indication of the failure in the log.
108 *
109 * We could be here as a result of native heap corruption, or while a
110 * mutex is being held, so we don't want to use any libc functions that
111 * could allocate memory or hold a lock.
112 */
log_signal_summary(int signum,const siginfo_t * info)113 static void log_signal_summary(int signum, const siginfo_t* info) {
114 const char* signal_name;
115 switch (signum) {
116 case SIGILL: signal_name = "SIGILL"; break;
117 case SIGABRT: signal_name = "SIGABRT"; break;
118 case SIGBUS: signal_name = "SIGBUS"; break;
119 case SIGFPE: signal_name = "SIGFPE"; break;
120 case SIGSEGV: signal_name = "SIGSEGV"; break;
121 #if defined(SIGSTKFLT)
122 case SIGSTKFLT: signal_name = "SIGSTKFLT"; break;
123 #endif
124 case SIGPIPE: signal_name = "SIGPIPE"; break;
125 default: signal_name = "???"; break;
126 }
127
128 char thread_name[MAX_TASK_NAME_LEN + 1]; // one more for termination
129 if (prctl(PR_GET_NAME, (unsigned long)thread_name, 0, 0, 0) != 0) {
130 strcpy(thread_name, "<name unknown>");
131 } else {
132 // short names are null terminated by prctl, but the man page
133 // implies that 16 byte names are not.
134 thread_name[MAX_TASK_NAME_LEN] = 0;
135 }
136
137 // "info" will be NULL if the siginfo_t information was not available.
138 if (info != NULL) {
139 __libc_format_log(ANDROID_LOG_FATAL, "libc",
140 "Fatal signal %d (%s) at 0x%08x (code=%d), thread %d (%s)",
141 signum, signal_name, reinterpret_cast<uintptr_t>(info->si_addr),
142 info->si_code, gettid(), thread_name);
143 } else {
144 __libc_format_log(ANDROID_LOG_FATAL, "libc",
145 "Fatal signal %d (%s), thread %d (%s)",
146 signum, signal_name, gettid(), thread_name);
147 }
148 }
149
150 /*
151 * Returns true if the handler for signal "signum" has SA_SIGINFO set.
152 */
have_siginfo(int signum)153 static bool have_siginfo(int signum) {
154 struct sigaction old_action, new_action;
155
156 memset(&new_action, 0, sizeof(new_action));
157 new_action.sa_handler = SIG_DFL;
158 new_action.sa_flags = SA_RESTART;
159 sigemptyset(&new_action.sa_mask);
160
161 if (sigaction(signum, &new_action, &old_action) < 0) {
162 __libc_format_log(ANDROID_LOG_WARN, "libc", "Failed testing for SA_SIGINFO: %s",
163 strerror(errno));
164 return false;
165 }
166 bool result = (old_action.sa_flags & SA_SIGINFO) != 0;
167
168 if (sigaction(signum, &old_action, NULL) == -1) {
169 __libc_format_log(ANDROID_LOG_WARN, "libc", "Restore failed in test for SA_SIGINFO: %s",
170 strerror(errno));
171 }
172 return result;
173 }
174
175 /*
176 * Catches fatal signals so we can ask debuggerd to ptrace us before
177 * we crash.
178 */
debuggerd_signal_handler(int n,siginfo_t * info,void *)179 void debuggerd_signal_handler(int n, siginfo_t* info, void*) {
180 /*
181 * It's possible somebody cleared the SA_SIGINFO flag, which would mean
182 * our "info" arg holds an undefined value.
183 */
184 if (!have_siginfo(n)) {
185 info = NULL;
186 }
187
188 log_signal_summary(n, info);
189
190 pid_t tid = gettid();
191 int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
192
193 if (s >= 0) {
194 // debuggerd knows our pid from the credentials on the
195 // local socket but we need to tell it the tid of the crashing thread.
196 // debuggerd will be paranoid and verify that we sent a tid
197 // that's actually in our process.
198 debugger_msg_t msg;
199 msg.action = DEBUGGER_ACTION_CRASH;
200 msg.tid = tid;
201 msg.abort_msg_address = reinterpret_cast<uintptr_t>(gAbortMessage);
202 int ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
203 if (ret == sizeof(msg)) {
204 // if the write failed, there is no point trying to read a response.
205 ret = TEMP_FAILURE_RETRY(read(s, &tid, 1));
206 int saved_errno = errno;
207 notify_gdb_of_libraries();
208 errno = saved_errno;
209 }
210
211 if (ret < 0) {
212 /* read or write failed -- broken connection? */
213 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
214 strerror(errno));
215 }
216
217 close(s);
218 } else {
219 /* socket failed; maybe process ran out of fds */
220 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
221 strerror(errno));
222 }
223
224 /* remove our net so we fault for real when we return */
225 signal(n, SIG_DFL);
226
227 /*
228 * These signals are not re-thrown when we resume. This means that
229 * crashing due to (say) SIGPIPE doesn't work the way you'd expect it
230 * to. We work around this by throwing them manually. We don't want
231 * to do this for *all* signals because it'll screw up the address for
232 * faults like SIGSEGV.
233 */
234 switch (n) {
235 case SIGABRT:
236 case SIGFPE:
237 case SIGPIPE:
238 #ifdef SIGSTKFLT
239 case SIGSTKFLT:
240 #endif
241 (void) tgkill(getpid(), gettid(), n);
242 break;
243 default: // SIGILL, SIGBUS, SIGSEGV
244 break;
245 }
246 }
247
debuggerd_init()248 void debuggerd_init() {
249 struct sigaction action;
250 memset(&action, 0, sizeof(action));
251 sigemptyset(&action.sa_mask);
252 action.sa_sigaction = debuggerd_signal_handler;
253 action.sa_flags = SA_RESTART | SA_SIGINFO;
254
255 // Use the alternate signal stack if available so we can catch stack overflows.
256 action.sa_flags |= SA_ONSTACK;
257
258 sigaction(SIGABRT, &action, NULL);
259 sigaction(SIGBUS, &action, NULL);
260 sigaction(SIGFPE, &action, NULL);
261 sigaction(SIGILL, &action, NULL);
262 sigaction(SIGPIPE, &action, NULL);
263 sigaction(SIGSEGV, &action, NULL);
264 #if defined(SIGSTKFLT)
265 sigaction(SIGSTKFLT, &action, NULL);
266 #endif
267 sigaction(SIGTRAP, &action, NULL);
268 }
269