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 <inttypes.h>
33 #include <signal.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <sys/mman.h>
37 #include <sys/prctl.h>
38 #include <sys/socket.h>
39 #include <sys/un.h>
40 #include <unistd.h>
41
42 extern "C" int tgkill(int tgid, int tid, int sig);
43
44 #if __LP64__
45 #define DEBUGGER_SOCKET_NAME "android:debuggerd64"
46 #else
47 #define DEBUGGER_SOCKET_NAME "android:debuggerd"
48 #endif
49
50 enum debugger_action_t {
51 // dump a crash
52 DEBUGGER_ACTION_CRASH,
53 // dump a tombstone file
54 DEBUGGER_ACTION_DUMP_TOMBSTONE,
55 // dump a backtrace only back to the socket
56 DEBUGGER_ACTION_DUMP_BACKTRACE,
57 };
58
59 /* message sent over the socket */
60 struct debugger_msg_t {
61 // version 1 included:
62 debugger_action_t action;
63 pid_t tid;
64
65 // version 2 added:
66 uintptr_t abort_msg_address;
67
68 // version 3 added:
69 int32_t original_si_code;
70 };
71
72 // see man(2) prctl, specifically the section about PR_GET_NAME
73 #define MAX_TASK_NAME_LEN (16)
74
socket_abstract_client(const char * name,int type)75 static int socket_abstract_client(const char* name, int type) {
76 sockaddr_un addr;
77
78 // Test with length +1 for the *initial* '\0'.
79 size_t namelen = strlen(name);
80 if ((namelen + 1) > sizeof(addr.sun_path)) {
81 errno = EINVAL;
82 return -1;
83 }
84
85 // This is used for abstract socket namespace, we need
86 // an initial '\0' at the start of the Unix socket path.
87 //
88 // Note: The path in this case is *not* supposed to be
89 // '\0'-terminated. ("man 7 unix" for the gory details.)
90 memset(&addr, 0, sizeof(addr));
91 addr.sun_family = AF_LOCAL;
92 addr.sun_path[0] = 0;
93 memcpy(addr.sun_path + 1, name, namelen);
94
95 socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
96
97 int s = socket(AF_LOCAL, type, 0);
98 if (s == -1) {
99 return -1;
100 }
101
102 int rc = TEMP_FAILURE_RETRY(connect(s, reinterpret_cast<sockaddr*>(&addr), alen));
103 if (rc == -1) {
104 close(s);
105 return -1;
106 }
107
108 return s;
109 }
110
111 /*
112 * Writes a summary of the signal to the log file. We do this so that, if
113 * for some reason we're not able to contact debuggerd, there is still some
114 * indication of the failure in the log.
115 *
116 * We could be here as a result of native heap corruption, or while a
117 * mutex is being held, so we don't want to use any libc functions that
118 * could allocate memory or hold a lock.
119 */
log_signal_summary(int signum,const siginfo_t * info)120 static void log_signal_summary(int signum, const siginfo_t* info) {
121 const char* signal_name = "???";
122 bool has_address = false;
123 switch (signum) {
124 case SIGABRT:
125 signal_name = "SIGABRT";
126 break;
127 case SIGBUS:
128 signal_name = "SIGBUS";
129 has_address = true;
130 break;
131 case SIGFPE:
132 signal_name = "SIGFPE";
133 has_address = true;
134 break;
135 case SIGILL:
136 signal_name = "SIGILL";
137 has_address = true;
138 break;
139 case SIGPIPE:
140 signal_name = "SIGPIPE";
141 break;
142 case SIGSEGV:
143 signal_name = "SIGSEGV";
144 has_address = true;
145 break;
146 #if defined(SIGSTKFLT)
147 case SIGSTKFLT:
148 signal_name = "SIGSTKFLT";
149 break;
150 #endif
151 case SIGTRAP:
152 signal_name = "SIGTRAP";
153 break;
154 }
155
156 char thread_name[MAX_TASK_NAME_LEN + 1]; // one more for termination
157 if (prctl(PR_GET_NAME, (unsigned long)thread_name, 0, 0, 0) != 0) {
158 strcpy(thread_name, "<name unknown>");
159 } else {
160 // short names are null terminated by prctl, but the man page
161 // implies that 16 byte names are not.
162 thread_name[MAX_TASK_NAME_LEN] = 0;
163 }
164
165 // "info" will be NULL if the siginfo_t information was not available.
166 // Many signals don't have an address or a code.
167 char code_desc[32]; // ", code -6"
168 char addr_desc[32]; // ", fault addr 0x1234"
169 addr_desc[0] = code_desc[0] = 0;
170 if (info != NULL) {
171 // For a rethrown signal, this si_code will be right and the one debuggerd shows will
172 // always be SI_TKILL.
173 __libc_format_buffer(code_desc, sizeof(code_desc), ", code %d", info->si_code);
174 if (has_address) {
175 __libc_format_buffer(addr_desc, sizeof(addr_desc), ", fault addr %p", info->si_addr);
176 }
177 }
178 __libc_format_log(ANDROID_LOG_FATAL, "libc",
179 "Fatal signal %d (%s)%s%s in tid %d (%s)",
180 signum, signal_name, code_desc, addr_desc, gettid(), thread_name);
181 }
182
183 /*
184 * Returns true if the handler for signal "signum" has SA_SIGINFO set.
185 */
have_siginfo(int signum)186 static bool have_siginfo(int signum) {
187 struct sigaction old_action, new_action;
188
189 memset(&new_action, 0, sizeof(new_action));
190 new_action.sa_handler = SIG_DFL;
191 new_action.sa_flags = SA_RESTART;
192 sigemptyset(&new_action.sa_mask);
193
194 if (sigaction(signum, &new_action, &old_action) < 0) {
195 __libc_format_log(ANDROID_LOG_WARN, "libc", "Failed testing for SA_SIGINFO: %s",
196 strerror(errno));
197 return false;
198 }
199 bool result = (old_action.sa_flags & SA_SIGINFO) != 0;
200
201 if (sigaction(signum, &old_action, NULL) == -1) {
202 __libc_format_log(ANDROID_LOG_WARN, "libc", "Restore failed in test for SA_SIGINFO: %s",
203 strerror(errno));
204 }
205 return result;
206 }
207
send_debuggerd_packet(siginfo_t * info)208 static void send_debuggerd_packet(siginfo_t* info) {
209 if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0) {
210 // process has disabled core dumps and PTRACE_ATTACH, and does not want to be dumped.
211 // Honor that intention by not connecting to debuggerd and asking it
212 // to dump our internal state.
213 __libc_format_log(ANDROID_LOG_INFO, "libc",
214 "Suppressing debuggerd output because prctl(PR_GET_DUMPABLE)==0");
215 return;
216 }
217
218 int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
219 if (s == -1) {
220 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
221 strerror(errno));
222 return;
223 }
224
225 // debuggerd knows our pid from the credentials on the
226 // local socket but we need to tell it the tid of the crashing thread.
227 // debuggerd will be paranoid and verify that we sent a tid
228 // that's actually in our process.
229 debugger_msg_t msg;
230 msg.action = DEBUGGER_ACTION_CRASH;
231 msg.tid = gettid();
232 msg.abort_msg_address = reinterpret_cast<uintptr_t>(g_abort_message);
233 msg.original_si_code = (info != NULL) ? info->si_code : 0;
234 int ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
235 if (ret == sizeof(msg)) {
236 char debuggerd_ack;
237 ret = TEMP_FAILURE_RETRY(read(s, &debuggerd_ack, 1));
238 int saved_errno = errno;
239 notify_gdb_of_libraries();
240 errno = saved_errno;
241 } else {
242 // read or write failed -- broken connection?
243 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
244 strerror(errno));
245 }
246
247 close(s);
248 }
249
250 /*
251 * Catches fatal signals so we can ask debuggerd to ptrace us before
252 * we crash.
253 */
debuggerd_signal_handler(int signal_number,siginfo_t * info,void *)254 static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
255 // It's possible somebody cleared the SA_SIGINFO flag, which would mean
256 // our "info" arg holds an undefined value.
257 if (!have_siginfo(signal_number)) {
258 info = NULL;
259 }
260
261 log_signal_summary(signal_number, info);
262
263 send_debuggerd_packet(info);
264
265 // Remove our net so we fault for real when we return.
266 signal(signal_number, SIG_DFL);
267
268 // These signals are not re-thrown when we resume. This means that
269 // crashing due to (say) SIGPIPE doesn't work the way you'd expect it
270 // to. We work around this by throwing them manually. We don't want
271 // to do this for *all* signals because it'll screw up the si_addr for
272 // faults like SIGSEGV. It does screw up the si_code, which is why we
273 // passed that to debuggerd above.
274 switch (signal_number) {
275 case SIGABRT:
276 case SIGFPE:
277 case SIGPIPE:
278 #if defined(SIGSTKFLT)
279 case SIGSTKFLT:
280 #endif
281 case SIGTRAP:
282 tgkill(getpid(), gettid(), signal_number);
283 break;
284 default: // SIGILL, SIGBUS, SIGSEGV
285 break;
286 }
287 }
288
debuggerd_init()289 __LIBC_HIDDEN__ void debuggerd_init() {
290 struct sigaction action;
291 memset(&action, 0, sizeof(action));
292 sigemptyset(&action.sa_mask);
293 action.sa_sigaction = debuggerd_signal_handler;
294 action.sa_flags = SA_RESTART | SA_SIGINFO;
295
296 // Use the alternate signal stack if available so we can catch stack overflows.
297 action.sa_flags |= SA_ONSTACK;
298
299 sigaction(SIGABRT, &action, NULL);
300 sigaction(SIGBUS, &action, NULL);
301 sigaction(SIGFPE, &action, NULL);
302 sigaction(SIGILL, &action, NULL);
303 sigaction(SIGPIPE, &action, NULL);
304 sigaction(SIGSEGV, &action, NULL);
305 #if defined(SIGSTKFLT)
306 sigaction(SIGSTKFLT, &action, NULL);
307 #endif
308 sigaction(SIGTRAP, &action, NULL);
309 }
310