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 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 */ 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 */ 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 */ 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 } 247 248 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
