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 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 */ 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 */ 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 } 207 208 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 */ 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 } 288 289 __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
