1 /* 2 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved. 3 * Copyright 2012, 2013 SAP AG. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #include "precompiled.hpp" 27 #include "runtime/interfaceSupport.hpp" 28 #include "runtime/os.inline.hpp" 29 #include "services/attachListener.hpp" 30 #include "services/dtraceAttacher.hpp" 31 32 #include <unistd.h> 33 #include <signal.h> 34 #include <sys/types.h> 35 #include <sys/socket.h> 36 #include <sys/un.h> 37 #include <sys/stat.h> 38 39 #ifndef UNIX_PATH_MAX 40 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) 41 #endif 42 43 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener 44 // thread is created at startup or is created on-demand via a signal from 45 // the client tool. The attach listener creates a socket and binds it to a file 46 // in the filesystem. The attach listener then acts as a simple (single- 47 // threaded) server - it waits for a client to connect, reads the request, 48 // executes it, and returns the response to the client via the socket 49 // connection. 50 // 51 // As the socket is a UNIX domain socket it means that only clients on the 52 // local machine can connect. In addition there are two other aspects to 53 // the security: 54 // 1. The well known file that the socket is bound to has permission 400 55 // 2. When a client connect, the SO_PEERID socket option is used to 56 // obtain the credentials of client. We check that the effective uid 57 // of the client matches this process. 58 59 // forward reference 60 class AixAttachOperation; 61 62 class AixAttachListener: AllStatic { 63 private: 64 // the path to which we bind the UNIX domain socket 65 static char _path[UNIX_PATH_MAX]; 66 static bool _has_path; 67 // Shutdown marker to prevent accept blocking during clean-up. 68 static bool _shutdown; 69 70 // the file descriptor for the listening socket 71 static int _listener; 72 73 static void set_path(char* path) { 74 if (path == NULL) { 75 _has_path = false; 76 } else { 77 strncpy(_path, path, UNIX_PATH_MAX); 78 _path[UNIX_PATH_MAX-1] = '\0'; 79 _has_path = true; 80 } 81 } 82 83 static void set_listener(int s) { _listener = s; } 84 85 // reads a request from the given connected socket 86 static AixAttachOperation* read_request(int s); 87 88 public: 89 enum { 90 ATTACH_PROTOCOL_VER = 1 // protocol version 91 }; 92 enum { 93 ATTACH_ERROR_BADVERSION = 101 // error codes 94 }; 95 96 // initialize the listener, returns 0 if okay 97 static int init(); 98 99 static char* path() { return _path; } 100 static bool has_path() { return _has_path; } 101 static int listener() { return _listener; } 102 // Shutdown marker to prevent accept blocking during clean-up 103 static void set_shutdown(bool shutdown) { _shutdown = shutdown; } 104 static bool is_shutdown() { return _shutdown; } 105 106 // write the given buffer to a socket 107 static int write_fully(int s, char* buf, int len); 108 109 static AixAttachOperation* dequeue(); 110 }; 111 112 class AixAttachOperation: public AttachOperation { 113 private: 114 // the connection to the client 115 int _socket; 116 117 public: 118 void complete(jint res, bufferedStream* st); 119 120 void set_socket(int s) { _socket = s; } 121 int socket() const { return _socket; } 122 123 AixAttachOperation(char* name) : AttachOperation(name) { 124 set_socket(-1); 125 } 126 }; 127 128 // statics 129 char AixAttachListener::_path[UNIX_PATH_MAX]; 130 bool AixAttachListener::_has_path; 131 int AixAttachListener::_listener = -1; 132 // Shutdown marker to prevent accept blocking during clean-up 133 bool AixAttachListener::_shutdown = false; 134 135 // Supporting class to help split a buffer into individual components 136 class ArgumentIterator : public StackObj { 137 private: 138 char* _pos; 139 char* _end; 140 public: 141 ArgumentIterator(char* arg_buffer, size_t arg_size) { 142 _pos = arg_buffer; 143 _end = _pos + arg_size - 1; 144 } 145 char* next() { 146 if (*_pos == '\0') { 147 return NULL; 148 } 149 char* res = _pos; 150 char* next_pos = strchr(_pos, '\0'); 151 if (next_pos < _end) { 152 next_pos++; 153 } 154 _pos = next_pos; 155 return res; 156 } 157 }; 158 159 // On AIX if sockets block until all data has been transmitted 160 // successfully in some communication domains a socket "close" may 161 // never complete. We have to take care that after the socket shutdown 162 // the listener never enters accept state. 163 164 // atexit hook to stop listener and unlink the file that it is 165 // bound too. 166 167 // Some modifications to the listener logic to prevent deadlocks on exit. 168 // 1. We Shutdown the socket here instead. AixAttachOperation::complete() is not the right place 169 // since more than one agent in a sequence in JPLIS live tests wouldn't work (Listener thread 170 // would be dead after the first operation completion). 171 // 2. close(s) may never return if the listener thread is in socket accept(). Unlinking the file 172 // should be sufficient for cleanup. 173 extern "C" { 174 static void listener_cleanup() { 175 static int cleanup_done; 176 if (!cleanup_done) { 177 cleanup_done = 1; 178 AixAttachListener::set_shutdown(true); 179 int s = AixAttachListener::listener(); 180 if (s != -1) { 181 ::shutdown(s, 2); 182 } 183 if (AixAttachListener::has_path()) { 184 ::unlink(AixAttachListener::path()); 185 } 186 } 187 } 188 } 189 190 // Initialization - create a listener socket and bind it to a file 191 192 int AixAttachListener::init() { 193 char path[UNIX_PATH_MAX]; // socket file 194 char initial_path[UNIX_PATH_MAX]; // socket file during setup 195 int listener; // listener socket (file descriptor) 196 197 // register function to cleanup 198 ::atexit(listener_cleanup); 199 200 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 201 os::get_temp_directory(), os::current_process_id()); 202 if (n < (int)UNIX_PATH_MAX) { 203 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 204 } 205 if (n >= (int)UNIX_PATH_MAX) { 206 return -1; 207 } 208 209 // create the listener socket 210 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 211 if (listener == -1) { 212 return -1; 213 } 214 215 // bind socket 216 struct sockaddr_un addr; 217 addr.sun_family = AF_UNIX; 218 strcpy(addr.sun_path, initial_path); 219 ::unlink(initial_path); 220 // We must call bind with the actual socketaddr length. This is obligatory for AS400. 221 int res = ::bind(listener, (struct sockaddr*)&addr, SUN_LEN(&addr)); 222 if (res == -1) { 223 RESTARTABLE(::close(listener), res); 224 return -1; 225 } 226 227 // put in listen mode, set permissions, and rename into place 228 res = ::listen(listener, 5); 229 if (res == 0) { 230 RESTARTABLE(::chmod(initial_path, (S_IREAD|S_IWRITE) & ~(S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)), res); 231 if (res == 0) { 232 res = ::rename(initial_path, path); 233 } 234 } 235 if (res == -1) { 236 RESTARTABLE(::close(listener), res); 237 ::unlink(initial_path); 238 return -1; 239 } 240 set_path(path); 241 set_listener(listener); 242 set_shutdown(false); 243 244 return 0; 245 } 246 247 // Given a socket that is connected to a peer we read the request and 248 // create an AttachOperation. As the socket is blocking there is potential 249 // for a denial-of-service if the peer does not response. However this happens 250 // after the peer credentials have been checked and in the worst case it just 251 // means that the attach listener thread is blocked. 252 // 253 AixAttachOperation* AixAttachListener::read_request(int s) { 254 char ver_str[8]; 255 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 256 257 // The request is a sequence of strings so we first figure out the 258 // expected count and the maximum possible length of the request. 259 // The request is: 260 // <ver>0<cmd>0<arg>0<arg>0<arg>0 261 // where <ver> is the protocol version (1), <cmd> is the command 262 // name ("load", "datadump", ...), and <arg> is an argument 263 int expected_str_count = 2 + AttachOperation::arg_count_max; 264 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 265 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 266 267 char buf[max_len]; 268 int str_count = 0; 269 270 // Read until all (expected) strings have been read, the buffer is 271 // full, or EOF. 272 273 int off = 0; 274 int left = max_len; 275 276 do { 277 int n; 278 // Don't block on interrupts because this will 279 // hang in the clean-up when shutting down. 280 n = read(s, buf+off, left); 281 if (n == -1) { 282 return NULL; // reset by peer or other error 283 } 284 if (n == 0) { // end of file reached 285 break; 286 } 287 for (int i=0; i<n; i++) { 288 if (buf[off+i] == 0) { 289 // EOS found 290 str_count++; 291 292 // The first string is <ver> so check it now to 293 // check for protocol mis-match 294 if (str_count == 1) { 295 if ((strlen(buf) != strlen(ver_str)) || 296 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 297 char msg[32]; 298 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 299 write_fully(s, msg, strlen(msg)); 300 return NULL; 301 } 302 } 303 } 304 } 305 off += n; 306 left -= n; 307 } while (left > 0 && str_count < expected_str_count); 308 309 if (str_count != expected_str_count) { 310 return NULL; // incomplete request 311 } 312 313 // parse request 314 315 ArgumentIterator args(buf, (max_len)-left); 316 317 // version already checked 318 char* v = args.next(); 319 320 char* name = args.next(); 321 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 322 return NULL; 323 } 324 325 AixAttachOperation* op = new AixAttachOperation(name); 326 327 for (int i=0; i<AttachOperation::arg_count_max; i++) { 328 char* arg = args.next(); 329 if (arg == NULL) { 330 op->set_arg(i, NULL); 331 } else { 332 if (strlen(arg) > AttachOperation::arg_length_max) { 333 delete op; 334 return NULL; 335 } 336 op->set_arg(i, arg); 337 } 338 } 339 340 op->set_socket(s); 341 return op; 342 } 343 344 345 // Dequeue an operation 346 // 347 // In the Linux implementation there is only a single operation and clients 348 // cannot queue commands (except at the socket level). 349 // 350 AixAttachOperation* AixAttachListener::dequeue() { 351 for (;;) { 352 int s; 353 354 // wait for client to connect 355 struct sockaddr addr; 356 socklen_t len = sizeof(addr); 357 memset(&addr, 0, len); 358 // We must prevent accept blocking on the socket if it has been shut down. 359 // Therefore we allow interrups and check whether we have been shut down already. 360 if (AixAttachListener::is_shutdown()) { 361 return NULL; 362 } 363 s=::accept(listener(), &addr, &len); 364 if (s == -1) { 365 return NULL; // log a warning? 366 } 367 368 // Added timeouts for read and write. If we get no request within the 369 // next AttachListenerTimeout milliseconds we just finish the connection. 370 struct timeval tv; 371 tv.tv_sec = 0; 372 tv.tv_usec = AttachListenerTimeout * 1000; 373 ::setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv)); 374 ::setsockopt(s, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv)); 375 376 // get the credentials of the peer and check the effective uid/guid 377 // - check with jeff on this. 378 struct peercred_struct cred_info; 379 socklen_t optlen = sizeof(cred_info); 380 if (::getsockopt(s, SOL_SOCKET, SO_PEERID, (void*)&cred_info, &optlen) == -1) { 381 int res; 382 RESTARTABLE(::close(s), res); 383 continue; 384 } 385 uid_t euid = geteuid(); 386 gid_t egid = getegid(); 387 388 if (cred_info.euid != euid || cred_info.egid != egid) { 389 int res; 390 RESTARTABLE(::close(s), res); 391 continue; 392 } 393 394 // peer credential look okay so we read the request 395 AixAttachOperation* op = read_request(s); 396 if (op == NULL) { 397 int res; 398 RESTARTABLE(::close(s), res); 399 continue; 400 } else { 401 return op; 402 } 403 } 404 } 405 406 // write the given buffer to the socket 407 int AixAttachListener::write_fully(int s, char* buf, int len) { 408 do { 409 int n = ::write(s, buf, len); 410 if (n == -1) { 411 if (errno != EINTR) return -1; 412 } else { 413 buf += n; 414 len -= n; 415 } 416 } 417 while (len > 0); 418 return 0; 419 } 420 421 // Complete an operation by sending the operation result and any result 422 // output to the client. At this time the socket is in blocking mode so 423 // potentially we can block if there is a lot of data and the client is 424 // non-responsive. For most operations this is a non-issue because the 425 // default send buffer is sufficient to buffer everything. In the future 426 // if there are operations that involves a very big reply then it the 427 // socket could be made non-blocking and a timeout could be used. 428 429 void AixAttachOperation::complete(jint result, bufferedStream* st) { 430 JavaThread* thread = JavaThread::current(); 431 ThreadBlockInVM tbivm(thread); 432 433 thread->set_suspend_equivalent(); 434 // cleared by handle_special_suspend_equivalent_condition() or 435 // java_suspend_self() via check_and_wait_while_suspended() 436 437 // write operation result 438 char msg[32]; 439 sprintf(msg, "%d\n", result); 440 int rc = AixAttachListener::write_fully(this->socket(), msg, strlen(msg)); 441 442 // write any result data 443 if (rc == 0) { 444 // Shutdown the socket in the cleanup function to enable more than 445 // one agent attach in a sequence (see comments to listener_cleanup()). 446 AixAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 447 } 448 449 // done 450 RESTARTABLE(::close(this->socket()), rc); 451 452 // were we externally suspended while we were waiting? 453 thread->check_and_wait_while_suspended(); 454 455 delete this; 456 } 457 458 459 // AttachListener functions 460 461 AttachOperation* AttachListener::dequeue() { 462 JavaThread* thread = JavaThread::current(); 463 ThreadBlockInVM tbivm(thread); 464 465 thread->set_suspend_equivalent(); 466 // cleared by handle_special_suspend_equivalent_condition() or 467 // java_suspend_self() via check_and_wait_while_suspended() 468 469 AttachOperation* op = AixAttachListener::dequeue(); 470 471 // were we externally suspended while we were waiting? 472 thread->check_and_wait_while_suspended(); 473 474 return op; 475 } 476 477 // Performs initialization at vm startup 478 // For AIX we remove any stale .java_pid file which could cause 479 // an attaching process to think we are ready to receive on the 480 // domain socket before we are properly initialized 481 482 void AttachListener::vm_start() { 483 char fn[UNIX_PATH_MAX]; 484 struct stat64 st; 485 int ret; 486 487 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", 488 os::get_temp_directory(), os::current_process_id()); 489 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); 490 491 RESTARTABLE(::stat64(fn, &st), ret); 492 if (ret == 0) { 493 ret = ::unlink(fn); 494 if (ret == -1) { 495 debug_only(warning("failed to remove stale attach pid file at %s", fn)); 496 } 497 } 498 } 499 500 int AttachListener::pd_init() { 501 JavaThread* thread = JavaThread::current(); 502 ThreadBlockInVM tbivm(thread); 503 504 thread->set_suspend_equivalent(); 505 // cleared by handle_special_suspend_equivalent_condition() or 506 // java_suspend_self() via check_and_wait_while_suspended() 507 508 int ret_code = AixAttachListener::init(); 509 510 // were we externally suspended while we were waiting? 511 thread->check_and_wait_while_suspended(); 512 513 return ret_code; 514 } 515 516 // Attach Listener is started lazily except in the case when 517 // +ReduseSignalUsage is used 518 bool AttachListener::init_at_startup() { 519 if (ReduceSignalUsage) { 520 return true; 521 } else { 522 return false; 523 } 524 } 525 526 // If the file .attach_pid<pid> exists in the working directory 527 // or /tmp then this is the trigger to start the attach mechanism 528 bool AttachListener::is_init_trigger() { 529 if (init_at_startup() || is_initialized()) { 530 return false; // initialized at startup or already initialized 531 } 532 char fn[PATH_MAX+1]; 533 sprintf(fn, ".attach_pid%d", os::current_process_id()); 534 int ret; 535 struct stat64 st; 536 RESTARTABLE(::stat64(fn, &st), ret); 537 if (ret == -1) { 538 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", 539 os::get_temp_directory(), os::current_process_id()); 540 RESTARTABLE(::stat64(fn, &st), ret); 541 } 542 if (ret == 0) { 543 // simple check to avoid starting the attach mechanism when 544 // a bogus user creates the file 545 if (st.st_uid == geteuid()) { 546 init(); 547 return true; 548 } 549 } 550 return false; 551 } 552 553 // if VM aborts then remove listener 554 void AttachListener::abort() { 555 listener_cleanup(); 556 } 557 558 void AttachListener::pd_data_dump() { 559 os::signal_notify(SIGQUIT); 560 } 561 562 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 563 return NULL; 564 } 565 566 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 567 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 568 return JNI_ERR; 569 } 570 571 void AttachListener::pd_detachall() { 572 // Cleanup server socket to detach clients. 573 listener_cleanup(); 574 }