1 /* 2 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "runtime/interfaceSupport.hpp" 27 #include "runtime/os.hpp" 28 #include "services/attachListener.hpp" 29 #include "services/dtraceAttacher.hpp" 30 31 #include <unistd.h> 32 #include <signal.h> 33 #include <sys/types.h> 34 #include <sys/socket.h> 35 #include <sys/un.h> 36 #include <sys/stat.h> 37 38 #ifndef UNIX_PATH_MAX 39 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) 40 #endif 41 42 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener 43 // thread is created at startup or is created on-demand via a signal from 44 // the client tool. The attach listener creates a socket and binds it to a file 45 // in the filesystem. The attach listener then acts as a simple (single- 46 // threaded) server - it waits for a client to connect, reads the request, 47 // executes it, and returns the response to the client via the socket 48 // connection. 49 // 50 // As the socket is a UNIX domain socket it means that only clients on the 51 // local machine can connect. In addition there are two other aspects to 52 // the security: 53 // 1. The well known file that the socket is bound to has permission 400 54 // 2. When a client connect, the SO_PEERCRED socket option is used to 55 // obtain the credentials of client. We check that the effective uid 56 // of the client matches this process. 57 58 // forward reference 59 class LinuxAttachOperation; 60 61 class LinuxAttachListener: AllStatic { 62 private: 63 // the path to which we bind the UNIX domain socket 64 static char _path[UNIX_PATH_MAX]; 65 static bool _has_path; 66 67 // the file descriptor for the listening socket 68 static int _listener; 69 70 static void set_path(char* path) { 71 if (path == NULL) { 72 _has_path = false; 73 } else { 74 strncpy(_path, path, UNIX_PATH_MAX); 75 _path[UNIX_PATH_MAX-1] = '\0'; 76 _has_path = true; 77 } 78 } 79 80 static void set_listener(int s) { _listener = s; } 81 82 // reads a request from the given connected socket 83 static LinuxAttachOperation* read_request(int s); 84 85 public: 86 enum { 87 ATTACH_PROTOCOL_VER = 1 // protocol version 88 }; 89 enum { 90 ATTACH_ERROR_BADVERSION = 101 // error codes 91 }; 92 93 // initialize the listener, returns 0 if okay 94 static int init(); 95 96 static char* path() { return _path; } 97 static bool has_path() { return _has_path; } 98 static int listener() { return _listener; } 99 100 // write the given buffer to a socket 101 static int write_fully(int s, char* buf, int len); 102 103 static LinuxAttachOperation* dequeue(); 104 }; 105 106 class LinuxAttachOperation: public AttachOperation { 107 private: 108 // the connection to the client 109 int _socket; 110 111 public: 112 void complete(jint res, bufferedStream* st); 113 114 void set_socket(int s) { _socket = s; } 115 int socket() const { return _socket; } 116 117 LinuxAttachOperation(char* name) : AttachOperation(name) { 118 set_socket(-1); 119 } 120 }; 121 122 // statics 123 char LinuxAttachListener::_path[UNIX_PATH_MAX]; 124 bool LinuxAttachListener::_has_path; 125 int LinuxAttachListener::_listener = -1; 126 127 // Supporting class to help split a buffer into individual components 128 class ArgumentIterator : public StackObj { 129 private: 130 char* _pos; 131 char* _end; 132 public: 133 ArgumentIterator(char* arg_buffer, size_t arg_size) { 134 _pos = arg_buffer; 135 _end = _pos + arg_size - 1; 136 } 137 char* next() { 138 if (*_pos == '\0') { 139 return NULL; 140 } 141 char* res = _pos; 142 char* next_pos = strchr(_pos, '\0'); 143 if (next_pos < _end) { 144 next_pos++; 145 } 146 _pos = next_pos; 147 return res; 148 } 149 }; 150 151 152 // atexit hook to stop listener and unlink the file that it is 153 // bound too. 154 extern "C" { 155 static void listener_cleanup() { 156 static int cleanup_done; 157 if (!cleanup_done) { 158 cleanup_done = 1; 159 int s = LinuxAttachListener::listener(); 160 if (s != -1) { 161 ::close(s); 162 } 163 if (LinuxAttachListener::has_path()) { 164 ::unlink(LinuxAttachListener::path()); 165 } 166 } 167 } 168 } 169 170 // Initialization - create a listener socket and bind it to a file 171 172 int LinuxAttachListener::init() { 173 char path[UNIX_PATH_MAX]; // socket file 174 char initial_path[UNIX_PATH_MAX]; // socket file during setup 175 int listener; // listener socket (file descriptor) 176 177 // register function to cleanup 178 ::atexit(listener_cleanup); 179 180 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 181 os::get_temp_directory(), os::current_process_id()); 182 if (n < (int)UNIX_PATH_MAX) { 183 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 184 } 185 if (n >= (int)UNIX_PATH_MAX) { 186 return -1; 187 } 188 189 // create the listener socket 190 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 191 if (listener == -1) { 192 return -1; 193 } 194 195 // bind socket 196 struct sockaddr_un addr; 197 addr.sun_family = AF_UNIX; 198 strcpy(addr.sun_path, initial_path); 199 ::unlink(initial_path); 200 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); 201 if (res == -1) { 202 RESTARTABLE(::close(listener), res); 203 return -1; 204 } 205 206 // put in listen mode, set permissions, and rename into place 207 res = ::listen(listener, 5); 208 if (res == 0) { 209 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 210 if (res == 0) { 211 res = ::rename(initial_path, path); 212 } 213 } 214 if (res == -1) { 215 RESTARTABLE(::close(listener), res); 216 ::unlink(initial_path); 217 return -1; 218 } 219 set_path(path); 220 set_listener(listener); 221 222 return 0; 223 } 224 225 // Given a socket that is connected to a peer we read the request and 226 // create an AttachOperation. As the socket is blocking there is potential 227 // for a denial-of-service if the peer does not response. However this happens 228 // after the peer credentials have been checked and in the worst case it just 229 // means that the attach listener thread is blocked. 230 // 231 LinuxAttachOperation* LinuxAttachListener::read_request(int s) { 232 char ver_str[8]; 233 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 234 235 // The request is a sequence of strings so we first figure out the 236 // expected count and the maximum possible length of the request. 237 // The request is: 238 // <ver>0<cmd>0<arg>0<arg>0<arg>0 239 // where <ver> is the protocol version (1), <cmd> is the command 240 // name ("load", "datadump", ...), and <arg> is an argument 241 int expected_str_count = 2 + AttachOperation::arg_count_max; 242 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 243 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 244 245 char buf[max_len]; 246 int str_count = 0; 247 248 // Read until all (expected) strings have been read, the buffer is 249 // full, or EOF. 250 251 int off = 0; 252 int left = max_len; 253 254 do { 255 int n; 256 RESTARTABLE(read(s, buf+off, left), n); 257 if (n == -1) { 258 return NULL; // reset by peer or other error 259 } 260 if (n == 0) { 261 break; 262 } 263 for (int i=0; i<n; i++) { 264 if (buf[off+i] == 0) { 265 // EOS found 266 str_count++; 267 268 // The first string is <ver> so check it now to 269 // check for protocol mis-match 270 if (str_count == 1) { 271 if ((strlen(buf) != strlen(ver_str)) || 272 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 273 char msg[32]; 274 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 275 write_fully(s, msg, strlen(msg)); 276 return NULL; 277 } 278 } 279 } 280 } 281 off += n; 282 left -= n; 283 } while (left > 0 && str_count < expected_str_count); 284 285 if (str_count != expected_str_count) { 286 return NULL; // incomplete request 287 } 288 289 // parse request 290 291 ArgumentIterator args(buf, (max_len)-left); 292 293 // version already checked 294 char* v = args.next(); 295 296 char* name = args.next(); 297 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 298 return NULL; 299 } 300 301 LinuxAttachOperation* op = new LinuxAttachOperation(name); 302 303 for (int i=0; i<AttachOperation::arg_count_max; i++) { 304 char* arg = args.next(); 305 if (arg == NULL) { 306 op->set_arg(i, NULL); 307 } else { 308 if (strlen(arg) > AttachOperation::arg_length_max) { 309 delete op; 310 return NULL; 311 } 312 op->set_arg(i, arg); 313 } 314 } 315 316 op->set_socket(s); 317 return op; 318 } 319 320 321 // Dequeue an operation 322 // 323 // In the Linux implementation there is only a single operation and clients 324 // cannot queue commands (except at the socket level). 325 // 326 LinuxAttachOperation* LinuxAttachListener::dequeue() { 327 for (;;) { 328 int s; 329 330 // wait for client to connect 331 struct sockaddr addr; 332 socklen_t len = sizeof(addr); 333 RESTARTABLE(::accept(listener(), &addr, &len), s); 334 if (s == -1) { 335 return NULL; // log a warning? 336 } 337 338 // get the credentials of the peer and check the effective uid/guid 339 // - check with jeff on this. 340 struct ucred cred_info; 341 socklen_t optlen = sizeof(cred_info); 342 if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) { 343 int res; 344 RESTARTABLE(::close(s), res); 345 continue; 346 } 347 uid_t euid = geteuid(); 348 gid_t egid = getegid(); 349 350 if (cred_info.uid != euid || cred_info.gid != egid) { 351 int res; 352 RESTARTABLE(::close(s), res); 353 continue; 354 } 355 356 // peer credential look okay so we read the request 357 LinuxAttachOperation* op = read_request(s); 358 if (op == NULL) { 359 int res; 360 RESTARTABLE(::close(s), res); 361 continue; 362 } else { 363 return op; 364 } 365 } 366 } 367 368 // write the given buffer to the socket 369 int LinuxAttachListener::write_fully(int s, char* buf, int len) { 370 do { 371 int n = ::write(s, buf, len); 372 if (n == -1) { 373 if (errno != EINTR) return -1; 374 } else { 375 buf += n; 376 len -= n; 377 } 378 } 379 while (len > 0); 380 return 0; 381 } 382 383 // Complete an operation by sending the operation result and any result 384 // output to the client. At this time the socket is in blocking mode so 385 // potentially we can block if there is a lot of data and the client is 386 // non-responsive. For most operations this is a non-issue because the 387 // default send buffer is sufficient to buffer everything. In the future 388 // if there are operations that involves a very big reply then it the 389 // socket could be made non-blocking and a timeout could be used. 390 391 void LinuxAttachOperation::complete(jint result, bufferedStream* st) { 392 JavaThread* thread = JavaThread::current(); 393 ThreadBlockInVM tbivm(thread); 394 395 thread->set_suspend_equivalent(); 396 // cleared by handle_special_suspend_equivalent_condition() or 397 // java_suspend_self() via check_and_wait_while_suspended() 398 399 // write operation result 400 char msg[32]; 401 sprintf(msg, "%d\n", result); 402 int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg)); 403 404 // write any result data 405 if (rc == 0) { 406 LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 407 ::shutdown(this->socket(), 2); 408 } 409 410 // done 411 RESTARTABLE(::close(this->socket()), rc); 412 413 // were we externally suspended while we were waiting? 414 thread->check_and_wait_while_suspended(); 415 416 delete this; 417 } 418 419 420 // AttachListener functions 421 422 AttachOperation* AttachListener::dequeue() { 423 JavaThread* thread = JavaThread::current(); 424 ThreadBlockInVM tbivm(thread); 425 426 thread->set_suspend_equivalent(); 427 // cleared by handle_special_suspend_equivalent_condition() or 428 // java_suspend_self() via check_and_wait_while_suspended() 429 430 AttachOperation* op = LinuxAttachListener::dequeue(); 431 432 // were we externally suspended while we were waiting? 433 thread->check_and_wait_while_suspended(); 434 435 return op; 436 } 437 438 int AttachListener::pd_init() { 439 JavaThread* thread = JavaThread::current(); 440 ThreadBlockInVM tbivm(thread); 441 442 thread->set_suspend_equivalent(); 443 // cleared by handle_special_suspend_equivalent_condition() or 444 // java_suspend_self() via check_and_wait_while_suspended() 445 446 int ret_code = LinuxAttachListener::init(); 447 448 // were we externally suspended while we were waiting? 449 thread->check_and_wait_while_suspended(); 450 451 return ret_code; 452 } 453 454 // Attach Listener is started lazily except in the case when 455 // +ReduseSignalUsage is used 456 bool AttachListener::init_at_startup() { 457 if (ReduceSignalUsage) { 458 return true; 459 } else { 460 return false; 461 } 462 } 463 464 // If the file .attach_pid<pid> exists in the working directory 465 // or /tmp then this is the trigger to start the attach mechanism 466 bool AttachListener::is_init_trigger() { 467 if (init_at_startup() || is_initialized()) { 468 return false; // initialized at startup or already initialized 469 } 470 char fn[PATH_MAX+1]; 471 sprintf(fn, ".attach_pid%d", os::current_process_id()); 472 int ret; 473 struct stat64 st; 474 RESTARTABLE(::stat64(fn, &st), ret); 475 if (ret == -1) { 476 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", 477 os::get_temp_directory(), os::current_process_id()); 478 RESTARTABLE(::stat64(fn, &st), ret); 479 } 480 if (ret == 0) { 481 // simple check to avoid starting the attach mechanism when 482 // a bogus user creates the file 483 if (st.st_uid == geteuid()) { 484 init(); 485 return true; 486 } 487 } 488 return false; 489 } 490 491 // if VM aborts then remove listener 492 void AttachListener::abort() { 493 listener_cleanup(); 494 } 495 496 void AttachListener::pd_data_dump() { 497 os::signal_notify(SIGQUIT); 498 } 499 500 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 501 return NULL; 502 } 503 504 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 505 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 506 return JNI_ERR; 507 } 508 509 void AttachListener::pd_detachall() { 510 // do nothing for now 511 }