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annotate src/os/linux/vm/attachListener_linux.cpp @ 1675:a81afd9c293c
6649594: Intermittent IOExceptions during dynamic attach on linux and solaris
Reviewed-by: dcubed, dholmes
| author | alanb |
|---|---|
| date | Fri, 16 Jul 2010 13:14:03 +0100 |
| parents | c18cbe5936b8 |
| children | 3dc12ef8735e |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2005, 2008, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 25 # include "incls/_precompiled.incl" | |
| 26 # include "incls/_attachListener_linux.cpp.incl" | |
| 27 | |
| 28 #include <unistd.h> | |
| 29 #include <signal.h> | |
| 30 #include <sys/types.h> | |
| 31 #include <sys/socket.h> | |
| 32 #include <sys/un.h> | |
| 33 #include <sys/stat.h> | |
| 34 | |
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35 #ifndef UNIX_PATH_MAX |
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36 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) |
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37 #endif |
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38 |
| 0 | 39 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener |
| 40 // thread is created at startup or is created on-demand via a signal from | |
| 41 // the client tool. The attach listener creates a socket and binds it to a file | |
| 42 // in the filesystem. The attach listener then acts as a simple (single- | |
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43 // threaded) server - it waits for a client to connect, reads the request, |
| 0 | 44 // executes it, and returns the response to the client via the socket |
| 45 // connection. | |
| 46 // | |
| 47 // As the socket is a UNIX domain socket it means that only clients on the | |
| 48 // local machine can connect. In addition there are two other aspects to | |
| 49 // the security: | |
| 50 // 1. The well known file that the socket is bound to has permission 400 | |
| 51 // 2. When a client connect, the SO_PEERCRED socket option is used to | |
| 52 // obtain the credentials of client. We check that the effective uid | |
| 53 // of the client matches this process. | |
| 54 | |
| 55 // forward reference | |
| 56 class LinuxAttachOperation; | |
| 57 | |
| 58 class LinuxAttachListener: AllStatic { | |
| 59 private: | |
| 60 // the path to which we bind the UNIX domain socket | |
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61 static char _path[UNIX_PATH_MAX]; |
| 0 | 62 static bool _has_path; |
| 63 | |
| 64 // the file descriptor for the listening socket | |
| 65 static int _listener; | |
| 66 | |
| 67 static void set_path(char* path) { | |
| 68 if (path == NULL) { | |
| 69 _has_path = false; | |
| 70 } else { | |
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71 strncpy(_path, path, UNIX_PATH_MAX); |
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72 _path[UNIX_PATH_MAX-1] = '\0'; |
| 0 | 73 _has_path = true; |
| 74 } | |
| 75 } | |
| 76 | |
| 77 static void set_listener(int s) { _listener = s; } | |
| 78 | |
| 79 // reads a request from the given connected socket | |
| 80 static LinuxAttachOperation* read_request(int s); | |
| 81 | |
| 82 public: | |
| 83 enum { | |
| 84 ATTACH_PROTOCOL_VER = 1 // protocol version | |
| 85 }; | |
| 86 enum { | |
| 87 ATTACH_ERROR_BADVERSION = 101 // error codes | |
| 88 }; | |
| 89 | |
| 90 // initialize the listener, returns 0 if okay | |
| 91 static int init(); | |
| 92 | |
| 93 static char* path() { return _path; } | |
| 94 static bool has_path() { return _has_path; } | |
| 95 static int listener() { return _listener; } | |
| 96 | |
| 97 // write the given buffer to a socket | |
| 98 static int write_fully(int s, char* buf, int len); | |
| 99 | |
| 100 static LinuxAttachOperation* dequeue(); | |
| 101 }; | |
| 102 | |
| 103 class LinuxAttachOperation: public AttachOperation { | |
| 104 private: | |
| 105 // the connection to the client | |
| 106 int _socket; | |
| 107 | |
| 108 public: | |
| 109 void complete(jint res, bufferedStream* st); | |
| 110 | |
| 111 void set_socket(int s) { _socket = s; } | |
| 112 int socket() const { return _socket; } | |
| 113 | |
| 114 LinuxAttachOperation(char* name) : AttachOperation(name) { | |
| 115 set_socket(-1); | |
| 116 } | |
| 117 }; | |
| 118 | |
| 119 // statics | |
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120 char LinuxAttachListener::_path[UNIX_PATH_MAX]; |
| 0 | 121 bool LinuxAttachListener::_has_path; |
| 122 int LinuxAttachListener::_listener = -1; | |
| 123 | |
| 124 // Supporting class to help split a buffer into individual components | |
| 125 class ArgumentIterator : public StackObj { | |
| 126 private: | |
| 127 char* _pos; | |
| 128 char* _end; | |
| 129 public: | |
| 130 ArgumentIterator(char* arg_buffer, size_t arg_size) { | |
| 131 _pos = arg_buffer; | |
| 132 _end = _pos + arg_size - 1; | |
| 133 } | |
| 134 char* next() { | |
| 135 if (*_pos == '\0') { | |
| 136 return NULL; | |
| 137 } | |
| 138 char* res = _pos; | |
| 139 char* next_pos = strchr(_pos, '\0'); | |
| 140 if (next_pos < _end) { | |
| 141 next_pos++; | |
| 142 } | |
| 143 _pos = next_pos; | |
| 144 return res; | |
| 145 } | |
| 146 }; | |
| 147 | |
| 148 | |
| 149 // atexit hook to stop listener and unlink the file that it is | |
| 150 // bound too. | |
| 151 extern "C" { | |
| 152 static void listener_cleanup() { | |
| 153 static int cleanup_done; | |
| 154 if (!cleanup_done) { | |
| 155 cleanup_done = 1; | |
| 156 int s = LinuxAttachListener::listener(); | |
| 157 if (s != -1) { | |
| 158 ::close(s); | |
| 159 } | |
| 160 if (LinuxAttachListener::has_path()) { | |
| 161 ::unlink(LinuxAttachListener::path()); | |
| 162 } | |
| 163 } | |
| 164 } | |
| 165 } | |
| 166 | |
| 167 // Initialization - create a listener socket and bind it to a file | |
| 168 | |
| 169 int LinuxAttachListener::init() { | |
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170 char path[UNIX_PATH_MAX]; // socket file |
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171 char initial_path[UNIX_PATH_MAX]; // socket file during setup |
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172 int listener; // listener socket (file descriptor) |
| 0 | 173 |
| 174 // register function to cleanup | |
| 175 ::atexit(listener_cleanup); | |
| 176 | |
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177 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", |
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178 os::get_temp_directory(), os::current_process_id()); |
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179 if (n <= (int)UNIX_PATH_MAX) { |
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180 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); |
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181 } |
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182 if (n > (int)UNIX_PATH_MAX) { |
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183 return -1; |
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184 } |
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185 |
| 0 | 186 // create the listener socket |
| 187 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); | |
| 188 if (listener == -1) { | |
| 189 return -1; | |
| 190 } | |
| 191 | |
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192 // bind socket |
| 0 | 193 struct sockaddr_un addr; |
| 194 addr.sun_family = AF_UNIX; | |
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195 strcpy(addr.sun_path, initial_path); |
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196 ::unlink(initial_path); |
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197 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); |
| 0 | 198 if (res == -1) { |
| 199 RESTARTABLE(::close(listener), res); | |
| 200 return -1; | |
| 201 } | |
| 202 | |
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203 // put in listen mode, set permissions, and rename into place |
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204 res = ::listen(listener, 5); |
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205 if (res == 0) { |
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206 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); |
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207 if (res == 0) { |
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208 res = ::rename(initial_path, path); |
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209 } |
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210 } |
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211 if (res == -1) { |
| 0 | 212 RESTARTABLE(::close(listener), res); |
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213 ::unlink(initial_path); |
| 0 | 214 return -1; |
| 215 } | |
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216 set_path(path); |
| 0 | 217 set_listener(listener); |
| 218 | |
| 219 return 0; | |
| 220 } | |
| 221 | |
| 222 // Given a socket that is connected to a peer we read the request and | |
| 223 // create an AttachOperation. As the socket is blocking there is potential | |
| 224 // for a denial-of-service if the peer does not response. However this happens | |
| 225 // after the peer credentials have been checked and in the worst case it just | |
| 226 // means that the attach listener thread is blocked. | |
| 227 // | |
| 228 LinuxAttachOperation* LinuxAttachListener::read_request(int s) { | |
| 229 char ver_str[8]; | |
| 230 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); | |
| 231 | |
| 232 // The request is a sequence of strings so we first figure out the | |
| 233 // expected count and the maximum possible length of the request. | |
| 234 // The request is: | |
| 235 // <ver>0<cmd>0<arg>0<arg>0<arg>0 | |
| 236 // where <ver> is the protocol version (1), <cmd> is the command | |
| 237 // name ("load", "datadump", ...), and <arg> is an argument | |
| 238 int expected_str_count = 2 + AttachOperation::arg_count_max; | |
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239 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + |
| 0 | 240 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); |
| 241 | |
| 242 char buf[max_len]; | |
| 243 int str_count = 0; | |
| 244 | |
| 245 // Read until all (expected) strings have been read, the buffer is | |
| 246 // full, or EOF. | |
| 247 | |
| 248 int off = 0; | |
| 249 int left = max_len; | |
| 250 | |
| 251 do { | |
| 252 int n; | |
| 253 RESTARTABLE(read(s, buf+off, left), n); | |
| 254 if (n == -1) { | |
| 255 return NULL; // reset by peer or other error | |
| 256 } | |
| 257 if (n == 0) { | |
| 258 break; | |
| 259 } | |
| 260 for (int i=0; i<n; i++) { | |
| 261 if (buf[off+i] == 0) { | |
| 262 // EOS found | |
| 263 str_count++; | |
| 264 | |
| 265 // The first string is <ver> so check it now to | |
| 266 // check for protocol mis-match | |
| 267 if (str_count == 1) { | |
| 268 if ((strlen(buf) != strlen(ver_str)) || | |
| 269 (atoi(buf) != ATTACH_PROTOCOL_VER)) { | |
| 270 char msg[32]; | |
| 271 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); | |
| 272 write_fully(s, msg, strlen(msg)); | |
| 273 return NULL; | |
| 274 } | |
| 275 } | |
| 276 } | |
| 277 } | |
| 278 off += n; | |
| 279 left -= n; | |
| 280 } while (left > 0 && str_count < expected_str_count); | |
| 281 | |
| 282 if (str_count != expected_str_count) { | |
| 283 return NULL; // incomplete request | |
| 284 } | |
| 285 | |
| 286 // parse request | |
| 287 | |
| 288 ArgumentIterator args(buf, (max_len)-left); | |
| 289 | |
| 290 // version already checked | |
| 291 char* v = args.next(); | |
| 292 | |
| 293 char* name = args.next(); | |
| 294 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { | |
| 295 return NULL; | |
| 296 } | |
| 297 | |
| 298 LinuxAttachOperation* op = new LinuxAttachOperation(name); | |
| 299 | |
| 300 for (int i=0; i<AttachOperation::arg_count_max; i++) { | |
| 301 char* arg = args.next(); | |
| 302 if (arg == NULL) { | |
| 303 op->set_arg(i, NULL); | |
| 304 } else { | |
| 305 if (strlen(arg) > AttachOperation::arg_length_max) { | |
| 306 delete op; | |
| 307 return NULL; | |
| 308 } | |
| 309 op->set_arg(i, arg); | |
| 310 } | |
| 311 } | |
| 312 | |
| 313 op->set_socket(s); | |
| 314 return op; | |
| 315 } | |
| 316 | |
| 317 | |
| 318 // Dequeue an operation | |
| 319 // | |
| 320 // In the Linux implementation there is only a single operation and clients | |
| 321 // cannot queue commands (except at the socket level). | |
| 322 // | |
| 323 LinuxAttachOperation* LinuxAttachListener::dequeue() { | |
| 324 for (;;) { | |
| 325 int s; | |
| 326 | |
| 327 // wait for client to connect | |
| 328 struct sockaddr addr; | |
| 329 socklen_t len = sizeof(addr); | |
| 330 RESTARTABLE(::accept(listener(), &addr, &len), s); | |
| 331 if (s == -1) { | |
| 332 return NULL; // log a warning? | |
| 333 } | |
| 334 | |
| 335 // get the credentials of the peer and check the effective uid/guid | |
| 336 // - check with jeff on this. | |
| 337 struct ucred cred_info; | |
| 338 socklen_t optlen = sizeof(cred_info); | |
| 339 if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) { | |
| 340 int res; | |
| 341 RESTARTABLE(::close(s), res); | |
| 342 continue; | |
| 343 } | |
| 344 uid_t euid = geteuid(); | |
| 345 gid_t egid = getegid(); | |
| 346 | |
| 347 if (cred_info.uid != euid || cred_info.gid != egid) { | |
| 348 int res; | |
| 349 RESTARTABLE(::close(s), res); | |
| 350 continue; | |
| 351 } | |
| 352 | |
| 353 // peer credential look okay so we read the request | |
| 354 LinuxAttachOperation* op = read_request(s); | |
| 355 if (op == NULL) { | |
| 356 int res; | |
| 357 RESTARTABLE(::close(s), res); | |
| 358 continue; | |
| 359 } else { | |
| 360 return op; | |
| 361 } | |
| 362 } | |
| 363 } | |
| 364 | |
| 365 // write the given buffer to the socket | |
| 366 int LinuxAttachListener::write_fully(int s, char* buf, int len) { | |
| 367 do { | |
| 368 int n = ::write(s, buf, len); | |
| 369 if (n == -1) { | |
| 370 if (errno != EINTR) return -1; | |
| 371 } else { | |
| 372 buf += n; | |
| 373 len -= n; | |
| 374 } | |
| 375 } | |
| 376 while (len > 0); | |
| 377 return 0; | |
| 378 } | |
| 379 | |
| 380 // Complete an operation by sending the operation result and any result | |
| 381 // output to the client. At this time the socket is in blocking mode so | |
| 382 // potentially we can block if there is a lot of data and the client is | |
| 383 // non-responsive. For most operations this is a non-issue because the | |
| 384 // default send buffer is sufficient to buffer everything. In the future | |
| 385 // if there are operations that involves a very big reply then it the | |
| 386 // socket could be made non-blocking and a timeout could be used. | |
| 387 | |
| 388 void LinuxAttachOperation::complete(jint result, bufferedStream* st) { | |
| 389 JavaThread* thread = JavaThread::current(); | |
| 390 ThreadBlockInVM tbivm(thread); | |
| 391 | |
| 392 thread->set_suspend_equivalent(); | |
| 393 // cleared by handle_special_suspend_equivalent_condition() or | |
| 394 // java_suspend_self() via check_and_wait_while_suspended() | |
| 395 | |
| 396 // write operation result | |
| 397 char msg[32]; | |
| 398 sprintf(msg, "%d\n", result); | |
| 399 int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg)); | |
| 400 | |
| 401 // write any result data | |
| 402 if (rc == 0) { | |
| 403 LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); | |
| 404 ::shutdown(this->socket(), 2); | |
| 405 } | |
| 406 | |
| 407 // done | |
| 408 RESTARTABLE(::close(this->socket()), rc); | |
| 409 | |
| 410 // were we externally suspended while we were waiting? | |
| 411 thread->check_and_wait_while_suspended(); | |
| 412 | |
| 413 delete this; | |
| 414 } | |
| 415 | |
| 416 | |
| 417 // AttachListener functions | |
| 418 | |
| 419 AttachOperation* AttachListener::dequeue() { | |
| 420 JavaThread* thread = JavaThread::current(); | |
| 421 ThreadBlockInVM tbivm(thread); | |
| 422 | |
| 423 thread->set_suspend_equivalent(); | |
| 424 // cleared by handle_special_suspend_equivalent_condition() or | |
| 425 // java_suspend_self() via check_and_wait_while_suspended() | |
| 426 | |
| 427 AttachOperation* op = LinuxAttachListener::dequeue(); | |
| 428 | |
| 429 // were we externally suspended while we were waiting? | |
| 430 thread->check_and_wait_while_suspended(); | |
| 431 | |
| 432 return op; | |
| 433 } | |
| 434 | |
| 435 int AttachListener::pd_init() { | |
| 436 JavaThread* thread = JavaThread::current(); | |
| 437 ThreadBlockInVM tbivm(thread); | |
| 438 | |
| 439 thread->set_suspend_equivalent(); | |
| 440 // cleared by handle_special_suspend_equivalent_condition() or | |
| 441 // java_suspend_self() via check_and_wait_while_suspended() | |
| 442 | |
| 443 int ret_code = LinuxAttachListener::init(); | |
| 444 | |
| 445 // were we externally suspended while we were waiting? | |
| 446 thread->check_and_wait_while_suspended(); | |
| 447 | |
| 448 return ret_code; | |
| 449 } | |
| 450 | |
| 451 // Attach Listener is started lazily except in the case when | |
| 452 // +ReduseSignalUsage is used | |
| 453 bool AttachListener::init_at_startup() { | |
| 454 if (ReduceSignalUsage) { | |
| 455 return true; | |
| 456 } else { | |
| 457 return false; | |
| 458 } | |
| 459 } | |
| 460 | |
| 461 // If the file .attach_pid<pid> exists in the working directory | |
| 462 // or /tmp then this is the trigger to start the attach mechanism | |
| 463 bool AttachListener::is_init_trigger() { | |
| 464 if (init_at_startup() || is_initialized()) { | |
| 465 return false; // initialized at startup or already initialized | |
| 466 } | |
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467 char fn[PATH_MAX+1]; |
| 0 | 468 sprintf(fn, ".attach_pid%d", os::current_process_id()); |
| 469 int ret; | |
| 470 struct stat64 st; | |
| 471 RESTARTABLE(::stat64(fn, &st), ret); | |
| 472 if (ret == -1) { | |
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473 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", |
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474 os::get_temp_directory(), os::current_process_id()); |
| 0 | 475 RESTARTABLE(::stat64(fn, &st), ret); |
| 476 } | |
| 477 if (ret == 0) { | |
| 478 // simple check to avoid starting the attach mechanism when | |
| 479 // a bogus user creates the file | |
| 480 if (st.st_uid == geteuid()) { | |
| 481 init(); | |
| 482 return true; | |
| 483 } | |
| 484 } | |
| 485 return false; | |
| 486 } | |
| 487 | |
| 488 // if VM aborts then remove listener | |
| 489 void AttachListener::abort() { | |
| 490 listener_cleanup(); | |
| 491 } | |
| 492 | |
| 493 void AttachListener::pd_data_dump() { | |
| 494 os::signal_notify(SIGQUIT); | |
| 495 } | |
| 496 | |
| 497 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { | |
| 498 return NULL; | |
| 499 } | |
| 500 | |
| 501 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { | |
| 502 out->print_cr("flag '%s' cannot be changed", op->arg(0)); | |
| 503 return JNI_ERR; | |
| 504 } | |
| 505 | |
| 506 void AttachListener::pd_detachall() { | |
| 507 // do nothing for now | |
| 508 } |