1 /* 2 * Copyright (c) 2005, 2019, 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 "logging/log.hpp" 27 #include "runtime/interfaceSupport.inline.hpp" 28 #include "runtime/os.hpp" 29 #include "services/attachListener.hpp" 30 #include "services/dtraceAttacher.hpp" 31 32 #include <windows.h> 33 #include <signal.h> // SIGBREAK 34 #include <stdio.h> 35 36 // The AttachListener thread services a queue of operations. It blocks in the dequeue 37 // function until an operation is enqueued. A client enqueues an operation by creating 38 // a thread in this process using the Win32 CreateRemoteThread function. That thread 39 // executes a small stub generated by the client. The stub invokes the 40 // JVM_EnqueueOperation function which checks the operation parameters and enqueues 41 // the operation to the queue serviced by the attach listener. The thread created by 42 // the client is a native thread and is restricted to a single page of stack. To keep 43 // it simple operations are pre-allocated at initialization time. An enqueue thus 44 // takes a preallocated operation, populates the operation parameters, adds it to 45 // queue and wakes up the attach listener. 46 // 47 // When an operation has completed the attach listener is required to send the 48 // operation result and any result data to the client. In this implementation the 49 // client is a pipe server. In the enqueue operation it provides the name of pipe 50 // to this process. When the operation is completed this process opens the pipe and 51 // sends the result and output back to the client. Note that writing to the pipe 52 // (and flushing the output) is a blocking operation. This means that a non-responsive 53 // client could potentially hang the attach listener thread indefinitely. In that 54 // case no new operations would be executed but the VM would continue as normal. 55 // As only suitably privileged processes can open this process we concluded that 56 // this wasn't worth worrying about. 57 58 59 // forward reference 60 class Win32AttachOperation; 61 62 63 class Win32AttachListener: AllStatic { 64 private: 65 enum { 66 max_enqueued_operations = 4 67 }; 68 69 // protects the preallocated list and the operation list 70 static HANDLE _mutex; 71 72 // head of preallocated operations list 73 static Win32AttachOperation* _avail; 74 75 // head and tail of enqueue operations list 76 static Win32AttachOperation* _head; 77 static Win32AttachOperation* _tail; 78 79 80 static Win32AttachOperation* head() { return _head; } 81 static void set_head(Win32AttachOperation* head) { _head = head; } 82 83 static Win32AttachOperation* tail() { return _tail; } 84 static void set_tail(Win32AttachOperation* tail) { _tail = tail; } 85 86 87 // A semaphore is used for communication about enqueued operations. 88 // The maximum count for the semaphore object will be set to "max_enqueued_operations". 89 // The state of a semaphore is signaled when its count is greater than 90 // zero (there are operations enqueued), and nonsignaled when it is zero. 91 static HANDLE _enqueued_ops_semaphore; 92 static HANDLE enqueued_ops_semaphore() { return _enqueued_ops_semaphore; } 93 94 public: 95 enum { 96 ATTACH_ERROR_DISABLED = 100, // error codes 97 ATTACH_ERROR_RESOURCE = 101, 98 ATTACH_ERROR_ILLEGALARG = 102, 99 ATTACH_ERROR_INTERNAL = 103 100 }; 101 102 static int init(); 103 static HANDLE mutex() { return _mutex; } 104 105 static Win32AttachOperation* available() { return _avail; } 106 static void set_available(Win32AttachOperation* avail) { _avail = avail; } 107 108 // enqueue an operation to the end of the list 109 static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename); 110 111 // dequeue an operation from from head of the list 112 static Win32AttachOperation* dequeue(); 113 }; 114 115 // statics 116 HANDLE Win32AttachListener::_mutex; 117 HANDLE Win32AttachListener::_enqueued_ops_semaphore; 118 Win32AttachOperation* Win32AttachListener::_avail; 119 Win32AttachOperation* Win32AttachListener::_head; 120 Win32AttachOperation* Win32AttachListener::_tail; 121 122 123 // Win32AttachOperation is an AttachOperation that additionally encapsulates the name 124 // of a pipe which is used to send the operation reply/output to the client. 125 // Win32AttachOperation can also be linked in a list. 126 127 class Win32AttachOperation: public AttachOperation { 128 private: 129 friend class Win32AttachListener; 130 131 enum { 132 pipe_name_max = 256 // maximum pipe name 133 }; 134 135 char _pipe[pipe_name_max + 1]; 136 137 const char* pipe() const { return _pipe; } 138 void set_pipe(const char* pipe) { 139 assert(strlen(pipe) <= pipe_name_max, "exceeds maximum length of pipe name"); 140 os::snprintf(_pipe, sizeof(_pipe), "%s", pipe); 141 } 142 143 HANDLE open_pipe(); 144 static BOOL write_pipe(HANDLE hPipe, char* buf, int len); 145 146 Win32AttachOperation* _next; 147 148 Win32AttachOperation* next() const { return _next; } 149 void set_next(Win32AttachOperation* next) { _next = next; } 150 151 // noarg constructor as operation is preallocated 152 Win32AttachOperation() : AttachOperation("<noname>") { 153 set_pipe("<nopipe>"); 154 set_next(NULL); 155 } 156 157 public: 158 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream); 159 }; 160 161 162 // Preallocate the maximum number of operations that can be enqueued. 163 int Win32AttachListener::init() { 164 _mutex = (void*)::CreateMutex(NULL, FALSE, NULL); 165 guarantee(_mutex != (HANDLE)NULL, "mutex creation failed"); 166 167 _enqueued_ops_semaphore = ::CreateSemaphore(NULL, 0, max_enqueued_operations, NULL); 168 guarantee(_enqueued_ops_semaphore != (HANDLE)NULL, "semaphore creation failed"); 169 170 set_head(NULL); 171 set_tail(NULL); 172 set_available(NULL); 173 174 for (int i=0; i<max_enqueued_operations; i++) { 175 Win32AttachOperation* op = new Win32AttachOperation(); 176 op->set_next(available()); 177 set_available(op); 178 } 179 180 return 0; 181 } 182 183 // Enqueue an operation. This is called from a native thread that is not attached to VM. 184 // Also we need to be careful not to execute anything that results in more than a 4k stack. 185 // 186 int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) { 187 // wait up to 10 seconds for listener to be up and running 188 int sleep_count = 0; 189 while (!AttachListener::is_initialized()) { 190 Sleep(1000); // 1 second 191 sleep_count++; 192 if (sleep_count > 10) { // try for 10 seconds 193 return ATTACH_ERROR_DISABLED; 194 } 195 } 196 197 // check that all paramteres to the operation 198 if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG; 199 if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG; 200 if (strlen(arg1) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG; 201 if (strlen(arg2) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG; 202 if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG; 203 204 // check for a well-formed pipename 205 if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG; 206 207 // grab the lock for the list 208 DWORD res = ::WaitForSingleObject(mutex(), INFINITE); 209 if (res != WAIT_OBJECT_0) { 210 return ATTACH_ERROR_INTERNAL; 211 } 212 213 // try to get an operation from the available list 214 Win32AttachOperation* op = available(); 215 if (op != NULL) { 216 set_available(op->next()); 217 218 // add to end (tail) of list 219 op->set_next(NULL); 220 if (tail() == NULL) { 221 set_head(op); 222 } else { 223 tail()->set_next(op); 224 } 225 set_tail(op); 226 227 op->set_name(cmd); 228 op->set_arg(0, arg0); 229 op->set_arg(1, arg1); 230 op->set_arg(2, arg2); 231 op->set_pipe(pipename); 232 233 // Increment number of enqueued operations. 234 // Side effect: Semaphore will be signaled and will release 235 // any blocking waiters (i.e. the AttachListener thread). 236 BOOL not_exceeding_semaphore_maximum_count = 237 ::ReleaseSemaphore(enqueued_ops_semaphore(), 1, NULL); 238 guarantee(not_exceeding_semaphore_maximum_count, "invariant"); 239 } 240 ::ReleaseMutex(mutex()); 241 242 return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE; 243 } 244 245 246 // dequeue the operation from the head of the operation list. 247 Win32AttachOperation* Win32AttachListener::dequeue() { 248 for (;;) { 249 DWORD res = ::WaitForSingleObject(enqueued_ops_semaphore(), INFINITE); 250 // returning from WaitForSingleObject will have decreased 251 // the current count of the semaphore by 1. 252 guarantee(res == WAIT_OBJECT_0, "wait failed"); 253 254 res = ::WaitForSingleObject(mutex(), INFINITE); 255 guarantee(res == WAIT_OBJECT_0, "wait failed"); 256 257 Win32AttachOperation* op = head(); 258 if (op != NULL) { 259 set_head(op->next()); 260 if (head() == NULL) { // list is empty 261 set_tail(NULL); 262 } 263 } 264 ::ReleaseMutex(mutex()); 265 266 if (op != NULL) { 267 return op; 268 } 269 } 270 } 271 272 273 // open the pipe to the client 274 HANDLE Win32AttachOperation::open_pipe() { 275 HANDLE hPipe; 276 277 hPipe = ::CreateFile( pipe(), // pipe name 278 GENERIC_WRITE, // write only 279 0, // no sharing 280 NULL, // default security attributes 281 OPEN_EXISTING, // opens existing pipe 282 0, // default attributes 283 NULL); // no template file 284 285 if (hPipe != INVALID_HANDLE_VALUE) { 286 // shouldn't happen as there is a pipe created per operation 287 if (::GetLastError() == ERROR_PIPE_BUSY) { 288 ::CloseHandle(hPipe); 289 return INVALID_HANDLE_VALUE; 290 } 291 } 292 return hPipe; 293 } 294 295 // write to the pipe 296 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) { 297 do { 298 DWORD nwrote; 299 300 BOOL fSuccess = WriteFile( hPipe, // pipe handle 301 (LPCVOID)buf, // message 302 (DWORD)len, // message length 303 &nwrote, // bytes written 304 NULL); // not overlapped 305 if (!fSuccess) { 306 return fSuccess; 307 } 308 buf += nwrote; 309 len -= nwrote; 310 } 311 while (len > 0); 312 return TRUE; 313 } 314 315 // Complete the operation: 316 // - open the pipe to the client 317 // - write the operation result (a jint) 318 // - write the operation output (the result stream) 319 // 320 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) { 321 JavaThread* thread = JavaThread::current(); 322 ThreadBlockInVM tbivm(thread); 323 324 thread->set_suspend_equivalent(); 325 // cleared by handle_special_suspend_equivalent_condition() or 326 // java_suspend_self() via check_and_wait_while_suspended() 327 328 HANDLE hPipe = open_pipe(); 329 if (hPipe != INVALID_HANDLE_VALUE) { 330 BOOL fSuccess; 331 332 char msg[32]; 333 _snprintf(msg, sizeof(msg), "%d\n", result); 334 msg[sizeof(msg) - 1] = '\0'; 335 336 fSuccess = write_pipe(hPipe, msg, (int)strlen(msg)); 337 if (fSuccess) { 338 fSuccess = write_pipe(hPipe, (char*)result_stream->base(), (int)(result_stream->size())); 339 } 340 341 // Need to flush buffers 342 FlushFileBuffers(hPipe); 343 CloseHandle(hPipe); 344 345 if (fSuccess) { 346 log_debug(attach)("wrote result of attach operation %s to pipe %s", name(), pipe()); 347 } else { 348 log_error(attach)("failure writing result of operation %s to pipe %s", name(), pipe()); 349 } 350 } else { 351 log_error(attach)("could not open pipe %s to send result of operation %s", pipe(), name()); 352 } 353 354 DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE); 355 if (res == WAIT_OBJECT_0) { 356 357 // put the operation back on the available list 358 set_next(Win32AttachListener::available()); 359 Win32AttachListener::set_available(this); 360 361 ::ReleaseMutex(Win32AttachListener::mutex()); 362 } 363 364 // were we externally suspended while we were waiting? 365 thread->check_and_wait_while_suspended(); 366 } 367 368 369 // AttachOperation functions 370 371 AttachOperation* AttachListener::dequeue() { 372 JavaThread* thread = JavaThread::current(); 373 ThreadBlockInVM tbivm(thread); 374 375 thread->set_suspend_equivalent(); 376 // cleared by handle_special_suspend_equivalent_condition() or 377 // java_suspend_self() via check_and_wait_while_suspended() 378 379 AttachOperation* op = Win32AttachListener::dequeue(); 380 381 // were we externally suspended while we were waiting? 382 thread->check_and_wait_while_suspended(); 383 384 return op; 385 } 386 387 void AttachListener::vm_start() { 388 // nothing to do 389 } 390 391 int AttachListener::pd_init() { 392 return Win32AttachListener::init(); 393 } 394 395 // This function is used for Un*x OSes only. 396 // We need not to implement it for Windows. 397 bool AttachListener::check_socket_file() { 398 return false; 399 } 400 401 bool AttachListener::init_at_startup() { 402 return true; 403 } 404 405 // no trigger mechanism on Windows to start Attach Listener lazily 406 bool AttachListener::is_init_trigger() { 407 return false; 408 } 409 410 void AttachListener::abort() { 411 // nothing to do 412 } 413 414 void AttachListener::pd_data_dump() { 415 os::signal_notify(SIGBREAK); 416 } 417 418 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 419 return NULL; 420 } 421 422 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 423 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 424 return JNI_ERR; 425 } 426 427 void AttachListener::pd_detachall() { 428 // do nothing for now 429 } 430 431 // Native thread started by remote client executes this. 432 extern "C" { 433 JNIEXPORT jint JNICALL 434 JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) { 435 return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename); 436 } 437 438 } // extern