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 = ::CreateFile( pipe(), // pipe name
276 GENERIC_WRITE, // write only
277 0, // no sharing
278 NULL, // default security attributes
279 OPEN_EXISTING, // opens existing pipe
280 0, // default attributes
281 NULL); // no template file
282 return hPipe;
283 }
284
285 // write to the pipe
286 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {
287 do {
288 DWORD nwrote;
289
290 BOOL fSuccess = WriteFile( hPipe, // pipe handle
291 (LPCVOID)buf, // message
292 (DWORD)len, // message length
293 &nwrote, // bytes written
294 NULL); // not overlapped
295 if (!fSuccess) {
296 return fSuccess;
297 }
298 buf += nwrote;
299 len -= nwrote;
300 } while (len > 0);
301 return TRUE;
302 }
303
304 // Complete the operation:
305 // - open the pipe to the client
306 // - write the operation result (a jint)
307 // - write the operation output (the result stream)
308 //
309 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {
310 JavaThread* thread = JavaThread::current();
311 ThreadBlockInVM tbivm(thread);
312
313 thread->set_suspend_equivalent();
314 // cleared by handle_special_suspend_equivalent_condition() or
315 // java_suspend_self() via check_and_wait_while_suspended()
316
317 HANDLE hPipe = open_pipe();
318 int lastError = (int)::GetLastError();
319 if (hPipe != INVALID_HANDLE_VALUE) {
320 BOOL fSuccess;
321
322 char msg[32];
323 _snprintf(msg, sizeof(msg), "%d\n", result);
324 msg[sizeof(msg) - 1] = '\0';
325
326 fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));
327 if (fSuccess) {
328 fSuccess = write_pipe(hPipe, (char*)result_stream->base(), (int)(result_stream->size()));
329 }
330 lastError = (int)::GetLastError();
331
332 // Need to flush buffers
333 FlushFileBuffers(hPipe);
334 CloseHandle(hPipe);
335
336 if (fSuccess) {
337 log_debug(attach)("wrote result of attach operation %s to pipe %s", name(), pipe());
338 } else {
339 log_error(attach)("failure (%d) writing result of operation %s to pipe %s", lastError, name(), pipe());
340 }
341 } else {
342 log_error(attach)("could not open (%d) pipe %s to send result of operation %s", lastError, pipe(), name());
343 }
344
345 DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);
346 if (res == WAIT_OBJECT_0) {
347
348 // put the operation back on the available list
349 set_next(Win32AttachListener::available());
350 Win32AttachListener::set_available(this);
351
352 ::ReleaseMutex(Win32AttachListener::mutex());
353 }
354
355 // were we externally suspended while we were waiting?
356 thread->check_and_wait_while_suspended();
357 }
358
359
360 // AttachOperation functions
361
362 AttachOperation* AttachListener::dequeue() {
363 JavaThread* thread = JavaThread::current();
364 ThreadBlockInVM tbivm(thread);
365
366 thread->set_suspend_equivalent();
367 // cleared by handle_special_suspend_equivalent_condition() or
368 // java_suspend_self() via check_and_wait_while_suspended()
369
370 AttachOperation* op = Win32AttachListener::dequeue();
371
372 // were we externally suspended while we were waiting?
373 thread->check_and_wait_while_suspended();
374
375 return op;
376 }
377
378 void AttachListener::vm_start() {
379 // nothing to do
380 }
381
382 int AttachListener::pd_init() {
383 return Win32AttachListener::init();
384 }
385
386 // This function is used for Un*x OSes only.
387 // We need not to implement it for Windows.
388 bool AttachListener::check_socket_file() {
389 return false;
390 }
391
392 bool AttachListener::init_at_startup() {
393 return true;
394 }
395
396 // no trigger mechanism on Windows to start Attach Listener lazily
397 bool AttachListener::is_init_trigger() {
398 return false;
399 }
400
401 void AttachListener::abort() {
402 // nothing to do
403 }
404
405 void AttachListener::pd_data_dump() {
406 os::signal_notify(SIGBREAK);
407 }
408
409 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
410 return NULL;
411 }
412
413 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
414 out->print_cr("flag '%s' cannot be changed", op->arg(0));
415 return JNI_ERR;
416 }
417
418 void AttachListener::pd_detachall() {
419 // do nothing for now
420 }
421
422 // Native thread started by remote client executes this.
423 extern "C" {
424 JNIEXPORT jint JNICALL
425 JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
426 return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);
427 }
428
429 } // extern