1 /*
2 * Copyright (c) 2005, 2018, 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.inline.hpp"
27 #include "runtime/os.hpp"
28 #include "services/attachListener.hpp"
29 #include "services/dtraceAttacher.hpp"
30
31 #include <windows.h>
32 #include <signal.h> // SIGBREAK
33 #include <stdio.h>
34
35 // The AttachListener thread services a queue of operations. It blocks in the dequeue
36 // function until an operation is enqueued. A client enqueues an operation by creating
37 // a thread in this process using the Win32 CreateRemoteThread function. That thread
38 // executes a small stub generated by the client. The stub invokes the
39 // JVM_EnqueueOperation function which checks the operation parameters and enqueues
40 // the operation to the queue serviced by the attach listener. The thread created by
41 // the client is a native thread and is restricted to a single page of stack. To keep
42 // it simple operations are pre-allocated at initialization time. An enqueue thus
43 // takes a preallocated operation, populates the operation parameters, adds it to
44 // queue and wakes up the attach listener.
45 //
46 // When an operation has completed the attach listener is required to send the
47 // operation result and any result data to the client. In this implementation the
48 // client is a pipe server. In the enqueue operation it provides the name of pipe
49 // to this process. When the operation is completed this process opens the pipe and
50 // sends the result and output back to the client. Note that writing to the pipe
51 // (and flushing the output) is a blocking operation. This means that a non-responsive
52 // client could potentially hang the attach listener thread indefinitely. In that
53 // case no new operations would be executed but the VM would continue as normal.
54 // As only suitably privileged processes can open this process we concluded that
55 // this wasn't worth worrying about.
56
57
58 // forward reference
59 class Win32AttachOperation;
60
61
62 class Win32AttachListener: AllStatic {
63 private:
64 enum {
65 max_enqueued_operations = 4
66 };
67
68 // protects the preallocated list and the operation list
69 static HANDLE _mutex;
70
71 // head of preallocated operations list
72 static Win32AttachOperation* _avail;
73
74 // head and tail of enqueue operations list
75 static Win32AttachOperation* _head;
76 static Win32AttachOperation* _tail;
77
78
79 static Win32AttachOperation* head() { return _head; }
80 static void set_head(Win32AttachOperation* head) { _head = head; }
81
82 static Win32AttachOperation* tail() { return _tail; }
83 static void set_tail(Win32AttachOperation* tail) { _tail = tail; }
84
85
86 // A semaphore is used for communication about enqueued operations.
87 // The maximum count for the semaphore object will be set to "max_enqueued_operations".
88 // The state of a semaphore is signaled when its count is greater than
89 // zero (there are operations enqueued), and nonsignaled when it is zero.
90 static HANDLE _enqueued_ops_semaphore;
91 static HANDLE enqueued_ops_semaphore() { return _enqueued_ops_semaphore; }
92
93 public:
94 enum {
95 ATTACH_ERROR_DISABLED = 100, // error codes
96 ATTACH_ERROR_RESOURCE = 101,
97 ATTACH_ERROR_ILLEGALARG = 102,
98 ATTACH_ERROR_INTERNAL = 103
99 };
100
101 static int init();
102 static HANDLE mutex() { return _mutex; }
103
104 static Win32AttachOperation* available() { return _avail; }
105 static void set_available(Win32AttachOperation* avail) { _avail = avail; }
106
107 // enqueue an operation to the end of the list
108 static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename);
109
110 // dequeue an operation from from head of the list
111 static Win32AttachOperation* dequeue();
112 };
113
114 // statics
115 HANDLE Win32AttachListener::_mutex;
116 HANDLE Win32AttachListener::_enqueued_ops_semaphore;
117 Win32AttachOperation* Win32AttachListener::_avail;
118 Win32AttachOperation* Win32AttachListener::_head;
119 Win32AttachOperation* Win32AttachListener::_tail;
120
121
122 // Win32AttachOperation is an AttachOperation that additionally encapsulates the name
123 // of a pipe which is used to send the operation reply/output to the client.
124 // Win32AttachOperation can also be linked in a list.
125
126 class Win32AttachOperation: public AttachOperation {
127 private:
128 friend class Win32AttachListener;
129
130 enum {
131 pipe_name_max = 256 // maximum pipe name
132 };
133
134 char _pipe[pipe_name_max + 1];
135
136 const char* pipe() const { return _pipe; }
137 void set_pipe(const char* pipe) {
138 assert(strlen(pipe) <= pipe_name_max, "exceeds maximum length of pipe name");
139 os::snprintf(_pipe, sizeof(_pipe), "%s", pipe);
140 }
141
142 HANDLE open_pipe();
143 static BOOL write_pipe(HANDLE hPipe, char* buf, int len);
144
145 Win32AttachOperation* _next;
146
147 Win32AttachOperation* next() const { return _next; }
148 void set_next(Win32AttachOperation* next) { _next = next; }
149
150 // noarg constructor as operation is preallocated
151 Win32AttachOperation() : AttachOperation("<noname>") {
152 set_pipe("<nopipe>");
153 set_next(NULL);
154 }
155
156 public:
157 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream);
158 };
159
160
161 // Preallocate the maximum number of operations that can be enqueued.
162 int Win32AttachListener::init() {
163 _mutex = (void*)::CreateMutex(NULL, FALSE, NULL);
164 guarantee(_mutex != (HANDLE)NULL, "mutex creation failed");
165
166 _enqueued_ops_semaphore = ::CreateSemaphore(NULL, 0, max_enqueued_operations, NULL);
167 guarantee(_enqueued_ops_semaphore != (HANDLE)NULL, "semaphore creation failed");
168
169 set_head(NULL);
170 set_tail(NULL);
171 set_available(NULL);
172
173 for (int i=0; i<max_enqueued_operations; i++) {
174 Win32AttachOperation* op = new Win32AttachOperation();
175 op->set_next(available());
176 set_available(op);
177 }
178
179 return 0;
180 }
181
182 // Enqueue an operation. This is called from a native thread that is not attached to VM.
183 // Also we need to be careful not to execute anything that results in more than a 4k stack.
184 //
185 int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
186 // listener not running
187 if (!AttachListener::is_initialized()) {
188 return ATTACH_ERROR_DISABLED;
189 }
190
191 // check that all paramteres to the operation
192 if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG;
193 if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
194 if (strlen(arg1) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
195 if (strlen(arg2) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
196 if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG;
197
198 // check for a well-formed pipename
199 if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG;
200
201 // grab the lock for the list
202 DWORD res = ::WaitForSingleObject(mutex(), INFINITE);
203 if (res != WAIT_OBJECT_0) {
204 return ATTACH_ERROR_INTERNAL;
205 }
206
207 // try to get an operation from the available list
208 Win32AttachOperation* op = available();
209 if (op != NULL) {
210 set_available(op->next());
211
212 // add to end (tail) of list
213 op->set_next(NULL);
214 if (tail() == NULL) {
215 set_head(op);
216 } else {
217 tail()->set_next(op);
218 }
219 set_tail(op);
220
221 op->set_name(cmd);
222 op->set_arg(0, arg0);
223 op->set_arg(1, arg1);
224 op->set_arg(2, arg2);
225 op->set_pipe(pipename);
226
227 // Increment number of enqueued operations.
228 // Side effect: Semaphore will be signaled and will release
229 // any blocking waiters (i.e. the AttachListener thread).
230 BOOL not_exceeding_semaphore_maximum_count =
231 ::ReleaseSemaphore(enqueued_ops_semaphore(), 1, NULL);
232 guarantee(not_exceeding_semaphore_maximum_count, "invariant");
233 }
234 ::ReleaseMutex(mutex());
235
236 return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE;
237 }
238
239
240 // dequeue the operation from the head of the operation list.
241 Win32AttachOperation* Win32AttachListener::dequeue() {
242 for (;;) {
243 DWORD res = ::WaitForSingleObject(enqueued_ops_semaphore(), INFINITE);
244 // returning from WaitForSingleObject will have decreased
245 // the current count of the semaphore by 1.
246 guarantee(res == WAIT_OBJECT_0, "wait failed");
247
248 res = ::WaitForSingleObject(mutex(), INFINITE);
249 guarantee(res == WAIT_OBJECT_0, "wait failed");
250
251 Win32AttachOperation* op = head();
252 if (op != NULL) {
253 set_head(op->next());
254 if (head() == NULL) { // list is empty
255 set_tail(NULL);
256 }
257 }
258 ::ReleaseMutex(mutex());
259
260 if (op != NULL) {
261 return op;
262 }
263 }
264 }
265
266
267 // open the pipe to the client
268 HANDLE Win32AttachOperation::open_pipe() {
269 HANDLE hPipe;
270
271 hPipe = ::CreateFile( pipe(), // pipe name
272 GENERIC_WRITE, // write only
273 0, // no sharing
274 NULL, // default security attributes
275 OPEN_EXISTING, // opens existing pipe
276 0, // default attributes
277 NULL); // no template file
278
279 if (hPipe != INVALID_HANDLE_VALUE) {
280 // shouldn't happen as there is a pipe created per operation
281 if (::GetLastError() == ERROR_PIPE_BUSY) {
282 ::CloseHandle(hPipe);
283 return INVALID_HANDLE_VALUE;
284 }
285 }
286 return hPipe;
287 }
288
289 // write to the pipe
290 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {
291 do {
292 DWORD nwrote;
293
294 BOOL fSuccess = WriteFile( hPipe, // pipe handle
295 (LPCVOID)buf, // message
296 (DWORD)len, // message length
297 &nwrote, // bytes written
298 NULL); // not overlapped
299 if (!fSuccess) {
300 return fSuccess;
301 }
302 buf += nwrote;
303 len -= nwrote;
304 }
305 while (len > 0);
306 return TRUE;
307 }
308
309 // Complete the operation:
310 // - open the pipe to the client
311 // - write the operation result (a jint)
312 // - write the operation output (the result stream)
313 //
314 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {
315 JavaThread* thread = JavaThread::current();
316 ThreadBlockInVM tbivm(thread);
317
318 thread->set_suspend_equivalent();
319 // cleared by handle_special_suspend_equivalent_condition() or
320 // java_suspend_self() via check_and_wait_while_suspended()
321
322 HANDLE hPipe = open_pipe();
323 if (hPipe != INVALID_HANDLE_VALUE) {
324 BOOL fSuccess;
325
326 char msg[32];
327 _snprintf(msg, sizeof(msg), "%d\n", result);
328 msg[sizeof(msg) - 1] = '\0';
329
330 fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));
331 if (fSuccess) {
332 fSuccess = write_pipe(hPipe, (char*)result_stream->base(), (int)(result_stream->size()));
333 }
334
335 // Need to flush buffers
336 FlushFileBuffers(hPipe);
337 CloseHandle(hPipe);
338
339 if (fSuccess) {
340 log_debug(attach)("wrote result of attach operation %s to pipe %s", name(), pipe());
341 } else {
342 log_error(attach)("failure writing result of operation %s to pipe %s", name(), pipe());
343 }
344 } else {
345 log_error(attach)("could not open pipe %s to send result of operation %s", pipe(), name());
346 }
347
348 DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);
349 if (res == WAIT_OBJECT_0) {
350
351 // put the operation back on the available list
352 set_next(Win32AttachListener::available());
353 Win32AttachListener::set_available(this);
354
355 ::ReleaseMutex(Win32AttachListener::mutex());
356 }
357
358 // were we externally suspended while we were waiting?
359 thread->check_and_wait_while_suspended();
360 }
361
362
363 // AttachOperation functions
364
365 AttachOperation* AttachListener::dequeue() {
366 JavaThread* thread = JavaThread::current();
367 ThreadBlockInVM tbivm(thread);
368
369 thread->set_suspend_equivalent();
370 // cleared by handle_special_suspend_equivalent_condition() or
371 // java_suspend_self() via check_and_wait_while_suspended()
372
373 AttachOperation* op = Win32AttachListener::dequeue();
374
375 // were we externally suspended while we were waiting?
376 thread->check_and_wait_while_suspended();
377
378 return op;
379 }
380
381 void AttachListener::vm_start() {
382 // nothing to do
383 }
384
385 int AttachListener::pd_init() {
386 return Win32AttachListener::init();
387 }
388
389 bool AttachListener::init_at_startup() {
390 return true;
391 }
392
393 // no trigger mechanism on Windows to start Attach Listener lazily
394 bool AttachListener::is_init_trigger() {
395 return false;
396 }
397
398 void AttachListener::abort() {
399 // nothing to do
400 }
401
402 void AttachListener::pd_data_dump() {
403 os::signal_notify(SIGBREAK);
404 }
405
406 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
407 return NULL;
408 }
409
410 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
411 out->print_cr("flag '%s' cannot be changed", op->arg(0));
412 return JNI_ERR;
413 }
414
415 void AttachListener::pd_detachall() {
416 // do nothing for now
417 }
418
419 // Native thread started by remote client executes this.
420 extern "C" {
421 JNIEXPORT jint JNICALL
422 JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
423 return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);
424 }
425
426 } // extern