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 "runtime/interfaceSupport.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
34 // The AttachListener thread services a queue of operations. It blocks in the dequeue
35 // function until an operation is enqueued. A client enqueues an operation by creating
36 // a thread in this process using the Win32 CreateRemoteThread function. That thread
37 // executes a small stub generated by the client. The stub invokes the
38 // JVM_EnqueueOperation function which checks the operation parameters and enqueues
39 // the operation to the queue serviced by the attach listener. The thread created by
40 // the client is a native thread and is restricted to a single page of stack. To keep
41 // it simple operations are pre-allocated at initialization time. An enqueue thus
42 // takes a preallocated operation, populates the operation parameters, adds it to
43 // queue and wakes up the attach listener.
44 //
45 // When an operation has completed the attach listener is required to send the
46 // operation result and any result data to the client. In this implementation the
47 // client is a pipe server. In the enqueue operation it provides the name of pipe
48 // to this process. When the operation is completed this process opens the pipe and
49 // sends the result and output back to the client. Note that writing to the pipe
50 // (and flushing the output) is a blocking operation. This means that a non-responsive
51 // client could potentially hang the attach listener thread indefinitely. In that
52 // case no new operations would be executed but the VM would continue as normal.
53 // As only suitably privileged processes can open this process we concluded that
54 // this wasn't worth worrying about.
55
56
57 // forward reference
58 class Win32AttachOperation;
59
60
61 class Win32AttachListener: AllStatic {
62 private:
63 enum {
64 preallocate_count = 4 // number of preallocated operations
65 };
66
67 // protects the preallocated list and the operation list
68 static HANDLE _mutex;
69
70 // head of preallocated operations list
71 static Win32AttachOperation* _avail;
72
73 // head and tail of enqueue operations list
74 static Win32AttachOperation* _head;
75 static Win32AttachOperation* _tail;
76
77
78 static Win32AttachOperation* head() { return _head; }
79 static void set_head(Win32AttachOperation* head) { _head = head; }
80
81 static Win32AttachOperation* tail() { return _tail; }
82 static void set_tail(Win32AttachOperation* tail) { _tail = tail; }
83
84
85 // used to wakeup the listener
86 static HANDLE _wakeup;
87 static HANDLE wakeup() { return _wakeup; }
88
89 public:
90 enum {
91 ATTACH_ERROR_DISABLED = 100, // error codes
92 ATTACH_ERROR_RESOURCE = 101,
93 ATTACH_ERROR_ILLEGALARG = 102,
94 ATTACH_ERROR_INTERNAL = 103
95 };
96
97 static int init();
98 static HANDLE mutex() { return _mutex; }
99
100 static Win32AttachOperation* available() { return _avail; }
101 static void set_available(Win32AttachOperation* avail) { _avail = avail; }
102
103 // enqueue an operation to the end of the list
104 static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename);
105
106 // dequeue an operation from from head of the list
107 static Win32AttachOperation* dequeue();
108 };
109
110 // statics
111 HANDLE Win32AttachListener::_mutex;
112 HANDLE Win32AttachListener::_wakeup;
113 Win32AttachOperation* Win32AttachListener::_avail;
114 Win32AttachOperation* Win32AttachListener::_head;
115 Win32AttachOperation* Win32AttachListener::_tail;
116
117
118 // Win32AttachOperation is an AttachOperation that additionally encapsulates the name
119 // of a pipe which is used to send the operation reply/output to the client.
120 // Win32AttachOperation can also be linked in a list.
121
122 class Win32AttachOperation: public AttachOperation {
123 private:
124 friend class Win32AttachListener;
125
126 enum {
127 pipe_name_max = 256 // maximum pipe name
128 };
129
130 char _pipe[pipe_name_max+1];
131
132 const char* pipe() const { return _pipe; }
133 void set_pipe(const char* pipe) {
134 assert(strlen(pipe) <= pipe_name_max, "execeds maximum length of pipe name");
135 strcpy(_pipe, pipe);
136 }
137
138 HANDLE open_pipe();
139 static BOOL write_pipe(HANDLE hPipe, char* buf, int len);
140
141 Win32AttachOperation* _next;
142
143 Win32AttachOperation* next() const { return _next; }
144 void set_next(Win32AttachOperation* next) { _next = next; }
145
146 // noarg constructor as operation is preallocated
147 Win32AttachOperation() : AttachOperation("<noname>") {
148 set_pipe("<nopipe>");
149 set_next(NULL);
150 }
151
152 public:
153 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream);
154 };
155
156
157 // preallocate the required number of operations
158 int Win32AttachListener::init() {
159 _mutex = (void*)::CreateMutex(NULL, FALSE, NULL);
160 guarantee(_mutex != (HANDLE)NULL, "mutex creation failed");
161
162 _wakeup = ::CreateSemaphore(NULL, 0, 1, NULL);
163 guarantee(_wakeup != (HANDLE)NULL, "semaphore creation failed");
164
165 set_head(NULL);
166 set_tail(NULL);
167
168 // preallocate a few operations
169 set_available(NULL);
170 for (int i=0; i<preallocate_count; i++) {
171 Win32AttachOperation* op = new Win32AttachOperation();
172 op->set_next(available());
173 set_available(op);
174 }
175
176 return 0;
177 }
178
179 // Enqueue an operation. This is called from a native thread that is not attached to VM.
180 // Also we need to be careful not to execute anything that results in more than a 4k stack.
181 //
182 int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
183 // listener not running
184 if (!AttachListener::is_initialized()) {
185 return ATTACH_ERROR_DISABLED;
186 }
187
188 // check that all paramteres to the operation
189 if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG;
190 if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
191 if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
192 if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG;
193
194 // check for a well-formed pipename
195 if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG;
196
197 // grab the lock for the list
198 DWORD res = ::WaitForSingleObject(mutex(), INFINITE);
199 if (res != WAIT_OBJECT_0) {
200 return ATTACH_ERROR_INTERNAL;
201 }
202
203 // try to get an operation from the available list
204 Win32AttachOperation* op = available();
205 if (op != NULL) {
206 set_available(op->next());
207
208 // add to end (tail) of list
209 op->set_next(NULL);
210 if (tail() == NULL) {
211 set_head(op);
212 } else {
213 tail()->set_next(op);
214 }
215 set_tail(op);
216
217 op->set_name(cmd);
218 op->set_arg(0, arg0);
219 op->set_arg(1, arg1);
220 op->set_arg(2, arg2);
221 op->set_pipe(pipename);
222
223 // wakeup the thread waiting for operations
224 ::ReleaseSemaphore(wakeup(), 1, NULL);
225 }
226 ::ReleaseMutex(mutex());
227
228 return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE;
229 }
230
231
232 // dequeue the operation from the head of the operation list. If
233 Win32AttachOperation* Win32AttachListener::dequeue() {
234 for (;;) {
235 DWORD res = ::WaitForSingleObject(wakeup(), INFINITE);
236 guarantee(res == WAIT_OBJECT_0, "wait failed");
237
238 res = ::WaitForSingleObject(mutex(), INFINITE);
239 guarantee(res == WAIT_OBJECT_0, "wait failed");
240
241 Win32AttachOperation* op = head();
242 if (op != NULL) {
243 set_head(op->next());
244 if (head() == NULL) { // list is empty
245 set_tail(NULL);
246 }
247 }
248 ::ReleaseMutex(mutex());
249
250 if (op != NULL) {
251 return op;
252 }
253 }
254 }
255
256
257 // open the pipe to the client
258 HANDLE Win32AttachOperation::open_pipe() {
259 HANDLE hPipe;
260
261 hPipe = ::CreateFile( pipe(), // pipe name
262 GENERIC_WRITE, // write only
263 0, // no sharing
264 NULL, // default security attributes
265 OPEN_EXISTING, // opens existing pipe
266 0, // default attributes
267 NULL); // no template file
268
269 if (hPipe != INVALID_HANDLE_VALUE) {
270 // shouldn't happen as there is a pipe created per operation
271 if (::GetLastError() == ERROR_PIPE_BUSY) {
272 return INVALID_HANDLE_VALUE;
273 }
274 }
275 return hPipe;
276 }
277
278 // write to the pipe
279 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {
280 do {
281 DWORD nwrote;
282
283 BOOL fSuccess = WriteFile( hPipe, // pipe handle
284 (LPCVOID)buf, // message
285 (DWORD)len, // message length
286 &nwrote, // bytes written
287 NULL); // not overlapped
288 if (!fSuccess) {
289 return fSuccess;
290 }
291 buf += nwrote;
292 len -= nwrote;
293 }
294 while (len > 0);
295 return TRUE;
296 }
297
298 // Complete the operation:
299 // - open the pipe to the client
300 // - write the operation result (a jint)
301 // - write the operation output (the result stream)
302 //
303 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {
304 JavaThread* thread = JavaThread::current();
305 ThreadBlockInVM tbivm(thread);
306
307 thread->set_suspend_equivalent();
308 // cleared by handle_special_suspend_equivalent_condition() or
309 // java_suspend_self() via check_and_wait_while_suspended()
310
311 HANDLE hPipe = open_pipe();
312 if (hPipe != INVALID_HANDLE_VALUE) {
313 BOOL fSuccess;
314
315 char msg[32];
316 sprintf(msg, "%d\n", result);
317
318 fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));
319 if (fSuccess) {
320 write_pipe(hPipe, (char*) result_stream->base(), (int)(result_stream->size()));
321 }
322
323 // Need to flush buffers
324 FlushFileBuffers(hPipe);
325 CloseHandle(hPipe);
326 }
327
328 DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);
329 if (res == WAIT_OBJECT_0) {
330
331 // put the operation back on the available list
332 set_next(Win32AttachListener::available());
333 Win32AttachListener::set_available(this);
334
335 ::ReleaseMutex(Win32AttachListener::mutex());
336 }
337
338 // were we externally suspended while we were waiting?
339 thread->check_and_wait_while_suspended();
340 }
341
342
343 // AttachOperation functions
344
345 AttachOperation* AttachListener::dequeue() {
346 JavaThread* thread = JavaThread::current();
347 ThreadBlockInVM tbivm(thread);
348
349 thread->set_suspend_equivalent();
350 // cleared by handle_special_suspend_equivalent_condition() or
351 // java_suspend_self() via check_and_wait_while_suspended()
352
353 AttachOperation* op = Win32AttachListener::dequeue();
354
355 // were we externally suspended while we were waiting?
356 thread->check_and_wait_while_suspended();
357
358 return op;
359 }
360
361 void AttachListener::vm_start() {
362 // nothing to do
363 }
364
365 int AttachListener::pd_init() {
366 return Win32AttachListener::init();
367 }
368
369 // This function is used for Un*x OSes only.
370 // We need not to implement it for Windows.
371 bool AttachListener::check_socket_file() {
372 return false;
373 }
374
375 // always startup on Windows NT/2000/XP
376 bool AttachListener::init_at_startup() {
377 return os::win32::is_nt();
378 }
379
380 // no trigger mechanism on Windows to start Attach Listener lazily
381 bool AttachListener::is_init_trigger() {
382 return false;
383 }
384
385 void AttachListener::abort() {
386 // nothing to do
387 }
388
389 void AttachListener::pd_data_dump() {
390 os::signal_notify(SIGBREAK);
391 }
392
393 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
394 return NULL;
395 }
396
397 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
398 out->print_cr("flag '%s' cannot be changed", op->arg(0));
399 return JNI_ERR;
400 }
401
402 void AttachListener::pd_detachall() {
403 // do nothing for now
404 }
405
406 // Native thread started by remote client executes this.
407 extern "C" {
408 JNIEXPORT jint JNICALL
409 JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
410 return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);
411 }
412
413 } // extern