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 /*

  * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_attachListener_windows.cpp.incl"

 #include <windows.h>

 #include <signal.h>             // SIGBREAK

 // The AttachListener thread services a queue of operations. It blocks in the dequeue

 // function until an operation is enqueued. A client enqueues an operation by creating

 // a thread in this process using the Win32 CreateRemoteThread function. That thread

 // executes a small stub generated by the client. The stub invokes the

 // JVM_EnqueueOperation function which checks the operation parameters and enqueues

 // the operation to the queue serviced by the attach listener. The thread created by

 // the client is a native thread and is restricted to a single page of stack. To keep

 // it simple operations are pre-allocated at initialization time. An enqueue thus

 // takes a preallocated operation, populates the operation parameters, adds it to

 // queue and wakes up the attach listener.

 //

 // When an operation has completed the attach listener is required to send the

 // operation result and any result data to the client. In this implementation the

 // client is a pipe server. In the enqueue operation it provides the name of pipe

 // to this process. When the operation is completed this process opens the pipe and

 // sends the result and output back to the client. Note that writing to the pipe

 // (and flushing the output) is a blocking operation. This means that a non-responsive

 // client could potentially hang the attach listener thread indefinitely. In that

 // case no new operations would be executed but the VM would continue as normal.

 // As only suitably privileged processes can open this process we concluded that

 // this wasn't worth worrying about.

 // forward reference

 class Win32AttachOperation;

 class Win32AttachListener: AllStatic {

  private:

   enum {

     preallocate_count = 4                   // number of preallocated operations

   };

   // protects the preallocated list and the operation list

   static HANDLE _mutex;

   // head of preallocated operations list

   static Win32AttachOperation* _avail;

   // head and tail of enqueue operations list

   static Win32AttachOperation* _head;

   static Win32AttachOperation* _tail;

   static Win32AttachOperation* head()                       { return _head; }

   static void set_head(Win32AttachOperation* head)          { _head = head; }

   static Win32AttachOperation* tail()                       { return _tail; }

   static void set_tail(Win32AttachOperation* tail)          { _tail = tail; }

   // used to wakeup the listener

   static HANDLE _wakeup;

   static HANDLE wakeup()                                    { return _wakeup; }

  public:

   enum {

     ATTACH_ERROR_DISABLED               = 100,              // error codes

     ATTACH_ERROR_RESOURCE               = 101,

     ATTACH_ERROR_ILLEGALARG             = 102,

     ATTACH_ERROR_INTERNAL               = 103

   };

   static int init();

   static HANDLE mutex()                                     { return _mutex; }

   static Win32AttachOperation* available()                  { return _avail; }

   static void set_available(Win32AttachOperation* avail)    { _avail = avail; }

   // enqueue an operation to the end of the list

   static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename);

   // dequeue an operation from from head of the list

   static Win32AttachOperation* dequeue();

 };

 // statics

 HANDLE Win32AttachListener::_mutex;

 HANDLE Win32AttachListener::_wakeup;

 Win32AttachOperation* Win32AttachListener::_avail;

 Win32AttachOperation* Win32AttachListener::_head;

 Win32AttachOperation* Win32AttachListener::_tail;

 // Win32AttachOperation is an AttachOperation that additionally encapsulates the name

 // of a pipe which is used to send the operation reply/output to the client.

 // Win32AttachOperation can also be linked in a list.

 class Win32AttachOperation: public AttachOperation {

  private:

   friend class Win32AttachListener;

   enum {

     pipe_name_max = 256             // maximum pipe name

   };

   char _pipe[pipe_name_max+1];

   const char* pipe() const                              { return _pipe; }

   void set_pipe(const char* pipe) {

     assert(strlen(pipe) <= pipe_name_max, "execeds maximum length of pipe name");

     strcpy(_pipe, pipe);

   }

   HANDLE open_pipe();

   static BOOL write_pipe(HANDLE hPipe, char* buf, int len);

   Win32AttachOperation* _next;

   Win32AttachOperation* next() const                    { return _next; }

   void set_next(Win32AttachOperation* next)             { _next = next; }

   // noarg constructor as operation is preallocated

   Win32AttachOperation() : AttachOperation("<noname>") {

     set_pipe("<nopipe>");

     set_next(NULL);

   }

  public:

   void Win32AttachOperation::complete(jint result, bufferedStream* result_stream);

 };

 // preallocate the required number of operations

 int Win32AttachListener::init() {

   _mutex = (void*)::CreateMutex(NULL, FALSE, NULL);

   guarantee(_mutex != (HANDLE)NULL, "mutex creation failed");

   _wakeup = ::CreateSemaphore(NULL, 0, 1, NULL);

   guarantee(_wakeup != (HANDLE)NULL, "semaphore creation failed");

   set_head(NULL);

   set_tail(NULL);

   // preallocate a few operations

   set_available(NULL);

   for (int i=0; i<preallocate_count; i++) {

     Win32AttachOperation* op = new Win32AttachOperation();

     op->set_next(available());

     set_available(op);

   }

   return 0;

 }

 // Enqueue an operation. This is called from a native thread that is not attached to VM.

 // Also we need to be careful not to execute anything that results in more than a 4k stack.

 //

 int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {

   // listener not running

   if (!AttachListener::is_initialized()) {

     return ATTACH_ERROR_DISABLED;

   }

   // check that all paramteres to the operation

   if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG;

   if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;

   if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;

   if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG;

   // check for a well-formed pipename

   if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG;

   // grab the lock for the list

   DWORD res = ::WaitForSingleObject(mutex(), INFINITE);

   if (res != WAIT_OBJECT_0) {

     return ATTACH_ERROR_INTERNAL;

   }

   // try to get an operation from the available list

   Win32AttachOperation* op = available();

   if (op != NULL) {

     set_available(op->next());

     // add to end (tail) of list

     op->set_next(NULL);

     if (tail() == NULL) {

       set_head(op);

     } else {

       tail()->set_next(op);

     }

     set_tail(op);

     op->set_name(cmd);

     op->set_arg(0, arg0);

     op->set_arg(1, arg1);

     op->set_arg(2, arg2);

     op->set_pipe(pipename);

     // wakeup the thread waiting for operations

     ::ReleaseSemaphore(wakeup(), 1, NULL);

   }

   ::ReleaseMutex(mutex());

   return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE;

 }

 // dequeue the operation from the head of the operation list. If

 Win32AttachOperation* Win32AttachListener::dequeue() {

   for (;;) {

     DWORD res = ::WaitForSingleObject(wakeup(), INFINITE);

     guarantee(res == WAIT_OBJECT_0, "wait failed");

     res = ::WaitForSingleObject(mutex(), INFINITE);

     guarantee(res == WAIT_OBJECT_0, "wait failed");

     Win32AttachOperation* op = head();

     if (op != NULL) {

       set_head(op->next());

       if (head() == NULL) {     // list is empty

         set_tail(NULL);

       }

     }

     ::ReleaseMutex(mutex());

     if (op != NULL) {

       return op;

     }

   }

 }

 // open the pipe to the client

 HANDLE Win32AttachOperation::open_pipe() {

   HANDLE hPipe;

   hPipe = ::CreateFile( pipe(),  // pipe name

                         GENERIC_WRITE,   // write only

                         0,              // no sharing

                         NULL,           // default security attributes

                         OPEN_EXISTING,  // opens existing pipe

                         0,              // default attributes

                         NULL);          // no template file

   if (hPipe != INVALID_HANDLE_VALUE) {

     // shouldn't happen as there is a pipe created per operation

     if (::GetLastError() == ERROR_PIPE_BUSY) {

       return INVALID_HANDLE_VALUE;

     }

   }

   return hPipe;

 }

 // write to the pipe

 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {

   do {

     DWORD nwrote;

     BOOL fSuccess = WriteFile(  hPipe,                  // pipe handle

                                 (LPCVOID)buf,           // message

                                 (DWORD)len,             // message length

                                 &nwrote,                // bytes written

                                 NULL);                  // not overlapped

     if (!fSuccess) {

       return fSuccess;

     }

     buf += nwrote;

     len -= nwrote;

   }

   while (len > 0);

   return TRUE;

 }

 // Complete the operation:

 //   - open the pipe to the client

 //   - write the operation result (a jint)

 //   - write the operation output (the result stream)

 //

 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {

   JavaThread* thread = JavaThread::current();

   ThreadBlockInVM tbivm(thread);

   thread->set_suspend_equivalent();

   // cleared by handle_special_suspend_equivalent_condition() or

   // java_suspend_self() via check_and_wait_while_suspended()

   HANDLE hPipe = open_pipe();

   if (hPipe != INVALID_HANDLE_VALUE) {

     BOOL fSuccess;

     char msg[32];

     sprintf(msg, "%d\n", result);

     fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));

     if (fSuccess) {

       write_pipe(hPipe, (char*) result_stream->base(), (int)(result_stream->size()));

     }

     // Need to flush buffers

     FlushFileBuffers(hPipe);

     CloseHandle(hPipe);

   }

   DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);

   if (res == WAIT_OBJECT_0) {

     // put the operation back on the available list

     set_next(Win32AttachListener::available());

     Win32AttachListener::set_available(this);

     ::ReleaseMutex(Win32AttachListener::mutex());

   }

   // were we externally suspended while we were waiting?

   thread->check_and_wait_while_suspended();

 }

 // AttachOperation functions

 AttachOperation* AttachListener::dequeue() {

   JavaThread* thread = JavaThread::current();

   ThreadBlockInVM tbivm(thread);

   thread->set_suspend_equivalent();

   // cleared by handle_special_suspend_equivalent_condition() or

   // java_suspend_self() via check_and_wait_while_suspended()

   AttachOperation* op = Win32AttachListener::dequeue();

   // were we externally suspended while we were waiting?

   thread->check_and_wait_while_suspended();

   return op;

 }

 int AttachListener::pd_init() {

   return Win32AttachListener::init();

 }

 // always startup on Windows NT/2000/XP

 bool AttachListener::init_at_startup() {

   return os::win32::is_nt();

 }

 // no trigger mechanism on Windows to start Attach Listener lazily

 bool AttachListener::is_init_trigger() {

   return false;

 }

 void AttachListener::abort() {

   // nothing to do

 }

 void AttachListener::pd_data_dump() {

   os::signal_notify(SIGBREAK);

 }

 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {

   return NULL;

 }

 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {

   out->print_cr("flag '%s' cannot be changed", op->arg(0));

   return JNI_ERR;

 }

 void AttachListener::pd_detachall() {

   // do nothing for now

 }

 // Native thread started by remote client executes this.

 extern "C" {

   JNIEXPORT jint JNICALL

     JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {

       return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);

     }

 } // extern