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 /*

  * Copyright (c) 2005, 2008, 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_linux.cpp.incl"

 #include <unistd.h>

 #include <signal.h>

 #include <sys/types.h>

 #include <sys/socket.h>

 #include <sys/un.h>

 #include <sys/stat.h>

 #ifndef UNIX_PATH_MAX

 #define UNIX_PATH_MAX   sizeof(((struct sockaddr_un *)0)->sun_path)

 #endif

 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener

 // thread is created at startup or is created on-demand via a signal from

 // the client tool. The attach listener creates a socket and binds it to a file

 // in the filesystem. The attach listener then acts as a simple (single-

 // threaded) server - it waits for a client to connect, reads the request,

 // executes it, and returns the response to the client via the socket

 // connection.

 //

 // As the socket is a UNIX domain socket it means that only clients on the

 // local machine can connect. In addition there are two other aspects to

 // the security:

 // 1. The well known file that the socket is bound to has permission 400

 // 2. When a client connect, the SO_PEERCRED socket option is used to

 //    obtain the credentials of client. We check that the effective uid

 //    of the client matches this process.

 // forward reference

 class LinuxAttachOperation;

 class LinuxAttachListener: AllStatic {

  private:

   // the path to which we bind the UNIX domain socket

   static char _path[UNIX_PATH_MAX];

   static bool _has_path;

   // the file descriptor for the listening socket

   static int _listener;

   static void set_path(char* path) {

     if (path == NULL) {

       _has_path = false;

     } else {

       strncpy(_path, path, UNIX_PATH_MAX);

       _path[UNIX_PATH_MAX-1] = '\0';

       _has_path = true;

     }

   }

   static void set_listener(int s)               { _listener = s; }

   // reads a request from the given connected socket

   static LinuxAttachOperation* read_request(int s);

  public:

   enum {

     ATTACH_PROTOCOL_VER = 1                     // protocol version

   };

   enum {

     ATTACH_ERROR_BADVERSION     = 101           // error codes

   };

   // initialize the listener, returns 0 if okay

   static int init();

   static char* path()                   { return _path; }

   static bool has_path()                { return _has_path; }

   static int listener()                 { return _listener; }

   // write the given buffer to a socket

   static int write_fully(int s, char* buf, int len);

   static LinuxAttachOperation* dequeue();

 };

 class LinuxAttachOperation: public AttachOperation {

  private:

   // the connection to the client

   int _socket;

  public:

   void complete(jint res, bufferedStream* st);

   void set_socket(int s)                                { _socket = s; }

   int socket() const                                    { return _socket; }

   LinuxAttachOperation(char* name) : AttachOperation(name) {

     set_socket(-1);

   }

 };

 // statics

 char LinuxAttachListener::_path[UNIX_PATH_MAX];

 bool LinuxAttachListener::_has_path;

 int LinuxAttachListener::_listener = -1;

 // Supporting class to help split a buffer into individual components

 class ArgumentIterator : public StackObj {

  private:

   char* _pos;

   char* _end;

  public:

   ArgumentIterator(char* arg_buffer, size_t arg_size) {

     _pos = arg_buffer;

     _end = _pos + arg_size - 1;

   }

   char* next() {

     if (*_pos == '\0') {

       return NULL;

     }

     char* res = _pos;

     char* next_pos = strchr(_pos, '\0');

     if (next_pos < _end)  {

       next_pos++;

     }

     _pos = next_pos;

     return res;

   }

 };

 // atexit hook to stop listener and unlink the file that it is

 // bound too.

 extern "C" {

   static void listener_cleanup() {

     static int cleanup_done;

     if (!cleanup_done) {

       cleanup_done = 1;

       int s = LinuxAttachListener::listener();

       if (s != -1) {

         ::close(s);

       }

       if (LinuxAttachListener::has_path()) {

         ::unlink(LinuxAttachListener::path());

       }

     }

   }

 }

 // Initialization - create a listener socket and bind it to a file

 int LinuxAttachListener::init() {

   char path[UNIX_PATH_MAX];          // socket file

   char initial_path[UNIX_PATH_MAX];  // socket file during setup

   int listener;                      // listener socket (file descriptor)

   // register function to cleanup

   ::atexit(listener_cleanup);

   int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",

                    os::get_temp_directory(), os::current_process_id());

   if (n <= (int)UNIX_PATH_MAX) {

     n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);

   }

   if (n > (int)UNIX_PATH_MAX) {

     return -1;

   }

   // create the listener socket

   listener = ::socket(PF_UNIX, SOCK_STREAM, 0);

   if (listener == -1) {

     return -1;

   }

   // bind socket

   struct sockaddr_un addr;

   addr.sun_family = AF_UNIX;

   strcpy(addr.sun_path, initial_path);

   ::unlink(initial_path);

   int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));

   if (res == -1) {

     RESTARTABLE(::close(listener), res);

     return -1;

   }

   // put in listen mode, set permissions, and rename into place

   res = ::listen(listener, 5);

   if (res == 0) {

       RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res);

       if (res == 0) {

           res = ::rename(initial_path, path);

       }

   }

   if (res == -1) {

     RESTARTABLE(::close(listener), res);

     ::unlink(initial_path);

     return -1;

   }

   set_path(path);

   set_listener(listener);

   return 0;

 }

 // Given a socket that is connected to a peer we read the request and

 // create an AttachOperation. As the socket is blocking there is potential

 // for a denial-of-service if the peer does not response. However this happens

 // after the peer credentials have been checked and in the worst case it just

 // means that the attach listener thread is blocked.

 //

 LinuxAttachOperation* LinuxAttachListener::read_request(int s) {

   char ver_str[8];

   sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);

   // The request is a sequence of strings so we first figure out the

   // expected count and the maximum possible length of the request.

   // The request is:

   //   <ver>0<cmd>0<arg>0<arg>0<arg>0

   // where <ver> is the protocol version (1), <cmd> is the command

   // name ("load", "datadump", ...), and <arg> is an argument

   int expected_str_count = 2 + AttachOperation::arg_count_max;

   const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +

     AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);

   char buf[max_len];

   int str_count = 0;

   // Read until all (expected) strings have been read, the buffer is

   // full, or EOF.

   int off = 0;

   int left = max_len;

   do {

     int n;

     RESTARTABLE(read(s, buf+off, left), n);

     if (n == -1) {

       return NULL;      // reset by peer or other error

     }

     if (n == 0) {

       break;

     }

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

       if (buf[off+i] == 0) {

         // EOS found

         str_count++;

         // The first string is <ver> so check it now to

         // check for protocol mis-match

         if (str_count == 1) {

           if ((strlen(buf) != strlen(ver_str)) ||

               (atoi(buf) != ATTACH_PROTOCOL_VER)) {

             char msg[32];

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

             write_fully(s, msg, strlen(msg));

             return NULL;

           }

         }

       }

     }

     off += n;

     left -= n;

   } while (left > 0 && str_count < expected_str_count);

   if (str_count != expected_str_count) {

     return NULL;        // incomplete request

   }

   // parse request

   ArgumentIterator args(buf, (max_len)-left);

   // version already checked

   char* v = args.next();

   char* name = args.next();

   if (name == NULL || strlen(name) > AttachOperation::name_length_max) {

     return NULL;

   }

   LinuxAttachOperation* op = new LinuxAttachOperation(name);

   for (int i=0; i<AttachOperation::arg_count_max; i++) {

     char* arg = args.next();

     if (arg == NULL) {

       op->set_arg(i, NULL);

     } else {

       if (strlen(arg) > AttachOperation::arg_length_max) {

         delete op;

         return NULL;

       }

       op->set_arg(i, arg);

     }

   }

   op->set_socket(s);

   return op;

 }

 // Dequeue an operation

 //

 // In the Linux implementation there is only a single operation and clients

 // cannot queue commands (except at the socket level).

 //

 LinuxAttachOperation* LinuxAttachListener::dequeue() {

   for (;;) {

     int s;

     // wait for client to connect

     struct sockaddr addr;

     socklen_t len = sizeof(addr);

     RESTARTABLE(::accept(listener(), &addr, &len), s);

     if (s == -1) {

       return NULL;      // log a warning?

     }

     // get the credentials of the peer and check the effective uid/guid

     // - check with jeff on this.

     struct ucred cred_info;

     socklen_t optlen = sizeof(cred_info);

     if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) {

       int res;

       RESTARTABLE(::close(s), res);

       continue;

     }

     uid_t euid = geteuid();

     gid_t egid = getegid();

     if (cred_info.uid != euid || cred_info.gid != egid) {

       int res;

       RESTARTABLE(::close(s), res);

       continue;

     }

     // peer credential look okay so we read the request

     LinuxAttachOperation* op = read_request(s);

     if (op == NULL) {

       int res;

       RESTARTABLE(::close(s), res);

       continue;

     } else {

       return op;

     }

   }

 }

 // write the given buffer to the socket

 int LinuxAttachListener::write_fully(int s, char* buf, int len) {

   do {

     int n = ::write(s, buf, len);

     if (n == -1) {

       if (errno != EINTR) return -1;

     } else {

       buf += n;

       len -= n;

     }

   }

   while (len > 0);

   return 0;

 }

 // Complete an operation by sending the operation result and any result

 // output to the client. At this time the socket is in blocking mode so

 // potentially we can block if there is a lot of data and the client is

 // non-responsive. For most operations this is a non-issue because the

 // default send buffer is sufficient to buffer everything. In the future

 // if there are operations that involves a very big reply then it the

 // socket could be made non-blocking and a timeout could be used.

 void LinuxAttachOperation::complete(jint result, bufferedStream* st) {

   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()

   // write operation result

   char msg[32];

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

   int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg));

   // write any result data

   if (rc == 0) {

     LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());

     ::shutdown(this->socket(), 2);

   }

   // done

   RESTARTABLE(::close(this->socket()), rc);

   // were we externally suspended while we were waiting?

   thread->check_and_wait_while_suspended();

   delete this;

 }

 // AttachListener 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 = LinuxAttachListener::dequeue();

   // were we externally suspended while we were waiting?

   thread->check_and_wait_while_suspended();

   return op;

 }

 int AttachListener::pd_init() {

   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()

   int ret_code = LinuxAttachListener::init();

   // were we externally suspended while we were waiting?

   thread->check_and_wait_while_suspended();

   return ret_code;

 }

 // Attach Listener is started lazily except in the case when

 // +ReduseSignalUsage is used

 bool AttachListener::init_at_startup() {

   if (ReduceSignalUsage) {

     return true;

   } else {

     return false;

   }

 }

 // If the file .attach_pid<pid> exists in the working directory

 // or /tmp then this is the trigger to start the attach mechanism

 bool AttachListener::is_init_trigger() {

   if (init_at_startup() || is_initialized()) {

     return false;               // initialized at startup or already initialized

   }

   char fn[PATH_MAX+1];

   sprintf(fn, ".attach_pid%d", os::current_process_id());

   int ret;

   struct stat64 st;

   RESTARTABLE(::stat64(fn, &st), ret);

   if (ret == -1) {

     snprintf(fn, sizeof(fn), "%s/.attach_pid%d",

              os::get_temp_directory(), os::current_process_id());

     RESTARTABLE(::stat64(fn, &st), ret);

   }

   if (ret == 0) {

     // simple check to avoid starting the attach mechanism when

     // a bogus user creates the file

     if (st.st_uid == geteuid()) {

       init();

       return true;

     }

   }

   return false;

 }

 // if VM aborts then remove listener

 void AttachListener::abort() {

   listener_cleanup();

 }

 void AttachListener::pd_data_dump() {

   os::signal_notify(SIGQUIT);

 }

 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

 }