/*

 * Copyright (c) 2005, 2018, 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 "precompiled.hpp"

#include "logging/log.hpp"

#include "runtime/interfaceSupport.inline.hpp"

#include "runtime/os.inline.hpp"

#include "services/attachListener.hpp"

#include "services/dtraceAttacher.hpp"

#include "utilities/vmError.hpp"

#include <door.h>

#include <limits.h>

#include <string.h>

#include <signal.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <sys/stat.h>

// stropts.h uses STR in stream ioctl defines

#undef STR

#include <stropts.h>

#undef STR

#define STR(a) #a

// The attach mechanism on Solaris is implemented using the Doors IPC

// mechanism. The first tool to attempt to attach causes the attach

// listener thread to startup. This thread creats a door that is

// associated with a function that enqueues an operation to the attach

// listener. The door is attached to a file in the file system so that

// client (tools) can locate it. To enqueue an operation to the VM the

// client calls through the door which invokes the enqueue function in

// this process. The credentials of the client are checked and if the

// effective uid matches this process then the operation is enqueued.

// When an operation completes the attach listener is required to send the

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

// the result is returned via a UNIX domain socket. A pair of connected

// sockets (socketpair) is created in the enqueue function and the file

// descriptor for one of the sockets is returned to the client as the

// return from the door call. The other end is retained in this process.

// When the operation completes the result is sent to the client and

// the socket is closed.

// forward reference

class SolarisAttachOperation;

class SolarisAttachListener: AllStatic {

 private:

  // the path to which we attach the door file descriptor

  static char _door_path[PATH_MAX+1];

  static volatile bool _has_door_path;

  // door descriptor returned by door_create

  static int _door_descriptor;

  static void set_door_path(char* path) {

    if (path == NULL) {

      _has_door_path = false;

    } else {

      strncpy(_door_path, path, PATH_MAX);

      _door_path[PATH_MAX] = '\0';      // ensure it's nul terminated

      _has_door_path = true;

    }

  }

  static void set_door_descriptor(int dd)               { _door_descriptor = dd; }

  // mutex to protect operation list

  static mutex_t _mutex;

  // semaphore to wakeup listener thread

  static sema_t _wakeup;

  static mutex_t* mutex()                               { return &_mutex; }

  static sema_t* wakeup()                               { return &_wakeup; }

  // enqueued operation list

  static SolarisAttachOperation* _head;

  static SolarisAttachOperation* _tail;

  static SolarisAttachOperation* head()                 { return _head; }

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

  static SolarisAttachOperation* tail()                 { return _tail; }

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

  // create the door

  static int create_door();

 public:

  enum {

    ATTACH_PROTOCOL_VER = 1                             // protocol version

  };

  enum {

    ATTACH_ERROR_BADREQUEST     = 100,                  // error code returned by

    ATTACH_ERROR_BADVERSION     = 101,                  // the door call

    ATTACH_ERROR_RESOURCE       = 102,

    ATTACH_ERROR_INTERNAL       = 103,

    ATTACH_ERROR_DENIED         = 104

  };

  // initialize the listener

  static int init();

  static bool has_door_path()                           { return _has_door_path; }

  static char* door_path()                              { return _door_path; }

  static int door_descriptor()                          { return _door_descriptor; }

  // enqueue an operation

  static void enqueue(SolarisAttachOperation* op);

  // dequeue an operation

  static SolarisAttachOperation* dequeue();

};

// SolarisAttachOperation is an AttachOperation that additionally encapsulates

// a socket connection to the requesting client/tool. SolarisAttachOperation

// can additionally be held in a linked list.

class SolarisAttachOperation: public AttachOperation {

 private:

  friend class SolarisAttachListener;

  // connection to client

  int _socket;

  // linked list support

  SolarisAttachOperation* _next;

  SolarisAttachOperation* next()                         { return _next; }

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

 public:

  void complete(jint res, bufferedStream* st);

  int socket() const                                     { return _socket; }

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

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

    set_socket(-1);

    set_next(NULL);

  }

};

// statics

char SolarisAttachListener::_door_path[PATH_MAX+1];

volatile bool SolarisAttachListener::_has_door_path;

int SolarisAttachListener::_door_descriptor = -1;

mutex_t SolarisAttachListener::_mutex;

sema_t SolarisAttachListener::_wakeup;

SolarisAttachOperation* SolarisAttachListener::_head = NULL;

SolarisAttachOperation* SolarisAttachListener::_tail = NULL;

// 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') {

      // advance the iterator if possible (null arguments)

      if (_pos < _end) {

        _pos += 1;

      }

      return NULL;

    }

    char* res = _pos;

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

    if (next_pos < _end)  {

      next_pos++;

    }

    _pos = next_pos;

    return res;

  }

};

// Calls from the door function to check that the client credentials

// match this process. Returns 0 if credentials okay, otherwise -1.

static int check_credentials() {

  ucred_t *cred_info = NULL;

  int ret = -1; // deny by default

  // get client credentials

  if (door_ucred(&cred_info) == -1) {

    return -1; // unable to get them, deny

  }

  // get our euid/eguid (probably could cache these)

  uid_t euid = geteuid();

  gid_t egid = getegid();

  // get euid/egid from ucred_free

  uid_t ucred_euid = ucred_geteuid(cred_info);

  gid_t ucred_egid = ucred_getegid(cred_info);

  // check that the effective uid/gid matches

  if (ucred_euid == euid && ucred_egid == egid) {

    ret =  0;  // allow

  }

  ucred_free(cred_info);

  return ret;

}

// Parses the argument buffer to create an AttachOperation that we should

// enqueue to the attach listener.

// The buffer is expected to be formatted as follows:

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

// where <ver> is the version number (must be "1"), <cmd> is the command

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

//

static SolarisAttachOperation* create_operation(char* argp, size_t arg_size, int* err) {

  // assume bad request until parsed

  *err = SolarisAttachListener::ATTACH_ERROR_BADREQUEST;

  if (arg_size < 2 || argp[arg_size-1] != '\0') {

    return NULL;   // no ver or not null terminated

  }

  // Use supporting class to iterate over the buffer

  ArgumentIterator args(argp, arg_size);

  // First check the protocol version

  char* ver = args.next();

  if (ver == NULL) {

    return NULL;

  }

  if (atoi(ver) != SolarisAttachListener::ATTACH_PROTOCOL_VER) {

    *err = SolarisAttachListener::ATTACH_ERROR_BADVERSION;

    return NULL;

  }

  // Get command name and create the operation

  char* name = args.next();

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

    return NULL;

  }

  SolarisAttachOperation* op = new SolarisAttachOperation(name);

  // Iterate over the arguments

  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);

    }

  }

  // return operation

  *err = 0;

  return op;

}

// create special operation to indicate all clients have detached

static SolarisAttachOperation* create_detachall_operation() {

  return new SolarisAttachOperation(AttachOperation::detachall_operation_name());

}

// This is door function which the client executes via a door_call.

extern "C" {

  static void enqueue_proc(void* cookie, char* argp, size_t arg_size,

                           door_desc_t* dt, uint_t n_desc)

  {

    int return_fd = -1;

    SolarisAttachOperation* op = NULL;

    // no listener

    jint res = 0;

    if (!AttachListener::is_initialized()) {

      // how did we get here?

      debug_only(warning("door_call when not enabled"));

      res = (jint)SolarisAttachListener::ATTACH_ERROR_INTERNAL;

    }

    // check client credentials

    if (res == 0) {

      if (check_credentials() != 0) {

        res = (jint)SolarisAttachListener::ATTACH_ERROR_DENIED;

      }

    }

    // if we are stopped at ShowMessageBoxOnError then maybe we can

    // load a diagnostic library

    if (res == 0 && VMError::is_error_reported()) {

      if (ShowMessageBoxOnError) {

        // TBD - support loading of diagnostic library here

      }

      // can't enqueue operation after fatal error

      res = (jint)SolarisAttachListener::ATTACH_ERROR_RESOURCE;

    }

    // create the operation

    if (res == 0) {

      int err;

      op = create_operation(argp, arg_size, &err);

      res = (op == NULL) ? (jint)err : 0;

    }

    // create a pair of connected sockets. Store the file descriptor

    // for one end in the operation and enqueue the operation. The

    // file descriptor for the other end wil be returned to the client.

    if (res == 0) {

      int s[2];

      if (socketpair(PF_UNIX, SOCK_STREAM, 0, s) < 0) {

        delete op;

        res = (jint)SolarisAttachListener::ATTACH_ERROR_RESOURCE;

      } else {

        op->set_socket(s[0]);

        return_fd = s[1];

        SolarisAttachListener::enqueue(op);

      }

    }

    // Return 0 (success) + file descriptor, or non-0 (error)

    if (res == 0) {

      door_desc_t desc;

      // DOOR_RELEASE flag makes sure fd is closed after passing it to

      // the client.  See door_return(3DOOR) man page.

      desc.d_attributes = DOOR_DESCRIPTOR | DOOR_RELEASE;

      desc.d_data.d_desc.d_descriptor = return_fd;

      door_return((char*)&res, sizeof(res), &desc, 1);

    } else {

      door_return((char*)&res, sizeof(res), NULL, 0);

    }

  }

}

// atexit hook to detach the door and remove the file

extern "C" {

  static void listener_cleanup() {

    static int cleanup_done;

    if (!cleanup_done) {

      cleanup_done = 1;

      int dd = SolarisAttachListener::door_descriptor();

      if (dd >= 0) {

        ::close(dd);

      }

      if (SolarisAttachListener::has_door_path()) {

        char* path = SolarisAttachListener::door_path();

        ::fdetach(path);

        ::unlink(path);

      }

    }

  }

}

// Create the door

int SolarisAttachListener::create_door() {

  char door_path[PATH_MAX+1];

  char initial_path[PATH_MAX+1];

  int fd, res;

  // register exit function

  ::atexit(listener_cleanup);

  // create the door descriptor

  int dd = ::door_create(enqueue_proc, NULL, 0);

  if (dd < 0) {

    return -1;

  }

  // create initial file to attach door descriptor

  snprintf(door_path, sizeof(door_path), "%s/.java_pid%d",

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

  snprintf(initial_path, sizeof(initial_path), "%s.tmp", door_path);

  RESTARTABLE(::creat(initial_path, S_IRUSR | S_IWUSR), fd);

  if (fd == -1) {

    log_debug(attach)("attempt to create door file %s failed (%d)", initial_path, errno);

    ::door_revoke(dd);

    return -1;

  }

  assert(fd >= 0, "bad file descriptor");

  ::close(fd);

  // attach the door descriptor to the file

  if ((res = ::fattach(dd, initial_path)) == -1) {

    // if busy then detach and try again

    if (errno == EBUSY) {

      ::fdetach(initial_path);

      res = ::fattach(dd, initial_path);

    }

    if (res == -1) {

      log_debug(attach)("unable to create door - fattach failed (%d)", errno);

      ::door_revoke(dd);

      dd = -1;

    }

  }

  // rename file so that clients can attach

  if (dd >= 0) {

    if (::rename(initial_path, door_path) == -1) {

        ::close(dd);

        ::fdetach(initial_path);

        log_debug(attach)("unable to create door - rename %s to %s failed (%d)", errno);

        dd = -1;

    }

  }

  if (dd >= 0) {

    set_door_descriptor(dd);

    set_door_path(door_path);

    log_trace(attach)("door file %s created succesfully", door_path);

  } else {

    // unable to create door, attach it to file, or rename file into place

    ::unlink(initial_path);

    return -1;

  }

  return 0;

}

// Initialization - create the door, locks, and other initialization

int SolarisAttachListener::init() {

  if (create_door()) {

    return -1;

  }

  int status = os::Solaris::mutex_init(&_mutex);

  assert_status(status==0, status, "mutex_init");

  status = ::sema_init(&_wakeup, 0, NULL, NULL);

  assert_status(status==0, status, "sema_init");

  set_head(NULL);

  set_tail(NULL);

  return 0;

}

// Dequeue an operation

SolarisAttachOperation* SolarisAttachListener::dequeue() {

  for (;;) {

    int res;

    // wait for somebody to enqueue something

    while ((res = ::sema_wait(wakeup())) == EINTR)

      ;

    if (res) {

      warning("sema_wait failed: %s", os::strerror(res));

      return NULL;

    }

    // lock the list

    res = os::Solaris::mutex_lock(mutex());

    assert(res == 0, "mutex_lock failed");

    // remove the head of the list

    SolarisAttachOperation* op = head();

    if (op != NULL) {

      set_head(op->next());

      if (head() == NULL) {

        set_tail(NULL);

      }

    }

    // unlock

    os::Solaris::mutex_unlock(mutex());

    // if we got an operation when return it.

    if (op != NULL) {

      return op;

    }

  }

}

// Enqueue an operation

void SolarisAttachListener::enqueue(SolarisAttachOperation* op) {

  // lock list

  int res = os::Solaris::mutex_lock(mutex());

  assert(res == 0, "mutex_lock failed");

  // enqueue at tail

  op->set_next(NULL);

  if (head() == NULL) {

    set_head(op);

  } else {

    tail()->set_next(op);

  }

  set_tail(op);

  // wakeup the attach listener

  RESTARTABLE(::sema_post(wakeup()), res);

  assert(res == 0, "sema_post failed");

  // unlock

  os::Solaris::mutex_unlock(mutex());

}