--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/os/linux/vm/attachListener_linux.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,503 @@
+/*
+ * Copyright 2005-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.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>
+
+// 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 - tt 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[PATH_MAX+1];
+  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, PATH_MAX);
+      _path[PATH_MAX] = '\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[PATH_MAX+1];
+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[PATH_MAX+1];        // socket file
+  int listener;                 // listener socket (file descriptor)
+
+  // register function to cleanup
+  ::atexit(listener_cleanup);
+
+  // create the listener socket
+  listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
+  if (listener == -1) {
+    return -1;
+  }
+
+  int res = -1;
+  struct sockaddr_un addr;
+  addr.sun_family = AF_UNIX;
+
+  // FIXME: Prior to b39 the tool-side API expected to find the well
+  // known file in the working directory. To allow this libjvm.so work with
+  // a pre-b39 SDK we create it in the working directory if
+  // +StartAttachListener is used is used. All unit tests for this feature
+  // currently used this flag. Once b39 SDK has been promoted we can remove
+  // this code.
+  if (StartAttachListener) {
+    sprintf(path, ".java_pid%d", os::current_process_id());
+    strcpy(addr.sun_path, path);
+    ::unlink(path);
+    res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
+  }
+  if (res == -1) {
+    sprintf(path, "%s/.java_pid%d", os::get_temp_directory(), os::current_process_id());
+    strcpy(addr.sun_path, path);
+    ::unlink(path);
+    res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
+  }
+  if (res == -1) {
+    RESTARTABLE(::close(listener), res);
+    return -1;
+  }
+  set_path(path);
+
+  // put in listen mode and set permission
+  if ((::listen(listener, 5) == -1) || (::chmod(path, S_IREAD|S_IWRITE) == -1)) {
+    RESTARTABLE(::close(listener), res);
+    ::unlink(path);
+    set_path(NULL);
+    return -1;
+  }
+  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;
+  int max_len = (strlen(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[32];
+  sprintf(fn, ".attach_pid%d", os::current_process_id());
+  int ret;
+  struct stat64 st;
+  RESTARTABLE(::stat64(fn, &st), ret);
+  if (ret == -1) {
+    sprintf(fn, "/tmp/.attach_pid%d", 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
+}