aoqi@0: /*
aoqi@0:  * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #include "precompiled.hpp"
aoqi@0: #include "runtime/interfaceSupport.hpp"
aoqi@0: #include "runtime/os.hpp"
aoqi@0: #include "services/attachListener.hpp"
aoqi@0: #include "services/dtraceAttacher.hpp"
aoqi@0: 
aoqi@0: #include <unistd.h>
aoqi@0: #include <signal.h>
aoqi@0: #include <sys/types.h>
aoqi@0: #include <sys/socket.h>
aoqi@0: #include <sys/un.h>
aoqi@0: #include <sys/stat.h>
aoqi@0: 
aoqi@0: #ifndef UNIX_PATH_MAX
aoqi@0: #define UNIX_PATH_MAX   sizeof(((struct sockaddr_un *)0)->sun_path)
aoqi@0: #endif
aoqi@0: 
aoqi@0: // The attach mechanism on Linux uses a UNIX domain socket. An attach listener
aoqi@0: // thread is created at startup or is created on-demand via a signal from
aoqi@0: // the client tool. The attach listener creates a socket and binds it to a file
aoqi@0: // in the filesystem. The attach listener then acts as a simple (single-
aoqi@0: // threaded) server - it waits for a client to connect, reads the request,
aoqi@0: // executes it, and returns the response to the client via the socket
aoqi@0: // connection.
aoqi@0: //
aoqi@0: // As the socket is a UNIX domain socket it means that only clients on the
aoqi@0: // local machine can connect. In addition there are two other aspects to
aoqi@0: // the security:
aoqi@0: // 1. The well known file that the socket is bound to has permission 400
aoqi@0: // 2. When a client connect, the SO_PEERCRED socket option is used to
aoqi@0: //    obtain the credentials of client. We check that the effective uid
aoqi@0: //    of the client matches this process.
aoqi@0: 
aoqi@0: // forward reference
aoqi@0: class LinuxAttachOperation;
aoqi@0: 
aoqi@0: class LinuxAttachListener: AllStatic {
aoqi@0:  private:
aoqi@0:   // the path to which we bind the UNIX domain socket
aoqi@0:   static char _path[UNIX_PATH_MAX];
aoqi@0:   static bool _has_path;
aoqi@0: 
aoqi@0:   // the file descriptor for the listening socket
aoqi@0:   static int _listener;
aoqi@0: 
aoqi@0:   static void set_path(char* path) {
aoqi@0:     if (path == NULL) {
aoqi@0:       _has_path = false;
aoqi@0:     } else {
aoqi@0:       strncpy(_path, path, UNIX_PATH_MAX);
aoqi@0:       _path[UNIX_PATH_MAX-1] = '\0';
aoqi@0:       _has_path = true;
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   static void set_listener(int s)               { _listener = s; }
aoqi@0: 
aoqi@0:   // reads a request from the given connected socket
aoqi@0:   static LinuxAttachOperation* read_request(int s);
aoqi@0: 
aoqi@0:  public:
aoqi@0:   enum {
aoqi@0:     ATTACH_PROTOCOL_VER = 1                     // protocol version
aoqi@0:   };
aoqi@0:   enum {
aoqi@0:     ATTACH_ERROR_BADVERSION     = 101           // error codes
aoqi@0:   };
aoqi@0: 
aoqi@0:   // initialize the listener, returns 0 if okay
aoqi@0:   static int init();
aoqi@0: 
aoqi@0:   static char* path()                   { return _path; }
aoqi@0:   static bool has_path()                { return _has_path; }
aoqi@0:   static int listener()                 { return _listener; }
aoqi@0: 
aoqi@0:   // write the given buffer to a socket
aoqi@0:   static int write_fully(int s, char* buf, int len);
aoqi@0: 
aoqi@0:   static LinuxAttachOperation* dequeue();
aoqi@0: };
aoqi@0: 
aoqi@0: class LinuxAttachOperation: public AttachOperation {
aoqi@0:  private:
aoqi@0:   // the connection to the client
aoqi@0:   int _socket;
aoqi@0: 
aoqi@0:  public:
aoqi@0:   void complete(jint res, bufferedStream* st);
aoqi@0: 
aoqi@0:   void set_socket(int s)                                { _socket = s; }
aoqi@0:   int socket() const                                    { return _socket; }
aoqi@0: 
aoqi@0:   LinuxAttachOperation(char* name) : AttachOperation(name) {
aoqi@0:     set_socket(-1);
aoqi@0:   }
aoqi@0: };
aoqi@0: 
aoqi@0: // statics
aoqi@0: char LinuxAttachListener::_path[UNIX_PATH_MAX];
aoqi@0: bool LinuxAttachListener::_has_path;
aoqi@0: int LinuxAttachListener::_listener = -1;
aoqi@0: 
aoqi@0: // Supporting class to help split a buffer into individual components
aoqi@0: class ArgumentIterator : public StackObj {
aoqi@0:  private:
aoqi@0:   char* _pos;
aoqi@0:   char* _end;
aoqi@0:  public:
aoqi@0:   ArgumentIterator(char* arg_buffer, size_t arg_size) {
aoqi@0:     _pos = arg_buffer;
aoqi@0:     _end = _pos + arg_size - 1;
aoqi@0:   }
aoqi@0:   char* next() {
aoqi@0:     if (*_pos == '\0') {
aoqi@0:       return NULL;
aoqi@0:     }
aoqi@0:     char* res = _pos;
aoqi@0:     char* next_pos = strchr(_pos, '\0');
aoqi@0:     if (next_pos < _end)  {
aoqi@0:       next_pos++;
aoqi@0:     }
aoqi@0:     _pos = next_pos;
aoqi@0:     return res;
aoqi@0:   }
aoqi@0: };
aoqi@0: 
aoqi@0: 
aoqi@0: // atexit hook to stop listener and unlink the file that it is
aoqi@0: // bound too.
aoqi@0: extern "C" {
aoqi@0:   static void listener_cleanup() {
aoqi@0:     static int cleanup_done;
aoqi@0:     if (!cleanup_done) {
aoqi@0:       cleanup_done = 1;
aoqi@0:       int s = LinuxAttachListener::listener();
aoqi@0:       if (s != -1) {
aoqi@0:         ::close(s);
aoqi@0:       }
aoqi@0:       if (LinuxAttachListener::has_path()) {
aoqi@0:         ::unlink(LinuxAttachListener::path());
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: // Initialization - create a listener socket and bind it to a file
aoqi@0: 
aoqi@0: int LinuxAttachListener::init() {
aoqi@0:   char path[UNIX_PATH_MAX];          // socket file
aoqi@0:   char initial_path[UNIX_PATH_MAX];  // socket file during setup
aoqi@0:   int listener;                      // listener socket (file descriptor)
aoqi@0: 
aoqi@0:   // register function to cleanup
aoqi@0:   ::atexit(listener_cleanup);
aoqi@0: 
aoqi@0:   int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
aoqi@0:                    os::get_temp_directory(), os::current_process_id());
aoqi@0:   if (n < (int)UNIX_PATH_MAX) {
aoqi@0:     n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
aoqi@0:   }
aoqi@0:   if (n >= (int)UNIX_PATH_MAX) {
aoqi@0:     return -1;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // create the listener socket
aoqi@0:   listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
aoqi@0:   if (listener == -1) {
aoqi@0:     return -1;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // bind socket
aoqi@0:   struct sockaddr_un addr;
aoqi@0:   addr.sun_family = AF_UNIX;
aoqi@0:   strcpy(addr.sun_path, initial_path);
aoqi@0:   ::unlink(initial_path);
aoqi@0:   int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
aoqi@0:   if (res == -1) {
aoqi@0:     ::close(listener);
aoqi@0:     return -1;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // put in listen mode, set permissions, and rename into place
aoqi@0:   res = ::listen(listener, 5);
aoqi@0:   if (res == 0) {
aoqi@0:       RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res);
aoqi@0:       if (res == 0) {
aoqi@0:           res = ::rename(initial_path, path);
aoqi@0:       }
aoqi@0:   }
aoqi@0:   if (res == -1) {
aoqi@0:     ::close(listener);
aoqi@0:     ::unlink(initial_path);
aoqi@0:     return -1;
aoqi@0:   }
aoqi@0:   set_path(path);
aoqi@0:   set_listener(listener);
aoqi@0: 
aoqi@0:   return 0;
aoqi@0: }
aoqi@0: 
aoqi@0: // Given a socket that is connected to a peer we read the request and
aoqi@0: // create an AttachOperation. As the socket is blocking there is potential
aoqi@0: // for a denial-of-service if the peer does not response. However this happens
aoqi@0: // after the peer credentials have been checked and in the worst case it just
aoqi@0: // means that the attach listener thread is blocked.
aoqi@0: //
aoqi@0: LinuxAttachOperation* LinuxAttachListener::read_request(int s) {
aoqi@0:   char ver_str[8];
aoqi@0:   sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
aoqi@0: 
aoqi@0:   // The request is a sequence of strings so we first figure out the
aoqi@0:   // expected count and the maximum possible length of the request.
aoqi@0:   // The request is:
aoqi@0:   //   <ver>0<cmd>0<arg>0<arg>0<arg>0
aoqi@0:   // where <ver> is the protocol version (1), <cmd> is the command
aoqi@0:   // name ("load", "datadump", ...), and <arg> is an argument
aoqi@0:   int expected_str_count = 2 + AttachOperation::arg_count_max;
aoqi@0:   const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
aoqi@0:     AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
aoqi@0: 
aoqi@0:   char buf[max_len];
aoqi@0:   int str_count = 0;
aoqi@0: 
aoqi@0:   // Read until all (expected) strings have been read, the buffer is
aoqi@0:   // full, or EOF.
aoqi@0: 
aoqi@0:   int off = 0;
aoqi@0:   int left = max_len;
aoqi@0: 
aoqi@0:   do {
aoqi@0:     int n;
aoqi@0:     RESTARTABLE(read(s, buf+off, left), n);
aoqi@0:     if (n == -1) {
aoqi@0:       return NULL;      // reset by peer or other error
aoqi@0:     }
aoqi@0:     if (n == 0) {
aoqi@0:       break;
aoqi@0:     }
aoqi@0:     for (int i=0; i<n; i++) {
aoqi@0:       if (buf[off+i] == 0) {
aoqi@0:         // EOS found
aoqi@0:         str_count++;
aoqi@0: 
aoqi@0:         // The first string is <ver> so check it now to
aoqi@0:         // check for protocol mis-match
aoqi@0:         if (str_count == 1) {
aoqi@0:           if ((strlen(buf) != strlen(ver_str)) ||
aoqi@0:               (atoi(buf) != ATTACH_PROTOCOL_VER)) {
aoqi@0:             char msg[32];
aoqi@0:             sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
aoqi@0:             write_fully(s, msg, strlen(msg));
aoqi@0:             return NULL;
aoqi@0:           }
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:     off += n;
aoqi@0:     left -= n;
aoqi@0:   } while (left > 0 && str_count < expected_str_count);
aoqi@0: 
aoqi@0:   if (str_count != expected_str_count) {
aoqi@0:     return NULL;        // incomplete request
aoqi@0:   }
aoqi@0: 
aoqi@0:   // parse request
aoqi@0: 
aoqi@0:   ArgumentIterator args(buf, (max_len)-left);
aoqi@0: 
aoqi@0:   // version already checked
aoqi@0:   char* v = args.next();
aoqi@0: 
aoqi@0:   char* name = args.next();
aoqi@0:   if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
aoqi@0:     return NULL;
aoqi@0:   }
aoqi@0: 
aoqi@0:   LinuxAttachOperation* op = new LinuxAttachOperation(name);
aoqi@0: 
aoqi@0:   for (int i=0; i<AttachOperation::arg_count_max; i++) {
aoqi@0:     char* arg = args.next();
aoqi@0:     if (arg == NULL) {
aoqi@0:       op->set_arg(i, NULL);
aoqi@0:     } else {
aoqi@0:       if (strlen(arg) > AttachOperation::arg_length_max) {
aoqi@0:         delete op;
aoqi@0:         return NULL;
aoqi@0:       }
aoqi@0:       op->set_arg(i, arg);
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   op->set_socket(s);
aoqi@0:   return op;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // Dequeue an operation
aoqi@0: //
aoqi@0: // In the Linux implementation there is only a single operation and clients
aoqi@0: // cannot queue commands (except at the socket level).
aoqi@0: //
aoqi@0: LinuxAttachOperation* LinuxAttachListener::dequeue() {
aoqi@0:   for (;;) {
aoqi@0:     int s;
aoqi@0: 
aoqi@0:     // wait for client to connect
aoqi@0:     struct sockaddr addr;
aoqi@0:     socklen_t len = sizeof(addr);
aoqi@0:     RESTARTABLE(::accept(listener(), &addr, &len), s);
aoqi@0:     if (s == -1) {
aoqi@0:       return NULL;      // log a warning?
aoqi@0:     }
aoqi@0: 
aoqi@0:     // get the credentials of the peer and check the effective uid/guid
aoqi@0:     // - check with jeff on this.
aoqi@0:     struct ucred cred_info;
aoqi@0:     socklen_t optlen = sizeof(cred_info);
aoqi@0:     if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) {
aoqi@0:       ::close(s);
aoqi@0:       continue;
aoqi@0:     }
aoqi@0:     uid_t euid = geteuid();
aoqi@0:     gid_t egid = getegid();
aoqi@0: 
aoqi@0:     if (cred_info.uid != euid || cred_info.gid != egid) {
aoqi@0:       ::close(s);
aoqi@0:       continue;
aoqi@0:     }
aoqi@0: 
aoqi@0:     // peer credential look okay so we read the request
aoqi@0:     LinuxAttachOperation* op = read_request(s);
aoqi@0:     if (op == NULL) {
aoqi@0:       ::close(s);
aoqi@0:       continue;
aoqi@0:     } else {
aoqi@0:       return op;
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: // write the given buffer to the socket
aoqi@0: int LinuxAttachListener::write_fully(int s, char* buf, int len) {
aoqi@0:   do {
aoqi@0:     int n = ::write(s, buf, len);
aoqi@0:     if (n == -1) {
aoqi@0:       if (errno != EINTR) return -1;
aoqi@0:     } else {
aoqi@0:       buf += n;
aoqi@0:       len -= n;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   while (len > 0);
aoqi@0:   return 0;
aoqi@0: }
aoqi@0: 
aoqi@0: // Complete an operation by sending the operation result and any result
aoqi@0: // output to the client. At this time the socket is in blocking mode so
aoqi@0: // potentially we can block if there is a lot of data and the client is
aoqi@0: // non-responsive. For most operations this is a non-issue because the
aoqi@0: // default send buffer is sufficient to buffer everything. In the future
aoqi@0: // if there are operations that involves a very big reply then it the
aoqi@0: // socket could be made non-blocking and a timeout could be used.
aoqi@0: 
aoqi@0: void LinuxAttachOperation::complete(jint result, bufferedStream* st) {
aoqi@0:   JavaThread* thread = JavaThread::current();
aoqi@0:   ThreadBlockInVM tbivm(thread);
aoqi@0: 
aoqi@0:   thread->set_suspend_equivalent();
aoqi@0:   // cleared by handle_special_suspend_equivalent_condition() or
aoqi@0:   // java_suspend_self() via check_and_wait_while_suspended()
aoqi@0: 
aoqi@0:   // write operation result
aoqi@0:   char msg[32];
aoqi@0:   sprintf(msg, "%d\n", result);
aoqi@0:   int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg));
aoqi@0: 
aoqi@0:   // write any result data
aoqi@0:   if (rc == 0) {
aoqi@0:     LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
aoqi@0:     ::shutdown(this->socket(), 2);
aoqi@0:   }
aoqi@0: 
aoqi@0:   // done
aoqi@0:   ::close(this->socket());
aoqi@0: 
aoqi@0:   // were we externally suspended while we were waiting?
aoqi@0:   thread->check_and_wait_while_suspended();
aoqi@0: 
aoqi@0:   delete this;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // AttachListener functions
aoqi@0: 
aoqi@0: AttachOperation* AttachListener::dequeue() {
aoqi@0:   JavaThread* thread = JavaThread::current();
aoqi@0:   ThreadBlockInVM tbivm(thread);
aoqi@0: 
aoqi@0:   thread->set_suspend_equivalent();
aoqi@0:   // cleared by handle_special_suspend_equivalent_condition() or
aoqi@0:   // java_suspend_self() via check_and_wait_while_suspended()
aoqi@0: 
aoqi@0:   AttachOperation* op = LinuxAttachListener::dequeue();
aoqi@0: 
aoqi@0:   // were we externally suspended while we were waiting?
aoqi@0:   thread->check_and_wait_while_suspended();
aoqi@0: 
aoqi@0:   return op;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // Performs initialization at vm startup
aoqi@0: // For Linux we remove any stale .java_pid file which could cause
aoqi@0: // an attaching process to think we are ready to receive on the
aoqi@0: // domain socket before we are properly initialized
aoqi@0: 
aoqi@0: void AttachListener::vm_start() {
aoqi@0:   char fn[UNIX_PATH_MAX];
aoqi@0:   struct stat64 st;
aoqi@0:   int ret;
aoqi@0: 
aoqi@0:   int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
aoqi@0:            os::get_temp_directory(), os::current_process_id());
aoqi@0:   assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
aoqi@0: 
aoqi@0:   RESTARTABLE(::stat64(fn, &st), ret);
aoqi@0:   if (ret == 0) {
aoqi@0:     ret = ::unlink(fn);
aoqi@0:     if (ret == -1) {
aoqi@0:       debug_only(warning("failed to remove stale attach pid file at %s", fn));
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: int AttachListener::pd_init() {
aoqi@0:   JavaThread* thread = JavaThread::current();
aoqi@0:   ThreadBlockInVM tbivm(thread);
aoqi@0: 
aoqi@0:   thread->set_suspend_equivalent();
aoqi@0:   // cleared by handle_special_suspend_equivalent_condition() or
aoqi@0:   // java_suspend_self() via check_and_wait_while_suspended()
aoqi@0: 
aoqi@0:   int ret_code = LinuxAttachListener::init();
aoqi@0: 
aoqi@0:   // were we externally suspended while we were waiting?
aoqi@0:   thread->check_and_wait_while_suspended();
aoqi@0: 
aoqi@0:   return ret_code;
aoqi@0: }
aoqi@0: 
aoqi@0: // Attach Listener is started lazily except in the case when
aoqi@0: // +ReduseSignalUsage is used
aoqi@0: bool AttachListener::init_at_startup() {
aoqi@0:   if (ReduceSignalUsage) {
aoqi@0:     return true;
aoqi@0:   } else {
aoqi@0:     return false;
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: // If the file .attach_pid<pid> exists in the working directory
aoqi@0: // or /tmp then this is the trigger to start the attach mechanism
aoqi@0: bool AttachListener::is_init_trigger() {
aoqi@0:   if (init_at_startup() || is_initialized()) {
aoqi@0:     return false;               // initialized at startup or already initialized
aoqi@0:   }
aoqi@0:   char fn[PATH_MAX+1];
aoqi@0:   sprintf(fn, ".attach_pid%d", os::current_process_id());
aoqi@0:   int ret;
aoqi@0:   struct stat64 st;
aoqi@0:   RESTARTABLE(::stat64(fn, &st), ret);
aoqi@0:   if (ret == -1) {
aoqi@0:     snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
aoqi@0:              os::get_temp_directory(), os::current_process_id());
aoqi@0:     RESTARTABLE(::stat64(fn, &st), ret);
aoqi@0:   }
aoqi@0:   if (ret == 0) {
aoqi@0:     // simple check to avoid starting the attach mechanism when
aoqi@0:     // a bogus user creates the file
aoqi@0:     if (st.st_uid == geteuid()) {
aoqi@0:       init();
aoqi@0:       return true;
aoqi@0:     }
aoqi@0:   }
aoqi@0:   return false;
aoqi@0: }
aoqi@0: 
aoqi@0: // if VM aborts then remove listener
aoqi@0: void AttachListener::abort() {
aoqi@0:   listener_cleanup();
aoqi@0: }
aoqi@0: 
aoqi@0: void AttachListener::pd_data_dump() {
aoqi@0:   os::signal_notify(SIGQUIT);
aoqi@0: }
aoqi@0: 
aoqi@0: AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
aoqi@0:   return NULL;
aoqi@0: }
aoqi@0: 
aoqi@0: jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
aoqi@0:   out->print_cr("flag '%s' cannot be changed", op->arg(0));
aoqi@0:   return JNI_ERR;
aoqi@0: }
aoqi@0: 
aoqi@0: void AttachListener::pd_detachall() {
aoqi@0:   // do nothing for now
aoqi@0: }