duke@435: /*
allwin@5412:  * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@2314: #include "runtime/interfaceSupport.hpp"
stefank@2314: #include "runtime/os.hpp"
stefank@2314: #include "services/attachListener.hpp"
stefank@2314: #include "services/dtraceAttacher.hpp"
duke@435: 
duke@435: #include <unistd.h>
duke@435: #include <signal.h>
duke@435: #include <sys/types.h>
duke@435: #include <sys/socket.h>
duke@435: #include <sys/un.h>
duke@435: #include <sys/stat.h>
duke@435: 
alanb@2030: #ifndef UNIX_PATH_MAX
alanb@2030: #define UNIX_PATH_MAX   sizeof(((struct sockaddr_un *)0)->sun_path)
alanb@2030: #endif
alanb@2030: 
duke@435: // The attach mechanism on Linux uses a UNIX domain socket. An attach listener
duke@435: // thread is created at startup or is created on-demand via a signal from
duke@435: // the client tool. The attach listener creates a socket and binds it to a file
duke@435: // in the filesystem. The attach listener then acts as a simple (single-
alanb@2030: // threaded) server - it waits for a client to connect, reads the request,
duke@435: // executes it, and returns the response to the client via the socket
duke@435: // connection.
duke@435: //
duke@435: // As the socket is a UNIX domain socket it means that only clients on the
duke@435: // local machine can connect. In addition there are two other aspects to
duke@435: // the security:
duke@435: // 1. The well known file that the socket is bound to has permission 400
duke@435: // 2. When a client connect, the SO_PEERCRED socket option is used to
duke@435: //    obtain the credentials of client. We check that the effective uid
duke@435: //    of the client matches this process.
duke@435: 
duke@435: // forward reference
duke@435: class LinuxAttachOperation;
duke@435: 
duke@435: class LinuxAttachListener: AllStatic {
duke@435:  private:
duke@435:   // the path to which we bind the UNIX domain socket
alanb@2030:   static char _path[UNIX_PATH_MAX];
duke@435:   static bool _has_path;
duke@435: 
duke@435:   // the file descriptor for the listening socket
duke@435:   static int _listener;
duke@435: 
duke@435:   static void set_path(char* path) {
duke@435:     if (path == NULL) {
duke@435:       _has_path = false;
duke@435:     } else {
alanb@2030:       strncpy(_path, path, UNIX_PATH_MAX);
alanb@2030:       _path[UNIX_PATH_MAX-1] = '\0';
duke@435:       _has_path = true;
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   static void set_listener(int s)               { _listener = s; }
duke@435: 
duke@435:   // reads a request from the given connected socket
duke@435:   static LinuxAttachOperation* read_request(int s);
duke@435: 
duke@435:  public:
duke@435:   enum {
duke@435:     ATTACH_PROTOCOL_VER = 1                     // protocol version
duke@435:   };
duke@435:   enum {
duke@435:     ATTACH_ERROR_BADVERSION     = 101           // error codes
duke@435:   };
duke@435: 
duke@435:   // initialize the listener, returns 0 if okay
duke@435:   static int init();
duke@435: 
duke@435:   static char* path()                   { return _path; }
duke@435:   static bool has_path()                { return _has_path; }
duke@435:   static int listener()                 { return _listener; }
duke@435: 
duke@435:   // write the given buffer to a socket
duke@435:   static int write_fully(int s, char* buf, int len);
duke@435: 
duke@435:   static LinuxAttachOperation* dequeue();
duke@435: };
duke@435: 
duke@435: class LinuxAttachOperation: public AttachOperation {
duke@435:  private:
duke@435:   // the connection to the client
duke@435:   int _socket;
duke@435: 
duke@435:  public:
duke@435:   void complete(jint res, bufferedStream* st);
duke@435: 
duke@435:   void set_socket(int s)                                { _socket = s; }
duke@435:   int socket() const                                    { return _socket; }
duke@435: 
duke@435:   LinuxAttachOperation(char* name) : AttachOperation(name) {
duke@435:     set_socket(-1);
duke@435:   }
duke@435: };
duke@435: 
duke@435: // statics
alanb@2030: char LinuxAttachListener::_path[UNIX_PATH_MAX];
duke@435: bool LinuxAttachListener::_has_path;
duke@435: int LinuxAttachListener::_listener = -1;
duke@435: 
duke@435: // Supporting class to help split a buffer into individual components
duke@435: class ArgumentIterator : public StackObj {
duke@435:  private:
duke@435:   char* _pos;
duke@435:   char* _end;
duke@435:  public:
duke@435:   ArgumentIterator(char* arg_buffer, size_t arg_size) {
duke@435:     _pos = arg_buffer;
duke@435:     _end = _pos + arg_size - 1;
duke@435:   }
duke@435:   char* next() {
duke@435:     if (*_pos == '\0') {
duke@435:       return NULL;
duke@435:     }
duke@435:     char* res = _pos;
duke@435:     char* next_pos = strchr(_pos, '\0');
duke@435:     if (next_pos < _end)  {
duke@435:       next_pos++;
duke@435:     }
duke@435:     _pos = next_pos;
duke@435:     return res;
duke@435:   }
duke@435: };
duke@435: 
duke@435: 
duke@435: // atexit hook to stop listener and unlink the file that it is
duke@435: // bound too.
duke@435: extern "C" {
duke@435:   static void listener_cleanup() {
duke@435:     static int cleanup_done;
duke@435:     if (!cleanup_done) {
duke@435:       cleanup_done = 1;
duke@435:       int s = LinuxAttachListener::listener();
duke@435:       if (s != -1) {
duke@435:         ::close(s);
duke@435:       }
duke@435:       if (LinuxAttachListener::has_path()) {
duke@435:         ::unlink(LinuxAttachListener::path());
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: // Initialization - create a listener socket and bind it to a file
duke@435: 
duke@435: int LinuxAttachListener::init() {
alanb@2030:   char path[UNIX_PATH_MAX];          // socket file
alanb@2030:   char initial_path[UNIX_PATH_MAX];  // socket file during setup
alanb@2030:   int listener;                      // listener socket (file descriptor)
duke@435: 
duke@435:   // register function to cleanup
duke@435:   ::atexit(listener_cleanup);
duke@435: 
alanb@2030:   int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
alanb@2030:                    os::get_temp_directory(), os::current_process_id());
bobv@2223:   if (n < (int)UNIX_PATH_MAX) {
alanb@2030:     n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
alanb@2030:   }
bobv@2223:   if (n >= (int)UNIX_PATH_MAX) {
alanb@2030:     return -1;
alanb@2030:   }
alanb@2030: 
duke@435:   // create the listener socket
duke@435:   listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
duke@435:   if (listener == -1) {
duke@435:     return -1;
duke@435:   }
duke@435: 
alanb@2030:   // bind socket
duke@435:   struct sockaddr_un addr;
duke@435:   addr.sun_family = AF_UNIX;
alanb@2030:   strcpy(addr.sun_path, initial_path);
alanb@2030:   ::unlink(initial_path);
alanb@2030:   int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
duke@435:   if (res == -1) {
rdurbin@5264:     ::close(listener);
duke@435:     return -1;
duke@435:   }
duke@435: 
alanb@2030:   // put in listen mode, set permissions, and rename into place
alanb@2030:   res = ::listen(listener, 5);
alanb@2030:   if (res == 0) {
alanb@2030:       RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res);
alanb@2030:       if (res == 0) {
alanb@2030:           res = ::rename(initial_path, path);
alanb@2030:       }
alanb@2030:   }
alanb@2030:   if (res == -1) {
rdurbin@5264:     ::close(listener);
alanb@2030:     ::unlink(initial_path);
duke@435:     return -1;
duke@435:   }
alanb@2030:   set_path(path);
duke@435:   set_listener(listener);
duke@435: 
duke@435:   return 0;
duke@435: }
duke@435: 
duke@435: // Given a socket that is connected to a peer we read the request and
duke@435: // create an AttachOperation. As the socket is blocking there is potential
duke@435: // for a denial-of-service if the peer does not response. However this happens
duke@435: // after the peer credentials have been checked and in the worst case it just
duke@435: // means that the attach listener thread is blocked.
duke@435: //
duke@435: LinuxAttachOperation* LinuxAttachListener::read_request(int s) {
duke@435:   char ver_str[8];
duke@435:   sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
duke@435: 
duke@435:   // The request is a sequence of strings so we first figure out the
duke@435:   // expected count and the maximum possible length of the request.
duke@435:   // The request is:
duke@435:   //   <ver>0<cmd>0<arg>0<arg>0<arg>0
duke@435:   // where <ver> is the protocol version (1), <cmd> is the command
duke@435:   // name ("load", "datadump", ...), and <arg> is an argument
duke@435:   int expected_str_count = 2 + AttachOperation::arg_count_max;
dcubed@485:   const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
duke@435:     AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
duke@435: 
duke@435:   char buf[max_len];
duke@435:   int str_count = 0;
duke@435: 
duke@435:   // Read until all (expected) strings have been read, the buffer is
duke@435:   // full, or EOF.
duke@435: 
duke@435:   int off = 0;
duke@435:   int left = max_len;
duke@435: 
duke@435:   do {
duke@435:     int n;
duke@435:     RESTARTABLE(read(s, buf+off, left), n);
duke@435:     if (n == -1) {
duke@435:       return NULL;      // reset by peer or other error
duke@435:     }
duke@435:     if (n == 0) {
duke@435:       break;
duke@435:     }
duke@435:     for (int i=0; i<n; i++) {
duke@435:       if (buf[off+i] == 0) {
duke@435:         // EOS found
duke@435:         str_count++;
duke@435: 
duke@435:         // The first string is <ver> so check it now to
duke@435:         // check for protocol mis-match
duke@435:         if (str_count == 1) {
duke@435:           if ((strlen(buf) != strlen(ver_str)) ||
duke@435:               (atoi(buf) != ATTACH_PROTOCOL_VER)) {
duke@435:             char msg[32];
duke@435:             sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
duke@435:             write_fully(s, msg, strlen(msg));
duke@435:             return NULL;
duke@435:           }
duke@435:         }
duke@435:       }
duke@435:     }
duke@435:     off += n;
duke@435:     left -= n;
duke@435:   } while (left > 0 && str_count < expected_str_count);
duke@435: 
duke@435:   if (str_count != expected_str_count) {
duke@435:     return NULL;        // incomplete request
duke@435:   }
duke@435: 
duke@435:   // parse request
duke@435: 
duke@435:   ArgumentIterator args(buf, (max_len)-left);
duke@435: 
duke@435:   // version already checked
duke@435:   char* v = args.next();
duke@435: 
duke@435:   char* name = args.next();
duke@435:   if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
duke@435:     return NULL;
duke@435:   }
duke@435: 
duke@435:   LinuxAttachOperation* op = new LinuxAttachOperation(name);
duke@435: 
duke@435:   for (int i=0; i<AttachOperation::arg_count_max; i++) {
duke@435:     char* arg = args.next();
duke@435:     if (arg == NULL) {
duke@435:       op->set_arg(i, NULL);
duke@435:     } else {
duke@435:       if (strlen(arg) > AttachOperation::arg_length_max) {
duke@435:         delete op;
duke@435:         return NULL;
duke@435:       }
duke@435:       op->set_arg(i, arg);
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   op->set_socket(s);
duke@435:   return op;
duke@435: }
duke@435: 
duke@435: 
duke@435: // Dequeue an operation
duke@435: //
duke@435: // In the Linux implementation there is only a single operation and clients
duke@435: // cannot queue commands (except at the socket level).
duke@435: //
duke@435: LinuxAttachOperation* LinuxAttachListener::dequeue() {
duke@435:   for (;;) {
duke@435:     int s;
duke@435: 
duke@435:     // wait for client to connect
duke@435:     struct sockaddr addr;
duke@435:     socklen_t len = sizeof(addr);
duke@435:     RESTARTABLE(::accept(listener(), &addr, &len), s);
duke@435:     if (s == -1) {
duke@435:       return NULL;      // log a warning?
duke@435:     }
duke@435: 
duke@435:     // get the credentials of the peer and check the effective uid/guid
duke@435:     // - check with jeff on this.
duke@435:     struct ucred cred_info;
duke@435:     socklen_t optlen = sizeof(cred_info);
duke@435:     if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) {
rdurbin@5264:       ::close(s);
duke@435:       continue;
duke@435:     }
duke@435:     uid_t euid = geteuid();
duke@435:     gid_t egid = getegid();
duke@435: 
duke@435:     if (cred_info.uid != euid || cred_info.gid != egid) {
rdurbin@5264:       ::close(s);
duke@435:       continue;
duke@435:     }
duke@435: 
duke@435:     // peer credential look okay so we read the request
duke@435:     LinuxAttachOperation* op = read_request(s);
duke@435:     if (op == NULL) {
rdurbin@5264:       ::close(s);
duke@435:       continue;
duke@435:     } else {
duke@435:       return op;
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: // write the given buffer to the socket
duke@435: int LinuxAttachListener::write_fully(int s, char* buf, int len) {
duke@435:   do {
duke@435:     int n = ::write(s, buf, len);
duke@435:     if (n == -1) {
duke@435:       if (errno != EINTR) return -1;
duke@435:     } else {
duke@435:       buf += n;
duke@435:       len -= n;
duke@435:     }
duke@435:   }
duke@435:   while (len > 0);
duke@435:   return 0;
duke@435: }
duke@435: 
duke@435: // Complete an operation by sending the operation result and any result
duke@435: // output to the client. At this time the socket is in blocking mode so
duke@435: // potentially we can block if there is a lot of data and the client is
duke@435: // non-responsive. For most operations this is a non-issue because the
duke@435: // default send buffer is sufficient to buffer everything. In the future
duke@435: // if there are operations that involves a very big reply then it the
duke@435: // socket could be made non-blocking and a timeout could be used.
duke@435: 
duke@435: void LinuxAttachOperation::complete(jint result, bufferedStream* st) {
duke@435:   JavaThread* thread = JavaThread::current();
duke@435:   ThreadBlockInVM tbivm(thread);
duke@435: 
duke@435:   thread->set_suspend_equivalent();
duke@435:   // cleared by handle_special_suspend_equivalent_condition() or
duke@435:   // java_suspend_self() via check_and_wait_while_suspended()
duke@435: 
duke@435:   // write operation result
duke@435:   char msg[32];
duke@435:   sprintf(msg, "%d\n", result);
duke@435:   int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg));
duke@435: 
duke@435:   // write any result data
duke@435:   if (rc == 0) {
duke@435:     LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
duke@435:     ::shutdown(this->socket(), 2);
duke@435:   }
duke@435: 
duke@435:   // done
rdurbin@5264:   ::close(this->socket());
duke@435: 
duke@435:   // were we externally suspended while we were waiting?
duke@435:   thread->check_and_wait_while_suspended();
duke@435: 
duke@435:   delete this;
duke@435: }
duke@435: 
duke@435: 
duke@435: // AttachListener functions
duke@435: 
duke@435: AttachOperation* AttachListener::dequeue() {
duke@435:   JavaThread* thread = JavaThread::current();
duke@435:   ThreadBlockInVM tbivm(thread);
duke@435: 
duke@435:   thread->set_suspend_equivalent();
duke@435:   // cleared by handle_special_suspend_equivalent_condition() or
duke@435:   // java_suspend_self() via check_and_wait_while_suspended()
duke@435: 
duke@435:   AttachOperation* op = LinuxAttachListener::dequeue();
duke@435: 
duke@435:   // were we externally suspended while we were waiting?
duke@435:   thread->check_and_wait_while_suspended();
duke@435: 
duke@435:   return op;
duke@435: }
duke@435: 
allwin@5412: 
allwin@5412: // Performs initialization at vm startup
allwin@5412: // For Linux we remove any stale .java_pid file which could cause
allwin@5412: // an attaching process to think we are ready to receive on the
allwin@5412: // domain socket before we are properly initialized
allwin@5412: 
allwin@5412: void AttachListener::vm_start() {
allwin@5412:   char fn[UNIX_PATH_MAX];
allwin@5412:   struct stat64 st;
allwin@5412:   int ret;
allwin@5412: 
allwin@5412:   int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
allwin@5412:            os::get_temp_directory(), os::current_process_id());
allwin@5412:   assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
allwin@5412: 
allwin@5412:   RESTARTABLE(::stat64(fn, &st), ret);
allwin@5412:   if (ret == 0) {
allwin@5412:     ret = ::unlink(fn);
allwin@5412:     if (ret == -1) {
allwin@5412:       debug_only(warning("failed to remove stale attach pid file at %s", fn));
allwin@5412:     }
allwin@5412:   }
allwin@5412: }
allwin@5412: 
duke@435: int AttachListener::pd_init() {
duke@435:   JavaThread* thread = JavaThread::current();
duke@435:   ThreadBlockInVM tbivm(thread);
duke@435: 
duke@435:   thread->set_suspend_equivalent();
duke@435:   // cleared by handle_special_suspend_equivalent_condition() or
duke@435:   // java_suspend_self() via check_and_wait_while_suspended()
duke@435: 
duke@435:   int ret_code = LinuxAttachListener::init();
duke@435: 
duke@435:   // were we externally suspended while we were waiting?
duke@435:   thread->check_and_wait_while_suspended();
duke@435: 
duke@435:   return ret_code;
duke@435: }
duke@435: 
duke@435: // Attach Listener is started lazily except in the case when
duke@435: // +ReduseSignalUsage is used
duke@435: bool AttachListener::init_at_startup() {
duke@435:   if (ReduceSignalUsage) {
duke@435:     return true;
duke@435:   } else {
duke@435:     return false;
duke@435:   }
duke@435: }
duke@435: 
duke@435: // If the file .attach_pid<pid> exists in the working directory
duke@435: // or /tmp then this is the trigger to start the attach mechanism
duke@435: bool AttachListener::is_init_trigger() {
duke@435:   if (init_at_startup() || is_initialized()) {
duke@435:     return false;               // initialized at startup or already initialized
duke@435:   }
coleenp@1852:   char fn[PATH_MAX+1];
duke@435:   sprintf(fn, ".attach_pid%d", os::current_process_id());
duke@435:   int ret;
duke@435:   struct stat64 st;
duke@435:   RESTARTABLE(::stat64(fn, &st), ret);
duke@435:   if (ret == -1) {
coleenp@1788:     snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
coleenp@1788:              os::get_temp_directory(), os::current_process_id());
duke@435:     RESTARTABLE(::stat64(fn, &st), ret);
duke@435:   }
duke@435:   if (ret == 0) {
duke@435:     // simple check to avoid starting the attach mechanism when
duke@435:     // a bogus user creates the file
duke@435:     if (st.st_uid == geteuid()) {
duke@435:       init();
duke@435:       return true;
duke@435:     }
duke@435:   }
duke@435:   return false;
duke@435: }
duke@435: 
duke@435: // if VM aborts then remove listener
duke@435: void AttachListener::abort() {
duke@435:   listener_cleanup();
duke@435: }
duke@435: 
duke@435: void AttachListener::pd_data_dump() {
duke@435:   os::signal_notify(SIGQUIT);
duke@435: }
duke@435: 
duke@435: AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
duke@435:   return NULL;
duke@435: }
duke@435: 
duke@435: jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
duke@435:   out->print_cr("flag '%s' cannot be changed", op->arg(0));
duke@435:   return JNI_ERR;
duke@435: }
duke@435: 
duke@435: void AttachListener::pd_detachall() {
duke@435:   // do nothing for now
duke@435: }