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view src/os/linux/vm/attachListener_linux.cpp @ 17124:7b3ece800806
Using getKind().format is unnecessary
author | Christian Wimmer <christian.wimmer@oracle.com> |
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date | Tue, 16 Sep 2014 18:36:19 -0700 |
parents | 2e8f19c2feef |
children |
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/* * Copyright (c) 2005, 2013, 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 "runtime/interfaceSupport.hpp" #include "runtime/os.hpp" #include "services/attachListener.hpp" #include "services/dtraceAttacher.hpp" #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) { ::close(listener); 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) { ::close(listener); ::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) { ::close(s); continue; } uid_t euid = geteuid(); gid_t egid = getegid(); if (cred_info.uid != euid || cred_info.gid != egid) { ::close(s); continue; } // peer credential look okay so we read the request LinuxAttachOperation* op = read_request(s); if (op == NULL) { ::close(s); 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 ::close(this->socket()); // 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; } // Performs initialization at vm startup // For Linux we remove any stale .java_pid file which could cause // an attaching process to think we are ready to receive on the // domain socket before we are properly initialized void AttachListener::vm_start() { char fn[UNIX_PATH_MAX]; struct stat64 st; int ret; int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", os::get_temp_directory(), os::current_process_id()); assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); RESTARTABLE(::stat64(fn, &st), ret); if (ret == 0) { ret = ::unlink(fn); if (ret == -1) { debug_only(warning("failed to remove stale attach pid file at %s", fn)); } } } 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 }