forked from openjdk/jdk
/
attachListener_aix.cpp
594 lines (511 loc) · 17.7 KB
/
attachListener_aix.cpp
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/*
* Copyright (c) 2005, 2021, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2018 SAP SE. 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 <signal.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#ifndef UNIX_PATH_MAX
#define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path)
#endif
// The attach mechanism on AIX 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_PEERID 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 AixAttachOperation;
class AixAttachListener: AllStatic {
private:
// the path to which we bind the UNIX domain socket
static char _path[UNIX_PATH_MAX];
static bool _has_path;
// Shutdown marker to prevent accept blocking during clean-up.
static volatile bool _shutdown;
// the file descriptor for the listening socket
static volatile int _listener;
static bool _atexit_registered;
// reads a request from the given connected socket
static AixAttachOperation* read_request(int s);
public:
enum {
ATTACH_PROTOCOL_VER = 1 // protocol version
};
enum {
ATTACH_ERROR_BADVERSION = 101 // error codes
};
static void set_path(char* path) {
if (path == NULL) {
_path[0] = '\0';
_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; }
// 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; }
// Shutdown marker to prevent accept blocking during clean-up
static void set_shutdown(bool shutdown) { _shutdown = shutdown; }
static bool is_shutdown() { return _shutdown; }
// write the given buffer to a socket
static int write_fully(int s, char* buf, int len);
static AixAttachOperation* dequeue();
};
class AixAttachOperation: 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; }
AixAttachOperation(char* name) : AttachOperation(name) {
set_socket(-1);
}
};
// statics
char AixAttachListener::_path[UNIX_PATH_MAX];
bool AixAttachListener::_has_path;
volatile int AixAttachListener::_listener = -1;
bool AixAttachListener::_atexit_registered = false;
// Shutdown marker to prevent accept blocking during clean-up
volatile bool AixAttachListener::_shutdown = false;
// 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;
}
};
// On AIX if sockets block until all data has been transmitted
// successfully in some communication domains a socket "close" may
// never complete. We have to take care that after the socket shutdown
// the listener never enters accept state.
// atexit hook to stop listener and unlink the file that it is
// bound too.
// Some modifications to the listener logic to prevent deadlocks on exit.
// 1. We Shutdown the socket here instead. AixAttachOperation::complete() is not the right place
// since more than one agent in a sequence in JPLIS live tests wouldn't work (Listener thread
// would be dead after the first operation completion).
// 2. close(s) may never return if the listener thread is in socket accept(). Unlinking the file
// should be sufficient for cleanup.
extern "C" {
static void listener_cleanup() {
AixAttachListener::set_shutdown(true);
int s = AixAttachListener::listener();
if (s != -1) {
::shutdown(s, 2);
}
if (AixAttachListener::has_path()) {
::unlink(AixAttachListener::path());
AixAttachListener::set_path(NULL);
}
}
}
// Initialization - create a listener socket and bind it to a file
int AixAttachListener::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
if (!_atexit_registered) {
_atexit_registered = true;
::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;
memset((void *)&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
strcpy(addr.sun_path, initial_path);
::unlink(initial_path);
// We must call bind with the actual socketaddr length. This is obligatory for AS400.
int res = ::bind(listener, (struct sockaddr*)&addr, SUN_LEN(&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) {
// make sure the file is owned by the effective user and effective group
// e.g. the group could be inherited from the directory in case the s bit is set
RESTARTABLE(::chown(initial_path, geteuid(), getegid()), 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);
set_shutdown(false);
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.
//
AixAttachOperation* AixAttachListener::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;
// Don't block on interrupts because this will
// hang in the clean-up when shutting down.
n = read(s, buf+off, left);
assert(n <= left, "buffer was too small, impossible!");
buf[max_len - 1] = '\0';
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;
}
AixAttachOperation* op = new AixAttachOperation(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 Aix implementation there is only a single operation and clients
// cannot queue commands (except at the socket level).
//
AixAttachOperation* AixAttachListener::dequeue() {
for (;;) {
int s;
// wait for client to connect
struct sockaddr addr;
socklen_t len = sizeof(addr);
memset(&addr, 0, len);
// We must prevent accept blocking on the socket if it has been shut down.
// Therefore we allow interrupts and check whether we have been shut down already.
if (AixAttachListener::is_shutdown()) {
::close(listener());
set_listener(-1);
return NULL;
}
s = ::accept(listener(), &addr, &len);
if (s == -1) {
::close(listener());
set_listener(-1);
return NULL; // log a warning?
}
// get the credentials of the peer and check the effective uid/guid
struct peercred_struct cred_info;
socklen_t optlen = sizeof(cred_info);
if (::getsockopt(s, SOL_SOCKET, SO_PEERID, (void*)&cred_info, &optlen) == -1) {
log_debug(attach)("Failed to get socket option SO_PEERID");
::close(s);
continue;
}
if (!os::Posix::matches_effective_uid_and_gid_or_root(cred_info.euid, cred_info.egid)) {
log_debug(attach)("euid/egid check failed (%d/%d vs %d/%d)",
cred_info.euid, cred_info.egid, geteuid(), getegid());
::close(s);
continue;
}
// peer credential look okay so we read the request
AixAttachOperation* op = read_request(s);
if (op == NULL) {
::close(s);
continue;
} else {
return op;
}
}
}
// write the given buffer to the socket
int AixAttachListener::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 AixAttachOperation::complete(jint result, bufferedStream* st) {
JavaThread* thread = JavaThread::current();
ThreadBlockInVM tbivm(thread);
// write operation result
char msg[32];
sprintf(msg, "%d\n", result);
int rc = AixAttachListener::write_fully(this->socket(), msg, strlen(msg));
// write any result data
if (rc == 0) {
// Shutdown the socket in the cleanup function to enable more than
// one agent attach in a sequence (see comments to listener_cleanup()).
AixAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
}
// done
::close(this->socket());
delete this;
}
// AttachListener functions
AttachOperation* AttachListener::dequeue() {
JavaThread* thread = JavaThread::current();
ThreadBlockInVM tbivm(thread);
AttachOperation* op = AixAttachListener::dequeue();
return op;
}
// Performs initialization at vm startup
// For AIX 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) {
log_debug(attach)("Failed to remove stale attach pid file at %s", fn);
}
}
}
int AttachListener::pd_init() {
JavaThread* thread = JavaThread::current();
ThreadBlockInVM tbivm(thread);
int ret_code = AixAttachListener::init();
return ret_code;
}
bool AttachListener::check_socket_file() {
int ret;
struct stat64 st;
ret = stat64(AixAttachListener::path(), &st);
if (ret == -1) { // need to restart attach listener.
log_debug(attach)("Socket file %s does not exist - Restart Attach Listener",
AixAttachListener::path());
listener_cleanup();
// wait to terminate current attach listener instance...
{
// avoid deadlock if AttachListener thread is blocked at safepoint
ThreadBlockInVM tbivm(JavaThread::current());
while (AttachListener::transit_state(AL_INITIALIZING,
AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) {
os::naked_yield();
}
}
return is_init_trigger();
}
return false;
}
// 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];
int ret;
struct stat64 st;
sprintf(fn, ".attach_pid%d", os::current_process_id());
RESTARTABLE(::stat64(fn, &st), ret);
if (ret == -1) {
log_trace(attach)("Failed to find attach file: %s, trying alternate", fn);
snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
os::get_temp_directory(), os::current_process_id());
RESTARTABLE(::stat64(fn, &st), ret);
if (ret == -1) {
log_debug(attach)("Failed to find attach file: %s", fn);
}
}
if (ret == 0) {
// simple check to avoid starting the attach mechanism when
// a bogus non-root user creates the file
if (os::Posix::matches_effective_uid_or_root(st.st_uid)) {
init();
log_trace(attach)("Attach triggered by %s", fn);
return true;
} else {
log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid());
}
}
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() {
// Cleanup server socket to detach clients.
listener_cleanup();
}