1 /*
2 * Copyright (c) 2005, 2015, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2015 SAP AG. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "runtime/interfaceSupport.hpp"
28 #include "runtime/os.inline.hpp"
29 #include "services/attachListener.hpp"
30 #include "services/dtraceAttacher.hpp"
31
32 #include <unistd.h>
33 #include <signal.h>
34 #include <sys/types.h>
35 #include <sys/socket.h>
36 #include <sys/un.h>
37 #include <sys/stat.h>
38
39 #ifndef UNIX_PATH_MAX
40 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path)
41 #endif
42
43 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener
44 // thread is created at startup or is created on-demand via a signal from
45 // the client tool. The attach listener creates a socket and binds it to a file
46 // in the filesystem. The attach listener then acts as a simple (single-
47 // threaded) server - it waits for a client to connect, reads the request,
48 // executes it, and returns the response to the client via the socket
49 // connection.
50 //
51 // As the socket is a UNIX domain socket it means that only clients on the
52 // local machine can connect. In addition there are two other aspects to
53 // the security:
54 // 1. The well known file that the socket is bound to has permission 400
55 // 2. When a client connect, the SO_PEERID socket option is used to
56 // obtain the credentials of client. We check that the effective uid
57 // of the client matches this process.
58
59 // forward reference
60 class AixAttachOperation;
61
62 class AixAttachListener: AllStatic {
63 private:
64 // the path to which we bind the UNIX domain socket
65 static char _path[UNIX_PATH_MAX];
66 static bool _has_path;
67 // Shutdown marker to prevent accept blocking during clean-up.
68 static bool _shutdown;
69
70 // the file descriptor for the listening socket
71 static int _listener;
72
73 static void set_path(char* path) {
74 if (path == NULL) {
75 _has_path = false;
76 } else {
77 strncpy(_path, path, UNIX_PATH_MAX);
78 _path[UNIX_PATH_MAX-1] = '\0';
79 _has_path = true;
80 }
81 }
82
83 static void set_listener(int s) { _listener = s; }
84
85 // reads a request from the given connected socket
86 static AixAttachOperation* read_request(int s);
87
88 public:
89 enum {
90 ATTACH_PROTOCOL_VER = 1 // protocol version
91 };
92 enum {
93 ATTACH_ERROR_BADVERSION = 101 // error codes
94 };
95
96 // initialize the listener, returns 0 if okay
97 static int init();
98
99 static char* path() { return _path; }
100 static bool has_path() { return _has_path; }
101 static int listener() { return _listener; }
102 // Shutdown marker to prevent accept blocking during clean-up
103 static void set_shutdown(bool shutdown) { _shutdown = shutdown; }
104 static bool is_shutdown() { return _shutdown; }
105
106 // write the given buffer to a socket
107 static int write_fully(int s, char* buf, int len);
108
109 static AixAttachOperation* dequeue();
110 };
111
112 class AixAttachOperation: public AttachOperation {
113 private:
114 // the connection to the client
115 int _socket;
116
117 public:
118 void complete(jint res, bufferedStream* st);
119
120 void set_socket(int s) { _socket = s; }
121 int socket() const { return _socket; }
122
123 AixAttachOperation(char* name) : AttachOperation(name) {
124 set_socket(-1);
125 }
126 };
127
128 // statics
129 char AixAttachListener::_path[UNIX_PATH_MAX];
130 bool AixAttachListener::_has_path;
131 int AixAttachListener::_listener = -1;
132 // Shutdown marker to prevent accept blocking during clean-up
133 bool AixAttachListener::_shutdown = false;
134
135 // Supporting class to help split a buffer into individual components
136 class ArgumentIterator : public StackObj {
137 private:
138 char* _pos;
139 char* _end;
140 public:
141 ArgumentIterator(char* arg_buffer, size_t arg_size) {
142 _pos = arg_buffer;
143 _end = _pos + arg_size - 1;
144 }
145 char* next() {
146 if (*_pos == '\0') {
147 if (_pos < _end) {
148 _pos += 1;
149 }
150
151 return NULL;
152 }
153 char* res = _pos;
154 char* next_pos = strchr(_pos, '\0');
155 if (next_pos < _end) {
156 next_pos++;
157 }
158 _pos = next_pos;
159 return res;
160 }
161 };
162
163 // On AIX if sockets block until all data has been transmitted
164 // successfully in some communication domains a socket "close" may
165 // never complete. We have to take care that after the socket shutdown
166 // the listener never enters accept state.
167
168 // atexit hook to stop listener and unlink the file that it is
169 // bound too.
170
171 // Some modifications to the listener logic to prevent deadlocks on exit.
172 // 1. We Shutdown the socket here instead. AixAttachOperation::complete() is not the right place
173 // since more than one agent in a sequence in JPLIS live tests wouldn't work (Listener thread
174 // would be dead after the first operation completion).
175 // 2. close(s) may never return if the listener thread is in socket accept(). Unlinking the file
176 // should be sufficient for cleanup.
177 extern "C" {
178 static void listener_cleanup() {
179 static int cleanup_done;
180 if (!cleanup_done) {
181 cleanup_done = 1;
182 AixAttachListener::set_shutdown(true);
183 int s = AixAttachListener::listener();
184 if (s != -1) {
185 ::shutdown(s, 2);
186 }
187 if (AixAttachListener::has_path()) {
188 ::unlink(AixAttachListener::path());
189 }
190 }
191 }
192 }
193
194 // Initialization - create a listener socket and bind it to a file
195
196 int AixAttachListener::init() {
197 char path[UNIX_PATH_MAX]; // socket file
198 char initial_path[UNIX_PATH_MAX]; // socket file during setup
199 int listener; // listener socket (file descriptor)
200
201 // register function to cleanup
202 ::atexit(listener_cleanup);
203
204 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
205 os::get_temp_directory(), os::current_process_id());
206 if (n < (int)UNIX_PATH_MAX) {
207 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
208 }
209 if (n >= (int)UNIX_PATH_MAX) {
210 return -1;
211 }
212
213 // create the listener socket
214 listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
215 if (listener == -1) {
216 return -1;
217 }
218
219 // bind socket
220 struct sockaddr_un addr;
221 memset((void *)&addr, 0, sizeof(addr));
222 addr.sun_family = AF_UNIX;
223 strcpy(addr.sun_path, initial_path);
224 ::unlink(initial_path);
225 // We must call bind with the actual socketaddr length. This is obligatory for AS400.
226 int res = ::bind(listener, (struct sockaddr*)&addr, SUN_LEN(&addr));
227 if (res == -1) {
228 RESTARTABLE(::close(listener), res);
229 return -1;
230 }
231
232 // put in listen mode, set permissions, and rename into place
233 res = ::listen(listener, 5);
234 if (res == 0) {
235 RESTARTABLE(::chmod(initial_path, (S_IREAD|S_IWRITE) & ~(S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)), res);
236 if (res == 0) {
237 res = ::rename(initial_path, path);
238 }
239 }
240 if (res == -1) {
241 RESTARTABLE(::close(listener), res);
242 ::unlink(initial_path);
243 return -1;
244 }
245 set_path(path);
246 set_listener(listener);
247 set_shutdown(false);
248
249 return 0;
250 }
251
252 // Given a socket that is connected to a peer we read the request and
253 // create an AttachOperation. As the socket is blocking there is potential
254 // for a denial-of-service if the peer does not response. However this happens
255 // after the peer credentials have been checked and in the worst case it just
256 // means that the attach listener thread is blocked.
257 //
258 AixAttachOperation* AixAttachListener::read_request(int s) {
259 char ver_str[8];
260 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
261
262 // The request is a sequence of strings so we first figure out the
263 // expected count and the maximum possible length of the request.
264 // The request is:
265 // <ver>0<cmd>0<arg>0<arg>0<arg>0
266 // where <ver> is the protocol version (1), <cmd> is the command
267 // name ("load", "datadump", ...), and <arg> is an argument
268 int expected_str_count = 2 + AttachOperation::arg_count_max;
269 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
270 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
271
272 char buf[max_len];
273 int str_count = 0;
274
275 // Read until all (expected) strings have been read, the buffer is
276 // full, or EOF.
277
278 int off = 0;
279 int left = max_len;
280
281 do {
282 int n;
283 // Don't block on interrupts because this will
284 // hang in the clean-up when shutting down.
285 n = read(s, buf+off, left);
286 if (n == -1) {
287 return NULL; // reset by peer or other error
288 }
289 if (n == 0) { // end of file reached
290 break;
291 }
292 for (int i=0; i<n; i++) {
293 if (buf[off+i] == 0) {
294 // EOS found
295 str_count++;
296
297 // The first string is <ver> so check it now to
298 // check for protocol mis-match
299 if (str_count == 1) {
300 if ((strlen(buf) != strlen(ver_str)) ||
301 (atoi(buf) != ATTACH_PROTOCOL_VER)) {
302 char msg[32];
303 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
304 write_fully(s, msg, strlen(msg));
305 return NULL;
306 }
307 }
308 }
309 }
310 off += n;
311 left -= n;
312 } while (left > 0 && str_count < expected_str_count);
313
314 if (str_count != expected_str_count) {
315 return NULL; // incomplete request
316 }
317
318 // parse request
319
320 ArgumentIterator args(buf, (max_len)-left);
321
322 // version already checked
323 char* v = args.next();
324
325 char* name = args.next();
326 if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
327 return NULL;
328 }
329
330 AixAttachOperation* op = new AixAttachOperation(name);
331
332 for (int i=0; i<AttachOperation::arg_count_max; i++) {
333 char* arg = args.next();
334 if (arg == NULL) {
335 op->set_arg(i, NULL);
336 } else {
337 if (strlen(arg) > AttachOperation::arg_length_max) {
338 delete op;
339 return NULL;
340 }
341 op->set_arg(i, arg);
342 }
343 }
344
345 op->set_socket(s);
346 return op;
347 }
348
349
350 // Dequeue an operation
351 //
352 // In the Linux implementation there is only a single operation and clients
353 // cannot queue commands (except at the socket level).
354 //
355 AixAttachOperation* AixAttachListener::dequeue() {
356 for (;;) {
357 int s;
358
359 // wait for client to connect
360 struct sockaddr addr;
361 socklen_t len = sizeof(addr);
362 memset(&addr, 0, len);
363 // We must prevent accept blocking on the socket if it has been shut down.
364 // Therefore we allow interrups and check whether we have been shut down already.
365 if (AixAttachListener::is_shutdown()) {
366 return NULL;
367 }
368 s=::accept(listener(), &addr, &len);
369 if (s == -1) {
370 return NULL; // log a warning?
371 }
372
373 // Added timeouts for read and write. If we get no request within the
374 // next AttachListenerTimeout milliseconds we just finish the connection.
375 struct timeval tv;
376 tv.tv_sec = 0;
377 tv.tv_usec = AttachListenerTimeout * 1000;
378 ::setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv));
379 ::setsockopt(s, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv));
380
381 // get the credentials of the peer and check the effective uid/guid
382 // - check with jeff on this.
383 struct peercred_struct cred_info;
384 socklen_t optlen = sizeof(cred_info);
385 if (::getsockopt(s, SOL_SOCKET, SO_PEERID, (void*)&cred_info, &optlen) == -1) {
386 int res;
387 RESTARTABLE(::close(s), res);
388 continue;
389 }
390 uid_t euid = geteuid();
391 gid_t egid = getegid();
392
393 if (cred_info.euid != euid || cred_info.egid != egid) {
394 int res;
395 RESTARTABLE(::close(s), res);
396 continue;
397 }
398
399 // peer credential look okay so we read the request
400 AixAttachOperation* op = read_request(s);
401 if (op == NULL) {
402 int res;
403 RESTARTABLE(::close(s), res);
404 continue;
405 } else {
406 return op;
407 }
408 }
409 }
410
411 // write the given buffer to the socket
412 int AixAttachListener::write_fully(int s, char* buf, int len) {
413 do {
414 int n = ::write(s, buf, len);
415 if (n == -1) {
416 if (errno != EINTR) return -1;
417 } else {
418 buf += n;
419 len -= n;
420 }
421 }
422 while (len > 0);
423 return 0;
424 }
425
426 // Complete an operation by sending the operation result and any result
427 // output to the client. At this time the socket is in blocking mode so
428 // potentially we can block if there is a lot of data and the client is
429 // non-responsive. For most operations this is a non-issue because the
430 // default send buffer is sufficient to buffer everything. In the future
431 // if there are operations that involves a very big reply then it the
432 // socket could be made non-blocking and a timeout could be used.
433
434 void AixAttachOperation::complete(jint result, bufferedStream* st) {
435 JavaThread* thread = JavaThread::current();
436 ThreadBlockInVM tbivm(thread);
437
438 thread->set_suspend_equivalent();
439 // cleared by handle_special_suspend_equivalent_condition() or
440 // java_suspend_self() via check_and_wait_while_suspended()
441
442 // write operation result
443 char msg[32];
444 sprintf(msg, "%d\n", result);
445 int rc = AixAttachListener::write_fully(this->socket(), msg, strlen(msg));
446
447 // write any result data
448 if (rc == 0) {
449 // Shutdown the socket in the cleanup function to enable more than
450 // one agent attach in a sequence (see comments to listener_cleanup()).
451 AixAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
452 }
453
454 // done
455 RESTARTABLE(::close(this->socket()), rc);
456
457 // were we externally suspended while we were waiting?
458 thread->check_and_wait_while_suspended();
459
460 delete this;
461 }
462
463
464 // AttachListener functions
465
466 AttachOperation* AttachListener::dequeue() {
467 JavaThread* thread = JavaThread::current();
468 ThreadBlockInVM tbivm(thread);
469
470 thread->set_suspend_equivalent();
471 // cleared by handle_special_suspend_equivalent_condition() or
472 // java_suspend_self() via check_and_wait_while_suspended()
473
474 AttachOperation* op = AixAttachListener::dequeue();
475
476 // were we externally suspended while we were waiting?
477 thread->check_and_wait_while_suspended();
478
479 return op;
480 }
481
482 // Performs initialization at vm startup
483 // For AIX we remove any stale .java_pid file which could cause
484 // an attaching process to think we are ready to receive on the
485 // domain socket before we are properly initialized
486
487 void AttachListener::vm_start() {
488 char fn[UNIX_PATH_MAX];
489 struct stat64 st;
490 int ret;
491
492 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
493 os::get_temp_directory(), os::current_process_id());
494 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
495
496 RESTARTABLE(::stat64(fn, &st), ret);
497 if (ret == 0) {
498 ret = ::unlink(fn);
499 if (ret == -1) {
500 debug_only(warning("failed to remove stale attach pid file at %s", fn));
501 }
502 }
503 }
504
505 int AttachListener::pd_init() {
506 JavaThread* thread = JavaThread::current();
507 ThreadBlockInVM tbivm(thread);
508
509 thread->set_suspend_equivalent();
510 // cleared by handle_special_suspend_equivalent_condition() or
511 // java_suspend_self() via check_and_wait_while_suspended()
512
513 int ret_code = AixAttachListener::init();
514
515 // were we externally suspended while we were waiting?
516 thread->check_and_wait_while_suspended();
517
518 return ret_code;
519 }
520
521 // Attach Listener is started lazily except in the case when
522 // +ReduseSignalUsage is used
523 bool AttachListener::init_at_startup() {
524 if (ReduceSignalUsage) {
525 return true;
526 } else {
527 return false;
528 }
529 }
530
531 // If the file .attach_pid<pid> exists in the working directory
532 // or /tmp then this is the trigger to start the attach mechanism
533 bool AttachListener::is_init_trigger() {
534 if (init_at_startup() || is_initialized()) {
535 return false; // initialized at startup or already initialized
536 }
537 char fn[PATH_MAX+1];
538 sprintf(fn, ".attach_pid%d", os::current_process_id());
539 int ret;
540 struct stat64 st;
541 RESTARTABLE(::stat64(fn, &st), ret);
542 if (ret == -1) {
543 snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
544 os::get_temp_directory(), os::current_process_id());
545 RESTARTABLE(::stat64(fn, &st), ret);
546 }
547 if (ret == 0) {
548 // simple check to avoid starting the attach mechanism when
549 // a bogus user creates the file
550 if (st.st_uid == geteuid()) {
551 init();
552 return true;
553 }
554 }
555 return false;
556 }
557
558 // if VM aborts then remove listener
559 void AttachListener::abort() {
560 listener_cleanup();
561 }
562
563 void AttachListener::pd_data_dump() {
564 os::signal_notify(SIGQUIT);
565 }
566
567 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
568 return NULL;
569 }
570
571 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
572 out->print_cr("flag '%s' cannot be changed", op->arg(0));
573 return JNI_ERR;
574 }
575
576 void AttachListener::pd_detachall() {
577 // Cleanup server socket to detach clients.
578 listener_cleanup();
579 }