1 /*
2 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2013 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.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 return NULL;
148 }
149 char* res = _pos;
150 char* next_pos = strchr(_pos, '\0');
151 if (next_pos < _end) {
152 next_pos++;
153 }
154 _pos = next_pos;
155 return res;
156 }
157 };
158
159 // On AIX if sockets block until all data has been transmitted
160 // successfully in some communication domains a socket "close" may
161 // never complete. We have to take care that after the socket shutdown
162 // the listener never enters accept state.
163
164 // atexit hook to stop listener and unlink the file that it is
165 // bound too.
166
167 // Some modifications to the listener logic to prevent deadlocks on exit.
168 // 1. We Shutdown the socket here instead. AixAttachOperation::complete() is not the right place
169 // since more than one agent in a sequence in JPLIS live tests wouldn't work (Listener thread
170 // would be dead after the first operation completion).
171 // 2. close(s) may never return if the listener thread is in socket accept(). Unlinking the file
172 // should be sufficient for cleanup.
173 extern "C" {
174 static void listener_cleanup() {
175 static int cleanup_done;
176 if (!cleanup_done) {
177 cleanup_done = 1;
178 AixAttachListener::set_shutdown(true);
179 int s = AixAttachListener::listener();
180 if (s != -1) {
181 ::shutdown(s, 2);
182 }
183 if (AixAttachListener::has_path()) {
184 ::unlink(AixAttachListener::path());
185 }
186 }
187 }
188 }
189
190 // Initialization - create a listener socket and bind it to a file
191
192 int AixAttachListener::init() {
193 char path[UNIX_PATH_MAX]; // socket file
194 char initial_path[UNIX_PATH_MAX]; // socket file during setup
195 int listener; // listener socket (file descriptor)
196
197 // register function to cleanup
198 ::atexit(listener_cleanup);
199
200 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
201 os::get_temp_directory(), os::current_process_id());
202 if (n < (int)UNIX_PATH_MAX) {
203 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
204 }
205 if (n >= (int)UNIX_PATH_MAX) {
206 return -1;
207 }
208
209 // create the listener socket
210 listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
211 if (listener == -1) {
212 return -1;
213 }
214
215 // bind socket
216 struct sockaddr_un addr;
217 addr.sun_family = AF_UNIX;
218 strcpy(addr.sun_path, initial_path);
219 ::unlink(initial_path);
220 // We must call bind with the actual socketaddr length. This is obligatory for AS400.
221 int res = ::bind(listener, (struct sockaddr*)&addr, SUN_LEN(&addr));
222 if (res == -1) {
223 RESTARTABLE(::close(listener), res);
224 return -1;
225 }
226
227 // put in listen mode, set permissions, and rename into place
228 res = ::listen(listener, 5);
229 if (res == 0) {
230 RESTARTABLE(::chmod(initial_path, (S_IREAD|S_IWRITE) & ~(S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)), res);
231 if (res == 0) {
232 res = ::rename(initial_path, path);
233 }
234 }
235 if (res == -1) {
236 RESTARTABLE(::close(listener), res);
237 ::unlink(initial_path);
238 return -1;
239 }
240 set_path(path);
241 set_listener(listener);
242 set_shutdown(false);
243
244 return 0;
245 }
246
247 // Given a socket that is connected to a peer we read the request and
248 // create an AttachOperation. As the socket is blocking there is potential
249 // for a denial-of-service if the peer does not response. However this happens
250 // after the peer credentials have been checked and in the worst case it just
251 // means that the attach listener thread is blocked.
252 //
253 AixAttachOperation* AixAttachListener::read_request(int s) {
254 char ver_str[8];
255 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
256
257 // The request is a sequence of strings so we first figure out the
258 // expected count and the maximum possible length of the request.
259 // The request is:
260 // <ver>0<cmd>0<arg>0<arg>0<arg>0
261 // where <ver> is the protocol version (1), <cmd> is the command
262 // name ("load", "datadump", ...), and <arg> is an argument
263 int expected_str_count = 2 + AttachOperation::arg_count_max;
264 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
265 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
266
267 char buf[max_len];
268 int str_count = 0;
269
270 // Read until all (expected) strings have been read, the buffer is
271 // full, or EOF.
272
273 int off = 0;
274 int left = max_len;
275
276 do {
277 int n;
278 // Don't block on interrupts because this will
279 // hang in the clean-up when shutting down.
280 n = read(s, buf+off, left);
281 if (n == -1) {
282 return NULL; // reset by peer or other error
283 }
284 if (n == 0) { // end of file reached
285 break;
286 }
287 for (int i=0; i<n; i++) {
288 if (buf[off+i] == 0) {
289 // EOS found
290 str_count++;
291
292 // The first string is <ver> so check it now to
293 // check for protocol mis-match
294 if (str_count == 1) {
295 if ((strlen(buf) != strlen(ver_str)) ||
296 (atoi(buf) != ATTACH_PROTOCOL_VER)) {
297 char msg[32];
298 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
299 write_fully(s, msg, strlen(msg));
300 return NULL;
301 }
302 }
303 }
304 }
305 off += n;
306 left -= n;
307 } while (left > 0 && str_count < expected_str_count);
308
309 if (str_count != expected_str_count) {
310 return NULL; // incomplete request
311 }
312
313 // parse request
314
315 ArgumentIterator args(buf, (max_len)-left);
316
317 // version already checked
318 char* v = args.next();
319
320 char* name = args.next();
321 if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
322 return NULL;
323 }
324
325 AixAttachOperation* op = new AixAttachOperation(name);
326
327 for (int i=0; i<AttachOperation::arg_count_max; i++) {
328 char* arg = args.next();
329 if (arg == NULL) {
330 op->set_arg(i, NULL);
331 } else {
332 if (strlen(arg) > AttachOperation::arg_length_max) {
333 delete op;
334 return NULL;
335 }
336 op->set_arg(i, arg);
337 }
338 }
339
340 op->set_socket(s);
341 return op;
342 }
343
344
345 // Dequeue an operation
346 //
347 // In the Linux implementation there is only a single operation and clients
348 // cannot queue commands (except at the socket level).
349 //
350 AixAttachOperation* AixAttachListener::dequeue() {
351 for (;;) {
352 int s;
353
354 // wait for client to connect
355 struct sockaddr addr;
356 socklen_t len = sizeof(addr);
357 memset(&addr, 0, len);
358 // We must prevent accept blocking on the socket if it has been shut down.
359 // Therefore we allow interrups and check whether we have been shut down already.
360 if (AixAttachListener::is_shutdown()) {
361 return NULL;
362 }
363 s=::accept(listener(), &addr, &len);
364 if (s == -1) {
365 return NULL; // log a warning?
366 }
367
368 // Added timeouts for read and write. If we get no request within the
369 // next AttachListenerTimeout milliseconds we just finish the connection.
370 struct timeval tv;
371 tv.tv_sec = 0;
372 tv.tv_usec = AttachListenerTimeout * 1000;
373 ::setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv));
374 ::setsockopt(s, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv));
375
376 // get the credentials of the peer and check the effective uid/guid
377 // - check with jeff on this.
378 struct peercred_struct cred_info;
379 socklen_t optlen = sizeof(cred_info);
380 if (::getsockopt(s, SOL_SOCKET, SO_PEERID, (void*)&cred_info, &optlen) == -1) {
381 int res;
382 RESTARTABLE(::close(s), res);
383 continue;
384 }
385 uid_t euid = geteuid();
386 gid_t egid = getegid();
387
388 if (cred_info.euid != euid || cred_info.egid != egid) {
389 int res;
390 RESTARTABLE(::close(s), res);
391 continue;
392 }
393
394 // peer credential look okay so we read the request
395 AixAttachOperation* op = read_request(s);
396 if (op == NULL) {
397 int res;
398 RESTARTABLE(::close(s), res);
399 continue;
400 } else {
401 return op;
402 }
403 }
404 }
405
406 // write the given buffer to the socket
407 int AixAttachListener::write_fully(int s, char* buf, int len) {
408 do {
409 int n = ::write(s, buf, len);
410 if (n == -1) {
411 if (errno != EINTR) return -1;
412 } else {
413 buf += n;
414 len -= n;
415 }
416 }
417 while (len > 0);
418 return 0;
419 }
420
421 // Complete an operation by sending the operation result and any result
422 // output to the client. At this time the socket is in blocking mode so
423 // potentially we can block if there is a lot of data and the client is
424 // non-responsive. For most operations this is a non-issue because the
425 // default send buffer is sufficient to buffer everything. In the future
426 // if there are operations that involves a very big reply then it the
427 // socket could be made non-blocking and a timeout could be used.
428
429 void AixAttachOperation::complete(jint result, bufferedStream* st) {
430 JavaThread* thread = JavaThread::current();
431 ThreadBlockInVM tbivm(thread);
432
433 thread->set_suspend_equivalent();
434 // cleared by handle_special_suspend_equivalent_condition() or
435 // java_suspend_self() via check_and_wait_while_suspended()
436
437 // write operation result
438 char msg[32];
439 sprintf(msg, "%d\n", result);
440 int rc = AixAttachListener::write_fully(this->socket(), msg, strlen(msg));
441
442 // write any result data
443 if (rc == 0) {
444 // Shutdown the socket in the cleanup function to enable more than
445 // one agent attach in a sequence (see comments to listener_cleanup()).
446 AixAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
447 }
448
449 // done
450 RESTARTABLE(::close(this->socket()), rc);
451
452 // were we externally suspended while we were waiting?
453 thread->check_and_wait_while_suspended();
454
455 delete this;
456 }
457
458
459 // AttachListener functions
460
461 AttachOperation* AttachListener::dequeue() {
462 JavaThread* thread = JavaThread::current();
463 ThreadBlockInVM tbivm(thread);
464
465 thread->set_suspend_equivalent();
466 // cleared by handle_special_suspend_equivalent_condition() or
467 // java_suspend_self() via check_and_wait_while_suspended()
468
469 AttachOperation* op = AixAttachListener::dequeue();
470
471 // were we externally suspended while we were waiting?
472 thread->check_and_wait_while_suspended();
473
474 return op;
475 }
476
477 // Performs initialization at vm startup
478 // For AIX we remove any stale .java_pid file which could cause
479 // an attaching process to think we are ready to receive on the
480 // domain socket before we are properly initialized
481
482 void AttachListener::vm_start() {
483 char fn[UNIX_PATH_MAX];
484 struct stat64 st;
485 int ret;
486
487 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
488 os::get_temp_directory(), os::current_process_id());
489 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
490
491 RESTARTABLE(::stat64(fn, &st), ret);
492 if (ret == 0) {
493 ret = ::unlink(fn);
494 if (ret == -1) {
495 debug_only(warning("failed to remove stale attach pid file at %s", fn));
496 }
497 }
498 }
499
500 int AttachListener::pd_init() {
501 JavaThread* thread = JavaThread::current();
502 ThreadBlockInVM tbivm(thread);
503
504 thread->set_suspend_equivalent();
505 // cleared by handle_special_suspend_equivalent_condition() or
506 // java_suspend_self() via check_and_wait_while_suspended()
507
508 int ret_code = AixAttachListener::init();
509
510 // were we externally suspended while we were waiting?
511 thread->check_and_wait_while_suspended();
512
513 return ret_code;
514 }
515
516 // Attach Listener is started lazily except in the case when
517 // +ReduseSignalUsage is used
518 bool AttachListener::init_at_startup() {
519 if (ReduceSignalUsage) {
520 return true;
521 } else {
522 return false;
523 }
524 }
525
526 // If the file .attach_pid<pid> exists in the working directory
527 // or /tmp then this is the trigger to start the attach mechanism
528 bool AttachListener::is_init_trigger() {
529 if (init_at_startup() || is_initialized()) {
530 return false; // initialized at startup or already initialized
531 }
532 char fn[PATH_MAX+1];
533 sprintf(fn, ".attach_pid%d", os::current_process_id());
534 int ret;
535 struct stat64 st;
536 RESTARTABLE(::stat64(fn, &st), ret);
537 if (ret == -1) {
538 snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
539 os::get_temp_directory(), os::current_process_id());
540 RESTARTABLE(::stat64(fn, &st), ret);
541 }
542 if (ret == 0) {
543 // simple check to avoid starting the attach mechanism when
544 // a bogus user creates the file
545 if (st.st_uid == geteuid()) {
546 init();
547 return true;
548 }
549 }
550 return false;
551 }
552
553 // if VM aborts then remove listener
554 void AttachListener::abort() {
555 listener_cleanup();
556 }
557
558 void AttachListener::pd_data_dump() {
559 os::signal_notify(SIGQUIT);
560 }
561
562 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
563 return NULL;
564 }
565
566 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
567 out->print_cr("flag '%s' cannot be changed", op->arg(0));
568 return JNI_ERR;
569 }
570
571 void AttachListener::pd_detachall() {
572 // Cleanup server socket to detach clients.
573 listener_cleanup();
574 }