1 /*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/vmSymbols.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "os_linux.inline.hpp"
31 #include "runtime/handles.inline.hpp"
32 #include "runtime/perfMemory.hpp"
33 #include "utilities/exceptions.hpp"
34
35 // put OS-includes here
36 # include <sys/types.h>
37 # include <sys/mman.h>
38 # include <errno.h>
39 # include <stdio.h>
40 # include <unistd.h>
41 # include <sys/stat.h>
42 # include <signal.h>
43 # include <pwd.h>
44
45 static char* backing_store_file_name = NULL; // name of the backing store
46 // file, if successfully created.
47
48 // Standard Memory Implementation Details
49
50 // create the PerfData memory region in standard memory.
51 //
52 static char* create_standard_memory(size_t size) {
53
54 // allocate an aligned chuck of memory
55 char* mapAddress = os::reserve_memory(size);
56
57 if (mapAddress == NULL) {
58 return NULL;
59 }
60
61 // commit memory
62 if (!os::commit_memory(mapAddress, size)) {
63 if (PrintMiscellaneous && Verbose) {
64 warning("Could not commit PerfData memory\n");
65 }
66 os::release_memory(mapAddress, size);
67 return NULL;
68 }
69
70 return mapAddress;
71 }
72
73 // delete the PerfData memory region
74 //
75 static void delete_standard_memory(char* addr, size_t size) {
76
77 // there are no persistent external resources to cleanup for standard
78 // memory. since DestroyJavaVM does not support unloading of the JVM,
79 // cleanup of the memory resource is not performed. The memory will be
80 // reclaimed by the OS upon termination of the process.
81 //
82 return;
83 }
84
85 // save the specified memory region to the given file
86 //
87 // Note: this function might be called from signal handler (by os::abort()),
88 // don't allocate heap memory.
89 //
90 static void save_memory_to_file(char* addr, size_t size) {
91
92 const char* destfile = PerfMemory::get_perfdata_file_path();
93 assert(destfile[0] != '\0', "invalid PerfData file path");
94
95 int result;
96
97 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
98 result);;
99 if (result == OS_ERR) {
100 if (PrintMiscellaneous && Verbose) {
101 warning("Could not create Perfdata save file: %s: %s\n",
102 destfile, strerror(errno));
103 }
104 } else {
105 int fd = result;
106
107 for (size_t remaining = size; remaining > 0;) {
108
109 RESTARTABLE(::write(fd, addr, remaining), result);
110 if (result == OS_ERR) {
111 if (PrintMiscellaneous && Verbose) {
112 warning("Could not write Perfdata save file: %s: %s\n",
113 destfile, strerror(errno));
114 }
115 break;
116 }
117
118 remaining -= (size_t)result;
119 addr += result;
120 }
121
122 RESTARTABLE(::close(fd), result);
123 if (PrintMiscellaneous && Verbose) {
124 if (result == OS_ERR) {
125 warning("Could not close %s: %s\n", destfile, strerror(errno));
126 }
127 }
128 }
129 FREE_C_HEAP_ARRAY(char, destfile);
130 }
131
132
133 // Shared Memory Implementation Details
134
135 // Note: the solaris and linux shared memory implementation uses the mmap
136 // interface with a backing store file to implement named shared memory.
137 // Using the file system as the name space for shared memory allows a
138 // common name space to be supported across a variety of platforms. It
139 // also provides a name space that Java applications can deal with through
140 // simple file apis.
141 //
142 // The solaris and linux implementations store the backing store file in
143 // a user specific temporary directory located in the /tmp file system,
144 // which is always a local file system and is sometimes a RAM based file
145 // system.
146
147 // return the user specific temporary directory name.
148 //
149 // the caller is expected to free the allocated memory.
150 //
151 static char* get_user_tmp_dir(const char* user) {
152
153 const char* tmpdir = os::get_temp_directory();
154 const char* perfdir = PERFDATA_NAME;
155 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
156 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes);
157
158 // construct the path name to user specific tmp directory
159 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
160
161 return dirname;
162 }
163
164 // convert the given file name into a process id. if the file
165 // does not meet the file naming constraints, return 0.
166 //
167 static pid_t filename_to_pid(const char* filename) {
168
169 // a filename that doesn't begin with a digit is not a
170 // candidate for conversion.
171 //
172 if (!isdigit(*filename)) {
173 return 0;
174 }
175
176 // check if file name can be converted to an integer without
177 // any leftover characters.
178 //
179 char* remainder = NULL;
180 errno = 0;
181 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
182
183 if (errno != 0) {
184 return 0;
185 }
186
187 // check for left over characters. If any, then the filename is
188 // not a candidate for conversion.
189 //
190 if (remainder != NULL && *remainder != '\0') {
191 return 0;
192 }
193
194 // successful conversion, return the pid
195 return pid;
196 }
197
198
199 // check if the given path is considered a secure directory for
200 // the backing store files. Returns true if the directory exists
201 // and is considered a secure location. Returns false if the path
202 // is a symbolic link or if an error occurred.
203 //
204 static bool is_directory_secure(const char* path) {
205 struct stat statbuf;
206 int result = 0;
207
208 RESTARTABLE(::lstat(path, &statbuf), result);
209 if (result == OS_ERR) {
210 return false;
211 }
212
213 // the path exists, now check it's mode
214 if (S_ISLNK(statbuf.st_mode) || !S_ISDIR(statbuf.st_mode)) {
215 // the path represents a link or some non-directory file type,
216 // which is not what we expected. declare it insecure.
217 //
218 return false;
219 }
220 else {
221 // we have an existing directory, check if the permissions are safe.
222 //
223 if ((statbuf.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
224 // the directory is open for writing and could be subjected
225 // to a symlnk attack. declare it insecure.
226 //
227 return false;
228 }
229 }
230 return true;
231 }
232
233
234 // return the user name for the given user id
235 //
236 // the caller is expected to free the allocated memory.
237 //
238 static char* get_user_name(uid_t uid) {
239
240 struct passwd pwent;
241
242 // determine the max pwbuf size from sysconf, and hardcode
243 // a default if this not available through sysconf.
244 //
245 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
246 if (bufsize == -1)
247 bufsize = 1024;
248
249 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize);
250
251 // POSIX interface to getpwuid_r is used on LINUX
252 struct passwd* p;
253 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
254
255 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
256 if (PrintMiscellaneous && Verbose) {
257 if (result != 0) {
258 warning("Could not retrieve passwd entry: %s\n",
259 strerror(result));
260 }
261 else if (p == NULL) {
262 // this check is added to protect against an observed problem
263 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
264 // indicating success, but has p == NULL. This was observed when
265 // inserting a file descriptor exhaustion fault prior to the call
266 // getpwuid_r() call. In this case, error is set to the appropriate
267 // error condition, but this is undocumented behavior. This check
268 // is safe under any condition, but the use of errno in the output
269 // message may result in an erroneous message.
270 // Bug Id 89052 was opened with RedHat.
271 //
272 warning("Could not retrieve passwd entry: %s\n",
273 strerror(errno));
274 }
275 else {
276 warning("Could not determine user name: %s\n",
277 p->pw_name == NULL ? "pw_name = NULL" :
278 "pw_name zero length");
279 }
280 }
281 FREE_C_HEAP_ARRAY(char, pwbuf);
282 return NULL;
283 }
284
285 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1);
286 strcpy(user_name, p->pw_name);
287
288 FREE_C_HEAP_ARRAY(char, pwbuf);
289 return user_name;
290 }
291
292 // return the name of the user that owns the process identified by vmid.
293 //
294 // This method uses a slow directory search algorithm to find the backing
295 // store file for the specified vmid and returns the user name, as determined
296 // by the user name suffix of the hsperfdata_<username> directory name.
297 //
298 // the caller is expected to free the allocated memory.
299 //
300 static char* get_user_name_slow(int vmid, TRAPS) {
301
302 // short circuit the directory search if the process doesn't even exist.
303 if (kill(vmid, 0) == OS_ERR) {
304 if (errno == ESRCH) {
305 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
306 "Process not found");
307 }
308 else /* EPERM */ {
309 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
310 }
311 }
312
313 // directory search
314 char* oldest_user = NULL;
315 time_t oldest_ctime = 0;
316
317 const char* tmpdirname = os::get_temp_directory();
318
319 DIR* tmpdirp = os::opendir(tmpdirname);
320
321 if (tmpdirp == NULL) {
322 return NULL;
323 }
324
325 // for each entry in the directory that matches the pattern hsperfdata_*,
326 // open the directory and check if the file for the given vmid exists.
327 // The file with the expected name and the latest creation date is used
328 // to determine the user name for the process id.
329 //
330 struct dirent* dentry;
331 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname));
332 errno = 0;
333 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
334
335 // check if the directory entry is a hsperfdata file
336 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
337 continue;
338 }
339
340 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
341 strlen(tmpdirname) + strlen(dentry->d_name) + 2);
342 strcpy(usrdir_name, tmpdirname);
343 strcat(usrdir_name, "/");
344 strcat(usrdir_name, dentry->d_name);
345
346 DIR* subdirp = os::opendir(usrdir_name);
347
348 if (subdirp == NULL) {
349 FREE_C_HEAP_ARRAY(char, usrdir_name);
350 continue;
351 }
352
353 // Since we don't create the backing store files in directories
354 // pointed to by symbolic links, we also don't follow them when
355 // looking for the files. We check for a symbolic link after the
356 // call to opendir in order to eliminate a small window where the
357 // symlink can be exploited.
358 //
359 if (!is_directory_secure(usrdir_name)) {
360 FREE_C_HEAP_ARRAY(char, usrdir_name);
361 os::closedir(subdirp);
362 continue;
363 }
364
365 struct dirent* udentry;
366 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name));
367 errno = 0;
368 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
369
370 if (filename_to_pid(udentry->d_name) == vmid) {
371 struct stat statbuf;
372 int result;
373
374 char* filename = NEW_C_HEAP_ARRAY(char,
375 strlen(usrdir_name) + strlen(udentry->d_name) + 2);
376
377 strcpy(filename, usrdir_name);
378 strcat(filename, "/");
379 strcat(filename, udentry->d_name);
380
381 // don't follow symbolic links for the file
382 RESTARTABLE(::lstat(filename, &statbuf), result);
383 if (result == OS_ERR) {
384 FREE_C_HEAP_ARRAY(char, filename);
385 continue;
386 }
387
388 // skip over files that are not regular files.
389 if (!S_ISREG(statbuf.st_mode)) {
390 FREE_C_HEAP_ARRAY(char, filename);
391 continue;
392 }
393
394 // compare and save filename with latest creation time
395 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
396
397 if (statbuf.st_ctime > oldest_ctime) {
398 char* user = strchr(dentry->d_name, '_') + 1;
399
400 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
401 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1);
402
403 strcpy(oldest_user, user);
404 oldest_ctime = statbuf.st_ctime;
405 }
406 }
407
408 FREE_C_HEAP_ARRAY(char, filename);
409 }
410 }
411 os::closedir(subdirp);
412 FREE_C_HEAP_ARRAY(char, udbuf);
413 FREE_C_HEAP_ARRAY(char, usrdir_name);
414 }
415 os::closedir(tmpdirp);
416 FREE_C_HEAP_ARRAY(char, tdbuf);
417
418 return(oldest_user);
419 }
420
421 // return the name of the user that owns the JVM indicated by the given vmid.
422 //
423 static char* get_user_name(int vmid, TRAPS) {
424 return get_user_name_slow(vmid, CHECK_NULL);
425 }
426
427 // return the file name of the backing store file for the named
428 // shared memory region for the given user name and vmid.
429 //
430 // the caller is expected to free the allocated memory.
431 //
432 static char* get_sharedmem_filename(const char* dirname, int vmid) {
433
434 // add 2 for the file separator and a null terminator.
435 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
436
437 char* name = NEW_C_HEAP_ARRAY(char, nbytes);
438 snprintf(name, nbytes, "%s/%d", dirname, vmid);
439
440 return name;
441 }
442
443
444 // remove file
445 //
446 // this method removes the file specified by the given path
447 //
448 static void remove_file(const char* path) {
449
450 int result;
451
452 // if the file is a directory, the following unlink will fail. since
453 // we don't expect to find directories in the user temp directory, we
454 // won't try to handle this situation. even if accidentially or
455 // maliciously planted, the directory's presence won't hurt anything.
456 //
457 RESTARTABLE(::unlink(path), result);
458 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
459 if (errno != ENOENT) {
460 warning("Could not unlink shared memory backing"
461 " store file %s : %s\n", path, strerror(errno));
462 }
463 }
464 }
465
466
467 // remove file
468 //
469 // this method removes the file with the given file name in the
470 // named directory.
471 //
472 static void remove_file(const char* dirname, const char* filename) {
473
474 size_t nbytes = strlen(dirname) + strlen(filename) + 2;
475 char* path = NEW_C_HEAP_ARRAY(char, nbytes);
476
477 strcpy(path, dirname);
478 strcat(path, "/");
479 strcat(path, filename);
480
481 remove_file(path);
482
483 FREE_C_HEAP_ARRAY(char, path);
484 }
485
486
487 // cleanup stale shared memory resources
488 //
489 // This method attempts to remove all stale shared memory files in
490 // the named user temporary directory. It scans the named directory
491 // for files matching the pattern ^$[0-9]*$. For each file found, the
492 // process id is extracted from the file name and a test is run to
493 // determine if the process is alive. If the process is not alive,
494 // any stale file resources are removed.
495 //
496 static void cleanup_sharedmem_resources(const char* dirname) {
497
498 // open the user temp directory
499 DIR* dirp = os::opendir(dirname);
500
501 if (dirp == NULL) {
502 // directory doesn't exist, so there is nothing to cleanup
503 return;
504 }
505
506 if (!is_directory_secure(dirname)) {
507 // the directory is not a secure directory
508 return;
509 }
510
511 // for each entry in the directory that matches the expected file
512 // name pattern, determine if the file resources are stale and if
513 // so, remove the file resources. Note, instrumented HotSpot processes
514 // for this user may start and/or terminate during this search and
515 // remove or create new files in this directory. The behavior of this
516 // loop under these conditions is dependent upon the implementation of
517 // opendir/readdir.
518 //
519 struct dirent* entry;
520 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname));
521 errno = 0;
522 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
523
524 pid_t pid = filename_to_pid(entry->d_name);
525
526 if (pid == 0) {
527
528 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
529
530 // attempt to remove all unexpected files, except "." and ".."
531 remove_file(dirname, entry->d_name);
532 }
533
534 errno = 0;
535 continue;
536 }
537
538 // we now have a file name that converts to a valid integer
539 // that could represent a process id . if this process id
540 // matches the current process id or the process is not running,
541 // then remove the stale file resources.
542 //
543 // process liveness is detected by sending signal number 0 to
544 // the process id (see kill(2)). if kill determines that the
545 // process does not exist, then the file resources are removed.
546 // if kill determines that that we don't have permission to
547 // signal the process, then the file resources are assumed to
548 // be stale and are removed because the resources for such a
549 // process should be in a different user specific directory.
550 //
551 if ((pid == os::current_process_id()) ||
552 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
553
554 remove_file(dirname, entry->d_name);
555 }
556 errno = 0;
557 }
558 os::closedir(dirp);
559 FREE_C_HEAP_ARRAY(char, dbuf);
560 }
561
562 // make the user specific temporary directory. Returns true if
563 // the directory exists and is secure upon return. Returns false
564 // if the directory exists but is either a symlink, is otherwise
565 // insecure, or if an error occurred.
566 //
567 static bool make_user_tmp_dir(const char* dirname) {
568
569 // create the directory with 0755 permissions. note that the directory
570 // will be owned by euid::egid, which may not be the same as uid::gid.
571 //
572 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
573 if (errno == EEXIST) {
574 // The directory already exists and was probably created by another
575 // JVM instance. However, this could also be the result of a
576 // deliberate symlink. Verify that the existing directory is safe.
577 //
578 if (!is_directory_secure(dirname)) {
579 // directory is not secure
580 if (PrintMiscellaneous && Verbose) {
581 warning("%s directory is insecure\n", dirname);
582 }
583 return false;
584 }
585 }
586 else {
587 // we encountered some other failure while attempting
588 // to create the directory
589 //
590 if (PrintMiscellaneous && Verbose) {
591 warning("could not create directory %s: %s\n",
592 dirname, strerror(errno));
593 }
594 return false;
595 }
596 }
597 return true;
598 }
599
600 // create the shared memory file resources
601 //
602 // This method creates the shared memory file with the given size
603 // This method also creates the user specific temporary directory, if
604 // it does not yet exist.
605 //
606 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
607
608 // make the user temporary directory
609 if (!make_user_tmp_dir(dirname)) {
610 // could not make/find the directory or the found directory
611 // was not secure
612 return -1;
613 }
614
615 int result;
616
617 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_TRUNC, S_IREAD|S_IWRITE), result);
618 if (result == OS_ERR) {
619 if (PrintMiscellaneous && Verbose) {
620 warning("could not create file %s: %s\n", filename, strerror(errno));
621 }
622 return -1;
623 }
624
625 // save the file descriptor
626 int fd = result;
627
628 // set the file size
629 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
630 if (result == OS_ERR) {
631 if (PrintMiscellaneous && Verbose) {
632 warning("could not set shared memory file size: %s\n", strerror(errno));
633 }
634 RESTARTABLE(::close(fd), result);
635 return -1;
636 }
637
638 // Verify that we have enough disk space for this file.
639 // We'll get random SIGBUS crashes on memory accesses if
640 // we don't.
641
642 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
643 int zero_int = 0;
644 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
645 if (result == -1 ) break;
646 RESTARTABLE(::write(fd, &zero_int, 1), result);
647 if (result != 1) {
648 if (errno == ENOSPC) {
649 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
650 }
651 break;
652 }
653 }
654
655 if (result != -1) {
656 return fd;
657 } else {
658 RESTARTABLE(::close(fd), result);
659 return -1;
660 }
661 }
662
663 // open the shared memory file for the given user and vmid. returns
664 // the file descriptor for the open file or -1 if the file could not
665 // be opened.
666 //
667 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
668
669 // open the file
670 int result;
671 RESTARTABLE(::open(filename, oflags), result);
672 if (result == OS_ERR) {
673 if (errno == ENOENT) {
674 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
675 "Process not found");
676 }
677 else if (errno == EACCES) {
678 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
679 "Permission denied");
680 }
681 else {
682 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
683 }
684 }
685
686 return result;
687 }
688
689 // create a named shared memory region. returns the address of the
690 // memory region on success or NULL on failure. A return value of
691 // NULL will ultimately disable the shared memory feature.
692 //
693 // On Solaris and Linux, the name space for shared memory objects
694 // is the file system name space.
695 //
696 // A monitoring application attaching to a JVM does not need to know
697 // the file system name of the shared memory object. However, it may
698 // be convenient for applications to discover the existence of newly
699 // created and terminating JVMs by watching the file system name space
700 // for files being created or removed.
701 //
702 static char* mmap_create_shared(size_t size) {
703
704 int result;
705 int fd;
706 char* mapAddress;
707
708 int vmid = os::current_process_id();
709
710 char* user_name = get_user_name(geteuid());
711
712 if (user_name == NULL)
713 return NULL;
714
715 char* dirname = get_user_tmp_dir(user_name);
716 char* filename = get_sharedmem_filename(dirname, vmid);
717
718 // cleanup any stale shared memory files
719 cleanup_sharedmem_resources(dirname);
720
721 assert(((size > 0) && (size % os::vm_page_size() == 0)),
722 "unexpected PerfMemory region size");
723
724 fd = create_sharedmem_resources(dirname, filename, size);
725
726 FREE_C_HEAP_ARRAY(char, user_name);
727 FREE_C_HEAP_ARRAY(char, dirname);
728
729 if (fd == -1) {
730 FREE_C_HEAP_ARRAY(char, filename);
731 return NULL;
732 }
733
734 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
735
736 // attempt to close the file - restart it if it was interrupted,
737 // but ignore other failures
738 RESTARTABLE(::close(fd), result);
739 assert(result != OS_ERR, "could not close file");
740
741 if (mapAddress == MAP_FAILED) {
742 if (PrintMiscellaneous && Verbose) {
743 warning("mmap failed - %s\n", strerror(errno));
744 }
745 remove_file(filename);
746 FREE_C_HEAP_ARRAY(char, filename);
747 return NULL;
748 }
749
750 // save the file name for use in delete_shared_memory()
751 backing_store_file_name = filename;
752
753 // clear the shared memory region
754 (void)::memset((void*) mapAddress, 0, size);
755
756 return mapAddress;
757 }
758
759 // release a named shared memory region
760 //
761 static void unmap_shared(char* addr, size_t bytes) {
762 os::release_memory(addr, bytes);
763 }
764
765 // create the PerfData memory region in shared memory.
766 //
767 static char* create_shared_memory(size_t size) {
768
769 // create the shared memory region.
770 return mmap_create_shared(size);
771 }
772
773 // delete the shared PerfData memory region
774 //
775 static void delete_shared_memory(char* addr, size_t size) {
776
777 // cleanup the persistent shared memory resources. since DestroyJavaVM does
778 // not support unloading of the JVM, unmapping of the memory resource is
779 // not performed. The memory will be reclaimed by the OS upon termination of
780 // the process. The backing store file is deleted from the file system.
781
782 assert(!PerfDisableSharedMem, "shouldn't be here");
783
784 if (backing_store_file_name != NULL) {
785 remove_file(backing_store_file_name);
786 // Don't.. Free heap memory could deadlock os::abort() if it is called
787 // from signal handler. OS will reclaim the heap memory.
788 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
789 backing_store_file_name = NULL;
790 }
791 }
792
793 // return the size of the file for the given file descriptor
794 // or 0 if it is not a valid size for a shared memory file
795 //
796 static size_t sharedmem_filesize(int fd, TRAPS) {
797
798 struct stat statbuf;
799 int result;
800
801 RESTARTABLE(::fstat(fd, &statbuf), result);
802 if (result == OS_ERR) {
803 if (PrintMiscellaneous && Verbose) {
804 warning("fstat failed: %s\n", strerror(errno));
805 }
806 THROW_MSG_0(vmSymbols::java_io_IOException(),
807 "Could not determine PerfMemory size");
808 }
809
810 if ((statbuf.st_size == 0) ||
811 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
812 THROW_MSG_0(vmSymbols::java_lang_Exception(),
813 "Invalid PerfMemory size");
814 }
815
816 return (size_t)statbuf.st_size;
817 }
818
819 // attach to a named shared memory region.
820 //
821 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
822
823 char* mapAddress;
824 int result;
825 int fd;
826 size_t size;
827 const char* luser = NULL;
828
829 int mmap_prot;
830 int file_flags;
831
832 ResourceMark rm;
833
834 // map the high level access mode to the appropriate permission
835 // constructs for the file and the shared memory mapping.
836 if (mode == PerfMemory::PERF_MODE_RO) {
837 mmap_prot = PROT_READ;
838 file_flags = O_RDONLY;
839 }
840 else if (mode == PerfMemory::PERF_MODE_RW) {
841 #ifdef LATER
842 mmap_prot = PROT_READ | PROT_WRITE;
843 file_flags = O_RDWR;
844 #else
845 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
846 "Unsupported access mode");
847 #endif
848 }
849 else {
850 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
851 "Illegal access mode");
852 }
853
854 if (user == NULL || strlen(user) == 0) {
855 luser = get_user_name(vmid, CHECK);
856 }
857 else {
858 luser = user;
859 }
860
861 if (luser == NULL) {
862 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
863 "Could not map vmid to user Name");
864 }
865
866 char* dirname = get_user_tmp_dir(luser);
867
868 // since we don't follow symbolic links when creating the backing
869 // store file, we don't follow them when attaching either.
870 //
871 if (!is_directory_secure(dirname)) {
872 FREE_C_HEAP_ARRAY(char, dirname);
873 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
874 "Process not found");
875 }
876
877 char* filename = get_sharedmem_filename(dirname, vmid);
878
879 // copy heap memory to resource memory. the open_sharedmem_file
880 // method below need to use the filename, but could throw an
881 // exception. using a resource array prevents the leak that
882 // would otherwise occur.
883 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
884 strcpy(rfilename, filename);
885
886 // free the c heap resources that are no longer needed
887 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
888 FREE_C_HEAP_ARRAY(char, dirname);
889 FREE_C_HEAP_ARRAY(char, filename);
890
891 // open the shared memory file for the give vmid
892 fd = open_sharedmem_file(rfilename, file_flags, CHECK);
893 assert(fd != OS_ERR, "unexpected value");
894
895 if (*sizep == 0) {
896 size = sharedmem_filesize(fd, CHECK);
897 assert(size != 0, "unexpected size");
898 }
899
900 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
901
902 // attempt to close the file - restart if it gets interrupted,
903 // but ignore other failures
904 RESTARTABLE(::close(fd), result);
905 assert(result != OS_ERR, "could not close file");
906
907 if (mapAddress == MAP_FAILED) {
908 if (PrintMiscellaneous && Verbose) {
909 warning("mmap failed: %s\n", strerror(errno));
910 }
911 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
912 "Could not map PerfMemory");
913 }
914
915 *addr = mapAddress;
916 *sizep = size;
917
918 if (PerfTraceMemOps) {
919 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
920 INTPTR_FORMAT "\n", size, vmid, (void*)mapAddress);
921 }
922 }
923
924
925
926
927 // create the PerfData memory region
928 //
929 // This method creates the memory region used to store performance
930 // data for the JVM. The memory may be created in standard or
931 // shared memory.
932 //
933 void PerfMemory::create_memory_region(size_t size) {
934
935 if (PerfDisableSharedMem) {
936 // do not share the memory for the performance data.
937 _start = create_standard_memory(size);
938 }
939 else {
940 _start = create_shared_memory(size);
941 if (_start == NULL) {
942
943 // creation of the shared memory region failed, attempt
944 // to create a contiguous, non-shared memory region instead.
945 //
946 if (PrintMiscellaneous && Verbose) {
947 warning("Reverting to non-shared PerfMemory region.\n");
948 }
949 PerfDisableSharedMem = true;
950 _start = create_standard_memory(size);
951 }
952 }
953
954 if (_start != NULL) _capacity = size;
955
956 }
957
958 // delete the PerfData memory region
959 //
960 // This method deletes the memory region used to store performance
961 // data for the JVM. The memory region indicated by the <address, size>
962 // tuple will be inaccessible after a call to this method.
963 //
964 void PerfMemory::delete_memory_region() {
965
966 assert((start() != NULL && capacity() > 0), "verify proper state");
967
968 // If user specifies PerfDataSaveFile, it will save the performance data
969 // to the specified file name no matter whether PerfDataSaveToFile is specified
970 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
971 // -XX:+PerfDataSaveToFile.
972 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
973 save_memory_to_file(start(), capacity());
974 }
975
976 if (PerfDisableSharedMem) {
977 delete_standard_memory(start(), capacity());
978 }
979 else {
980 delete_shared_memory(start(), capacity());
981 }
982 }
983
984 // attach to the PerfData memory region for another JVM
985 //
986 // This method returns an <address, size> tuple that points to
987 // a memory buffer that is kept reasonably synchronized with
988 // the PerfData memory region for the indicated JVM. This
989 // buffer may be kept in synchronization via shared memory
990 // or some other mechanism that keeps the buffer updated.
991 //
992 // If the JVM chooses not to support the attachability feature,
993 // this method should throw an UnsupportedOperation exception.
994 //
995 // This implementation utilizes named shared memory to map
996 // the indicated process's PerfData memory region into this JVMs
997 // address space.
998 //
999 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1000
1001 if (vmid == 0 || vmid == os::current_process_id()) {
1002 *addrp = start();
1003 *sizep = capacity();
1004 return;
1005 }
1006
1007 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1008 }
1009
1010 // detach from the PerfData memory region of another JVM
1011 //
1012 // This method detaches the PerfData memory region of another
1013 // JVM, specified as an <address, size> tuple of a buffer
1014 // in this process's address space. This method may perform
1015 // arbitrary actions to accomplish the detachment. The memory
1016 // region specified by <address, size> will be inaccessible after
1017 // a call to this method.
1018 //
1019 // If the JVM chooses not to support the attachability feature,
1020 // this method should throw an UnsupportedOperation exception.
1021 //
1022 // This implementation utilizes named shared memory to detach
1023 // the indicated process's PerfData memory region from this
1024 // process's address space.
1025 //
1026 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1027
1028 assert(addr != 0, "address sanity check");
1029 assert(bytes > 0, "capacity sanity check");
1030
1031 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1032 // prevent accidental detachment of this process's PerfMemory region
1033 return;
1034 }
1035
1036 unmap_shared(addr, bytes);
1037 }
1038
1039 char* PerfMemory::backing_store_filename() {
1040 return backing_store_file_name;
1041 }