1 /*
2 * Copyright (c) 2001, 2014, 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 "services/memTracker.hpp"
34 #include "utilities/exceptions.hpp"
35
36 // put OS-includes here
37 # include <sys/types.h>
38 # include <sys/mman.h>
39 # include <errno.h>
40 # include <stdio.h>
41 # include <unistd.h>
42 # include <sys/stat.h>
43 # include <signal.h>
44 # include <pwd.h>
45
46 static char* backing_store_file_name = NULL; // name of the backing store
47 // file, if successfully created.
48
49 // Standard Memory Implementation Details
50
51 // create the PerfData memory region in standard memory.
52 //
53 static char* create_standard_memory(size_t size) {
54
55 // allocate an aligned chuck of memory
56 char* mapAddress = os::reserve_memory(size);
57
58 if (mapAddress == NULL) {
59 return NULL;
60 }
61
62 // commit memory
63 if (!os::commit_memory(mapAddress, size, !ExecMem)) {
64 if (PrintMiscellaneous && Verbose) {
65 warning("Could not commit PerfData memory\n");
66 }
67 os::release_memory(mapAddress, size);
68 return NULL;
69 }
70
71 return mapAddress;
72 }
73
74 // delete the PerfData memory region
75 //
76 static void delete_standard_memory(char* addr, size_t size) {
77
78 // there are no persistent external resources to cleanup for standard
79 // memory. since DestroyJavaVM does not support unloading of the JVM,
80 // cleanup of the memory resource is not performed. The memory will be
81 // reclaimed by the OS upon termination of the process.
82 //
83 return;
84 }
85
86 // save the specified memory region to the given file
87 //
88 // Note: this function might be called from signal handler (by os::abort()),
89 // don't allocate heap memory.
90 //
91 static void save_memory_to_file(char* addr, size_t size) {
92
93 const char* destfile = PerfMemory::get_perfdata_file_path();
94 assert(destfile[0] != '\0', "invalid PerfData file path");
95
96 int result;
97
98 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
99 result);;
100 if (result == OS_ERR) {
101 if (PrintMiscellaneous && Verbose) {
102 warning("Could not create Perfdata save file: %s: %s\n",
103 destfile, strerror(errno));
104 }
105 } else {
106 int fd = result;
107
108 for (size_t remaining = size; remaining > 0;) {
109
110 RESTARTABLE(::write(fd, addr, remaining), result);
111 if (result == OS_ERR) {
112 if (PrintMiscellaneous && Verbose) {
113 warning("Could not write Perfdata save file: %s: %s\n",
114 destfile, strerror(errno));
115 }
116 break;
117 }
118
119 remaining -= (size_t)result;
120 addr += result;
121 }
122
123 result = ::close(fd);
124 if (PrintMiscellaneous && Verbose) {
125 if (result == OS_ERR) {
126 warning("Could not close %s: %s\n", destfile, strerror(errno));
127 }
128 }
129 }
130 FREE_C_HEAP_ARRAY(char, destfile);
131 }
132
133
134 // Shared Memory Implementation Details
135
136 // Note: the solaris and linux shared memory implementation uses the mmap
137 // interface with a backing store file to implement named shared memory.
138 // Using the file system as the name space for shared memory allows a
139 // common name space to be supported across a variety of platforms. It
140 // also provides a name space that Java applications can deal with through
141 // simple file apis.
142 //
143 // The solaris and linux implementations store the backing store file in
144 // a user specific temporary directory located in the /tmp file system,
145 // which is always a local file system and is sometimes a RAM based file
146 // system.
147
148 // return the user specific temporary directory name.
149 //
150 // the caller is expected to free the allocated memory.
151 //
152 static char* get_user_tmp_dir(const char* user) {
153
154 const char* tmpdir = os::get_temp_directory();
155 const char* perfdir = PERFDATA_NAME;
156 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
157 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
158
159 // construct the path name to user specific tmp directory
160 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
161
162 return dirname;
163 }
164
165 // convert the given file name into a process id. if the file
166 // does not meet the file naming constraints, return 0.
167 //
168 static pid_t filename_to_pid(const char* filename) {
169
170 // a filename that doesn't begin with a digit is not a
171 // candidate for conversion.
172 //
173 if (!isdigit(*filename)) {
174 return 0;
175 }
176
177 // check if file name can be converted to an integer without
178 // any leftover characters.
179 //
180 char* remainder = NULL;
181 errno = 0;
182 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
183
184 if (errno != 0) {
185 return 0;
186 }
187
188 // check for left over characters. If any, then the filename is
189 // not a candidate for conversion.
190 //
191 if (remainder != NULL && *remainder != '\0') {
192 return 0;
193 }
194
195 // successful conversion, return the pid
196 return pid;
197 }
198
199
200 // Check if the given statbuf is considered a secure directory for
201 // the backing store files. Returns true if the directory is considered
202 // a secure location. Returns false if the statbuf is a symbolic link or
203 // if an error occurred.
204 //
205 static bool is_statbuf_secure(struct stat *statp) {
206 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
207 // The path represents a link or some non-directory file type,
208 // which is not what we expected. Declare it insecure.
209 //
210 return false;
211 }
212 // We have an existing directory, check if the permissions are safe.
213 //
214 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
215 // The directory is open for writing and could be subjected
216 // to a symlink or a hard link attack. Declare it insecure.
217 //
218 return false;
219 }
220 // See if the uid of the directory matches the effective uid of the process.
221 //
222 if (statp->st_uid != geteuid()) {
223 // The directory was not created by this user, declare it insecure.
224 //
225 return false;
226 }
227 return true;
228 }
229
230
231 // Check if the given path is considered a secure directory for
232 // the backing store files. Returns true if the directory exists
233 // and is considered a secure location. Returns false if the path
234 // is a symbolic link or if an error occurred.
235 //
236 static bool is_directory_secure(const char* path) {
237 struct stat statbuf;
238 int result = 0;
239
240 RESTARTABLE(::lstat(path, &statbuf), result);
241 if (result == OS_ERR) {
242 return false;
243 }
244
245 // The path exists, see if it is secure.
246 return is_statbuf_secure(&statbuf);
247 }
248
249
250 // Check if the given directory file descriptor is considered a secure
251 // directory for the backing store files. Returns true if the directory
252 // exists and is considered a secure location. Returns false if the path
253 // is a symbolic link or if an error occurred.
254 //
255 static bool is_dirfd_secure(int dir_fd) {
256 struct stat statbuf;
257 int result = 0;
258
259 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
260 if (result == OS_ERR) {
261 return false;
262 }
263
264 // The path exists, now check its mode.
265 return is_statbuf_secure(&statbuf);
266 }
267
268
269 // Check to make sure fd1 and fd2 are referencing the same file system object.
270 //
271 static bool is_same_fsobject(int fd1, int fd2) {
272 struct stat statbuf1;
273 struct stat statbuf2;
274 int result = 0;
275
276 RESTARTABLE(::fstat(fd1, &statbuf1), result);
277 if (result == OS_ERR) {
278 return false;
279 }
280 RESTARTABLE(::fstat(fd2, &statbuf2), result);
281 if (result == OS_ERR) {
282 return false;
283 }
284
285 if ((statbuf1.st_ino == statbuf2.st_ino) &&
286 (statbuf1.st_dev == statbuf2.st_dev)) {
287 return true;
288 } else {
289 return false;
290 }
291 }
292
293
294 // Open the directory of the given path and validate it.
295 // Return a DIR * of the open directory.
296 //
297 static DIR *open_directory_secure(const char* dirname) {
298 // Open the directory using open() so that it can be verified
299 // to be secure by calling is_dirfd_secure(), opendir() and then check
300 // to see if they are the same file system object. This method does not
301 // introduce a window of opportunity for the directory to be attacked that
302 // calling opendir() and is_directory_secure() does.
303 int result;
304 DIR *dirp = NULL;
305 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
306 if (result == OS_ERR) {
307 if (PrintMiscellaneous && Verbose) {
308 if (errno == ELOOP) {
309 warning("directory %s is a symlink and is not secure\n", dirname);
310 } else {
311 warning("could not open directory %s: %s\n", dirname, strerror(errno));
312 }
313 }
314 return dirp;
315 }
316 int fd = result;
317
318 // Determine if the open directory is secure.
319 if (!is_dirfd_secure(fd)) {
320 // The directory is not a secure directory.
321 os::close(fd);
322 return dirp;
323 }
324
325 // Open the directory.
326 dirp = ::opendir(dirname);
327 if (dirp == NULL) {
328 // The directory doesn't exist, close fd and return.
329 os::close(fd);
330 return dirp;
331 }
332
333 // Check to make sure fd and dirp are referencing the same file system object.
334 if (!is_same_fsobject(fd, dirfd(dirp))) {
335 // The directory is not secure.
336 os::close(fd);
337 os::closedir(dirp);
338 dirp = NULL;
339 return dirp;
340 }
341
342 // Close initial open now that we know directory is secure
343 os::close(fd);
344
345 return dirp;
346 }
347
348 // NOTE: The code below uses fchdir(), open() and unlink() because
349 // fdopendir(), openat() and unlinkat() are not supported on all
350 // versions. Once the support for fdopendir(), openat() and unlinkat()
351 // is available on all supported versions the code can be changed
352 // to use these functions.
353
354 // Open the directory of the given path, validate it and set the
355 // current working directory to it.
356 // Return a DIR * of the open directory and the saved cwd fd.
357 //
358 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
359
360 // Open the directory.
361 DIR* dirp = open_directory_secure(dirname);
362 if (dirp == NULL) {
363 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
364 return dirp;
365 }
366 int fd = dirfd(dirp);
367
368 // Open a fd to the cwd and save it off.
369 int result;
370 RESTARTABLE(::open(".", O_RDONLY), result);
371 if (result == OS_ERR) {
372 *saved_cwd_fd = -1;
373 } else {
374 *saved_cwd_fd = result;
375 }
376
377 // Set the current directory to dirname by using the fd of the directory.
378 result = fchdir(fd);
379
380 return dirp;
381 }
382
383 // Close the directory and restore the current working directory.
384 //
385 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
386
387 int result;
388 // If we have a saved cwd change back to it and close the fd.
389 if (saved_cwd_fd != -1) {
390 result = fchdir(saved_cwd_fd);
391 ::close(saved_cwd_fd);
392 }
393
394 // Close the directory.
395 os::closedir(dirp);
396 }
397
398 // Check if the given file descriptor is considered a secure.
399 //
400 static bool is_file_secure(int fd, const char *filename) {
401
402 int result;
403 struct stat statbuf;
404
405 // Determine if the file is secure.
406 RESTARTABLE(::fstat(fd, &statbuf), result);
407 if (result == OS_ERR) {
408 if (PrintMiscellaneous && Verbose) {
409 warning("fstat failed on %s: %s\n", filename, strerror(errno));
410 }
411 return false;
412 }
413 if (statbuf.st_nlink > 1) {
414 // A file with multiple links is not expected.
415 if (PrintMiscellaneous && Verbose) {
416 warning("file %s has multiple links\n", filename);
417 }
418 return false;
419 }
420 return true;
421 }
422
423
424 // return the user name for the given user id
425 //
426 // the caller is expected to free the allocated memory.
427 //
428 static char* get_user_name(uid_t uid) {
429
430 struct passwd pwent;
431
432 // determine the max pwbuf size from sysconf, and hardcode
433 // a default if this not available through sysconf.
434 //
435 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
436 if (bufsize == -1)
437 bufsize = 1024;
438
439 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
440
441 // POSIX interface to getpwuid_r is used on LINUX
442 struct passwd* p;
443 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
444
445 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
446 if (PrintMiscellaneous && Verbose) {
447 if (result != 0) {
448 warning("Could not retrieve passwd entry: %s\n",
449 strerror(result));
450 }
451 else if (p == NULL) {
452 // this check is added to protect against an observed problem
453 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
454 // indicating success, but has p == NULL. This was observed when
455 // inserting a file descriptor exhaustion fault prior to the call
456 // getpwuid_r() call. In this case, error is set to the appropriate
457 // error condition, but this is undocumented behavior. This check
458 // is safe under any condition, but the use of errno in the output
459 // message may result in an erroneous message.
460 // Bug Id 89052 was opened with RedHat.
461 //
462 warning("Could not retrieve passwd entry: %s\n",
463 strerror(errno));
464 }
465 else {
466 warning("Could not determine user name: %s\n",
467 p->pw_name == NULL ? "pw_name = NULL" :
468 "pw_name zero length");
469 }
470 }
471 FREE_C_HEAP_ARRAY(char, pwbuf);
472 return NULL;
473 }
474
475 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
476 strcpy(user_name, p->pw_name);
477
478 FREE_C_HEAP_ARRAY(char, pwbuf);
479 return user_name;
480 }
481
482 // return the name of the user that owns the process identified by vmid.
483 //
484 // This method uses a slow directory search algorithm to find the backing
485 // store file for the specified vmid and returns the user name, as determined
486 // by the user name suffix of the hsperfdata_<username> directory name.
487 //
488 // the caller is expected to free the allocated memory.
489 //
490 static char* get_user_name_slow(int vmid, TRAPS) {
491
492 // short circuit the directory search if the process doesn't even exist.
493 if (kill(vmid, 0) == OS_ERR) {
494 if (errno == ESRCH) {
495 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
496 "Process not found");
497 }
498 else /* EPERM */ {
499 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
500 }
501 }
502
503 // directory search
504 char* oldest_user = NULL;
505 time_t oldest_ctime = 0;
506
507 const char* tmpdirname = os::get_temp_directory();
508
509 // open the temp directory
510 DIR* tmpdirp = os::opendir(tmpdirname);
511
512 if (tmpdirp == NULL) {
513 // Cannot open the directory to get the user name, return.
514 return NULL;
515 }
516
517 // for each entry in the directory that matches the pattern hsperfdata_*,
518 // open the directory and check if the file for the given vmid exists.
519 // The file with the expected name and the latest creation date is used
520 // to determine the user name for the process id.
521 //
522 struct dirent* dentry;
523 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
524 errno = 0;
525 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
526
527 // check if the directory entry is a hsperfdata file
528 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
529 continue;
530 }
531
532 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
533 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
534 strcpy(usrdir_name, tmpdirname);
535 strcat(usrdir_name, "/");
536 strcat(usrdir_name, dentry->d_name);
537
538 // open the user directory
539 DIR* subdirp = open_directory_secure(usrdir_name);
540
541 if (subdirp == NULL) {
542 FREE_C_HEAP_ARRAY(char, usrdir_name);
543 continue;
544 }
545
546 // Since we don't create the backing store files in directories
547 // pointed to by symbolic links, we also don't follow them when
548 // looking for the files. We check for a symbolic link after the
549 // call to opendir in order to eliminate a small window where the
550 // symlink can be exploited.
551 //
552 if (!is_directory_secure(usrdir_name)) {
553 FREE_C_HEAP_ARRAY(char, usrdir_name);
554 os::closedir(subdirp);
555 continue;
556 }
557
558 struct dirent* udentry;
559 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
560 errno = 0;
561 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
562
563 if (filename_to_pid(udentry->d_name) == vmid) {
564 struct stat statbuf;
565 int result;
566
567 char* filename = NEW_C_HEAP_ARRAY(char,
568 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
569
570 strcpy(filename, usrdir_name);
571 strcat(filename, "/");
572 strcat(filename, udentry->d_name);
573
574 // don't follow symbolic links for the file
575 RESTARTABLE(::lstat(filename, &statbuf), result);
576 if (result == OS_ERR) {
577 FREE_C_HEAP_ARRAY(char, filename);
578 continue;
579 }
580
581 // skip over files that are not regular files.
582 if (!S_ISREG(statbuf.st_mode)) {
583 FREE_C_HEAP_ARRAY(char, filename);
584 continue;
585 }
586
587 // compare and save filename with latest creation time
588 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
589
590 if (statbuf.st_ctime > oldest_ctime) {
591 char* user = strchr(dentry->d_name, '_') + 1;
592
593 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
594 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
595
596 strcpy(oldest_user, user);
597 oldest_ctime = statbuf.st_ctime;
598 }
599 }
600
601 FREE_C_HEAP_ARRAY(char, filename);
602 }
603 }
604 os::closedir(subdirp);
605 FREE_C_HEAP_ARRAY(char, udbuf);
606 FREE_C_HEAP_ARRAY(char, usrdir_name);
607 }
608 os::closedir(tmpdirp);
609 FREE_C_HEAP_ARRAY(char, tdbuf);
610
611 return(oldest_user);
612 }
613
614 // return the name of the user that owns the JVM indicated by the given vmid.
615 //
616 static char* get_user_name(int vmid, TRAPS) {
617 return get_user_name_slow(vmid, THREAD);
618 }
619
620 // return the file name of the backing store file for the named
621 // shared memory region for the given user name and vmid.
622 //
623 // the caller is expected to free the allocated memory.
624 //
625 static char* get_sharedmem_filename(const char* dirname, int vmid) {
626
627 // add 2 for the file separator and a null terminator.
628 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
629
630 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
631 snprintf(name, nbytes, "%s/%d", dirname, vmid);
632
633 return name;
634 }
635
636
637 // remove file
638 //
639 // this method removes the file specified by the given path
640 //
641 static void remove_file(const char* path) {
642
643 int result;
644
645 // if the file is a directory, the following unlink will fail. since
646 // we don't expect to find directories in the user temp directory, we
647 // won't try to handle this situation. even if accidentially or
648 // maliciously planted, the directory's presence won't hurt anything.
649 //
650 RESTARTABLE(::unlink(path), result);
651 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
652 if (errno != ENOENT) {
653 warning("Could not unlink shared memory backing"
654 " store file %s : %s\n", path, strerror(errno));
655 }
656 }
657 }
658
659
660 // cleanup stale shared memory resources
661 //
662 // This method attempts to remove all stale shared memory files in
663 // the named user temporary directory. It scans the named directory
664 // for files matching the pattern ^$[0-9]*$. For each file found, the
665 // process id is extracted from the file name and a test is run to
666 // determine if the process is alive. If the process is not alive,
667 // any stale file resources are removed.
668 //
669 static void cleanup_sharedmem_resources(const char* dirname) {
670
671 int saved_cwd_fd;
672 // open the directory
673 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
674 if (dirp == NULL) {
675 // directory doesn't exist or is insecure, so there is nothing to cleanup
676 return;
677 }
678
679 // for each entry in the directory that matches the expected file
680 // name pattern, determine if the file resources are stale and if
681 // so, remove the file resources. Note, instrumented HotSpot processes
682 // for this user may start and/or terminate during this search and
683 // remove or create new files in this directory. The behavior of this
684 // loop under these conditions is dependent upon the implementation of
685 // opendir/readdir.
686 //
687 struct dirent* entry;
688 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
689
690 errno = 0;
691 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
692
693 pid_t pid = filename_to_pid(entry->d_name);
694
695 if (pid == 0) {
696
697 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
698 // attempt to remove all unexpected files, except "." and ".."
699 unlink(entry->d_name);
700 }
701
702 errno = 0;
703 continue;
704 }
705
706 // we now have a file name that converts to a valid integer
707 // that could represent a process id . if this process id
708 // matches the current process id or the process is not running,
709 // then remove the stale file resources.
710 //
711 // process liveness is detected by sending signal number 0 to
712 // the process id (see kill(2)). if kill determines that the
713 // process does not exist, then the file resources are removed.
714 // if kill determines that that we don't have permission to
715 // signal the process, then the file resources are assumed to
716 // be stale and are removed because the resources for such a
717 // process should be in a different user specific directory.
718 //
719 if ((pid == os::current_process_id()) ||
720 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
721 unlink(entry->d_name);
722 }
723 errno = 0;
724 }
725
726 // close the directory and reset the current working directory
727 close_directory_secure_cwd(dirp, saved_cwd_fd);
728
729 FREE_C_HEAP_ARRAY(char, dbuf);
730 }
731
732 // make the user specific temporary directory. Returns true if
733 // the directory exists and is secure upon return. Returns false
734 // if the directory exists but is either a symlink, is otherwise
735 // insecure, or if an error occurred.
736 //
737 static bool make_user_tmp_dir(const char* dirname) {
738
739 // create the directory with 0755 permissions. note that the directory
740 // will be owned by euid::egid, which may not be the same as uid::gid.
741 //
742 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
743 if (errno == EEXIST) {
744 // The directory already exists and was probably created by another
745 // JVM instance. However, this could also be the result of a
746 // deliberate symlink. Verify that the existing directory is safe.
747 //
748 if (!is_directory_secure(dirname)) {
749 // directory is not secure
750 if (PrintMiscellaneous && Verbose) {
751 warning("%s directory is insecure\n", dirname);
752 }
753 return false;
754 }
755 }
756 else {
757 // we encountered some other failure while attempting
758 // to create the directory
759 //
760 if (PrintMiscellaneous && Verbose) {
761 warning("could not create directory %s: %s\n",
762 dirname, strerror(errno));
763 }
764 return false;
765 }
766 }
767 return true;
768 }
769
770 // create the shared memory file resources
771 //
772 // This method creates the shared memory file with the given size
773 // This method also creates the user specific temporary directory, if
774 // it does not yet exist.
775 //
776 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
777
778 // make the user temporary directory
779 if (!make_user_tmp_dir(dirname)) {
780 // could not make/find the directory or the found directory
781 // was not secure
782 return -1;
783 }
784
785 int saved_cwd_fd;
786 // open the directory and set the current working directory to it
787 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
788 if (dirp == NULL) {
789 // Directory doesn't exist or is insecure, so cannot create shared
790 // memory file.
791 return -1;
792 }
793
794 // Open the filename in the current directory.
795 // Cannot use O_TRUNC here; truncation of an existing file has to happen
796 // after the is_file_secure() check below.
797 int result;
798 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
799 if (result == OS_ERR) {
800 if (PrintMiscellaneous && Verbose) {
801 if (errno == ELOOP) {
802 warning("file %s is a symlink and is not secure\n", filename);
803 } else {
804 warning("could not create file %s: %s\n", filename, strerror(errno));
805 }
806 }
807 // close the directory and reset the current working directory
808 close_directory_secure_cwd(dirp, saved_cwd_fd);
809
810 return -1;
811 }
812 // close the directory and reset the current working directory
813 close_directory_secure_cwd(dirp, saved_cwd_fd);
814
815 // save the file descriptor
816 int fd = result;
817
818 // check to see if the file is secure
819 if (!is_file_secure(fd, filename)) {
820 ::close(fd);
821 return -1;
822 }
823
824 // truncate the file to get rid of any existing data
825 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
826 if (result == OS_ERR) {
827 if (PrintMiscellaneous && Verbose) {
828 warning("could not truncate shared memory file: %s\n", strerror(errno));
829 }
830 ::close(fd);
831 return -1;
832 }
833 // set the file size
834 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
835 if (result == OS_ERR) {
836 if (PrintMiscellaneous && Verbose) {
837 warning("could not set shared memory file size: %s\n", strerror(errno));
838 }
839 ::close(fd);
840 return -1;
841 }
842
843 // Verify that we have enough disk space for this file.
844 // We'll get random SIGBUS crashes on memory accesses if
845 // we don't.
846
847 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
848 int zero_int = 0;
849 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
850 if (result == -1 ) break;
851 RESTARTABLE(::write(fd, &zero_int, 1), result);
852 if (result != 1) {
853 if (errno == ENOSPC) {
854 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
855 }
856 break;
857 }
858 }
859
860 if (result != -1) {
861 return fd;
862 } else {
863 ::close(fd);
864 return -1;
865 }
866 }
867
868 // open the shared memory file for the given user and vmid. returns
869 // the file descriptor for the open file or -1 if the file could not
870 // be opened.
871 //
872 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
873
874 // open the file
875 int result;
876 RESTARTABLE(::open(filename, oflags), result);
877 if (result == OS_ERR) {
878 if (errno == ENOENT) {
879 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
880 "Process not found", OS_ERR);
881 }
882 else if (errno == EACCES) {
883 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
884 "Permission denied", OS_ERR);
885 }
886 else {
887 THROW_MSG_(vmSymbols::java_io_IOException(), strerror(errno), OS_ERR);
888 }
889 }
890 int fd = result;
891
892 // check to see if the file is secure
893 if (!is_file_secure(fd, filename)) {
894 ::close(fd);
895 return -1;
896 }
897
898 return fd;
899 }
900
901 // create a named shared memory region. returns the address of the
902 // memory region on success or NULL on failure. A return value of
903 // NULL will ultimately disable the shared memory feature.
904 //
905 // On Solaris and Linux, the name space for shared memory objects
906 // is the file system name space.
907 //
908 // A monitoring application attaching to a JVM does not need to know
909 // the file system name of the shared memory object. However, it may
910 // be convenient for applications to discover the existence of newly
911 // created and terminating JVMs by watching the file system name space
912 // for files being created or removed.
913 //
914 static char* mmap_create_shared(size_t size) {
915
916 int result;
917 int fd;
918 char* mapAddress;
919
920 int vmid = os::current_process_id();
921
922 char* user_name = get_user_name(geteuid());
923
924 if (user_name == NULL)
925 return NULL;
926
927 char* dirname = get_user_tmp_dir(user_name);
928 char* filename = get_sharedmem_filename(dirname, vmid);
929 // get the short filename
930 char* short_filename = strrchr(filename, '/');
931 if (short_filename == NULL) {
932 short_filename = filename;
933 } else {
934 short_filename++;
935 }
936
937 // cleanup any stale shared memory files
938 cleanup_sharedmem_resources(dirname);
939
940 assert(((size > 0) && (size % os::vm_page_size() == 0)),
941 "unexpected PerfMemory region size");
942
943 fd = create_sharedmem_resources(dirname, short_filename, size);
944
945 FREE_C_HEAP_ARRAY(char, user_name);
946 FREE_C_HEAP_ARRAY(char, dirname);
947
948 if (fd == -1) {
949 FREE_C_HEAP_ARRAY(char, filename);
950 return NULL;
951 }
952
953 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
954
955 result = ::close(fd);
956 assert(result != OS_ERR, "could not close file");
957
958 if (mapAddress == MAP_FAILED) {
959 if (PrintMiscellaneous && Verbose) {
960 warning("mmap failed - %s\n", strerror(errno));
961 }
962 remove_file(filename);
963 FREE_C_HEAP_ARRAY(char, filename);
964 return NULL;
965 }
966
967 // save the file name for use in delete_shared_memory()
968 backing_store_file_name = filename;
969
970 // clear the shared memory region
971 (void)::memset((void*) mapAddress, 0, size);
972
973 // it does not go through os api, the operation has to record from here
974 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
975
976 return mapAddress;
977 }
978
979 // release a named shared memory region
980 //
981 static void unmap_shared(char* addr, size_t bytes) {
982 os::release_memory(addr, bytes);
983 }
984
985 // create the PerfData memory region in shared memory.
986 //
987 static char* create_shared_memory(size_t size) {
988
989 // create the shared memory region.
990 return mmap_create_shared(size);
991 }
992
993 // delete the shared PerfData memory region
994 //
995 static void delete_shared_memory(char* addr, size_t size) {
996
997 // cleanup the persistent shared memory resources. since DestroyJavaVM does
998 // not support unloading of the JVM, unmapping of the memory resource is
999 // not performed. The memory will be reclaimed by the OS upon termination of
1000 // the process. The backing store file is deleted from the file system.
1001
1002 assert(!PerfDisableSharedMem, "shouldn't be here");
1003
1004 if (backing_store_file_name != NULL) {
1005 remove_file(backing_store_file_name);
1006 // Don't.. Free heap memory could deadlock os::abort() if it is called
1007 // from signal handler. OS will reclaim the heap memory.
1008 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1009 backing_store_file_name = NULL;
1010 }
1011 }
1012
1013 // return the size of the file for the given file descriptor
1014 // or 0 if it is not a valid size for a shared memory file
1015 //
1016 static size_t sharedmem_filesize(int fd, TRAPS) {
1017
1018 struct stat statbuf;
1019 int result;
1020
1021 RESTARTABLE(::fstat(fd, &statbuf), result);
1022 if (result == OS_ERR) {
1023 if (PrintMiscellaneous && Verbose) {
1024 warning("fstat failed: %s\n", strerror(errno));
1025 }
1026 THROW_MSG_0(vmSymbols::java_io_IOException(),
1027 "Could not determine PerfMemory size");
1028 }
1029
1030 if ((statbuf.st_size == 0) ||
1031 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1032 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1033 "Invalid PerfMemory size");
1034 }
1035
1036 return (size_t)statbuf.st_size;
1037 }
1038
1039 // attach to a named shared memory region.
1040 //
1041 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1042
1043 char* mapAddress;
1044 int result;
1045 int fd;
1046 size_t size = 0;
1047 const char* luser = NULL;
1048
1049 int mmap_prot;
1050 int file_flags;
1051
1052 ResourceMark rm;
1053
1054 // map the high level access mode to the appropriate permission
1055 // constructs for the file and the shared memory mapping.
1056 if (mode == PerfMemory::PERF_MODE_RO) {
1057 mmap_prot = PROT_READ;
1058 file_flags = O_RDONLY | O_NOFOLLOW;
1059 }
1060 else if (mode == PerfMemory::PERF_MODE_RW) {
1061 #ifdef LATER
1062 mmap_prot = PROT_READ | PROT_WRITE;
1063 file_flags = O_RDWR | O_NOFOLLOW;
1064 #else
1065 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1066 "Unsupported access mode");
1067 #endif
1068 }
1069 else {
1070 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1071 "Illegal access mode");
1072 }
1073
1074 if (user == NULL || strlen(user) == 0) {
1075 luser = get_user_name(vmid, CHECK);
1076 }
1077 else {
1078 luser = user;
1079 }
1080
1081 if (luser == NULL) {
1082 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1083 "Could not map vmid to user Name");
1084 }
1085
1086 char* dirname = get_user_tmp_dir(luser);
1087
1088 // since we don't follow symbolic links when creating the backing
1089 // store file, we don't follow them when attaching either.
1090 //
1091 if (!is_directory_secure(dirname)) {
1092 FREE_C_HEAP_ARRAY(char, dirname);
1093 if (luser != user) {
1094 FREE_C_HEAP_ARRAY(char, luser);
1095 }
1096 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1097 "Process not found");
1098 }
1099
1100 char* filename = get_sharedmem_filename(dirname, vmid);
1101
1102 // copy heap memory to resource memory. the open_sharedmem_file
1103 // method below need to use the filename, but could throw an
1104 // exception. using a resource array prevents the leak that
1105 // would otherwise occur.
1106 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1107 strcpy(rfilename, filename);
1108
1109 // free the c heap resources that are no longer needed
1110 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
1111 FREE_C_HEAP_ARRAY(char, dirname);
1112 FREE_C_HEAP_ARRAY(char, filename);
1113
1114 // open the shared memory file for the give vmid
1115 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1116
1117 if (fd == OS_ERR) {
1118 return;
1119 }
1120
1121 if (HAS_PENDING_EXCEPTION) {
1122 ::close(fd);
1123 return;
1124 }
1125
1126 if (*sizep == 0) {
1127 size = sharedmem_filesize(fd, CHECK);
1128 } else {
1129 size = *sizep;
1130 }
1131
1132 assert(size > 0, "unexpected size <= 0");
1133
1134 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1135
1136 result = ::close(fd);
1137 assert(result != OS_ERR, "could not close file");
1138
1139 if (mapAddress == MAP_FAILED) {
1140 if (PrintMiscellaneous && Verbose) {
1141 warning("mmap failed: %s\n", strerror(errno));
1142 }
1143 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1144 "Could not map PerfMemory");
1145 }
1146
1147 // it does not go through os api, the operation has to record from here
1148 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1149
1150 *addr = mapAddress;
1151 *sizep = size;
1152
1153 if (PerfTraceMemOps) {
1154 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1155 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1156 }
1157 }
1158
1159
1160
1161
1162 // create the PerfData memory region
1163 //
1164 // This method creates the memory region used to store performance
1165 // data for the JVM. The memory may be created in standard or
1166 // shared memory.
1167 //
1168 void PerfMemory::create_memory_region(size_t size) {
1169
1170 if (PerfDisableSharedMem) {
1171 // do not share the memory for the performance data.
1172 _start = create_standard_memory(size);
1173 }
1174 else {
1175 _start = create_shared_memory(size);
1176 if (_start == NULL) {
1177
1178 // creation of the shared memory region failed, attempt
1179 // to create a contiguous, non-shared memory region instead.
1180 //
1181 if (PrintMiscellaneous && Verbose) {
1182 warning("Reverting to non-shared PerfMemory region.\n");
1183 }
1184 PerfDisableSharedMem = true;
1185 _start = create_standard_memory(size);
1186 }
1187 }
1188
1189 if (_start != NULL) _capacity = size;
1190
1191 }
1192
1193 // delete the PerfData memory region
1194 //
1195 // This method deletes the memory region used to store performance
1196 // data for the JVM. The memory region indicated by the <address, size>
1197 // tuple will be inaccessible after a call to this method.
1198 //
1199 void PerfMemory::delete_memory_region() {
1200
1201 assert((start() != NULL && capacity() > 0), "verify proper state");
1202
1203 // If user specifies PerfDataSaveFile, it will save the performance data
1204 // to the specified file name no matter whether PerfDataSaveToFile is specified
1205 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1206 // -XX:+PerfDataSaveToFile.
1207 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1208 save_memory_to_file(start(), capacity());
1209 }
1210
1211 if (PerfDisableSharedMem) {
1212 delete_standard_memory(start(), capacity());
1213 }
1214 else {
1215 delete_shared_memory(start(), capacity());
1216 }
1217 }
1218
1219 // attach to the PerfData memory region for another JVM
1220 //
1221 // This method returns an <address, size> tuple that points to
1222 // a memory buffer that is kept reasonably synchronized with
1223 // the PerfData memory region for the indicated JVM. This
1224 // buffer may be kept in synchronization via shared memory
1225 // or some other mechanism that keeps the buffer updated.
1226 //
1227 // If the JVM chooses not to support the attachability feature,
1228 // this method should throw an UnsupportedOperation exception.
1229 //
1230 // This implementation utilizes named shared memory to map
1231 // the indicated process's PerfData memory region into this JVMs
1232 // address space.
1233 //
1234 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1235
1236 if (vmid == 0 || vmid == os::current_process_id()) {
1237 *addrp = start();
1238 *sizep = capacity();
1239 return;
1240 }
1241
1242 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1243 }
1244
1245 // detach from the PerfData memory region of another JVM
1246 //
1247 // This method detaches the PerfData memory region of another
1248 // JVM, specified as an <address, size> tuple of a buffer
1249 // in this process's address space. This method may perform
1250 // arbitrary actions to accomplish the detachment. The memory
1251 // region specified by <address, size> will be inaccessible after
1252 // a call to this method.
1253 //
1254 // If the JVM chooses not to support the attachability feature,
1255 // this method should throw an UnsupportedOperation exception.
1256 //
1257 // This implementation utilizes named shared memory to detach
1258 // the indicated process's PerfData memory region from this
1259 // process's address space.
1260 //
1261 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1262
1263 assert(addr != 0, "address sanity check");
1264 assert(bytes > 0, "capacity sanity check");
1265
1266 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1267 // prevent accidental detachment of this process's PerfMemory region
1268 return;
1269 }
1270
1271 unmap_shared(addr, bytes);
1272 }