1 /*
2 * Copyright (c) 2001, 2015, 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, mtInternal);
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 // If user is not root then see if the uid of the directory matches the effective uid of the process.
221 uid_t euid = geteuid();
222 if ((euid != 0) && (statp->st_uid != euid)) {
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 and
378 // handle errors, otherwise shared memory files will be created in cwd.
379 result = fchdir(fd);
380 if (result == OS_ERR) {
381 if (PrintMiscellaneous && Verbose) {
382 warning("could not change to directory %s", dirname);
383 }
384 if (*saved_cwd_fd != -1) {
385 ::close(*saved_cwd_fd);
386 *saved_cwd_fd = -1;
387 }
388 // Close the directory.
389 os::closedir(dirp);
390 return NULL;
391 } else {
392 return dirp;
393 }
394 }
395
396 // Close the directory and restore the current working directory.
397 //
398 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
399
400 int result;
401 // If we have a saved cwd change back to it and close the fd.
402 if (saved_cwd_fd != -1) {
403 result = fchdir(saved_cwd_fd);
404 ::close(saved_cwd_fd);
405 }
406
407 // Close the directory.
408 os::closedir(dirp);
409 }
410
411 // Check if the given file descriptor is considered a secure.
412 //
413 static bool is_file_secure(int fd, const char *filename) {
414
415 int result;
416 struct stat statbuf;
417
418 // Determine if the file is secure.
419 RESTARTABLE(::fstat(fd, &statbuf), result);
420 if (result == OS_ERR) {
421 if (PrintMiscellaneous && Verbose) {
422 warning("fstat failed on %s: %s\n", filename, strerror(errno));
423 }
424 return false;
425 }
426 if (statbuf.st_nlink > 1) {
427 // A file with multiple links is not expected.
428 if (PrintMiscellaneous && Verbose) {
429 warning("file %s has multiple links\n", filename);
430 }
431 return false;
432 }
433 return true;
434 }
435
436
437 // return the user name for the given user id
438 //
439 // the caller is expected to free the allocated memory.
440 //
441 static char* get_user_name(uid_t uid) {
442
443 struct passwd pwent;
444
445 // determine the max pwbuf size from sysconf, and hardcode
446 // a default if this not available through sysconf.
447 //
448 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
449 if (bufsize == -1)
450 bufsize = 1024;
451
452 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
453
454 // POSIX interface to getpwuid_r is used on LINUX
455 struct passwd* p;
456 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
457
458 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
459 if (PrintMiscellaneous && Verbose) {
460 if (result != 0) {
461 warning("Could not retrieve passwd entry: %s\n",
462 strerror(result));
463 }
464 else if (p == NULL) {
465 // this check is added to protect against an observed problem
466 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
467 // indicating success, but has p == NULL. This was observed when
468 // inserting a file descriptor exhaustion fault prior to the call
469 // getpwuid_r() call. In this case, error is set to the appropriate
470 // error condition, but this is undocumented behavior. This check
471 // is safe under any condition, but the use of errno in the output
472 // message may result in an erroneous message.
473 // Bug Id 89052 was opened with RedHat.
474 //
475 warning("Could not retrieve passwd entry: %s\n",
476 strerror(errno));
477 }
478 else {
479 warning("Could not determine user name: %s\n",
480 p->pw_name == NULL ? "pw_name = NULL" :
481 "pw_name zero length");
482 }
483 }
484 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
485 return NULL;
486 }
487
488 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
489 strcpy(user_name, p->pw_name);
490
491 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
492 return user_name;
493 }
494
495 // return the name of the user that owns the process identified by vmid.
496 //
497 // This method uses a slow directory search algorithm to find the backing
498 // store file for the specified vmid and returns the user name, as determined
499 // by the user name suffix of the hsperfdata_<username> directory name.
500 //
501 // the caller is expected to free the allocated memory.
502 //
503 static char* get_user_name_slow(int vmid, TRAPS) {
504
505 // short circuit the directory search if the process doesn't even exist.
506 if (kill(vmid, 0) == OS_ERR) {
507 if (errno == ESRCH) {
508 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
509 "Process not found");
510 }
511 else /* EPERM */ {
512 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
513 }
514 }
515
516 // directory search
517 char* oldest_user = NULL;
518 time_t oldest_ctime = 0;
519
520 const char* tmpdirname = os::get_temp_directory();
521
522 // open the temp directory
523 DIR* tmpdirp = os::opendir(tmpdirname);
524
525 if (tmpdirp == NULL) {
526 // Cannot open the directory to get the user name, return.
527 return NULL;
528 }
529
530 // for each entry in the directory that matches the pattern hsperfdata_*,
531 // open the directory and check if the file for the given vmid exists.
532 // The file with the expected name and the latest creation date is used
533 // to determine the user name for the process id.
534 //
535 struct dirent* dentry;
536 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
537 errno = 0;
538 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
539
540 // check if the directory entry is a hsperfdata file
541 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
542 continue;
543 }
544
545 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
546 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
547 strcpy(usrdir_name, tmpdirname);
548 strcat(usrdir_name, "/");
549 strcat(usrdir_name, dentry->d_name);
550
551 // open the user directory
552 DIR* subdirp = open_directory_secure(usrdir_name);
553
554 if (subdirp == NULL) {
555 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
556 continue;
557 }
558
559 // Since we don't create the backing store files in directories
560 // pointed to by symbolic links, we also don't follow them when
561 // looking for the files. We check for a symbolic link after the
562 // call to opendir in order to eliminate a small window where the
563 // symlink can be exploited.
564 //
565 if (!is_directory_secure(usrdir_name)) {
566 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
567 os::closedir(subdirp);
568 continue;
569 }
570
571 struct dirent* udentry;
572 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
573 errno = 0;
574 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
575
576 if (filename_to_pid(udentry->d_name) == vmid) {
577 struct stat statbuf;
578 int result;
579
580 char* filename = NEW_C_HEAP_ARRAY(char,
581 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
582
583 strcpy(filename, usrdir_name);
584 strcat(filename, "/");
585 strcat(filename, udentry->d_name);
586
587 // don't follow symbolic links for the file
588 RESTARTABLE(::lstat(filename, &statbuf), result);
589 if (result == OS_ERR) {
590 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
591 continue;
592 }
593
594 // skip over files that are not regular files.
595 if (!S_ISREG(statbuf.st_mode)) {
596 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
597 continue;
598 }
599
600 // compare and save filename with latest creation time
601 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
602
603 if (statbuf.st_ctime > oldest_ctime) {
604 char* user = strchr(dentry->d_name, '_') + 1;
605
606 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user, mtInternal);
607 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
608
609 strcpy(oldest_user, user);
610 oldest_ctime = statbuf.st_ctime;
611 }
612 }
613
614 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
615 }
616 }
617 os::closedir(subdirp);
618 FREE_C_HEAP_ARRAY(char, udbuf, mtInternal);
619 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
620 }
621 os::closedir(tmpdirp);
622 FREE_C_HEAP_ARRAY(char, tdbuf, mtInternal);
623
624 return(oldest_user);
625 }
626
627 // return the name of the user that owns the JVM indicated by the given vmid.
628 //
629 static char* get_user_name(int vmid, TRAPS) {
630 return get_user_name_slow(vmid, CHECK_NULL);
631 }
632
633 // return the file name of the backing store file for the named
634 // shared memory region for the given user name and vmid.
635 //
636 // the caller is expected to free the allocated memory.
637 //
638 static char* get_sharedmem_filename(const char* dirname, int vmid) {
639
640 // add 2 for the file separator and a null terminator.
641 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
642
643 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
644 snprintf(name, nbytes, "%s/%d", dirname, vmid);
645
646 return name;
647 }
648
649
650 // remove file
651 //
652 // this method removes the file specified by the given path
653 //
654 static void remove_file(const char* path) {
655
656 int result;
657
658 // if the file is a directory, the following unlink will fail. since
659 // we don't expect to find directories in the user temp directory, we
660 // won't try to handle this situation. even if accidentially or
661 // maliciously planted, the directory's presence won't hurt anything.
662 //
663 RESTARTABLE(::unlink(path), result);
664 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
665 if (errno != ENOENT) {
666 warning("Could not unlink shared memory backing"
667 " store file %s : %s\n", path, strerror(errno));
668 }
669 }
670 }
671
672
673 // cleanup stale shared memory resources
674 //
675 // This method attempts to remove all stale shared memory files in
676 // the named user temporary directory. It scans the named directory
677 // for files matching the pattern ^$[0-9]*$. For each file found, the
678 // process id is extracted from the file name and a test is run to
679 // determine if the process is alive. If the process is not alive,
680 // any stale file resources are removed.
681 //
682 static void cleanup_sharedmem_resources(const char* dirname) {
683
684 int saved_cwd_fd;
685 // open the directory
686 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
687 if (dirp == NULL) {
688 // directory doesn't exist or is insecure, so there is nothing to cleanup
689 return;
690 }
691
692 // for each entry in the directory that matches the expected file
693 // name pattern, determine if the file resources are stale and if
694 // so, remove the file resources. Note, instrumented HotSpot processes
695 // for this user may start and/or terminate during this search and
696 // remove or create new files in this directory. The behavior of this
697 // loop under these conditions is dependent upon the implementation of
698 // opendir/readdir.
699 //
700 struct dirent* entry;
701 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
702
703 errno = 0;
704 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
705
706 pid_t pid = filename_to_pid(entry->d_name);
707
708 if (pid == 0) {
709
710 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
711 // attempt to remove all unexpected files, except "." and ".."
712 unlink(entry->d_name);
713 }
714
715 errno = 0;
716 continue;
717 }
718
719 // we now have a file name that converts to a valid integer
720 // that could represent a process id . if this process id
721 // matches the current process id or the process is not running,
722 // then remove the stale file resources.
723 //
724 // process liveness is detected by sending signal number 0 to
725 // the process id (see kill(2)). if kill determines that the
726 // process does not exist, then the file resources are removed.
727 // if kill determines that that we don't have permission to
728 // signal the process, then the file resources are assumed to
729 // be stale and are removed because the resources for such a
730 // process should be in a different user specific directory.
731 //
732 if ((pid == os::current_process_id()) ||
733 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
734 unlink(entry->d_name);
735 }
736 errno = 0;
737 }
738
739 // close the directory and reset the current working directory
740 close_directory_secure_cwd(dirp, saved_cwd_fd);
741
742 FREE_C_HEAP_ARRAY(char, dbuf, mtInternal);
743 }
744
745 // make the user specific temporary directory. Returns true if
746 // the directory exists and is secure upon return. Returns false
747 // if the directory exists but is either a symlink, is otherwise
748 // insecure, or if an error occurred.
749 //
750 static bool make_user_tmp_dir(const char* dirname) {
751
752 // create the directory with 0755 permissions. note that the directory
753 // will be owned by euid::egid, which may not be the same as uid::gid.
754 //
755 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
756 if (errno == EEXIST) {
757 // The directory already exists and was probably created by another
758 // JVM instance. However, this could also be the result of a
759 // deliberate symlink. Verify that the existing directory is safe.
760 //
761 if (!is_directory_secure(dirname)) {
762 // directory is not secure
763 if (PrintMiscellaneous && Verbose) {
764 warning("%s directory is insecure\n", dirname);
765 }
766 return false;
767 }
768 }
769 else {
770 // we encountered some other failure while attempting
771 // to create the directory
772 //
773 if (PrintMiscellaneous && Verbose) {
774 warning("could not create directory %s: %s\n",
775 dirname, strerror(errno));
776 }
777 return false;
778 }
779 }
780 return true;
781 }
782
783 // create the shared memory file resources
784 //
785 // This method creates the shared memory file with the given size
786 // This method also creates the user specific temporary directory, if
787 // it does not yet exist.
788 //
789 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
790
791 // make the user temporary directory
792 if (!make_user_tmp_dir(dirname)) {
793 // could not make/find the directory or the found directory
794 // was not secure
795 return -1;
796 }
797
798 int saved_cwd_fd;
799 // open the directory and set the current working directory to it
800 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
801 if (dirp == NULL) {
802 // Directory doesn't exist or is insecure, so cannot create shared
803 // memory file.
804 return -1;
805 }
806
807 // Open the filename in the current directory.
808 // Cannot use O_TRUNC here; truncation of an existing file has to happen
809 // after the is_file_secure() check below.
810 int result;
811 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
812 if (result == OS_ERR) {
813 if (PrintMiscellaneous && Verbose) {
814 if (errno == ELOOP) {
815 warning("file %s is a symlink and is not secure\n", filename);
816 } else {
817 warning("could not create file %s: %s\n", filename, strerror(errno));
818 }
819 }
820 // close the directory and reset the current working directory
821 close_directory_secure_cwd(dirp, saved_cwd_fd);
822
823 return -1;
824 }
825 // close the directory and reset the current working directory
826 close_directory_secure_cwd(dirp, saved_cwd_fd);
827
828 // save the file descriptor
829 int fd = result;
830
831 // check to see if the file is secure
832 if (!is_file_secure(fd, filename)) {
833 ::close(fd);
834 return -1;
835 }
836
837 // truncate the file to get rid of any existing data
838 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
839 if (result == OS_ERR) {
840 if (PrintMiscellaneous && Verbose) {
841 warning("could not truncate shared memory file: %s\n", strerror(errno));
842 }
843 ::close(fd);
844 return -1;
845 }
846 // set the file size
847 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
848 if (result == OS_ERR) {
849 if (PrintMiscellaneous && Verbose) {
850 warning("could not set shared memory file size: %s\n", strerror(errno));
851 }
852 ::close(fd);
853 return -1;
854 }
855
856 // Verify that we have enough disk space for this file.
857 // We'll get random SIGBUS crashes on memory accesses if
858 // we don't.
859
860 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
861 int zero_int = 0;
862 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
863 if (result == -1 ) break;
864 RESTARTABLE(::write(fd, &zero_int, 1), result);
865 if (result != 1) {
866 if (errno == ENOSPC) {
867 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
868 }
869 break;
870 }
871 }
872
873 if (result != -1) {
874 return fd;
875 } else {
876 ::close(fd);
877 return -1;
878 }
879 }
880
881 // open the shared memory file for the given user and vmid. returns
882 // the file descriptor for the open file or -1 if the file could not
883 // be opened.
884 //
885 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
886
887 // open the file
888 int result;
889 RESTARTABLE(::open(filename, oflags), result);
890 if (result == OS_ERR) {
891 if (errno == ENOENT) {
892 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
893 "Process not found", OS_ERR);
894 }
895 else if (errno == EACCES) {
896 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
897 "Permission denied", OS_ERR);
898 }
899 else {
900 THROW_MSG_(vmSymbols::java_io_IOException(), strerror(errno), OS_ERR);
901 }
902 }
903 int fd = result;
904
905 // check to see if the file is secure
906 if (!is_file_secure(fd, filename)) {
907 ::close(fd);
908 return -1;
909 }
910
911 return fd;
912 }
913
914 // create a named shared memory region. returns the address of the
915 // memory region on success or NULL on failure. A return value of
916 // NULL will ultimately disable the shared memory feature.
917 //
918 // On Solaris and Linux, the name space for shared memory objects
919 // is the file system name space.
920 //
921 // A monitoring application attaching to a JVM does not need to know
922 // the file system name of the shared memory object. However, it may
923 // be convenient for applications to discover the existence of newly
924 // created and terminating JVMs by watching the file system name space
925 // for files being created or removed.
926 //
927 static char* mmap_create_shared(size_t size) {
928
929 int result;
930 int fd;
931 char* mapAddress;
932
933 int vmid = os::current_process_id();
934
935 char* user_name = get_user_name(geteuid());
936
937 if (user_name == NULL)
938 return NULL;
939
940 char* dirname = get_user_tmp_dir(user_name);
941 char* filename = get_sharedmem_filename(dirname, vmid);
942 // get the short filename
943 char* short_filename = strrchr(filename, '/');
944 if (short_filename == NULL) {
945 short_filename = filename;
946 } else {
947 short_filename++;
948 }
949
950 // cleanup any stale shared memory files
951 cleanup_sharedmem_resources(dirname);
952
953 assert(((size > 0) && (size % os::vm_page_size() == 0)),
954 "unexpected PerfMemory region size");
955
956 fd = create_sharedmem_resources(dirname, short_filename, size);
957
958 FREE_C_HEAP_ARRAY(char, user_name, mtInternal);
959 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
960
961 if (fd == -1) {
962 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
963 return NULL;
964 }
965
966 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
967
968 result = ::close(fd);
969 assert(result != OS_ERR, "could not close file");
970
971 if (mapAddress == MAP_FAILED) {
972 if (PrintMiscellaneous && Verbose) {
973 warning("mmap failed - %s\n", strerror(errno));
974 }
975 remove_file(filename);
976 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
977 return NULL;
978 }
979
980 // save the file name for use in delete_shared_memory()
981 backing_store_file_name = filename;
982
983 // clear the shared memory region
984 (void)::memset((void*) mapAddress, 0, size);
985
986 // it does not go through os api, the operation has to record from here
987 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
988
989 return mapAddress;
990 }
991
992 // release a named shared memory region
993 //
994 static void unmap_shared(char* addr, size_t bytes) {
995 os::release_memory(addr, bytes);
996 }
997
998 // create the PerfData memory region in shared memory.
999 //
1000 static char* create_shared_memory(size_t size) {
1001
1002 // create the shared memory region.
1003 return mmap_create_shared(size);
1004 }
1005
1006 // delete the shared PerfData memory region
1007 //
1008 static void delete_shared_memory(char* addr, size_t size) {
1009
1010 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1011 // not support unloading of the JVM, unmapping of the memory resource is
1012 // not performed. The memory will be reclaimed by the OS upon termination of
1013 // the process. The backing store file is deleted from the file system.
1014
1015 assert(!PerfDisableSharedMem, "shouldn't be here");
1016
1017 if (backing_store_file_name != NULL) {
1018 remove_file(backing_store_file_name);
1019 // Don't.. Free heap memory could deadlock os::abort() if it is called
1020 // from signal handler. OS will reclaim the heap memory.
1021 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1022 backing_store_file_name = NULL;
1023 }
1024 }
1025
1026 // return the size of the file for the given file descriptor
1027 // or 0 if it is not a valid size for a shared memory file
1028 //
1029 static size_t sharedmem_filesize(int fd, TRAPS) {
1030
1031 struct stat statbuf;
1032 int result;
1033
1034 RESTARTABLE(::fstat(fd, &statbuf), result);
1035 if (result == OS_ERR) {
1036 if (PrintMiscellaneous && Verbose) {
1037 warning("fstat failed: %s\n", strerror(errno));
1038 }
1039 THROW_MSG_0(vmSymbols::java_io_IOException(),
1040 "Could not determine PerfMemory size");
1041 }
1042
1043 if ((statbuf.st_size == 0) ||
1044 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1045 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1046 "Invalid PerfMemory size");
1047 }
1048
1049 return (size_t)statbuf.st_size;
1050 }
1051
1052 // attach to a named shared memory region.
1053 //
1054 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1055
1056 char* mapAddress;
1057 int result;
1058 int fd;
1059 size_t size = 0;
1060 const char* luser = NULL;
1061
1062 int mmap_prot;
1063 int file_flags;
1064
1065 ResourceMark rm;
1066
1067 // map the high level access mode to the appropriate permission
1068 // constructs for the file and the shared memory mapping.
1069 if (mode == PerfMemory::PERF_MODE_RO) {
1070 mmap_prot = PROT_READ;
1071 file_flags = O_RDONLY | O_NOFOLLOW;
1072 }
1073 else if (mode == PerfMemory::PERF_MODE_RW) {
1074 #ifdef LATER
1075 mmap_prot = PROT_READ | PROT_WRITE;
1076 file_flags = O_RDWR | O_NOFOLLOW;
1077 #else
1078 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1079 "Unsupported access mode");
1080 #endif
1081 }
1082 else {
1083 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1084 "Illegal access mode");
1085 }
1086
1087 if (user == NULL || strlen(user) == 0) {
1088 luser = get_user_name(vmid, CHECK);
1089 }
1090 else {
1091 luser = user;
1092 }
1093
1094 if (luser == NULL) {
1095 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1096 "Could not map vmid to user Name");
1097 }
1098
1099 char* dirname = get_user_tmp_dir(luser);
1100
1101 // since we don't follow symbolic links when creating the backing
1102 // store file, we don't follow them when attaching either.
1103 //
1104 if (!is_directory_secure(dirname)) {
1105 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1106 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1107 "Process not found");
1108 }
1109
1110 char* filename = get_sharedmem_filename(dirname, vmid);
1111
1112 // copy heap memory to resource memory. the open_sharedmem_file
1113 // method below need to use the filename, but could throw an
1114 // exception. using a resource array prevents the leak that
1115 // would otherwise occur.
1116 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1117 strcpy(rfilename, filename);
1118
1119 // free the c heap resources that are no longer needed
1120 if (luser != user) FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1121 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1122 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1123
1124 // open the shared memory file for the give vmid
1125 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1126
1127 if (fd == OS_ERR) {
1128 return;
1129 }
1130
1131 if (HAS_PENDING_EXCEPTION) {
1132 ::close(fd);
1133 return;
1134 }
1135
1136 if (*sizep == 0) {
1137 size = sharedmem_filesize(fd, CHECK);
1138 } else {
1139 size = *sizep;
1140 }
1141
1142 assert(size > 0, "unexpected size <= 0");
1143
1144 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1145
1146 result = ::close(fd);
1147 assert(result != OS_ERR, "could not close file");
1148
1149 if (mapAddress == MAP_FAILED) {
1150 if (PrintMiscellaneous && Verbose) {
1151 warning("mmap failed: %s\n", strerror(errno));
1152 }
1153 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1154 "Could not map PerfMemory");
1155 }
1156
1157 // it does not go through os api, the operation has to record from here
1158 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1159
1160 *addr = mapAddress;
1161 *sizep = size;
1162
1163 if (PerfTraceMemOps) {
1164 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1165 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1166 }
1167 }
1168
1169
1170
1171
1172 // create the PerfData memory region
1173 //
1174 // This method creates the memory region used to store performance
1175 // data for the JVM. The memory may be created in standard or
1176 // shared memory.
1177 //
1178 void PerfMemory::create_memory_region(size_t size) {
1179
1180 if (PerfDisableSharedMem) {
1181 // do not share the memory for the performance data.
1182 _start = create_standard_memory(size);
1183 }
1184 else {
1185 _start = create_shared_memory(size);
1186 if (_start == NULL) {
1187
1188 // creation of the shared memory region failed, attempt
1189 // to create a contiguous, non-shared memory region instead.
1190 //
1191 if (PrintMiscellaneous && Verbose) {
1192 warning("Reverting to non-shared PerfMemory region.\n");
1193 }
1194 PerfDisableSharedMem = true;
1195 _start = create_standard_memory(size);
1196 }
1197 }
1198
1199 if (_start != NULL) _capacity = size;
1200
1201 }
1202
1203 // delete the PerfData memory region
1204 //
1205 // This method deletes the memory region used to store performance
1206 // data for the JVM. The memory region indicated by the <address, size>
1207 // tuple will be inaccessible after a call to this method.
1208 //
1209 void PerfMemory::delete_memory_region() {
1210
1211 assert((start() != NULL && capacity() > 0), "verify proper state");
1212
1213 // If user specifies PerfDataSaveFile, it will save the performance data
1214 // to the specified file name no matter whether PerfDataSaveToFile is specified
1215 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1216 // -XX:+PerfDataSaveToFile.
1217 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1218 save_memory_to_file(start(), capacity());
1219 }
1220
1221 if (PerfDisableSharedMem) {
1222 delete_standard_memory(start(), capacity());
1223 }
1224 else {
1225 delete_shared_memory(start(), capacity());
1226 }
1227 }
1228
1229 // attach to the PerfData memory region for another JVM
1230 //
1231 // This method returns an <address, size> tuple that points to
1232 // a memory buffer that is kept reasonably synchronized with
1233 // the PerfData memory region for the indicated JVM. This
1234 // buffer may be kept in synchronization via shared memory
1235 // or some other mechanism that keeps the buffer updated.
1236 //
1237 // If the JVM chooses not to support the attachability feature,
1238 // this method should throw an UnsupportedOperation exception.
1239 //
1240 // This implementation utilizes named shared memory to map
1241 // the indicated process's PerfData memory region into this JVMs
1242 // address space.
1243 //
1244 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1245
1246 if (vmid == 0 || vmid == os::current_process_id()) {
1247 *addrp = start();
1248 *sizep = capacity();
1249 return;
1250 }
1251
1252 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1253 }
1254
1255 // detach from the PerfData memory region of another JVM
1256 //
1257 // This method detaches the PerfData memory region of another
1258 // JVM, specified as an <address, size> tuple of a buffer
1259 // in this process's address space. This method may perform
1260 // arbitrary actions to accomplish the detachment. The memory
1261 // region specified by <address, size> will be inaccessible after
1262 // a call to this method.
1263 //
1264 // If the JVM chooses not to support the attachability feature,
1265 // this method should throw an UnsupportedOperation exception.
1266 //
1267 // This implementation utilizes named shared memory to detach
1268 // the indicated process's PerfData memory region from this
1269 // process's address space.
1270 //
1271 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1272
1273 assert(addr != 0, "address sanity check");
1274 assert(bytes > 0, "capacity sanity check");
1275
1276 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1277 // prevent accidental detachment of this process's PerfMemory region
1278 return;
1279 }
1280
1281 unmap_shared(addr, bytes);
1282 }
1283
1284 char* PerfMemory::backing_store_filename() {
1285 return backing_store_file_name;
1286 }