1 /*
2 * Copyright (c) 2001, 2016, 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/os.hpp"
33 #include "runtime/perfMemory.hpp"
34 #include "services/memTracker.hpp"
35 #include "utilities/exceptions.hpp"
36
37 // put OS-includes here
38 # include <sys/types.h>
39 # include <sys/mman.h>
40 # include <errno.h>
41 # include <stdio.h>
42 # include <unistd.h>
43 # include <sys/stat.h>
44 # include <signal.h>
45 # include <pwd.h>
46
47 static char* backing_store_file_name = NULL; // name of the backing store
48 // file, if successfully created.
49
50 // Standard Memory Implementation Details
51
52 // create the PerfData memory region in standard memory.
53 //
54 static char* create_standard_memory(size_t size) {
55
56 // allocate an aligned chuck of memory
57 char* mapAddress = os::reserve_memory(size);
58
59 if (mapAddress == NULL) {
60 return NULL;
61 }
62
63 // commit memory
64 if (!os::commit_memory(mapAddress, size, !ExecMem)) {
65 if (PrintMiscellaneous && Verbose) {
66 warning("Could not commit PerfData memory\n");
67 }
68 os::release_memory(mapAddress, size);
69 return NULL;
70 }
71
72 return mapAddress;
73 }
74
75 // delete the PerfData memory region
76 //
77 static void delete_standard_memory(char* addr, size_t size) {
78
79 // there are no persistent external resources to cleanup for standard
80 // memory. since DestroyJavaVM does not support unloading of the JVM,
81 // cleanup of the memory resource is not performed. The memory will be
82 // reclaimed by the OS upon termination of the process.
83 //
84 return;
85 }
86
87 // save the specified memory region to the given file
88 //
89 // Note: this function might be called from signal handler (by os::abort()),
90 // don't allocate heap memory.
91 //
92 static void save_memory_to_file(char* addr, size_t size) {
93
94 const char* destfile = PerfMemory::get_perfdata_file_path();
95 assert(destfile[0] != '\0', "invalid PerfData file path");
96
97 int result;
98
99 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
100 result);;
101 if (result == OS_ERR) {
102 if (PrintMiscellaneous && Verbose) {
103 warning("Could not create Perfdata save file: %s: %s\n",
104 destfile, os::strerror(errno));
105 }
106 } else {
107 int fd = result;
108
109 for (size_t remaining = size; remaining > 0;) {
110
111 RESTARTABLE(::write(fd, addr, remaining), result);
112 if (result == OS_ERR) {
113 if (PrintMiscellaneous && Verbose) {
114 warning("Could not write Perfdata save file: %s: %s\n",
115 destfile, os::strerror(errno));
116 }
117 break;
118 }
119
120 remaining -= (size_t)result;
121 addr += result;
122 }
123
124 result = ::close(fd);
125 if (PrintMiscellaneous && Verbose) {
126 if (result == OS_ERR) {
127 warning("Could not close %s: %s\n", destfile, os::strerror(errno));
128 }
129 }
130 }
131 FREE_C_HEAP_ARRAY(char, destfile);
132 }
133
134
135 // Shared Memory Implementation Details
136
137 // Note: the solaris and linux shared memory implementation uses the mmap
138 // interface with a backing store file to implement named shared memory.
139 // Using the file system as the name space for shared memory allows a
140 // common name space to be supported across a variety of platforms. It
141 // also provides a name space that Java applications can deal with through
142 // simple file apis.
143 //
144 // The solaris and linux implementations store the backing store file in
145 // a user specific temporary directory located in the /tmp file system,
146 // which is always a local file system and is sometimes a RAM based file
147 // system.
148
149 // return the user specific temporary directory name.
150 //
151 // the caller is expected to free the allocated memory.
152 //
153 static char* get_user_tmp_dir(const char* user) {
154
155 const char* tmpdir = os::get_temp_directory();
156 const char* perfdir = PERFDATA_NAME;
157 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
158 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
159
160 // construct the path name to user specific tmp directory
161 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
162
163 return dirname;
164 }
165
166 // convert the given file name into a process id. if the file
167 // does not meet the file naming constraints, return 0.
168 //
169 static pid_t filename_to_pid(const char* filename) {
170
171 // a filename that doesn't begin with a digit is not a
172 // candidate for conversion.
173 //
174 if (!isdigit(*filename)) {
175 return 0;
176 }
177
178 // check if file name can be converted to an integer without
179 // any leftover characters.
180 //
181 char* remainder = NULL;
182 errno = 0;
183 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
184
185 if (errno != 0) {
186 return 0;
187 }
188
189 // check for left over characters. If any, then the filename is
190 // not a candidate for conversion.
191 //
192 if (remainder != NULL && *remainder != '\0') {
193 return 0;
194 }
195
196 // successful conversion, return the pid
197 return pid;
198 }
199
200
201 // Check if the given statbuf is considered a secure directory for
202 // the backing store files. Returns true if the directory is considered
203 // a secure location. Returns false if the statbuf is a symbolic link or
204 // if an error occurred.
205 //
206 static bool is_statbuf_secure(struct stat *statp) {
207 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
208 // The path represents a link or some non-directory file type,
209 // which is not what we expected. Declare it insecure.
210 //
211 return false;
212 }
213 // We have an existing directory, check if the permissions are safe.
214 //
215 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
216 // The directory is open for writing and could be subjected
217 // to a symlink or a hard link attack. Declare it insecure.
218 //
219 return false;
220 }
221 // If user is not root then see if the uid of the directory matches the effective uid of the process.
222 uid_t euid = geteuid();
223 if ((euid != 0) && (statp->st_uid != euid)) {
224 // The directory was not created by this user, declare it insecure.
225 //
226 return false;
227 }
228 return true;
229 }
230
231
232 // Check if the given path is considered a secure directory for
233 // the backing store files. Returns true if the directory exists
234 // and is considered a secure location. Returns false if the path
235 // is a symbolic link or if an error occurred.
236 //
237 static bool is_directory_secure(const char* path) {
238 struct stat statbuf;
239 int result = 0;
240
241 RESTARTABLE(::lstat(path, &statbuf), result);
242 if (result == OS_ERR) {
243 return false;
244 }
245
246 // The path exists, see if it is secure.
247 return is_statbuf_secure(&statbuf);
248 }
249
250
251 // Check if the given directory file descriptor is considered a secure
252 // directory for the backing store files. Returns true if the directory
253 // exists and is considered a secure location. Returns false if the path
254 // is a symbolic link or if an error occurred.
255 //
256 static bool is_dirfd_secure(int dir_fd) {
257 struct stat statbuf;
258 int result = 0;
259
260 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
261 if (result == OS_ERR) {
262 return false;
263 }
264
265 // The path exists, now check its mode.
266 return is_statbuf_secure(&statbuf);
267 }
268
269
270 // Check to make sure fd1 and fd2 are referencing the same file system object.
271 //
272 static bool is_same_fsobject(int fd1, int fd2) {
273 struct stat statbuf1;
274 struct stat statbuf2;
275 int result = 0;
276
277 RESTARTABLE(::fstat(fd1, &statbuf1), result);
278 if (result == OS_ERR) {
279 return false;
280 }
281 RESTARTABLE(::fstat(fd2, &statbuf2), result);
282 if (result == OS_ERR) {
283 return false;
284 }
285
286 if ((statbuf1.st_ino == statbuf2.st_ino) &&
287 (statbuf1.st_dev == statbuf2.st_dev)) {
288 return true;
289 } else {
290 return false;
291 }
292 }
293
294
295 // Open the directory of the given path and validate it.
296 // Return a DIR * of the open directory.
297 //
298 static DIR *open_directory_secure(const char* dirname) {
299 // Open the directory using open() so that it can be verified
300 // to be secure by calling is_dirfd_secure(), opendir() and then check
301 // to see if they are the same file system object. This method does not
302 // introduce a window of opportunity for the directory to be attacked that
303 // calling opendir() and is_directory_secure() does.
304 int result;
305 DIR *dirp = NULL;
306 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
307 if (result == OS_ERR) {
308 if (PrintMiscellaneous && Verbose) {
309 if (errno == ELOOP) {
310 warning("directory %s is a symlink and is not secure\n", dirname);
311 } else {
312 warning("could not open directory %s: %s\n", dirname, os::strerror(errno));
313 }
314 }
315 return dirp;
316 }
317 int fd = result;
318
319 // Determine if the open directory is secure.
320 if (!is_dirfd_secure(fd)) {
321 // The directory is not a secure directory.
322 os::close(fd);
323 return dirp;
324 }
325
326 // Open the directory.
327 dirp = ::opendir(dirname);
328 if (dirp == NULL) {
329 // The directory doesn't exist, close fd and return.
330 os::close(fd);
331 return dirp;
332 }
333
334 // Check to make sure fd and dirp are referencing the same file system object.
335 if (!is_same_fsobject(fd, dirfd(dirp))) {
336 // The directory is not secure.
337 os::close(fd);
338 os::closedir(dirp);
339 dirp = NULL;
340 return dirp;
341 }
342
343 // Close initial open now that we know directory is secure
344 os::close(fd);
345
346 return dirp;
347 }
348
349 // NOTE: The code below uses fchdir(), open() and unlink() because
350 // fdopendir(), openat() and unlinkat() are not supported on all
351 // versions. Once the support for fdopendir(), openat() and unlinkat()
352 // is available on all supported versions the code can be changed
353 // to use these functions.
354
355 // Open the directory of the given path, validate it and set the
356 // current working directory to it.
357 // Return a DIR * of the open directory and the saved cwd fd.
358 //
359 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
360
361 // Open the directory.
362 DIR* dirp = open_directory_secure(dirname);
363 if (dirp == NULL) {
364 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
365 return dirp;
366 }
367 int fd = dirfd(dirp);
368
369 // Open a fd to the cwd and save it off.
370 int result;
371 RESTARTABLE(::open(".", O_RDONLY), result);
372 if (result == OS_ERR) {
373 *saved_cwd_fd = -1;
374 } else {
375 *saved_cwd_fd = result;
376 }
377
378 // Set the current directory to dirname by using the fd of the directory and
379 // handle errors, otherwise shared memory files will be created in cwd.
380 result = fchdir(fd);
381 if (result == OS_ERR) {
382 if (PrintMiscellaneous && Verbose) {
383 warning("could not change to directory %s", dirname);
384 }
385 if (*saved_cwd_fd != -1) {
386 ::close(*saved_cwd_fd);
387 *saved_cwd_fd = -1;
388 }
389 // Close the directory.
390 os::closedir(dirp);
391 return NULL;
392 } else {
393 return dirp;
394 }
395 }
396
397 // Close the directory and restore the current working directory.
398 //
399 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
400
401 int result;
402 // If we have a saved cwd change back to it and close the fd.
403 if (saved_cwd_fd != -1) {
404 result = fchdir(saved_cwd_fd);
405 ::close(saved_cwd_fd);
406 }
407
408 // Close the directory.
409 os::closedir(dirp);
410 }
411
412 // Check if the given file descriptor is considered a secure.
413 //
414 static bool is_file_secure(int fd, const char *filename) {
415
416 int result;
417 struct stat statbuf;
418
419 // Determine if the file is secure.
420 RESTARTABLE(::fstat(fd, &statbuf), result);
421 if (result == OS_ERR) {
422 if (PrintMiscellaneous && Verbose) {
423 warning("fstat failed on %s: %s\n", filename, os::strerror(errno));
424 }
425 return false;
426 }
427 if (statbuf.st_nlink > 1) {
428 // A file with multiple links is not expected.
429 if (PrintMiscellaneous && Verbose) {
430 warning("file %s has multiple links\n", filename);
431 }
432 return false;
433 }
434 return true;
435 }
436
437
438 // return the user name for the given user id
439 //
440 // the caller is expected to free the allocated memory.
441 //
442 static char* get_user_name(uid_t uid) {
443
444 struct passwd pwent;
445
446 // determine the max pwbuf size from sysconf, and hardcode
447 // a default if this not available through sysconf.
448 //
449 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
450 if (bufsize == -1)
451 bufsize = 1024;
452
453 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
454
455 // POSIX interface to getpwuid_r is used on LINUX
456 struct passwd* p;
457 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
458
459 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
460 if (PrintMiscellaneous && Verbose) {
461 if (result != 0) {
462 warning("Could not retrieve passwd entry: %s\n",
463 os::strerror(result));
464 }
465 else if (p == NULL) {
466 // this check is added to protect against an observed problem
467 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
468 // indicating success, but has p == NULL. This was observed when
469 // inserting a file descriptor exhaustion fault prior to the call
470 // getpwuid_r() call. In this case, error is set to the appropriate
471 // error condition, but this is undocumented behavior. This check
472 // is safe under any condition, but the use of errno in the output
473 // message may result in an erroneous message.
474 // Bug Id 89052 was opened with RedHat.
475 //
476 warning("Could not retrieve passwd entry: %s\n",
477 os::strerror(errno));
478 }
479 else {
480 warning("Could not determine user name: %s\n",
481 p->pw_name == NULL ? "pw_name = NULL" :
482 "pw_name zero length");
483 }
484 }
485 FREE_C_HEAP_ARRAY(char, pwbuf);
486 return NULL;
487 }
488
489 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
490 strcpy(user_name, p->pw_name);
491
492 FREE_C_HEAP_ARRAY(char, pwbuf);
493 return user_name;
494 }
495
496 // return the name of the user that owns the process identified by vmid.
497 //
498 // This method uses a slow directory search algorithm to find the backing
499 // store file for the specified vmid and returns the user name, as determined
500 // by the user name suffix of the hsperfdata_<username> directory name.
501 //
502 // the caller is expected to free the allocated memory.
503 //
504 static char* get_user_name_slow(int vmid, TRAPS) {
505
506 // short circuit the directory search if the process doesn't even exist.
507 if (kill(vmid, 0) == OS_ERR) {
508 if (errno == ESRCH) {
509 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
510 "Process not found");
511 }
512 else /* EPERM */ {
513 THROW_MSG_0(vmSymbols::java_io_IOException(), os::strerror(errno));
514 }
515 }
516
517 // directory search
518 char* oldest_user = NULL;
519 time_t oldest_ctime = 0;
520
521 const char* tmpdirname = os::get_temp_directory();
522
523 // open the temp directory
524 DIR* tmpdirp = os::opendir(tmpdirname);
525
526 if (tmpdirp == NULL) {
527 // Cannot open the directory to get the user name, return.
528 return NULL;
529 }
530
531 // for each entry in the directory that matches the pattern hsperfdata_*,
532 // open the directory and check if the file for the given vmid exists.
533 // The file with the expected name and the latest creation date is used
534 // to determine the user name for the process id.
535 //
536 struct dirent* dentry;
537 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
538 errno = 0;
539 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
540
541 // check if the directory entry is a hsperfdata file
542 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
543 continue;
544 }
545
546 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
547 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
548 strcpy(usrdir_name, tmpdirname);
549 strcat(usrdir_name, "/");
550 strcat(usrdir_name, dentry->d_name);
551
552 // open the user directory
553 DIR* subdirp = open_directory_secure(usrdir_name);
554
555 if (subdirp == NULL) {
556 FREE_C_HEAP_ARRAY(char, usrdir_name);
557 continue;
558 }
559
560 // Since we don't create the backing store files in directories
561 // pointed to by symbolic links, we also don't follow them when
562 // looking for the files. We check for a symbolic link after the
563 // call to opendir in order to eliminate a small window where the
564 // symlink can be exploited.
565 //
566 if (!is_directory_secure(usrdir_name)) {
567 FREE_C_HEAP_ARRAY(char, usrdir_name);
568 os::closedir(subdirp);
569 continue;
570 }
571
572 struct dirent* udentry;
573 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
574 errno = 0;
575 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
576
577 if (filename_to_pid(udentry->d_name) == vmid) {
578 struct stat statbuf;
579 int result;
580
581 char* filename = NEW_C_HEAP_ARRAY(char,
582 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
583
584 strcpy(filename, usrdir_name);
585 strcat(filename, "/");
586 strcat(filename, udentry->d_name);
587
588 // don't follow symbolic links for the file
589 RESTARTABLE(::lstat(filename, &statbuf), result);
590 if (result == OS_ERR) {
591 FREE_C_HEAP_ARRAY(char, filename);
592 continue;
593 }
594
595 // skip over files that are not regular files.
596 if (!S_ISREG(statbuf.st_mode)) {
597 FREE_C_HEAP_ARRAY(char, filename);
598 continue;
599 }
600
601 // compare and save filename with latest creation time
602 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
603
604 if (statbuf.st_ctime > oldest_ctime) {
605 char* user = strchr(dentry->d_name, '_') + 1;
606
607 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
608 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
609
610 strcpy(oldest_user, user);
611 oldest_ctime = statbuf.st_ctime;
612 }
613 }
614
615 FREE_C_HEAP_ARRAY(char, filename);
616 }
617 }
618 os::closedir(subdirp);
619 FREE_C_HEAP_ARRAY(char, udbuf);
620 FREE_C_HEAP_ARRAY(char, usrdir_name);
621 }
622 os::closedir(tmpdirp);
623 FREE_C_HEAP_ARRAY(char, tdbuf);
624
625 return(oldest_user);
626 }
627
628 // return the name of the user that owns the JVM indicated by the given vmid.
629 //
630 static char* get_user_name(int vmid, TRAPS) {
631 return get_user_name_slow(vmid, THREAD);
632 }
633
634 // return the file name of the backing store file for the named
635 // shared memory region for the given user name and vmid.
636 //
637 // the caller is expected to free the allocated memory.
638 //
639 static char* get_sharedmem_filename(const char* dirname, int vmid) {
640
641 // add 2 for the file separator and a null terminator.
642 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
643
644 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
645 snprintf(name, nbytes, "%s/%d", dirname, vmid);
646
647 return name;
648 }
649
650
651 // remove file
652 //
653 // this method removes the file specified by the given path
654 //
655 static void remove_file(const char* path) {
656
657 int result;
658
659 // if the file is a directory, the following unlink will fail. since
660 // we don't expect to find directories in the user temp directory, we
661 // won't try to handle this situation. even if accidentially or
662 // maliciously planted, the directory's presence won't hurt anything.
663 //
664 RESTARTABLE(::unlink(path), result);
665 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
666 if (errno != ENOENT) {
667 warning("Could not unlink shared memory backing"
668 " store file %s : %s\n", path, os::strerror(errno));
669 }
670 }
671 }
672
673
674 // cleanup stale shared memory resources
675 //
676 // This method attempts to remove all stale shared memory files in
677 // the named user temporary directory. It scans the named directory
678 // for files matching the pattern ^$[0-9]*$. For each file found, the
679 // process id is extracted from the file name and a test is run to
680 // determine if the process is alive. If the process is not alive,
681 // any stale file resources are removed.
682 //
683 static void cleanup_sharedmem_resources(const char* dirname) {
684
685 int saved_cwd_fd;
686 // open the directory
687 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
688 if (dirp == NULL) {
689 // directory doesn't exist or is insecure, so there is nothing to cleanup
690 return;
691 }
692
693 // for each entry in the directory that matches the expected file
694 // name pattern, determine if the file resources are stale and if
695 // so, remove the file resources. Note, instrumented HotSpot processes
696 // for this user may start and/or terminate during this search and
697 // remove or create new files in this directory. The behavior of this
698 // loop under these conditions is dependent upon the implementation of
699 // opendir/readdir.
700 //
701 struct dirent* entry;
702 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
703
704 errno = 0;
705 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
706
707 pid_t pid = filename_to_pid(entry->d_name);
708
709 if (pid == 0) {
710
711 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
712 // attempt to remove all unexpected files, except "." and ".."
713 unlink(entry->d_name);
714 }
715
716 errno = 0;
717 continue;
718 }
719
720 // we now have a file name that converts to a valid integer
721 // that could represent a process id . if this process id
722 // matches the current process id or the process is not running,
723 // then remove the stale file resources.
724 //
725 // process liveness is detected by sending signal number 0 to
726 // the process id (see kill(2)). if kill determines that the
727 // process does not exist, then the file resources are removed.
728 // if kill determines that that we don't have permission to
729 // signal the process, then the file resources are assumed to
730 // be stale and are removed because the resources for such a
731 // process should be in a different user specific directory.
732 //
733 if ((pid == os::current_process_id()) ||
734 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
735 unlink(entry->d_name);
736 }
737 errno = 0;
738 }
739
740 // close the directory and reset the current working directory
741 close_directory_secure_cwd(dirp, saved_cwd_fd);
742
743 FREE_C_HEAP_ARRAY(char, dbuf);
744 }
745
746 // make the user specific temporary directory. Returns true if
747 // the directory exists and is secure upon return. Returns false
748 // if the directory exists but is either a symlink, is otherwise
749 // insecure, or if an error occurred.
750 //
751 static bool make_user_tmp_dir(const char* dirname) {
752
753 // create the directory with 0755 permissions. note that the directory
754 // will be owned by euid::egid, which may not be the same as uid::gid.
755 //
756 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
757 if (errno == EEXIST) {
758 // The directory already exists and was probably created by another
759 // JVM instance. However, this could also be the result of a
760 // deliberate symlink. Verify that the existing directory is safe.
761 //
762 if (!is_directory_secure(dirname)) {
763 // directory is not secure
764 if (PrintMiscellaneous && Verbose) {
765 warning("%s directory is insecure\n", dirname);
766 }
767 return false;
768 }
769 }
770 else {
771 // we encountered some other failure while attempting
772 // to create the directory
773 //
774 if (PrintMiscellaneous && Verbose) {
775 warning("could not create directory %s: %s\n",
776 dirname, os::strerror(errno));
777 }
778 return false;
779 }
780 }
781 return true;
782 }
783
784 // create the shared memory file resources
785 //
786 // This method creates the shared memory file with the given size
787 // This method also creates the user specific temporary directory, if
788 // it does not yet exist.
789 //
790 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
791
792 // make the user temporary directory
793 if (!make_user_tmp_dir(dirname)) {
794 // could not make/find the directory or the found directory
795 // was not secure
796 return -1;
797 }
798
799 int saved_cwd_fd;
800 // open the directory and set the current working directory to it
801 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
802 if (dirp == NULL) {
803 // Directory doesn't exist or is insecure, so cannot create shared
804 // memory file.
805 return -1;
806 }
807
808 // Open the filename in the current directory.
809 // Cannot use O_TRUNC here; truncation of an existing file has to happen
810 // after the is_file_secure() check below.
811 int result;
812 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
813 if (result == OS_ERR) {
814 if (PrintMiscellaneous && Verbose) {
815 if (errno == ELOOP) {
816 warning("file %s is a symlink and is not secure\n", filename);
817 } else {
818 warning("could not create file %s: %s\n", filename, os::strerror(errno));
819 }
820 }
821 // close the directory and reset the current working directory
822 close_directory_secure_cwd(dirp, saved_cwd_fd);
823
824 return -1;
825 }
826 // close the directory and reset the current working directory
827 close_directory_secure_cwd(dirp, saved_cwd_fd);
828
829 // save the file descriptor
830 int fd = result;
831
832 // check to see if the file is secure
833 if (!is_file_secure(fd, filename)) {
834 ::close(fd);
835 return -1;
836 }
837
838 // truncate the file to get rid of any existing data
839 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
840 if (result == OS_ERR) {
841 if (PrintMiscellaneous && Verbose) {
842 warning("could not truncate shared memory file: %s\n", os::strerror(errno));
843 }
844 ::close(fd);
845 return -1;
846 }
847 // set the file size
848 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
849 if (result == OS_ERR) {
850 if (PrintMiscellaneous && Verbose) {
851 warning("could not set shared memory file size: %s\n", os::strerror(errno));
852 }
853 ::close(fd);
854 return -1;
855 }
856
857 // Verify that we have enough disk space for this file.
858 // We'll get random SIGBUS crashes on memory accesses if
859 // we don't.
860
861 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
862 int zero_int = 0;
863 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
864 if (result == -1 ) break;
865 RESTARTABLE(::write(fd, &zero_int, 1), result);
866 if (result != 1) {
867 if (errno == ENOSPC) {
868 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
869 }
870 break;
871 }
872 }
873
874 if (result != -1) {
875 return fd;
876 } else {
877 ::close(fd);
878 return -1;
879 }
880 }
881
882 // open the shared memory file for the given user and vmid. returns
883 // the file descriptor for the open file or -1 if the file could not
884 // be opened.
885 //
886 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
887
888 // open the file
889 int result;
890 RESTARTABLE(::open(filename, oflags), result);
891 if (result == OS_ERR) {
892 if (errno == ENOENT) {
893 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
894 "Process not found", OS_ERR);
895 }
896 else if (errno == EACCES) {
897 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
898 "Permission denied", OS_ERR);
899 }
900 else {
901 THROW_MSG_(vmSymbols::java_io_IOException(), os::strerror(errno), OS_ERR);
902 }
903 }
904 int fd = result;
905
906 // check to see if the file is secure
907 if (!is_file_secure(fd, filename)) {
908 ::close(fd);
909 return -1;
910 }
911
912 return fd;
913 }
914
915 // create a named shared memory region. returns the address of the
916 // memory region on success or NULL on failure. A return value of
917 // NULL will ultimately disable the shared memory feature.
918 //
919 // On Solaris and Linux, the name space for shared memory objects
920 // is the file system name space.
921 //
922 // A monitoring application attaching to a JVM does not need to know
923 // the file system name of the shared memory object. However, it may
924 // be convenient for applications to discover the existence of newly
925 // created and terminating JVMs by watching the file system name space
926 // for files being created or removed.
927 //
928 static char* mmap_create_shared(size_t size) {
929
930 int result;
931 int fd;
932 char* mapAddress;
933
934 int vmid = os::current_process_id();
935
936 char* user_name = get_user_name(geteuid());
937
938 if (user_name == NULL)
939 return NULL;
940
941 char* dirname = get_user_tmp_dir(user_name);
942 char* filename = get_sharedmem_filename(dirname, vmid);
943 // get the short filename
944 char* short_filename = strrchr(filename, '/');
945 if (short_filename == NULL) {
946 short_filename = filename;
947 } else {
948 short_filename++;
949 }
950
951 // cleanup any stale shared memory files
952 cleanup_sharedmem_resources(dirname);
953
954 assert(((size > 0) && (size % os::vm_page_size() == 0)),
955 "unexpected PerfMemory region size");
956
957 fd = create_sharedmem_resources(dirname, short_filename, size);
958
959 FREE_C_HEAP_ARRAY(char, user_name);
960 FREE_C_HEAP_ARRAY(char, dirname);
961
962 if (fd == -1) {
963 FREE_C_HEAP_ARRAY(char, filename);
964 return NULL;
965 }
966
967 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
968
969 result = ::close(fd);
970 assert(result != OS_ERR, "could not close file");
971
972 if (mapAddress == MAP_FAILED) {
973 if (PrintMiscellaneous && Verbose) {
974 warning("mmap failed - %s\n", os::strerror(errno));
975 }
976 remove_file(filename);
977 FREE_C_HEAP_ARRAY(char, filename);
978 return NULL;
979 }
980
981 // save the file name for use in delete_shared_memory()
982 backing_store_file_name = filename;
983
984 // clear the shared memory region
985 (void)::memset((void*) mapAddress, 0, size);
986
987 // it does not go through os api, the operation has to record from here
988 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
989
990 return mapAddress;
991 }
992
993 // release a named shared memory region
994 //
995 static void unmap_shared(char* addr, size_t bytes) {
996 os::release_memory(addr, bytes);
997 }
998
999 // create the PerfData memory region in shared memory.
1000 //
1001 static char* create_shared_memory(size_t size) {
1002
1003 // create the shared memory region.
1004 return mmap_create_shared(size);
1005 }
1006
1007 // delete the shared PerfData memory region
1008 //
1009 static void delete_shared_memory(char* addr, size_t size) {
1010
1011 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1012 // not support unloading of the JVM, unmapping of the memory resource is
1013 // not performed. The memory will be reclaimed by the OS upon termination of
1014 // the process. The backing store file is deleted from the file system.
1015
1016 assert(!PerfDisableSharedMem, "shouldn't be here");
1017
1018 if (backing_store_file_name != NULL) {
1019 remove_file(backing_store_file_name);
1020 // Don't.. Free heap memory could deadlock os::abort() if it is called
1021 // from signal handler. OS will reclaim the heap memory.
1022 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1023 backing_store_file_name = NULL;
1024 }
1025 }
1026
1027 // return the size of the file for the given file descriptor
1028 // or 0 if it is not a valid size for a shared memory file
1029 //
1030 static size_t sharedmem_filesize(int fd, TRAPS) {
1031
1032 struct stat statbuf;
1033 int result;
1034
1035 RESTARTABLE(::fstat(fd, &statbuf), result);
1036 if (result == OS_ERR) {
1037 if (PrintMiscellaneous && Verbose) {
1038 warning("fstat failed: %s\n", os::strerror(errno));
1039 }
1040 THROW_MSG_0(vmSymbols::java_io_IOException(),
1041 "Could not determine PerfMemory size");
1042 }
1043
1044 if ((statbuf.st_size == 0) ||
1045 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1046 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1047 "Invalid PerfMemory size");
1048 }
1049
1050 return (size_t)statbuf.st_size;
1051 }
1052
1053 // attach to a named shared memory region.
1054 //
1055 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1056
1057 char* mapAddress;
1058 int result;
1059 int fd;
1060 size_t size = 0;
1061 const char* luser = NULL;
1062
1063 int mmap_prot;
1064 int file_flags;
1065
1066 ResourceMark rm;
1067
1068 // map the high level access mode to the appropriate permission
1069 // constructs for the file and the shared memory mapping.
1070 if (mode == PerfMemory::PERF_MODE_RO) {
1071 mmap_prot = PROT_READ;
1072 file_flags = O_RDONLY | O_NOFOLLOW;
1073 }
1074 else if (mode == PerfMemory::PERF_MODE_RW) {
1075 #ifdef LATER
1076 mmap_prot = PROT_READ | PROT_WRITE;
1077 file_flags = O_RDWR | O_NOFOLLOW;
1078 #else
1079 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1080 "Unsupported access mode");
1081 #endif
1082 }
1083 else {
1084 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1085 "Illegal access mode");
1086 }
1087
1088 if (user == NULL || strlen(user) == 0) {
1089 luser = get_user_name(vmid, CHECK);
1090 }
1091 else {
1092 luser = user;
1093 }
1094
1095 if (luser == NULL) {
1096 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1097 "Could not map vmid to user Name");
1098 }
1099
1100 char* dirname = get_user_tmp_dir(luser);
1101
1102 // since we don't follow symbolic links when creating the backing
1103 // store file, we don't follow them when attaching either.
1104 //
1105 if (!is_directory_secure(dirname)) {
1106 FREE_C_HEAP_ARRAY(char, dirname);
1107 if (luser != user) {
1108 FREE_C_HEAP_ARRAY(char, luser);
1109 }
1110 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1111 "Process not found");
1112 }
1113
1114 char* filename = get_sharedmem_filename(dirname, vmid);
1115
1116 // copy heap memory to resource memory. the open_sharedmem_file
1117 // method below need to use the filename, but could throw an
1118 // exception. using a resource array prevents the leak that
1119 // would otherwise occur.
1120 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1121 strcpy(rfilename, filename);
1122
1123 // free the c heap resources that are no longer needed
1124 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
1125 FREE_C_HEAP_ARRAY(char, dirname);
1126 FREE_C_HEAP_ARRAY(char, filename);
1127
1128 // open the shared memory file for the give vmid
1129 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1130
1131 if (fd == OS_ERR) {
1132 return;
1133 }
1134
1135 if (HAS_PENDING_EXCEPTION) {
1136 ::close(fd);
1137 return;
1138 }
1139
1140 if (*sizep == 0) {
1141 size = sharedmem_filesize(fd, CHECK);
1142 } else {
1143 size = *sizep;
1144 }
1145
1146 assert(size > 0, "unexpected size <= 0");
1147
1148 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1149
1150 result = ::close(fd);
1151 assert(result != OS_ERR, "could not close file");
1152
1153 if (mapAddress == MAP_FAILED) {
1154 if (PrintMiscellaneous && Verbose) {
1155 warning("mmap failed: %s\n", os::strerror(errno));
1156 }
1157 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1158 "Could not map PerfMemory");
1159 }
1160
1161 // it does not go through os api, the operation has to record from here
1162 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1163
1164 *addr = mapAddress;
1165 *sizep = size;
1166
1167 if (PerfTraceMemOps) {
1168 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1169 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1170 }
1171 }
1172
1173
1174
1175
1176 // create the PerfData memory region
1177 //
1178 // This method creates the memory region used to store performance
1179 // data for the JVM. The memory may be created in standard or
1180 // shared memory.
1181 //
1182 void PerfMemory::create_memory_region(size_t size) {
1183
1184 if (PerfDisableSharedMem) {
1185 // do not share the memory for the performance data.
1186 _start = create_standard_memory(size);
1187 }
1188 else {
1189 _start = create_shared_memory(size);
1190 if (_start == NULL) {
1191
1192 // creation of the shared memory region failed, attempt
1193 // to create a contiguous, non-shared memory region instead.
1194 //
1195 if (PrintMiscellaneous && Verbose) {
1196 warning("Reverting to non-shared PerfMemory region.\n");
1197 }
1198 PerfDisableSharedMem = true;
1199 _start = create_standard_memory(size);
1200 }
1201 }
1202
1203 if (_start != NULL) _capacity = size;
1204
1205 }
1206
1207 // delete the PerfData memory region
1208 //
1209 // This method deletes the memory region used to store performance
1210 // data for the JVM. The memory region indicated by the <address, size>
1211 // tuple will be inaccessible after a call to this method.
1212 //
1213 void PerfMemory::delete_memory_region() {
1214
1215 assert((start() != NULL && capacity() > 0), "verify proper state");
1216
1217 // If user specifies PerfDataSaveFile, it will save the performance data
1218 // to the specified file name no matter whether PerfDataSaveToFile is specified
1219 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1220 // -XX:+PerfDataSaveToFile.
1221 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1222 save_memory_to_file(start(), capacity());
1223 }
1224
1225 if (PerfDisableSharedMem) {
1226 delete_standard_memory(start(), capacity());
1227 }
1228 else {
1229 delete_shared_memory(start(), capacity());
1230 }
1231 }
1232
1233 // attach to the PerfData memory region for another JVM
1234 //
1235 // This method returns an <address, size> tuple that points to
1236 // a memory buffer that is kept reasonably synchronized with
1237 // the PerfData memory region for the indicated JVM. This
1238 // buffer may be kept in synchronization via shared memory
1239 // or some other mechanism that keeps the buffer updated.
1240 //
1241 // If the JVM chooses not to support the attachability feature,
1242 // this method should throw an UnsupportedOperation exception.
1243 //
1244 // This implementation utilizes named shared memory to map
1245 // the indicated process's PerfData memory region into this JVMs
1246 // address space.
1247 //
1248 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1249
1250 if (vmid == 0 || vmid == os::current_process_id()) {
1251 *addrp = start();
1252 *sizep = capacity();
1253 return;
1254 }
1255
1256 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1257 }
1258
1259 // detach from the PerfData memory region of another JVM
1260 //
1261 // This method detaches the PerfData memory region of another
1262 // JVM, specified as an <address, size> tuple of a buffer
1263 // in this process's address space. This method may perform
1264 // arbitrary actions to accomplish the detachment. The memory
1265 // region specified by <address, size> will be inaccessible after
1266 // a call to this method.
1267 //
1268 // If the JVM chooses not to support the attachability feature,
1269 // this method should throw an UnsupportedOperation exception.
1270 //
1271 // This implementation utilizes named shared memory to detach
1272 // the indicated process's PerfData memory region from this
1273 // process's address space.
1274 //
1275 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1276
1277 assert(addr != 0, "address sanity check");
1278 assert(bytes > 0, "capacity sanity check");
1279
1280 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1281 // prevent accidental detachment of this process's PerfMemory region
1282 return;
1283 }
1284
1285 unmap_shared(addr, bytes);
1286 }