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 <dirent.h>
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, 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, 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, strerror(errno));
128 }
129 }
130 }
131 FREE_C_HEAP_ARRAY(char, destfile, mtInternal);
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, 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, 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 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 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, mtInternal);
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, mtInternal);
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(), 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 errno = 0;
538 while ((dentry = os::readdir(tmpdirp)) != 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 errno = 0;
573 while ((udentry = os::readdir(subdirp)) != NULL) {
574
575 if (filename_to_pid(udentry->d_name) == vmid) {
576 struct stat statbuf;
577 int result;
578
579 char* filename = NEW_C_HEAP_ARRAY(char,
580 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
581
582 strcpy(filename, usrdir_name);
583 strcat(filename, "/");
584 strcat(filename, udentry->d_name);
585
586 // don't follow symbolic links for the file
587 RESTARTABLE(::lstat(filename, &statbuf), result);
588 if (result == OS_ERR) {
589 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
590 continue;
591 }
592
593 // skip over files that are not regular files.
594 if (!S_ISREG(statbuf.st_mode)) {
595 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
596 continue;
597 }
598
599 // compare and save filename with latest creation time
600 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
601
602 if (statbuf.st_ctime > oldest_ctime) {
603 char* user = strchr(dentry->d_name, '_') + 1;
604
605 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user, mtInternal);
606 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
607
608 strcpy(oldest_user, user);
609 oldest_ctime = statbuf.st_ctime;
610 }
611 }
612
613 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
614 }
615 }
616 os::closedir(subdirp);
617 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
618 }
619 os::closedir(tmpdirp);
620
621 return(oldest_user);
622 }
623
624 // return the name of the user that owns the JVM indicated by the given vmid.
625 //
626 static char* get_user_name(int vmid, TRAPS) {
627 return get_user_name_slow(vmid, CHECK_NULL);
628 }
629
630 // return the file name of the backing store file for the named
631 // shared memory region for the given user name and vmid.
632 //
633 // the caller is expected to free the allocated memory.
634 //
635 static char* get_sharedmem_filename(const char* dirname, int vmid) {
636
637 // add 2 for the file separator and a null terminator.
638 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
639
640 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
641 snprintf(name, nbytes, "%s/%d", dirname, vmid);
642
643 return name;
644 }
645
646
647 // remove file
648 //
649 // this method removes the file specified by the given path
650 //
651 static void remove_file(const char* path) {
652
653 int result;
654
655 // if the file is a directory, the following unlink will fail. since
656 // we don't expect to find directories in the user temp directory, we
657 // won't try to handle this situation. even if accidentially or
658 // maliciously planted, the directory's presence won't hurt anything.
659 //
660 RESTARTABLE(::unlink(path), result);
661 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
662 if (errno != ENOENT) {
663 warning("Could not unlink shared memory backing"
664 " store file %s : %s\n", path, strerror(errno));
665 }
666 }
667 }
668
669
670 // cleanup stale shared memory resources
671 //
672 // This method attempts to remove all stale shared memory files in
673 // the named user temporary directory. It scans the named directory
674 // for files matching the pattern ^$[0-9]*$. For each file found, the
675 // process id is extracted from the file name and a test is run to
676 // determine if the process is alive. If the process is not alive,
677 // any stale file resources are removed.
678 //
679 static void cleanup_sharedmem_resources(const char* dirname) {
680
681 int saved_cwd_fd;
682 // open the directory
683 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
684 if (dirp == NULL) {
685 // directory doesn't exist or is insecure, so there is nothing to cleanup
686 return;
687 }
688
689 // for each entry in the directory that matches the expected file
690 // name pattern, determine if the file resources are stale and if
691 // so, remove the file resources. Note, instrumented HotSpot processes
692 // for this user may start and/or terminate during this search and
693 // remove or create new files in this directory. The behavior of this
694 // loop under these conditions is dependent upon the implementation of
695 // opendir/readdir.
696 //
697 struct dirent* entry;
698 errno = 0;
699 while ((entry = os::readdir(dirp)) != NULL) {
700
701 pid_t pid = filename_to_pid(entry->d_name);
702
703 if (pid == 0) {
704
705 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
706 // attempt to remove all unexpected files, except "." and ".."
707 unlink(entry->d_name);
708 }
709
710 errno = 0;
711 continue;
712 }
713
714 // we now have a file name that converts to a valid integer
715 // that could represent a process id . if this process id
716 // matches the current process id or the process is not running,
717 // then remove the stale file resources.
718 //
719 // process liveness is detected by sending signal number 0 to
720 // the process id (see kill(2)). if kill determines that the
721 // process does not exist, then the file resources are removed.
722 // if kill determines that that we don't have permission to
723 // signal the process, then the file resources are assumed to
724 // be stale and are removed because the resources for such a
725 // process should be in a different user specific directory.
726 //
727 if ((pid == os::current_process_id()) ||
728 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
729 unlink(entry->d_name);
730 }
731 errno = 0;
732 }
733
734 // close the directory and reset the current working directory
735 close_directory_secure_cwd(dirp, saved_cwd_fd);
736 }
737
738 // make the user specific temporary directory. Returns true if
739 // the directory exists and is secure upon return. Returns false
740 // if the directory exists but is either a symlink, is otherwise
741 // insecure, or if an error occurred.
742 //
743 static bool make_user_tmp_dir(const char* dirname) {
744
745 // create the directory with 0755 permissions. note that the directory
746 // will be owned by euid::egid, which may not be the same as uid::gid.
747 //
748 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
749 if (errno == EEXIST) {
750 // The directory already exists and was probably created by another
751 // JVM instance. However, this could also be the result of a
752 // deliberate symlink. Verify that the existing directory is safe.
753 //
754 if (!is_directory_secure(dirname)) {
755 // directory is not secure
756 if (PrintMiscellaneous && Verbose) {
757 warning("%s directory is insecure\n", dirname);
758 }
759 return false;
760 }
761 }
762 else {
763 // we encountered some other failure while attempting
764 // to create the directory
765 //
766 if (PrintMiscellaneous && Verbose) {
767 warning("could not create directory %s: %s\n",
768 dirname, strerror(errno));
769 }
770 return false;
771 }
772 }
773 return true;
774 }
775
776 // create the shared memory file resources
777 //
778 // This method creates the shared memory file with the given size
779 // This method also creates the user specific temporary directory, if
780 // it does not yet exist.
781 //
782 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
783
784 // make the user temporary directory
785 if (!make_user_tmp_dir(dirname)) {
786 // could not make/find the directory or the found directory
787 // was not secure
788 return -1;
789 }
790
791 int saved_cwd_fd;
792 // open the directory and set the current working directory to it
793 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
794 if (dirp == NULL) {
795 // Directory doesn't exist or is insecure, so cannot create shared
796 // memory file.
797 return -1;
798 }
799
800 // Open the filename in the current directory.
801 // Cannot use O_TRUNC here; truncation of an existing file has to happen
802 // after the is_file_secure() check below.
803 int result;
804 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
805 if (result == OS_ERR) {
806 if (PrintMiscellaneous && Verbose) {
807 if (errno == ELOOP) {
808 warning("file %s is a symlink and is not secure\n", filename);
809 } else {
810 warning("could not create file %s: %s\n", filename, strerror(errno));
811 }
812 }
813 // close the directory and reset the current working directory
814 close_directory_secure_cwd(dirp, saved_cwd_fd);
815
816 return -1;
817 }
818 // close the directory and reset the current working directory
819 close_directory_secure_cwd(dirp, saved_cwd_fd);
820
821 // save the file descriptor
822 int fd = result;
823
824 // check to see if the file is secure
825 if (!is_file_secure(fd, filename)) {
826 ::close(fd);
827 return -1;
828 }
829
830 // truncate the file to get rid of any existing data
831 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
832 if (result == OS_ERR) {
833 if (PrintMiscellaneous && Verbose) {
834 warning("could not truncate shared memory file: %s\n", strerror(errno));
835 }
836 ::close(fd);
837 return -1;
838 }
839 // set the file size
840 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
841 if (result == OS_ERR) {
842 if (PrintMiscellaneous && Verbose) {
843 warning("could not set shared memory file size: %s\n", strerror(errno));
844 }
845 ::close(fd);
846 return -1;
847 }
848
849 // Verify that we have enough disk space for this file.
850 // We'll get random SIGBUS crashes on memory accesses if
851 // we don't.
852
853 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
854 int zero_int = 0;
855 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
856 if (result == -1 ) break;
857 RESTARTABLE(::write(fd, &zero_int, 1), result);
858 if (result != 1) {
859 if (errno == ENOSPC) {
860 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
861 }
862 break;
863 }
864 }
865
866 if (result != -1) {
867 return fd;
868 } else {
869 ::close(fd);
870 return -1;
871 }
872 }
873
874 // open the shared memory file for the given user and vmid. returns
875 // the file descriptor for the open file or -1 if the file could not
876 // be opened.
877 //
878 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
879
880 // open the file
881 int result;
882 RESTARTABLE(::open(filename, oflags), result);
883 if (result == OS_ERR) {
884 if (errno == ENOENT) {
885 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
886 "Process not found", OS_ERR);
887 }
888 else if (errno == EACCES) {
889 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
890 "Permission denied", OS_ERR);
891 }
892 else {
893 THROW_MSG_(vmSymbols::java_io_IOException(), strerror(errno), OS_ERR);
894 }
895 }
896 int fd = result;
897
898 // check to see if the file is secure
899 if (!is_file_secure(fd, filename)) {
900 ::close(fd);
901 return -1;
902 }
903
904 return fd;
905 }
906
907 // create a named shared memory region. returns the address of the
908 // memory region on success or NULL on failure. A return value of
909 // NULL will ultimately disable the shared memory feature.
910 //
911 // On Solaris and Linux, the name space for shared memory objects
912 // is the file system name space.
913 //
914 // A monitoring application attaching to a JVM does not need to know
915 // the file system name of the shared memory object. However, it may
916 // be convenient for applications to discover the existence of newly
917 // created and terminating JVMs by watching the file system name space
918 // for files being created or removed.
919 //
920 static char* mmap_create_shared(size_t size) {
921
922 int result;
923 int fd;
924 char* mapAddress;
925
926 int vmid = os::current_process_id();
927
928 char* user_name = get_user_name(geteuid());
929
930 if (user_name == NULL)
931 return NULL;
932
933 char* dirname = get_user_tmp_dir(user_name);
934 char* filename = get_sharedmem_filename(dirname, vmid);
935 // get the short filename
936 char* short_filename = strrchr(filename, '/');
937 if (short_filename == NULL) {
938 short_filename = filename;
939 } else {
940 short_filename++;
941 }
942
943 // cleanup any stale shared memory files
944 cleanup_sharedmem_resources(dirname);
945
946 assert(((size > 0) && (size % os::vm_page_size() == 0)),
947 "unexpected PerfMemory region size");
948
949 fd = create_sharedmem_resources(dirname, short_filename, size);
950
951 FREE_C_HEAP_ARRAY(char, user_name, mtInternal);
952 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
953
954 if (fd == -1) {
955 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
956 return NULL;
957 }
958
959 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
960
961 result = ::close(fd);
962 assert(result != OS_ERR, "could not close file");
963
964 if (mapAddress == MAP_FAILED) {
965 if (PrintMiscellaneous && Verbose) {
966 warning("mmap failed - %s\n", strerror(errno));
967 }
968 remove_file(filename);
969 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
970 return NULL;
971 }
972
973 // save the file name for use in delete_shared_memory()
974 backing_store_file_name = filename;
975
976 // clear the shared memory region
977 (void)::memset((void*) mapAddress, 0, size);
978
979 // it does not go through os api, the operation has to record from here
980 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
981
982 return mapAddress;
983 }
984
985 // release a named shared memory region
986 //
987 static void unmap_shared(char* addr, size_t bytes) {
988 os::release_memory(addr, bytes);
989 }
990
991 // create the PerfData memory region in shared memory.
992 //
993 static char* create_shared_memory(size_t size) {
994
995 // create the shared memory region.
996 return mmap_create_shared(size);
997 }
998
999 // delete the shared PerfData memory region
1000 //
1001 static void delete_shared_memory(char* addr, size_t size) {
1002
1003 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1004 // not support unloading of the JVM, unmapping of the memory resource is
1005 // not performed. The memory will be reclaimed by the OS upon termination of
1006 // the process. The backing store file is deleted from the file system.
1007
1008 assert(!PerfDisableSharedMem, "shouldn't be here");
1009
1010 if (backing_store_file_name != NULL) {
1011 remove_file(backing_store_file_name);
1012 // Don't.. Free heap memory could deadlock os::abort() if it is called
1013 // from signal handler. OS will reclaim the heap memory.
1014 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1015 backing_store_file_name = NULL;
1016 }
1017 }
1018
1019 // return the size of the file for the given file descriptor
1020 // or 0 if it is not a valid size for a shared memory file
1021 //
1022 static size_t sharedmem_filesize(int fd, TRAPS) {
1023
1024 struct stat statbuf;
1025 int result;
1026
1027 RESTARTABLE(::fstat(fd, &statbuf), result);
1028 if (result == OS_ERR) {
1029 if (PrintMiscellaneous && Verbose) {
1030 warning("fstat failed: %s\n", strerror(errno));
1031 }
1032 THROW_MSG_0(vmSymbols::java_io_IOException(),
1033 "Could not determine PerfMemory size");
1034 }
1035
1036 if ((statbuf.st_size == 0) ||
1037 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1038 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1039 "Invalid PerfMemory size");
1040 }
1041
1042 return (size_t)statbuf.st_size;
1043 }
1044
1045 // attach to a named shared memory region.
1046 //
1047 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1048
1049 char* mapAddress;
1050 int result;
1051 int fd;
1052 size_t size = 0;
1053 const char* luser = NULL;
1054
1055 int mmap_prot;
1056 int file_flags;
1057
1058 ResourceMark rm;
1059
1060 // map the high level access mode to the appropriate permission
1061 // constructs for the file and the shared memory mapping.
1062 if (mode == PerfMemory::PERF_MODE_RO) {
1063 mmap_prot = PROT_READ;
1064 file_flags = O_RDONLY | O_NOFOLLOW;
1065 }
1066 else if (mode == PerfMemory::PERF_MODE_RW) {
1067 #ifdef LATER
1068 mmap_prot = PROT_READ | PROT_WRITE;
1069 file_flags = O_RDWR | O_NOFOLLOW;
1070 #else
1071 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1072 "Unsupported access mode");
1073 #endif
1074 }
1075 else {
1076 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1077 "Illegal access mode");
1078 }
1079
1080 if (user == NULL || strlen(user) == 0) {
1081 luser = get_user_name(vmid, CHECK);
1082 }
1083 else {
1084 luser = user;
1085 }
1086
1087 if (luser == NULL) {
1088 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1089 "Could not map vmid to user Name");
1090 }
1091
1092 char* dirname = get_user_tmp_dir(luser);
1093
1094 // since we don't follow symbolic links when creating the backing
1095 // store file, we don't follow them when attaching either.
1096 //
1097 if (!is_directory_secure(dirname)) {
1098 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1099 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1100 "Process not found");
1101 }
1102
1103 char* filename = get_sharedmem_filename(dirname, vmid);
1104
1105 // copy heap memory to resource memory. the open_sharedmem_file
1106 // method below need to use the filename, but could throw an
1107 // exception. using a resource array prevents the leak that
1108 // would otherwise occur.
1109 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1110 strcpy(rfilename, filename);
1111
1112 // free the c heap resources that are no longer needed
1113 if (luser != user) FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1114 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1115 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1116
1117 // open the shared memory file for the give vmid
1118 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1119
1120 if (fd == OS_ERR) {
1121 return;
1122 }
1123
1124 if (HAS_PENDING_EXCEPTION) {
1125 ::close(fd);
1126 return;
1127 }
1128
1129 if (*sizep == 0) {
1130 size = sharedmem_filesize(fd, CHECK);
1131 } else {
1132 size = *sizep;
1133 }
1134
1135 assert(size > 0, "unexpected size <= 0");
1136
1137 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1138
1139 result = ::close(fd);
1140 assert(result != OS_ERR, "could not close file");
1141
1142 if (mapAddress == MAP_FAILED) {
1143 if (PrintMiscellaneous && Verbose) {
1144 warning("mmap failed: %s\n", strerror(errno));
1145 }
1146 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1147 "Could not map PerfMemory");
1148 }
1149
1150 // it does not go through os api, the operation has to record from here
1151 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1152
1153 *addr = mapAddress;
1154 *sizep = size;
1155
1156 if (PerfTraceMemOps) {
1157 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1158 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1159 }
1160 }
1161
1162
1163
1164
1165 // create the PerfData memory region
1166 //
1167 // This method creates the memory region used to store performance
1168 // data for the JVM. The memory may be created in standard or
1169 // shared memory.
1170 //
1171 void PerfMemory::create_memory_region(size_t size) {
1172
1173 if (PerfDisableSharedMem) {
1174 // do not share the memory for the performance data.
1175 _start = create_standard_memory(size);
1176 }
1177 else {
1178 _start = create_shared_memory(size);
1179 if (_start == NULL) {
1180
1181 // creation of the shared memory region failed, attempt
1182 // to create a contiguous, non-shared memory region instead.
1183 //
1184 if (PrintMiscellaneous && Verbose) {
1185 warning("Reverting to non-shared PerfMemory region.\n");
1186 }
1187 PerfDisableSharedMem = true;
1188 _start = create_standard_memory(size);
1189 }
1190 }
1191
1192 if (_start != NULL) _capacity = size;
1193
1194 }
1195
1196 // delete the PerfData memory region
1197 //
1198 // This method deletes the memory region used to store performance
1199 // data for the JVM. The memory region indicated by the <address, size>
1200 // tuple will be inaccessible after a call to this method.
1201 //
1202 void PerfMemory::delete_memory_region() {
1203
1204 assert((start() != NULL && capacity() > 0), "verify proper state");
1205
1206 // If user specifies PerfDataSaveFile, it will save the performance data
1207 // to the specified file name no matter whether PerfDataSaveToFile is specified
1208 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1209 // -XX:+PerfDataSaveToFile.
1210 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1211 save_memory_to_file(start(), capacity());
1212 }
1213
1214 if (PerfDisableSharedMem) {
1215 delete_standard_memory(start(), capacity());
1216 }
1217 else {
1218 delete_shared_memory(start(), capacity());
1219 }
1220 }
1221
1222 // attach to the PerfData memory region for another JVM
1223 //
1224 // This method returns an <address, size> tuple that points to
1225 // a memory buffer that is kept reasonably synchronized with
1226 // the PerfData memory region for the indicated JVM. This
1227 // buffer may be kept in synchronization via shared memory
1228 // or some other mechanism that keeps the buffer updated.
1229 //
1230 // If the JVM chooses not to support the attachability feature,
1231 // this method should throw an UnsupportedOperation exception.
1232 //
1233 // This implementation utilizes named shared memory to map
1234 // the indicated process's PerfData memory region into this JVMs
1235 // address space.
1236 //
1237 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1238
1239 if (vmid == 0 || vmid == os::current_process_id()) {
1240 *addrp = start();
1241 *sizep = capacity();
1242 return;
1243 }
1244
1245 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1246 }
1247
1248 // detach from the PerfData memory region of another JVM
1249 //
1250 // This method detaches the PerfData memory region of another
1251 // JVM, specified as an <address, size> tuple of a buffer
1252 // in this process's address space. This method may perform
1253 // arbitrary actions to accomplish the detachment. The memory
1254 // region specified by <address, size> will be inaccessible after
1255 // a call to this method.
1256 //
1257 // If the JVM chooses not to support the attachability feature,
1258 // this method should throw an UnsupportedOperation exception.
1259 //
1260 // This implementation utilizes named shared memory to detach
1261 // the indicated process's PerfData memory region from this
1262 // process's address space.
1263 //
1264 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1265
1266 assert(addr != 0, "address sanity check");
1267 assert(bytes > 0, "capacity sanity check");
1268
1269 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1270 // prevent accidental detachment of this process's PerfMemory region
1271 return;
1272 }
1273
1274 unmap_shared(addr, bytes);
1275 }
1276
1277 char* PerfMemory::backing_store_filename() {
1278 return backing_store_file_name;
1279 }