1 /*
2 * Copyright (c) 2001, 2006, 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 "incls/_precompiled.incl"
26 # include "incls/_perfMemory_linux.cpp.incl"
27
28 // put OS-includes here
29 # include <sys/types.h>
30 # include <sys/mman.h>
31 # include <errno.h>
32 # include <stdio.h>
33 # include <unistd.h>
34 # include <sys/stat.h>
35 # include <signal.h>
36 # include <pwd.h>
37
38 static char* backing_store_file_name = NULL; // name of the backing store
39 // file, if successfully created.
40
41 // Standard Memory Implementation Details
42
43 // create the PerfData memory region in standard memory.
44 //
45 static char* create_standard_memory(size_t size) {
46
47 // allocate an aligned chuck of memory
48 char* mapAddress = os::reserve_memory(size);
49
50 if (mapAddress == NULL) {
51 return NULL;
52 }
53
54 // commit memory
55 if (!os::commit_memory(mapAddress, size)) {
56 if (PrintMiscellaneous && Verbose) {
57 warning("Could not commit PerfData memory\n");
58 }
59 os::release_memory(mapAddress, size);
60 return NULL;
61 }
62
63 return mapAddress;
64 }
65
66 // delete the PerfData memory region
67 //
68 static void delete_standard_memory(char* addr, size_t size) {
69
70 // there are no persistent external resources to cleanup for standard
71 // memory. since DestroyJavaVM does not support unloading of the JVM,
72 // cleanup of the memory resource is not performed. The memory will be
73 // reclaimed by the OS upon termination of the process.
74 //
75 return;
76 }
77
78 // save the specified memory region to the given file
79 //
80 // Note: this function might be called from signal handler (by os::abort()),
81 // don't allocate heap memory.
82 //
83 static void save_memory_to_file(char* addr, size_t size) {
84
85 const char* destfile = PerfMemory::get_perfdata_file_path();
86 assert(destfile[0] != '\0', "invalid PerfData file path");
87
88 int result;
89
90 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
91 result);;
92 if (result == OS_ERR) {
93 if (PrintMiscellaneous && Verbose) {
94 warning("Could not create Perfdata save file: %s: %s\n",
95 destfile, strerror(errno));
96 }
97 } else {
98 int fd = result;
99
100 for (size_t remaining = size; remaining > 0;) {
101
102 RESTARTABLE(::write(fd, addr, remaining), result);
103 if (result == OS_ERR) {
104 if (PrintMiscellaneous && Verbose) {
105 warning("Could not write Perfdata save file: %s: %s\n",
106 destfile, strerror(errno));
107 }
108 break;
109 }
110
111 remaining -= (size_t)result;
112 addr += result;
113 }
114
115 RESTARTABLE(::close(fd), result);
116 if (PrintMiscellaneous && Verbose) {
117 if (result == OS_ERR) {
118 warning("Could not close %s: %s\n", destfile, strerror(errno));
119 }
120 }
121 }
122 FREE_C_HEAP_ARRAY(char, destfile);
123 }
124
125
126 // Shared Memory Implementation Details
127
128 // Note: the solaris and linux shared memory implementation uses the mmap
129 // interface with a backing store file to implement named shared memory.
130 // Using the file system as the name space for shared memory allows a
131 // common name space to be supported across a variety of platforms. It
132 // also provides a name space that Java applications can deal with through
133 // simple file apis.
134 //
135 // The solaris and linux implementations store the backing store file in
136 // a user specific temporary directory located in the /tmp file system,
137 // which is always a local file system and is sometimes a RAM based file
138 // system.
139
140 // return the user specific temporary directory name.
141 //
142 // the caller is expected to free the allocated memory.
143 //
144 static char* get_user_tmp_dir(const char* user) {
145
146 const char* tmpdir = os::get_temp_directory();
147 const char* perfdir = PERFDATA_NAME;
148 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
149 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes);
150
151 // construct the path name to user specific tmp directory
152 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
153
154 return dirname;
155 }
156
157 // convert the given file name into a process id. if the file
158 // does not meet the file naming constraints, return 0.
159 //
160 static pid_t filename_to_pid(const char* filename) {
161
162 // a filename that doesn't begin with a digit is not a
163 // candidate for conversion.
164 //
165 if (!isdigit(*filename)) {
166 return 0;
167 }
168
169 // check if file name can be converted to an integer without
170 // any leftover characters.
171 //
172 char* remainder = NULL;
173 errno = 0;
174 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
175
176 if (errno != 0) {
177 return 0;
178 }
179
180 // check for left over characters. If any, then the filename is
181 // not a candidate for conversion.
182 //
183 if (remainder != NULL && *remainder != '\0') {
184 return 0;
185 }
186
187 // successful conversion, return the pid
188 return pid;
189 }
190
191
192 // check if the given path is considered a secure directory for
193 // the backing store files. Returns true if the directory exists
194 // and is considered a secure location. Returns false if the path
195 // is a symbolic link or if an error occurred.
196 //
197 static bool is_directory_secure(const char* path) {
198 struct stat statbuf;
199 int result = 0;
200
201 RESTARTABLE(::lstat(path, &statbuf), result);
202 if (result == OS_ERR) {
203 return false;
204 }
205
206 // the path exists, now check it's mode
207 if (S_ISLNK(statbuf.st_mode) || !S_ISDIR(statbuf.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 else {
214 // we have an existing directory, check if the permissions are safe.
215 //
216 if ((statbuf.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
217 // the directory is open for writing and could be subjected
218 // to a symlnk attack. declare it insecure.
219 //
220 return false;
221 }
222 }
223 return true;
224 }
225
226
227 // return the user name for the given user id
228 //
229 // the caller is expected to free the allocated memory.
230 //
231 static char* get_user_name(uid_t uid) {
232
233 struct passwd pwent;
234
235 // determine the max pwbuf size from sysconf, and hardcode
236 // a default if this not available through sysconf.
237 //
238 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
239 if (bufsize == -1)
240 bufsize = 1024;
241
242 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize);
243
244 // POSIX interface to getpwuid_r is used on LINUX
245 struct passwd* p;
246 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
247
248 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
249 if (PrintMiscellaneous && Verbose) {
250 if (result != 0) {
251 warning("Could not retrieve passwd entry: %s\n",
252 strerror(result));
253 }
254 else if (p == NULL) {
255 // this check is added to protect against an observed problem
256 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
257 // indicating success, but has p == NULL. This was observed when
258 // inserting a file descriptor exhaustion fault prior to the call
259 // getpwuid_r() call. In this case, error is set to the appropriate
260 // error condition, but this is undocumented behavior. This check
261 // is safe under any condition, but the use of errno in the output
262 // message may result in an erroneous message.
263 // Bug Id 89052 was opened with RedHat.
264 //
265 warning("Could not retrieve passwd entry: %s\n",
266 strerror(errno));
267 }
268 else {
269 warning("Could not determine user name: %s\n",
270 p->pw_name == NULL ? "pw_name = NULL" :
271 "pw_name zero length");
272 }
273 }
274 FREE_C_HEAP_ARRAY(char, pwbuf);
275 return NULL;
276 }
277
278 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1);
279 strcpy(user_name, p->pw_name);
280
281 FREE_C_HEAP_ARRAY(char, pwbuf);
282 return user_name;
283 }
284
285 // return the name of the user that owns the process identified by vmid.
286 //
287 // This method uses a slow directory search algorithm to find the backing
288 // store file for the specified vmid and returns the user name, as determined
289 // by the user name suffix of the hsperfdata_<username> directory name.
290 //
291 // the caller is expected to free the allocated memory.
292 //
293 static char* get_user_name_slow(int vmid, TRAPS) {
294
295 // short circuit the directory search if the process doesn't even exist.
296 if (kill(vmid, 0) == OS_ERR) {
297 if (errno == ESRCH) {
298 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
299 "Process not found");
300 }
301 else /* EPERM */ {
302 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
303 }
304 }
305
306 // directory search
307 char* oldest_user = NULL;
308 time_t oldest_ctime = 0;
309
310 const char* tmpdirname = os::get_temp_directory();
311
312 DIR* tmpdirp = os::opendir(tmpdirname);
313
314 if (tmpdirp == NULL) {
315 return NULL;
316 }
317
318 // for each entry in the directory that matches the pattern hsperfdata_*,
319 // open the directory and check if the file for the given vmid exists.
320 // The file with the expected name and the latest creation date is used
321 // to determine the user name for the process id.
322 //
323 struct dirent* dentry;
324 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname));
325 errno = 0;
326 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
327
328 // check if the directory entry is a hsperfdata file
329 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
330 continue;
331 }
332
333 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
334 strlen(tmpdirname) + strlen(dentry->d_name) + 2);
335 strcpy(usrdir_name, tmpdirname);
336 strcat(usrdir_name, "/");
337 strcat(usrdir_name, dentry->d_name);
338
339 DIR* subdirp = os::opendir(usrdir_name);
340
341 if (subdirp == NULL) {
342 FREE_C_HEAP_ARRAY(char, usrdir_name);
343 continue;
344 }
345
346 // Since we don't create the backing store files in directories
347 // pointed to by symbolic links, we also don't follow them when
348 // looking for the files. We check for a symbolic link after the
349 // call to opendir in order to eliminate a small window where the
350 // symlink can be exploited.
351 //
352 if (!is_directory_secure(usrdir_name)) {
353 FREE_C_HEAP_ARRAY(char, usrdir_name);
354 os::closedir(subdirp);
355 continue;
356 }
357
358 struct dirent* udentry;
359 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name));
360 errno = 0;
361 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
362
363 if (filename_to_pid(udentry->d_name) == vmid) {
364 struct stat statbuf;
365 int result;
366
367 char* filename = NEW_C_HEAP_ARRAY(char,
368 strlen(usrdir_name) + strlen(udentry->d_name) + 2);
369
370 strcpy(filename, usrdir_name);
371 strcat(filename, "/");
372 strcat(filename, udentry->d_name);
373
374 // don't follow symbolic links for the file
375 RESTARTABLE(::lstat(filename, &statbuf), result);
376 if (result == OS_ERR) {
377 FREE_C_HEAP_ARRAY(char, filename);
378 continue;
379 }
380
381 // skip over files that are not regular files.
382 if (!S_ISREG(statbuf.st_mode)) {
383 FREE_C_HEAP_ARRAY(char, filename);
384 continue;
385 }
386
387 // compare and save filename with latest creation time
388 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
389
390 if (statbuf.st_ctime > oldest_ctime) {
391 char* user = strchr(dentry->d_name, '_') + 1;
392
393 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
394 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1);
395
396 strcpy(oldest_user, user);
397 oldest_ctime = statbuf.st_ctime;
398 }
399 }
400
401 FREE_C_HEAP_ARRAY(char, filename);
402 }
403 }
404 os::closedir(subdirp);
405 FREE_C_HEAP_ARRAY(char, udbuf);
406 FREE_C_HEAP_ARRAY(char, usrdir_name);
407 }
408 os::closedir(tmpdirp);
409 FREE_C_HEAP_ARRAY(char, tdbuf);
410
411 return(oldest_user);
412 }
413
414 // return the name of the user that owns the JVM indicated by the given vmid.
415 //
416 static char* get_user_name(int vmid, TRAPS) {
417 return get_user_name_slow(vmid, CHECK_NULL);
418 }
419
420 // return the file name of the backing store file for the named
421 // shared memory region for the given user name and vmid.
422 //
423 // the caller is expected to free the allocated memory.
424 //
425 static char* get_sharedmem_filename(const char* dirname, int vmid) {
426
427 // add 2 for the file separator and a null terminator.
428 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
429
430 char* name = NEW_C_HEAP_ARRAY(char, nbytes);
431 snprintf(name, nbytes, "%s/%d", dirname, vmid);
432
433 return name;
434 }
435
436
437 // remove file
438 //
439 // this method removes the file specified by the given path
440 //
441 static void remove_file(const char* path) {
442
443 int result;
444
445 // if the file is a directory, the following unlink will fail. since
446 // we don't expect to find directories in the user temp directory, we
447 // won't try to handle this situation. even if accidentially or
448 // maliciously planted, the directory's presence won't hurt anything.
449 //
450 RESTARTABLE(::unlink(path), result);
451 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
452 if (errno != ENOENT) {
453 warning("Could not unlink shared memory backing"
454 " store file %s : %s\n", path, strerror(errno));
455 }
456 }
457 }
458
459
460 // remove file
461 //
462 // this method removes the file with the given file name in the
463 // named directory.
464 //
465 static void remove_file(const char* dirname, const char* filename) {
466
467 size_t nbytes = strlen(dirname) + strlen(filename) + 2;
468 char* path = NEW_C_HEAP_ARRAY(char, nbytes);
469
470 strcpy(path, dirname);
471 strcat(path, "/");
472 strcat(path, filename);
473
474 remove_file(path);
475
476 FREE_C_HEAP_ARRAY(char, path);
477 }
478
479
480 // cleanup stale shared memory resources
481 //
482 // This method attempts to remove all stale shared memory files in
483 // the named user temporary directory. It scans the named directory
484 // for files matching the pattern ^$[0-9]*$. For each file found, the
485 // process id is extracted from the file name and a test is run to
486 // determine if the process is alive. If the process is not alive,
487 // any stale file resources are removed.
488 //
489 static void cleanup_sharedmem_resources(const char* dirname) {
490
491 // open the user temp directory
492 DIR* dirp = os::opendir(dirname);
493
494 if (dirp == NULL) {
495 // directory doesn't exist, so there is nothing to cleanup
496 return;
497 }
498
499 if (!is_directory_secure(dirname)) {
500 // the directory is not a secure directory
501 return;
502 }
503
504 // for each entry in the directory that matches the expected file
505 // name pattern, determine if the file resources are stale and if
506 // so, remove the file resources. Note, instrumented HotSpot processes
507 // for this user may start and/or terminate during this search and
508 // remove or create new files in this directory. The behavior of this
509 // loop under these conditions is dependent upon the implementation of
510 // opendir/readdir.
511 //
512 struct dirent* entry;
513 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname));
514 errno = 0;
515 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
516
517 pid_t pid = filename_to_pid(entry->d_name);
518
519 if (pid == 0) {
520
521 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
522
523 // attempt to remove all unexpected files, except "." and ".."
524 remove_file(dirname, entry->d_name);
525 }
526
527 errno = 0;
528 continue;
529 }
530
531 // we now have a file name that converts to a valid integer
532 // that could represent a process id . if this process id
533 // matches the current process id or the process is not running,
534 // then remove the stale file resources.
535 //
536 // process liveness is detected by sending signal number 0 to
537 // the process id (see kill(2)). if kill determines that the
538 // process does not exist, then the file resources are removed.
539 // if kill determines that that we don't have permission to
540 // signal the process, then the file resources are assumed to
541 // be stale and are removed because the resources for such a
542 // process should be in a different user specific directory.
543 //
544 if ((pid == os::current_process_id()) ||
545 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
546
547 remove_file(dirname, entry->d_name);
548 }
549 errno = 0;
550 }
551 os::closedir(dirp);
552 FREE_C_HEAP_ARRAY(char, dbuf);
553 }
554
555 // make the user specific temporary directory. Returns true if
556 // the directory exists and is secure upon return. Returns false
557 // if the directory exists but is either a symlink, is otherwise
558 // insecure, or if an error occurred.
559 //
560 static bool make_user_tmp_dir(const char* dirname) {
561
562 // create the directory with 0755 permissions. note that the directory
563 // will be owned by euid::egid, which may not be the same as uid::gid.
564 //
565 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
566 if (errno == EEXIST) {
567 // The directory already exists and was probably created by another
568 // JVM instance. However, this could also be the result of a
569 // deliberate symlink. Verify that the existing directory is safe.
570 //
571 if (!is_directory_secure(dirname)) {
572 // directory is not secure
573 if (PrintMiscellaneous && Verbose) {
574 warning("%s directory is insecure\n", dirname);
575 }
576 return false;
577 }
578 }
579 else {
580 // we encountered some other failure while attempting
581 // to create the directory
582 //
583 if (PrintMiscellaneous && Verbose) {
584 warning("could not create directory %s: %s\n",
585 dirname, strerror(errno));
586 }
587 return false;
588 }
589 }
590 return true;
591 }
592
593 // create the shared memory file resources
594 //
595 // This method creates the shared memory file with the given size
596 // This method also creates the user specific temporary directory, if
597 // it does not yet exist.
598 //
599 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
600
601 // make the user temporary directory
602 if (!make_user_tmp_dir(dirname)) {
603 // could not make/find the directory or the found directory
604 // was not secure
605 return -1;
606 }
607
608 int result;
609
610 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_TRUNC, S_IREAD|S_IWRITE), result);
611 if (result == OS_ERR) {
612 if (PrintMiscellaneous && Verbose) {
613 warning("could not create file %s: %s\n", filename, strerror(errno));
614 }
615 return -1;
616 }
617
618 // save the file descriptor
619 int fd = result;
620
621 // set the file size
622 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
623 if (result == OS_ERR) {
624 if (PrintMiscellaneous && Verbose) {
625 warning("could not set shared memory file size: %s\n", strerror(errno));
626 }
627 RESTARTABLE(::close(fd), result);
628 return -1;
629 }
630
631 return fd;
632 }
633
634 // open the shared memory file for the given user and vmid. returns
635 // the file descriptor for the open file or -1 if the file could not
636 // be opened.
637 //
638 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
639
640 // open the file
641 int result;
642 RESTARTABLE(::open(filename, oflags), result);
643 if (result == OS_ERR) {
644 if (errno == ENOENT) {
645 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
646 "Process not found");
647 }
648 else if (errno == EACCES) {
649 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
650 "Permission denied");
651 }
652 else {
653 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
654 }
655 }
656
657 return result;
658 }
659
660 // create a named shared memory region. returns the address of the
661 // memory region on success or NULL on failure. A return value of
662 // NULL will ultimately disable the shared memory feature.
663 //
664 // On Solaris and Linux, the name space for shared memory objects
665 // is the file system name space.
666 //
667 // A monitoring application attaching to a JVM does not need to know
668 // the file system name of the shared memory object. However, it may
669 // be convenient for applications to discover the existence of newly
670 // created and terminating JVMs by watching the file system name space
671 // for files being created or removed.
672 //
673 static char* mmap_create_shared(size_t size) {
674
675 int result;
676 int fd;
677 char* mapAddress;
678
679 int vmid = os::current_process_id();
680
681 char* user_name = get_user_name(geteuid());
682
683 if (user_name == NULL)
684 return NULL;
685
686 char* dirname = get_user_tmp_dir(user_name);
687 char* filename = get_sharedmem_filename(dirname, vmid);
688
689 // cleanup any stale shared memory files
690 cleanup_sharedmem_resources(dirname);
691
692 assert(((size > 0) && (size % os::vm_page_size() == 0)),
693 "unexpected PerfMemory region size");
694
695 fd = create_sharedmem_resources(dirname, filename, size);
696
697 FREE_C_HEAP_ARRAY(char, user_name);
698 FREE_C_HEAP_ARRAY(char, dirname);
699
700 if (fd == -1) {
701 FREE_C_HEAP_ARRAY(char, filename);
702 return NULL;
703 }
704
705 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
706
707 // attempt to close the file - restart it if it was interrupted,
708 // but ignore other failures
709 RESTARTABLE(::close(fd), result);
710 assert(result != OS_ERR, "could not close file");
711
712 if (mapAddress == MAP_FAILED) {
713 if (PrintMiscellaneous && Verbose) {
714 warning("mmap failed - %s\n", strerror(errno));
715 }
716 remove_file(filename);
717 FREE_C_HEAP_ARRAY(char, filename);
718 return NULL;
719 }
720
721 // save the file name for use in delete_shared_memory()
722 backing_store_file_name = filename;
723
724 // clear the shared memory region
725 (void)::memset((void*) mapAddress, 0, size);
726
727 return mapAddress;
728 }
729
730 // release a named shared memory region
731 //
732 static void unmap_shared(char* addr, size_t bytes) {
733 os::release_memory(addr, bytes);
734 }
735
736 // create the PerfData memory region in shared memory.
737 //
738 static char* create_shared_memory(size_t size) {
739
740 // create the shared memory region.
741 return mmap_create_shared(size);
742 }
743
744 // delete the shared PerfData memory region
745 //
746 static void delete_shared_memory(char* addr, size_t size) {
747
748 // cleanup the persistent shared memory resources. since DestroyJavaVM does
749 // not support unloading of the JVM, unmapping of the memory resource is
750 // not performed. The memory will be reclaimed by the OS upon termination of
751 // the process. The backing store file is deleted from the file system.
752
753 assert(!PerfDisableSharedMem, "shouldn't be here");
754
755 if (backing_store_file_name != NULL) {
756 remove_file(backing_store_file_name);
757 // Don't.. Free heap memory could deadlock os::abort() if it is called
758 // from signal handler. OS will reclaim the heap memory.
759 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
760 backing_store_file_name = NULL;
761 }
762 }
763
764 // return the size of the file for the given file descriptor
765 // or 0 if it is not a valid size for a shared memory file
766 //
767 static size_t sharedmem_filesize(int fd, TRAPS) {
768
769 struct stat statbuf;
770 int result;
771
772 RESTARTABLE(::fstat(fd, &statbuf), result);
773 if (result == OS_ERR) {
774 if (PrintMiscellaneous && Verbose) {
775 warning("fstat failed: %s\n", strerror(errno));
776 }
777 THROW_MSG_0(vmSymbols::java_io_IOException(),
778 "Could not determine PerfMemory size");
779 }
780
781 if ((statbuf.st_size == 0) ||
782 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
783 THROW_MSG_0(vmSymbols::java_lang_Exception(),
784 "Invalid PerfMemory size");
785 }
786
787 return (size_t)statbuf.st_size;
788 }
789
790 // attach to a named shared memory region.
791 //
792 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
793
794 char* mapAddress;
795 int result;
796 int fd;
797 size_t size;
798 const char* luser = NULL;
799
800 int mmap_prot;
801 int file_flags;
802
803 ResourceMark rm;
804
805 // map the high level access mode to the appropriate permission
806 // constructs for the file and the shared memory mapping.
807 if (mode == PerfMemory::PERF_MODE_RO) {
808 mmap_prot = PROT_READ;
809 file_flags = O_RDONLY;
810 }
811 else if (mode == PerfMemory::PERF_MODE_RW) {
812 #ifdef LATER
813 mmap_prot = PROT_READ | PROT_WRITE;
814 file_flags = O_RDWR;
815 #else
816 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
817 "Unsupported access mode");
818 #endif
819 }
820 else {
821 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
822 "Illegal access mode");
823 }
824
825 if (user == NULL || strlen(user) == 0) {
826 luser = get_user_name(vmid, CHECK);
827 }
828 else {
829 luser = user;
830 }
831
832 if (luser == NULL) {
833 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
834 "Could not map vmid to user Name");
835 }
836
837 char* dirname = get_user_tmp_dir(luser);
838
839 // since we don't follow symbolic links when creating the backing
840 // store file, we don't follow them when attaching either.
841 //
842 if (!is_directory_secure(dirname)) {
843 FREE_C_HEAP_ARRAY(char, dirname);
844 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
845 "Process not found");
846 }
847
848 char* filename = get_sharedmem_filename(dirname, vmid);
849
850 // copy heap memory to resource memory. the open_sharedmem_file
851 // method below need to use the filename, but could throw an
852 // exception. using a resource array prevents the leak that
853 // would otherwise occur.
854 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
855 strcpy(rfilename, filename);
856
857 // free the c heap resources that are no longer needed
858 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
859 FREE_C_HEAP_ARRAY(char, dirname);
860 FREE_C_HEAP_ARRAY(char, filename);
861
862 // open the shared memory file for the give vmid
863 fd = open_sharedmem_file(rfilename, file_flags, CHECK);
864 assert(fd != OS_ERR, "unexpected value");
865
866 if (*sizep == 0) {
867 size = sharedmem_filesize(fd, CHECK);
868 assert(size != 0, "unexpected size");
869 }
870
871 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
872
873 // attempt to close the file - restart if it gets interrupted,
874 // but ignore other failures
875 RESTARTABLE(::close(fd), result);
876 assert(result != OS_ERR, "could not close file");
877
878 if (mapAddress == MAP_FAILED) {
879 if (PrintMiscellaneous && Verbose) {
880 warning("mmap failed: %s\n", strerror(errno));
881 }
882 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
883 "Could not map PerfMemory");
884 }
885
886 *addr = mapAddress;
887 *sizep = size;
888
889 if (PerfTraceMemOps) {
890 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
891 INTPTR_FORMAT "\n", size, vmid, (void*)mapAddress);
892 }
893 }
894
895
896
897
898 // create the PerfData memory region
899 //
900 // This method creates the memory region used to store performance
901 // data for the JVM. The memory may be created in standard or
902 // shared memory.
903 //
904 void PerfMemory::create_memory_region(size_t size) {
905
906 if (PerfDisableSharedMem) {
907 // do not share the memory for the performance data.
908 _start = create_standard_memory(size);
909 }
910 else {
911 _start = create_shared_memory(size);
912 if (_start == NULL) {
913
914 // creation of the shared memory region failed, attempt
915 // to create a contiguous, non-shared memory region instead.
916 //
917 if (PrintMiscellaneous && Verbose) {
918 warning("Reverting to non-shared PerfMemory region.\n");
919 }
920 PerfDisableSharedMem = true;
921 _start = create_standard_memory(size);
922 }
923 }
924
925 if (_start != NULL) _capacity = size;
926
927 }
928
929 // delete the PerfData memory region
930 //
931 // This method deletes the memory region used to store performance
932 // data for the JVM. The memory region indicated by the <address, size>
933 // tuple will be inaccessible after a call to this method.
934 //
935 void PerfMemory::delete_memory_region() {
936
937 assert((start() != NULL && capacity() > 0), "verify proper state");
938
939 // If user specifies PerfDataSaveFile, it will save the performance data
940 // to the specified file name no matter whether PerfDataSaveToFile is specified
941 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
942 // -XX:+PerfDataSaveToFile.
943 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
944 save_memory_to_file(start(), capacity());
945 }
946
947 if (PerfDisableSharedMem) {
948 delete_standard_memory(start(), capacity());
949 }
950 else {
951 delete_shared_memory(start(), capacity());
952 }
953 }
954
955 // attach to the PerfData memory region for another JVM
956 //
957 // This method returns an <address, size> tuple that points to
958 // a memory buffer that is kept reasonably synchronized with
959 // the PerfData memory region for the indicated JVM. This
960 // buffer may be kept in synchronization via shared memory
961 // or some other mechanism that keeps the buffer updated.
962 //
963 // If the JVM chooses not to support the attachability feature,
964 // this method should throw an UnsupportedOperation exception.
965 //
966 // This implementation utilizes named shared memory to map
967 // the indicated process's PerfData memory region into this JVMs
968 // address space.
969 //
970 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
971
972 if (vmid == 0 || vmid == os::current_process_id()) {
973 *addrp = start();
974 *sizep = capacity();
975 return;
976 }
977
978 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
979 }
980
981 // detach from the PerfData memory region of another JVM
982 //
983 // This method detaches the PerfData memory region of another
984 // JVM, specified as an <address, size> tuple of a buffer
985 // in this process's address space. This method may perform
986 // arbitrary actions to accomplish the detachment. The memory
987 // region specified by <address, size> will be inaccessible after
988 // a call to this method.
989 //
990 // If the JVM chooses not to support the attachability feature,
991 // this method should throw an UnsupportedOperation exception.
992 //
993 // This implementation utilizes named shared memory to detach
994 // the indicated process's PerfData memory region from this
995 // process's address space.
996 //
997 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
998
999 assert(addr != 0, "address sanity check");
1000 assert(bytes > 0, "capacity sanity check");
1001
1002 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1003 // prevent accidental detachment of this process's PerfMemory region
1004 return;
1005 }
1006
1007 unmap_shared(addr, bytes);
1008 }
1009
1010 char* PerfMemory::backing_store_filename() {
1011 return backing_store_file_name;
1012 }