Fri, 24 Oct 2014 15:02:37 -0400
8050807: Better performing performance data handling
Reviewed-by: dcubed, dholmes, pnauman, ctornqvi, mschoene
Contributed-by: gerald.thornbrugh@oracle.com
1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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_bsd.inline.hpp"
31 #include "runtime/handles.inline.hpp"
32 #include "runtime/perfMemory.hpp"
33 #include "services/memTracker.hpp"
34 #include "utilities/exceptions.hpp"
36 // put OS-includes here
37 # include <sys/types.h>
38 # include <sys/mman.h>
39 # include <errno.h>
40 # include <stdio.h>
41 # include <unistd.h>
42 # include <sys/stat.h>
43 # include <signal.h>
44 # include <pwd.h>
46 static char* backing_store_file_name = NULL; // name of the backing store
47 // file, if successfully created.
49 // Standard Memory Implementation Details
51 // create the PerfData memory region in standard memory.
52 //
53 static char* create_standard_memory(size_t size) {
55 // allocate an aligned chuck of memory
56 char* mapAddress = os::reserve_memory(size);
58 if (mapAddress == NULL) {
59 return NULL;
60 }
62 // commit memory
63 if (!os::commit_memory(mapAddress, size, !ExecMem)) {
64 if (PrintMiscellaneous && Verbose) {
65 warning("Could not commit PerfData memory\n");
66 }
67 os::release_memory(mapAddress, size);
68 return NULL;
69 }
71 return mapAddress;
72 }
74 // delete the PerfData memory region
75 //
76 static void delete_standard_memory(char* addr, size_t size) {
78 // there are no persistent external resources to cleanup for standard
79 // memory. since DestroyJavaVM does not support unloading of the JVM,
80 // cleanup of the memory resource is not performed. The memory will be
81 // reclaimed by the OS upon termination of the process.
82 //
83 return;
84 }
86 // save the specified memory region to the given file
87 //
88 // Note: this function might be called from signal handler (by os::abort()),
89 // don't allocate heap memory.
90 //
91 static void save_memory_to_file(char* addr, size_t size) {
93 const char* destfile = PerfMemory::get_perfdata_file_path();
94 assert(destfile[0] != '\0', "invalid PerfData file path");
96 int result;
98 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
99 result);;
100 if (result == OS_ERR) {
101 if (PrintMiscellaneous && Verbose) {
102 warning("Could not create Perfdata save file: %s: %s\n",
103 destfile, strerror(errno));
104 }
105 } else {
106 int fd = result;
108 for (size_t remaining = size; remaining > 0;) {
110 RESTARTABLE(::write(fd, addr, remaining), result);
111 if (result == OS_ERR) {
112 if (PrintMiscellaneous && Verbose) {
113 warning("Could not write Perfdata save file: %s: %s\n",
114 destfile, strerror(errno));
115 }
116 break;
117 }
119 remaining -= (size_t)result;
120 addr += result;
121 }
123 result = ::close(fd);
124 if (PrintMiscellaneous && Verbose) {
125 if (result == OS_ERR) {
126 warning("Could not close %s: %s\n", destfile, strerror(errno));
127 }
128 }
129 }
130 FREE_C_HEAP_ARRAY(char, destfile, mtInternal);
131 }
134 // Shared Memory Implementation Details
136 // Note: the solaris and bsd shared memory implementation uses the mmap
137 // interface with a backing store file to implement named shared memory.
138 // Using the file system as the name space for shared memory allows a
139 // common name space to be supported across a variety of platforms. It
140 // also provides a name space that Java applications can deal with through
141 // simple file apis.
142 //
143 // The solaris and bsd implementations store the backing store file in
144 // a user specific temporary directory located in the /tmp file system,
145 // which is always a local file system and is sometimes a RAM based file
146 // system.
148 // return the user specific temporary directory name.
149 //
150 // the caller is expected to free the allocated memory.
151 //
152 static char* get_user_tmp_dir(const char* user) {
154 const char* tmpdir = os::get_temp_directory();
155 const char* perfdir = PERFDATA_NAME;
156 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
157 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
159 // construct the path name to user specific tmp directory
160 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
162 return dirname;
163 }
165 // convert the given file name into a process id. if the file
166 // does not meet the file naming constraints, return 0.
167 //
168 static pid_t filename_to_pid(const char* filename) {
170 // a filename that doesn't begin with a digit is not a
171 // candidate for conversion.
172 //
173 if (!isdigit(*filename)) {
174 return 0;
175 }
177 // check if file name can be converted to an integer without
178 // any leftover characters.
179 //
180 char* remainder = NULL;
181 errno = 0;
182 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
184 if (errno != 0) {
185 return 0;
186 }
188 // check for left over characters. If any, then the filename is
189 // not a candidate for conversion.
190 //
191 if (remainder != NULL && *remainder != '\0') {
192 return 0;
193 }
195 // successful conversion, return the pid
196 return pid;
197 }
200 // Check if the given statbuf is considered a secure directory for
201 // the backing store files. Returns true if the directory is considered
202 // a secure location. Returns false if the statbuf is a symbolic link or
203 // if an error occurred.
204 //
205 static bool is_statbuf_secure(struct stat *statp) {
206 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
207 // The path represents a link or some non-directory file type,
208 // which is not what we expected. Declare it insecure.
209 //
210 return false;
211 }
212 // We have an existing directory, check if the permissions are safe.
213 //
214 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
215 // The directory is open for writing and could be subjected
216 // to a symlink or a hard link attack. Declare it insecure.
217 //
218 return false;
219 }
220 // See if the uid of the directory matches the effective uid of the process.
221 //
222 if (statp->st_uid != geteuid()) {
223 // The directory was not created by this user, declare it insecure.
224 //
225 return false;
226 }
227 return true;
228 }
231 // Check if the given path is considered a secure directory for
232 // the backing store files. Returns true if the directory exists
233 // and is considered a secure location. Returns false if the path
234 // is a symbolic link or if an error occurred.
235 //
236 static bool is_directory_secure(const char* path) {
237 struct stat statbuf;
238 int result = 0;
240 RESTARTABLE(::lstat(path, &statbuf), result);
241 if (result == OS_ERR) {
242 return false;
243 }
245 // The path exists, see if it is secure.
246 return is_statbuf_secure(&statbuf);
247 }
250 // Check if the given directory file descriptor is considered a secure
251 // directory for the backing store files. Returns true if the directory
252 // exists and is considered a secure location. Returns false if the path
253 // is a symbolic link or if an error occurred.
254 //
255 static bool is_dirfd_secure(int dir_fd) {
256 struct stat statbuf;
257 int result = 0;
259 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
260 if (result == OS_ERR) {
261 return false;
262 }
264 // The path exists, now check its mode.
265 return is_statbuf_secure(&statbuf);
266 }
269 // Check to make sure fd1 and fd2 are referencing the same file system object.
270 //
271 static bool is_same_fsobject(int fd1, int fd2) {
272 struct stat statbuf1;
273 struct stat statbuf2;
274 int result = 0;
276 RESTARTABLE(::fstat(fd1, &statbuf1), result);
277 if (result == OS_ERR) {
278 return false;
279 }
280 RESTARTABLE(::fstat(fd2, &statbuf2), result);
281 if (result == OS_ERR) {
282 return false;
283 }
285 if ((statbuf1.st_ino == statbuf2.st_ino) &&
286 (statbuf1.st_dev == statbuf2.st_dev)) {
287 return true;
288 } else {
289 return false;
290 }
291 }
294 // Open the directory of the given path and validate it.
295 // Return a DIR * of the open directory.
296 //
297 static DIR *open_directory_secure(const char* dirname) {
298 // Open the directory using open() so that it can be verified
299 // to be secure by calling is_dirfd_secure(), opendir() and then check
300 // to see if they are the same file system object. This method does not
301 // introduce a window of opportunity for the directory to be attacked that
302 // calling opendir() and is_directory_secure() does.
303 int result;
304 DIR *dirp = NULL;
305 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
306 if (result == OS_ERR) {
307 // Directory doesn't exist or is a symlink, so there is nothing to cleanup.
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;
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 }
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 }
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 }
343 // Close initial open now that we know directory is secure
344 os::close(fd);
346 return dirp;
347 }
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.
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) {
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);
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 }
378 // Set the current directory to dirname by using the fd of the directory.
379 result = fchdir(fd);
381 return dirp;
382 }
384 // Close the directory and restore the current working directory.
385 //
386 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
388 int result;
389 // If we have a saved cwd change back to it and close the fd.
390 if (saved_cwd_fd != -1) {
391 result = fchdir(saved_cwd_fd);
392 ::close(saved_cwd_fd);
393 }
395 // Close the directory.
396 os::closedir(dirp);
397 }
399 // Check if the given file descriptor is considered a secure.
400 //
401 static bool is_file_secure(int fd, const char *filename) {
403 int result;
404 struct stat statbuf;
406 // Determine if the file is secure.
407 RESTARTABLE(::fstat(fd, &statbuf), result);
408 if (result == OS_ERR) {
409 if (PrintMiscellaneous && Verbose) {
410 warning("fstat failed on %s: %s\n", filename, strerror(errno));
411 }
412 return false;
413 }
414 if (statbuf.st_nlink > 1) {
415 // A file with multiple links is not expected.
416 if (PrintMiscellaneous && Verbose) {
417 warning("file %s has multiple links\n", filename);
418 }
419 return false;
420 }
421 return true;
422 }
424 // return the user name for the given user id
425 //
426 // the caller is expected to free the allocated memory.
427 //
428 static char* get_user_name(uid_t uid) {
430 struct passwd pwent;
432 // determine the max pwbuf size from sysconf, and hardcode
433 // a default if this not available through sysconf.
434 //
435 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
436 if (bufsize == -1)
437 bufsize = 1024;
439 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
441 // POSIX interface to getpwuid_r is used on LINUX
442 struct passwd* p;
443 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
445 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
446 if (PrintMiscellaneous && Verbose) {
447 if (result != 0) {
448 warning("Could not retrieve passwd entry: %s\n",
449 strerror(result));
450 }
451 else if (p == NULL) {
452 // this check is added to protect against an observed problem
453 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
454 // indicating success, but has p == NULL. This was observed when
455 // inserting a file descriptor exhaustion fault prior to the call
456 // getpwuid_r() call. In this case, error is set to the appropriate
457 // error condition, but this is undocumented behavior. This check
458 // is safe under any condition, but the use of errno in the output
459 // message may result in an erroneous message.
460 // Bug Id 89052 was opened with RedHat.
461 //
462 warning("Could not retrieve passwd entry: %s\n",
463 strerror(errno));
464 }
465 else {
466 warning("Could not determine user name: %s\n",
467 p->pw_name == NULL ? "pw_name = NULL" :
468 "pw_name zero length");
469 }
470 }
471 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
472 return NULL;
473 }
475 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
476 strcpy(user_name, p->pw_name);
478 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
479 return user_name;
480 }
482 // return the name of the user that owns the process identified by vmid.
483 //
484 // This method uses a slow directory search algorithm to find the backing
485 // store file for the specified vmid and returns the user name, as determined
486 // by the user name suffix of the hsperfdata_<username> directory name.
487 //
488 // the caller is expected to free the allocated memory.
489 //
490 static char* get_user_name_slow(int vmid, TRAPS) {
492 // short circuit the directory search if the process doesn't even exist.
493 if (kill(vmid, 0) == OS_ERR) {
494 if (errno == ESRCH) {
495 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
496 "Process not found");
497 }
498 else /* EPERM */ {
499 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
500 }
501 }
503 // directory search
504 char* oldest_user = NULL;
505 time_t oldest_ctime = 0;
507 const char* tmpdirname = os::get_temp_directory();
509 // open the temp directory
510 DIR* tmpdirp = open_directory_secure(tmpdirname);
511 if (tmpdirp == NULL) {
512 // Cannot open the directory to get the user name, return.
513 return NULL;
514 }
516 // for each entry in the directory that matches the pattern hsperfdata_*,
517 // open the directory and check if the file for the given vmid exists.
518 // The file with the expected name and the latest creation date is used
519 // to determine the user name for the process id.
520 //
521 struct dirent* dentry;
522 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
523 errno = 0;
524 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
526 // check if the directory entry is a hsperfdata file
527 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
528 continue;
529 }
531 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
532 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
533 strcpy(usrdir_name, tmpdirname);
534 strcat(usrdir_name, "/");
535 strcat(usrdir_name, dentry->d_name);
537 // open the user directory
538 DIR* subdirp = open_directory_secure(usrdir_name);
540 if (subdirp == NULL) {
541 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
542 continue;
543 }
545 struct dirent* udentry;
546 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
547 errno = 0;
548 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
550 if (filename_to_pid(udentry->d_name) == vmid) {
551 struct stat statbuf;
552 int result;
554 char* filename = NEW_C_HEAP_ARRAY(char,
555 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
557 strcpy(filename, usrdir_name);
558 strcat(filename, "/");
559 strcat(filename, udentry->d_name);
561 // don't follow symbolic links for the file
562 RESTARTABLE(::lstat(filename, &statbuf), result);
563 if (result == OS_ERR) {
564 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
565 continue;
566 }
568 // skip over files that are not regular files.
569 if (!S_ISREG(statbuf.st_mode)) {
570 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
571 continue;
572 }
574 // compare and save filename with latest creation time
575 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
577 if (statbuf.st_ctime > oldest_ctime) {
578 char* user = strchr(dentry->d_name, '_') + 1;
580 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user, mtInternal);
581 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
583 strcpy(oldest_user, user);
584 oldest_ctime = statbuf.st_ctime;
585 }
586 }
588 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
589 }
590 }
591 os::closedir(subdirp);
592 FREE_C_HEAP_ARRAY(char, udbuf, mtInternal);
593 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
594 }
595 os::closedir(tmpdirp);
596 FREE_C_HEAP_ARRAY(char, tdbuf, mtInternal);
598 return(oldest_user);
599 }
601 // return the name of the user that owns the JVM indicated by the given vmid.
602 //
603 static char* get_user_name(int vmid, TRAPS) {
604 return get_user_name_slow(vmid, CHECK_NULL);
605 }
607 // return the file name of the backing store file for the named
608 // shared memory region for the given user name and vmid.
609 //
610 // the caller is expected to free the allocated memory.
611 //
612 static char* get_sharedmem_filename(const char* dirname, int vmid) {
614 // add 2 for the file separator and a null terminator.
615 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
617 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
618 snprintf(name, nbytes, "%s/%d", dirname, vmid);
620 return name;
621 }
624 // remove file
625 //
626 // this method removes the file specified by the given path
627 //
628 static void remove_file(const char* path) {
630 int result;
632 // if the file is a directory, the following unlink will fail. since
633 // we don't expect to find directories in the user temp directory, we
634 // won't try to handle this situation. even if accidentially or
635 // maliciously planted, the directory's presence won't hurt anything.
636 //
637 RESTARTABLE(::unlink(path), result);
638 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
639 if (errno != ENOENT) {
640 warning("Could not unlink shared memory backing"
641 " store file %s : %s\n", path, strerror(errno));
642 }
643 }
644 }
647 // cleanup stale shared memory resources
648 //
649 // This method attempts to remove all stale shared memory files in
650 // the named user temporary directory. It scans the named directory
651 // for files matching the pattern ^$[0-9]*$. For each file found, the
652 // process id is extracted from the file name and a test is run to
653 // determine if the process is alive. If the process is not alive,
654 // any stale file resources are removed.
655 //
656 static void cleanup_sharedmem_resources(const char* dirname) {
658 int saved_cwd_fd;
659 // open the directory and set the current working directory to it
660 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
661 if (dirp == NULL) {
662 // directory doesn't exist or is insecure, so there is nothing to cleanup
663 return;
664 }
666 // for each entry in the directory that matches the expected file
667 // name pattern, determine if the file resources are stale and if
668 // so, remove the file resources. Note, instrumented HotSpot processes
669 // for this user may start and/or terminate during this search and
670 // remove or create new files in this directory. The behavior of this
671 // loop under these conditions is dependent upon the implementation of
672 // opendir/readdir.
673 //
674 struct dirent* entry;
675 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
677 errno = 0;
678 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
680 pid_t pid = filename_to_pid(entry->d_name);
682 if (pid == 0) {
684 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
686 // attempt to remove all unexpected files, except "." and ".."
687 unlink(entry->d_name);
688 }
690 errno = 0;
691 continue;
692 }
694 // we now have a file name that converts to a valid integer
695 // that could represent a process id . if this process id
696 // matches the current process id or the process is not running,
697 // then remove the stale file resources.
698 //
699 // process liveness is detected by sending signal number 0 to
700 // the process id (see kill(2)). if kill determines that the
701 // process does not exist, then the file resources are removed.
702 // if kill determines that that we don't have permission to
703 // signal the process, then the file resources are assumed to
704 // be stale and are removed because the resources for such a
705 // process should be in a different user specific directory.
706 //
707 if ((pid == os::current_process_id()) ||
708 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
710 unlink(entry->d_name);
711 }
712 errno = 0;
713 }
715 // close the directory and reset the current working directory
716 close_directory_secure_cwd(dirp, saved_cwd_fd);
718 FREE_C_HEAP_ARRAY(char, dbuf, mtInternal);
719 }
721 // make the user specific temporary directory. Returns true if
722 // the directory exists and is secure upon return. Returns false
723 // if the directory exists but is either a symlink, is otherwise
724 // insecure, or if an error occurred.
725 //
726 static bool make_user_tmp_dir(const char* dirname) {
728 // create the directory with 0755 permissions. note that the directory
729 // will be owned by euid::egid, which may not be the same as uid::gid.
730 //
731 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
732 if (errno == EEXIST) {
733 // The directory already exists and was probably created by another
734 // JVM instance. However, this could also be the result of a
735 // deliberate symlink. Verify that the existing directory is safe.
736 //
737 if (!is_directory_secure(dirname)) {
738 // directory is not secure
739 if (PrintMiscellaneous && Verbose) {
740 warning("%s directory is insecure\n", dirname);
741 }
742 return false;
743 }
744 }
745 else {
746 // we encountered some other failure while attempting
747 // to create the directory
748 //
749 if (PrintMiscellaneous && Verbose) {
750 warning("could not create directory %s: %s\n",
751 dirname, strerror(errno));
752 }
753 return false;
754 }
755 }
756 return true;
757 }
759 // create the shared memory file resources
760 //
761 // This method creates the shared memory file with the given size
762 // This method also creates the user specific temporary directory, if
763 // it does not yet exist.
764 //
765 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
767 // make the user temporary directory
768 if (!make_user_tmp_dir(dirname)) {
769 // could not make/find the directory or the found directory
770 // was not secure
771 return -1;
772 }
774 int saved_cwd_fd;
775 // open the directory and set the current working directory to it
776 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
777 if (dirp == NULL) {
778 // Directory doesn't exist or is insecure, so cannot create shared
779 // memory file.
780 return -1;
781 }
783 // Open the filename in the current directory.
784 // Cannot use O_TRUNC here; truncation of an existing file has to happen
785 // after the is_file_secure() check below.
786 int result;
787 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
788 if (result == OS_ERR) {
789 if (PrintMiscellaneous && Verbose) {
790 if (errno == ELOOP) {
791 warning("file %s is a symlink and is not secure\n", filename);
792 } else {
793 warning("could not create file %s: %s\n", filename, strerror(errno));
794 }
795 }
796 // close the directory and reset the current working directory
797 close_directory_secure_cwd(dirp, saved_cwd_fd);
799 return -1;
800 }
801 // close the directory and reset the current working directory
802 close_directory_secure_cwd(dirp, saved_cwd_fd);
804 // save the file descriptor
805 int fd = result;
807 // check to see if the file is secure
808 if (!is_file_secure(fd, filename)) {
809 ::close(fd);
810 return -1;
811 }
813 // truncate the file to get rid of any existing data
814 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
815 if (result == OS_ERR) {
816 if (PrintMiscellaneous && Verbose) {
817 warning("could not truncate shared memory file: %s\n", strerror(errno));
818 }
819 ::close(fd);
820 return -1;
821 }
822 // set the file size
823 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
824 if (result == OS_ERR) {
825 if (PrintMiscellaneous && Verbose) {
826 warning("could not set shared memory file size: %s\n", strerror(errno));
827 }
828 ::close(fd);
829 return -1;
830 }
832 // Verify that we have enough disk space for this file.
833 // We'll get random SIGBUS crashes on memory accesses if
834 // we don't.
836 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
837 int zero_int = 0;
838 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
839 if (result == -1 ) break;
840 RESTARTABLE(::write(fd, &zero_int, 1), result);
841 if (result != 1) {
842 if (errno == ENOSPC) {
843 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
844 }
845 break;
846 }
847 }
849 if (result != -1) {
850 return fd;
851 } else {
852 ::close(fd);
853 return -1;
854 }
855 }
857 // open the shared memory file for the given user and vmid. returns
858 // the file descriptor for the open file or -1 if the file could not
859 // be opened.
860 //
861 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
863 // open the file
864 int result;
865 RESTARTABLE(::open(filename, oflags), result);
866 if (result == OS_ERR) {
867 if (errno == ENOENT) {
868 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
869 "Process not found", OS_ERR);
870 }
871 else if (errno == EACCES) {
872 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
873 "Permission denied", OS_ERR);
874 }
875 else {
876 THROW_MSG_(vmSymbols::java_io_IOException(), strerror(errno), OS_ERR);
877 }
878 }
879 int fd = result;
881 // check to see if the file is secure
882 if (!is_file_secure(fd, filename)) {
883 ::close(fd);
884 return -1;
885 }
887 return fd;
888 }
890 // create a named shared memory region. returns the address of the
891 // memory region on success or NULL on failure. A return value of
892 // NULL will ultimately disable the shared memory feature.
893 //
894 // On Solaris and Bsd, the name space for shared memory objects
895 // is the file system name space.
896 //
897 // A monitoring application attaching to a JVM does not need to know
898 // the file system name of the shared memory object. However, it may
899 // be convenient for applications to discover the existence of newly
900 // created and terminating JVMs by watching the file system name space
901 // for files being created or removed.
902 //
903 static char* mmap_create_shared(size_t size) {
905 int result;
906 int fd;
907 char* mapAddress;
909 int vmid = os::current_process_id();
911 char* user_name = get_user_name(geteuid());
913 if (user_name == NULL)
914 return NULL;
916 char* dirname = get_user_tmp_dir(user_name);
917 char* filename = get_sharedmem_filename(dirname, vmid);
919 // get the short filename
920 char* short_filename = strrchr(filename, '/');
921 if (short_filename == NULL) {
922 short_filename = filename;
923 } else {
924 short_filename++;
925 }
927 // cleanup any stale shared memory files
928 cleanup_sharedmem_resources(dirname);
930 assert(((size > 0) && (size % os::vm_page_size() == 0)),
931 "unexpected PerfMemory region size");
933 fd = create_sharedmem_resources(dirname, short_filename, size);
935 FREE_C_HEAP_ARRAY(char, user_name, mtInternal);
936 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
938 if (fd == -1) {
939 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
940 return NULL;
941 }
943 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
945 result = ::close(fd);
946 assert(result != OS_ERR, "could not close file");
948 if (mapAddress == MAP_FAILED) {
949 if (PrintMiscellaneous && Verbose) {
950 warning("mmap failed - %s\n", strerror(errno));
951 }
952 remove_file(filename);
953 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
954 return NULL;
955 }
957 // save the file name for use in delete_shared_memory()
958 backing_store_file_name = filename;
960 // clear the shared memory region
961 (void)::memset((void*) mapAddress, 0, size);
963 // it does not go through os api, the operation has to record from here
964 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, mtInternal, CURRENT_PC);
966 return mapAddress;
967 }
969 // release a named shared memory region
970 //
971 static void unmap_shared(char* addr, size_t bytes) {
972 os::release_memory(addr, bytes);
973 }
975 // create the PerfData memory region in shared memory.
976 //
977 static char* create_shared_memory(size_t size) {
979 // create the shared memory region.
980 return mmap_create_shared(size);
981 }
983 // delete the shared PerfData memory region
984 //
985 static void delete_shared_memory(char* addr, size_t size) {
987 // cleanup the persistent shared memory resources. since DestroyJavaVM does
988 // not support unloading of the JVM, unmapping of the memory resource is
989 // not performed. The memory will be reclaimed by the OS upon termination of
990 // the process. The backing store file is deleted from the file system.
992 assert(!PerfDisableSharedMem, "shouldn't be here");
994 if (backing_store_file_name != NULL) {
995 remove_file(backing_store_file_name);
996 // Don't.. Free heap memory could deadlock os::abort() if it is called
997 // from signal handler. OS will reclaim the heap memory.
998 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
999 backing_store_file_name = NULL;
1000 }
1001 }
1003 // return the size of the file for the given file descriptor
1004 // or 0 if it is not a valid size for a shared memory file
1005 //
1006 static size_t sharedmem_filesize(int fd, TRAPS) {
1008 struct stat statbuf;
1009 int result;
1011 RESTARTABLE(::fstat(fd, &statbuf), result);
1012 if (result == OS_ERR) {
1013 if (PrintMiscellaneous && Verbose) {
1014 warning("fstat failed: %s\n", strerror(errno));
1015 }
1016 THROW_MSG_0(vmSymbols::java_io_IOException(),
1017 "Could not determine PerfMemory size");
1018 }
1020 if ((statbuf.st_size == 0) ||
1021 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1022 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1023 "Invalid PerfMemory size");
1024 }
1026 return (size_t)statbuf.st_size;
1027 }
1029 // attach to a named shared memory region.
1030 //
1031 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1033 char* mapAddress;
1034 int result;
1035 int fd;
1036 size_t size = 0;
1037 const char* luser = NULL;
1039 int mmap_prot;
1040 int file_flags;
1042 ResourceMark rm;
1044 // map the high level access mode to the appropriate permission
1045 // constructs for the file and the shared memory mapping.
1046 if (mode == PerfMemory::PERF_MODE_RO) {
1047 mmap_prot = PROT_READ;
1048 file_flags = O_RDONLY | O_NOFOLLOW;
1049 }
1050 else if (mode == PerfMemory::PERF_MODE_RW) {
1051 #ifdef LATER
1052 mmap_prot = PROT_READ | PROT_WRITE;
1053 file_flags = O_RDWR | O_NOFOLLOW;
1054 #else
1055 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1056 "Unsupported access mode");
1057 #endif
1058 }
1059 else {
1060 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1061 "Illegal access mode");
1062 }
1064 if (user == NULL || strlen(user) == 0) {
1065 luser = get_user_name(vmid, CHECK);
1066 }
1067 else {
1068 luser = user;
1069 }
1071 if (luser == NULL) {
1072 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1073 "Could not map vmid to user Name");
1074 }
1076 char* dirname = get_user_tmp_dir(luser);
1078 // since we don't follow symbolic links when creating the backing
1079 // store file, we don't follow them when attaching either.
1080 //
1081 if (!is_directory_secure(dirname)) {
1082 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1083 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1084 "Process not found");
1085 }
1087 char* filename = get_sharedmem_filename(dirname, vmid);
1089 // copy heap memory to resource memory. the open_sharedmem_file
1090 // method below need to use the filename, but could throw an
1091 // exception. using a resource array prevents the leak that
1092 // would otherwise occur.
1093 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1094 strcpy(rfilename, filename);
1096 // free the c heap resources that are no longer needed
1097 if (luser != user) FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1098 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1099 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1101 // open the shared memory file for the give vmid
1102 fd = open_sharedmem_file(rfilename, file_flags, CHECK);
1103 assert(fd != OS_ERR, "unexpected value");
1105 if (*sizep == 0) {
1106 size = sharedmem_filesize(fd, CHECK);
1107 } else {
1108 size = *sizep;
1109 }
1111 assert(size > 0, "unexpected size <= 0");
1113 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1115 // attempt to close the file - restart if it gets interrupted,
1116 // but ignore other failures
1117 result = ::close(fd);
1118 assert(result != OS_ERR, "could not close file");
1120 if (mapAddress == MAP_FAILED) {
1121 if (PrintMiscellaneous && Verbose) {
1122 warning("mmap failed: %s\n", strerror(errno));
1123 }
1124 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1125 "Could not map PerfMemory");
1126 }
1128 // it does not go through os api, the operation has to record from here
1129 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, mtInternal, CURRENT_PC);
1131 *addr = mapAddress;
1132 *sizep = size;
1134 if (PerfTraceMemOps) {
1135 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1136 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1137 }
1138 }
1143 // create the PerfData memory region
1144 //
1145 // This method creates the memory region used to store performance
1146 // data for the JVM. The memory may be created in standard or
1147 // shared memory.
1148 //
1149 void PerfMemory::create_memory_region(size_t size) {
1151 if (PerfDisableSharedMem) {
1152 // do not share the memory for the performance data.
1153 _start = create_standard_memory(size);
1154 }
1155 else {
1156 _start = create_shared_memory(size);
1157 if (_start == NULL) {
1159 // creation of the shared memory region failed, attempt
1160 // to create a contiguous, non-shared memory region instead.
1161 //
1162 if (PrintMiscellaneous && Verbose) {
1163 warning("Reverting to non-shared PerfMemory region.\n");
1164 }
1165 PerfDisableSharedMem = true;
1166 _start = create_standard_memory(size);
1167 }
1168 }
1170 if (_start != NULL) _capacity = size;
1172 }
1174 // delete the PerfData memory region
1175 //
1176 // This method deletes the memory region used to store performance
1177 // data for the JVM. The memory region indicated by the <address, size>
1178 // tuple will be inaccessible after a call to this method.
1179 //
1180 void PerfMemory::delete_memory_region() {
1182 assert((start() != NULL && capacity() > 0), "verify proper state");
1184 // If user specifies PerfDataSaveFile, it will save the performance data
1185 // to the specified file name no matter whether PerfDataSaveToFile is specified
1186 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1187 // -XX:+PerfDataSaveToFile.
1188 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1189 save_memory_to_file(start(), capacity());
1190 }
1192 if (PerfDisableSharedMem) {
1193 delete_standard_memory(start(), capacity());
1194 }
1195 else {
1196 delete_shared_memory(start(), capacity());
1197 }
1198 }
1200 // attach to the PerfData memory region for another JVM
1201 //
1202 // This method returns an <address, size> tuple that points to
1203 // a memory buffer that is kept reasonably synchronized with
1204 // the PerfData memory region for the indicated JVM. This
1205 // buffer may be kept in synchronization via shared memory
1206 // or some other mechanism that keeps the buffer updated.
1207 //
1208 // If the JVM chooses not to support the attachability feature,
1209 // this method should throw an UnsupportedOperation exception.
1210 //
1211 // This implementation utilizes named shared memory to map
1212 // the indicated process's PerfData memory region into this JVMs
1213 // address space.
1214 //
1215 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1217 if (vmid == 0 || vmid == os::current_process_id()) {
1218 *addrp = start();
1219 *sizep = capacity();
1220 return;
1221 }
1223 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1224 }
1226 // detach from the PerfData memory region of another JVM
1227 //
1228 // This method detaches the PerfData memory region of another
1229 // JVM, specified as an <address, size> tuple of a buffer
1230 // in this process's address space. This method may perform
1231 // arbitrary actions to accomplish the detachment. The memory
1232 // region specified by <address, size> will be inaccessible after
1233 // a call to this method.
1234 //
1235 // If the JVM chooses not to support the attachability feature,
1236 // this method should throw an UnsupportedOperation exception.
1237 //
1238 // This implementation utilizes named shared memory to detach
1239 // the indicated process's PerfData memory region from this
1240 // process's address space.
1241 //
1242 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1244 assert(addr != 0, "address sanity check");
1245 assert(bytes > 0, "capacity sanity check");
1247 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1248 // prevent accidental detachment of this process's PerfMemory region
1249 return;
1250 }
1252 unmap_shared(addr, bytes);
1253 }
1255 char* PerfMemory::backing_store_filename() {
1256 return backing_store_file_name;
1257 }