1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2013 SAP AG. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "os_aix.inline.hpp"
32 #include "runtime/handles.inline.hpp"
33 #include "runtime/perfMemory.hpp"
34 #include "services/memTracker.hpp"
35 #include "utilities/exceptions.hpp"
36
37 // put OS-includes here
38 # include <sys/types.h>
39 # include <sys/mman.h>
40 # include <errno.h>
41 # include <stdio.h>
42 # include <unistd.h>
43 # include <sys/stat.h>
44 # include <signal.h>
45 # include <pwd.h>
46
47 static char* backing_store_file_name = NULL; // name of the backing store
48 // file, if successfully created.
49
50 // Standard Memory Implementation Details
51
52 // create the PerfData memory region in standard memory.
53 //
create_standard_memory(size_t size)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 //
delete_standard_memory(char * addr,size_t size)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 //
save_memory_to_file(char * addr,size_t size)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 RESTARTABLE(::close(fd), result);
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 //
get_user_tmp_dir(const char * user)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 //
filename_to_pid(const char * filename)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 // 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 //
is_statbuf_secure(struct stat * statp)205 static bool is_statbuf_secure(struct stat *statp) {
206 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
207 // The path represents a link or some non-directory file type,
208 // which is not what we expected. Declare it insecure.
209 //
210 return false;
211 }
212 // We have an existing directory, check if the permissions are safe.
213 //
214 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
215 // The directory is open for writing and could be subjected
216 // to a symlink or a hard link attack. Declare it insecure.
217 //
218 return false;
219 }
220 // If user is not root then see if the uid of the directory matches the effective uid of the process.
221 uid_t euid = geteuid();
222 if ((euid != 0) && (statp->st_uid != euid)) {
223 // The directory was not created by this user, declare it insecure.
224 //
225 return false;
226 }
227 return true;
228 }
229
230
231 // Check if the given path is considered a secure directory for
232 // the backing store files. Returns true if the directory exists
233 // and is considered a secure location. Returns false if the path
234 // is a symbolic link or if an error occurred.
235 //
is_directory_secure(const char * path)236 static bool is_directory_secure(const char* path) {
237 struct stat statbuf;
238 int result = 0;
239
240 RESTARTABLE(::lstat(path, &statbuf), result);
241 if (result == OS_ERR) {
242 return false;
243 }
244
245 // The path exists, see if it is secure.
246 return is_statbuf_secure(&statbuf);
247 }
248
249 // (Taken over from Solaris to support the O_NOFOLLOW case on AIX.)
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.
is_dirfd_secure(int dir_fd)254 static bool is_dirfd_secure(int dir_fd) {
255 struct stat statbuf;
256 int result = 0;
257
258 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
259 if (result == OS_ERR) {
260 return false;
261 }
262
263 // The path exists, now check its mode.
264 return is_statbuf_secure(&statbuf);
265 }
266
267
268 // Check to make sure fd1 and fd2 are referencing the same file system object.
is_same_fsobject(int fd1,int fd2)269 static bool is_same_fsobject(int fd1, int fd2) {
270 struct stat statbuf1;
271 struct stat statbuf2;
272 int result = 0;
273
274 RESTARTABLE(::fstat(fd1, &statbuf1), result);
275 if (result == OS_ERR) {
276 return false;
277 }
278 RESTARTABLE(::fstat(fd2, &statbuf2), result);
279 if (result == OS_ERR) {
280 return false;
281 }
282
283 if ((statbuf1.st_ino == statbuf2.st_ino) &&
284 (statbuf1.st_dev == statbuf2.st_dev)) {
285 return true;
286 } else {
287 return false;
288 }
289 }
290
291 // Helper functions for open without O_NOFOLLOW which is not present on AIX 5.3/6.1.
292 // We use the jdk6 implementation here.
293 #ifndef O_NOFOLLOW
294 // The O_NOFOLLOW oflag doesn't exist before solaris 5.10, this is to simulate that behaviour
295 // was done in jdk 5/6 hotspot by Oracle this way
open_o_nofollow_impl(const char * path,int oflag,mode_t mode,bool use_mode)296 static int open_o_nofollow_impl(const char* path, int oflag, mode_t mode, bool use_mode) {
297 struct stat orig_st;
298 struct stat new_st;
299 bool create;
300 int error;
301 int fd;
302
303 create = false;
304
305 if (lstat(path, &orig_st) != 0) {
306 if (errno == ENOENT && (oflag & O_CREAT) != 0) {
307 // File doesn't exist, but_we want to create it, add O_EXCL flag
308 // to make sure no-one creates it (or a symlink) before us
309 // This works as we expect with symlinks, from posix man page:
310 // 'If O_EXCL and O_CREAT are set, and path names a symbolic
311 // link, open() shall fail and set errno to [EEXIST]'.
312 oflag |= O_EXCL;
313 create = true;
314 } else {
315 // File doesn't exist, and we are not creating it.
316 return OS_ERR;
317 }
318 } else {
319 // Lstat success, check if existing file is a link.
320 if ((orig_st.st_mode & S_IFMT) == S_IFLNK) {
321 // File is a symlink.
322 errno = ELOOP;
323 return OS_ERR;
324 }
325 }
326
327 if (use_mode == true) {
328 fd = open(path, oflag, mode);
329 } else {
330 fd = open(path, oflag);
331 }
332
333 if (fd == OS_ERR) {
334 return fd;
335 }
336
337 // Can't do inode checks on before/after if we created the file.
338 if (create == false) {
339 if (fstat(fd, &new_st) != 0) {
340 // Keep errno from fstat, in case close also fails.
341 error = errno;
342 ::close(fd);
343 errno = error;
344 return OS_ERR;
345 }
346
347 if (orig_st.st_dev != new_st.st_dev || orig_st.st_ino != new_st.st_ino) {
348 // File was tampered with during race window.
349 ::close(fd);
350 errno = EEXIST;
351 if (PrintMiscellaneous && Verbose) {
352 warning("possible file tampering attempt detected when opening %s", path);
353 }
354 return OS_ERR;
355 }
356 }
357
358 return fd;
359 }
360
open_o_nofollow(const char * path,int oflag,mode_t mode)361 static int open_o_nofollow(const char* path, int oflag, mode_t mode) {
362 return open_o_nofollow_impl(path, oflag, mode, true);
363 }
364
open_o_nofollow(const char * path,int oflag)365 static int open_o_nofollow(const char* path, int oflag) {
366 return open_o_nofollow_impl(path, oflag, 0, false);
367 }
368 #endif
369
370 // Open the directory of the given path and validate it.
371 // Return a DIR * of the open directory.
open_directory_secure(const char * dirname)372 static DIR *open_directory_secure(const char* dirname) {
373 // Open the directory using open() so that it can be verified
374 // to be secure by calling is_dirfd_secure(), opendir() and then check
375 // to see if they are the same file system object. This method does not
376 // introduce a window of opportunity for the directory to be attacked that
377 // calling opendir() and is_directory_secure() does.
378 int result;
379 DIR *dirp = NULL;
380
381 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
382 // so provide a workaround in this case.
383 #ifdef O_NOFOLLOW
384 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
385 #else
386 // workaround (jdk6 coding)
387 RESTARTABLE(::open_o_nofollow(dirname, O_RDONLY), result);
388 #endif
389
390 if (result == OS_ERR) {
391 // Directory doesn't exist or is a symlink, so there is nothing to cleanup.
392 if (PrintMiscellaneous && Verbose) {
393 if (errno == ELOOP) {
394 warning("directory %s is a symlink and is not secure\n", dirname);
395 } else {
396 warning("could not open directory %s: %s\n", dirname, strerror(errno));
397 }
398 }
399 return dirp;
400 }
401 int fd = result;
402
403 // Determine if the open directory is secure.
404 if (!is_dirfd_secure(fd)) {
405 // The directory is not a secure directory.
406 os::close(fd);
407 return dirp;
408 }
409
410 // Open the directory.
411 dirp = ::opendir(dirname);
412 if (dirp == NULL) {
413 // The directory doesn't exist, close fd and return.
414 os::close(fd);
415 return dirp;
416 }
417
418 // Check to make sure fd and dirp are referencing the same file system object.
419 if (!is_same_fsobject(fd, dirp->dd_fd)) {
420 // The directory is not secure.
421 os::close(fd);
422 os::closedir(dirp);
423 dirp = NULL;
424 return dirp;
425 }
426
427 // Close initial open now that we know directory is secure
428 os::close(fd);
429
430 return dirp;
431 }
432
433 // NOTE: The code below uses fchdir(), open() and unlink() because
434 // fdopendir(), openat() and unlinkat() are not supported on all
435 // versions. Once the support for fdopendir(), openat() and unlinkat()
436 // is available on all supported versions the code can be changed
437 // to use these functions.
438
439 // Open the directory of the given path, validate it and set the
440 // current working directory to it.
441 // Return a DIR * of the open directory and the saved cwd fd.
442 //
open_directory_secure_cwd(const char * dirname,int * saved_cwd_fd)443 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
444
445 // Open the directory.
446 DIR* dirp = open_directory_secure(dirname);
447 if (dirp == NULL) {
448 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
449 return dirp;
450 }
451 int fd = dirp->dd_fd;
452
453 // Open a fd to the cwd and save it off.
454 int result;
455 RESTARTABLE(::open(".", O_RDONLY), result);
456 if (result == OS_ERR) {
457 *saved_cwd_fd = -1;
458 } else {
459 *saved_cwd_fd = result;
460 }
461
462 // Set the current directory to dirname by using the fd of the directory and
463 // handle errors, otherwise shared memory files will be created in cwd.
464 result = fchdir(fd);
465 if (result == OS_ERR) {
466 if (PrintMiscellaneous && Verbose) {
467 warning("could not change to directory %s", dirname);
468 }
469 if (*saved_cwd_fd != -1) {
470 ::close(*saved_cwd_fd);
471 *saved_cwd_fd = -1;
472 }
473 // Close the directory.
474 os::closedir(dirp);
475 return NULL;
476 } else {
477 return dirp;
478 }
479 }
480
481 // Close the directory and restore the current working directory.
482 //
close_directory_secure_cwd(DIR * dirp,int saved_cwd_fd)483 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
484
485 int result;
486 // If we have a saved cwd change back to it and close the fd.
487 if (saved_cwd_fd != -1) {
488 result = fchdir(saved_cwd_fd);
489 ::close(saved_cwd_fd);
490 }
491
492 // Close the directory.
493 os::closedir(dirp);
494 }
495
496 // Check if the given file descriptor is considered a secure.
is_file_secure(int fd,const char * filename)497 static bool is_file_secure(int fd, const char *filename) {
498
499 int result;
500 struct stat statbuf;
501
502 // Determine if the file is secure.
503 RESTARTABLE(::fstat(fd, &statbuf), result);
504 if (result == OS_ERR) {
505 if (PrintMiscellaneous && Verbose) {
506 warning("fstat failed on %s: %s\n", filename, strerror(errno));
507 }
508 return false;
509 }
510 if (statbuf.st_nlink > 1) {
511 // A file with multiple links is not expected.
512 if (PrintMiscellaneous && Verbose) {
513 warning("file %s has multiple links\n", filename);
514 }
515 return false;
516 }
517 return true;
518 }
519
520 // Return the user name for the given user id.
521 //
522 // The caller is expected to free the allocated memory.
get_user_name(uid_t uid)523 static char* get_user_name(uid_t uid) {
524
525 struct passwd pwent;
526
527 // Determine the max pwbuf size from sysconf, and hardcode
528 // a default if this not available through sysconf.
529 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
530 if (bufsize == -1)
531 bufsize = 1024;
532
533 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
534
535 // POSIX interface to getpwuid_r is used on LINUX
536 struct passwd* p;
537 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
538
539 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
540 if (PrintMiscellaneous && Verbose) {
541 if (result != 0) {
542 warning("Could not retrieve passwd entry: %s\n",
543 strerror(result));
544 }
545 else if (p == NULL) {
546 // this check is added to protect against an observed problem
547 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
548 // indicating success, but has p == NULL. This was observed when
549 // inserting a file descriptor exhaustion fault prior to the call
550 // getpwuid_r() call. In this case, error is set to the appropriate
551 // error condition, but this is undocumented behavior. This check
552 // is safe under any condition, but the use of errno in the output
553 // message may result in an erroneous message.
554 // Bug Id 89052 was opened with RedHat.
555 //
556 warning("Could not retrieve passwd entry: %s\n",
557 strerror(errno));
558 }
559 else {
560 warning("Could not determine user name: %s\n",
561 p->pw_name == NULL ? "pw_name = NULL" :
562 "pw_name zero length");
563 }
564 }
565 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
566 return NULL;
567 }
568
569 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
570 strcpy(user_name, p->pw_name);
571
572 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
573 return user_name;
574 }
575
576 // return the name of the user that owns the process identified by vmid.
577 //
578 // This method uses a slow directory search algorithm to find the backing
579 // store file for the specified vmid and returns the user name, as determined
580 // by the user name suffix of the hsperfdata_<username> directory name.
581 //
582 // the caller is expected to free the allocated memory.
583 //
get_user_name_slow(int vmid,TRAPS)584 static char* get_user_name_slow(int vmid, TRAPS) {
585
586 // short circuit the directory search if the process doesn't even exist.
587 if (kill(vmid, 0) == OS_ERR) {
588 if (errno == ESRCH) {
589 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
590 "Process not found");
591 }
592 else /* EPERM */ {
593 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
594 }
595 }
596
597 // directory search
598 char* oldest_user = NULL;
599 time_t oldest_ctime = 0;
600
601 const char* tmpdirname = os::get_temp_directory();
602
603 DIR* tmpdirp = os::opendir(tmpdirname);
604
605 if (tmpdirp == NULL) {
606 return NULL;
607 }
608
609 // for each entry in the directory that matches the pattern hsperfdata_*,
610 // open the directory and check if the file for the given vmid exists.
611 // The file with the expected name and the latest creation date is used
612 // to determine the user name for the process id.
613 //
614 struct dirent* dentry;
615 errno = 0;
616 while ((dentry = os::readdir(tmpdirp)) != NULL) {
617
618 // check if the directory entry is a hsperfdata file
619 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
620 continue;
621 }
622
623 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
624 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
625 strcpy(usrdir_name, tmpdirname);
626 strcat(usrdir_name, "/");
627 strcat(usrdir_name, dentry->d_name);
628
629 // Open the user directory.
630 DIR* subdirp = open_directory_secure(usrdir_name);
631
632 if (subdirp == NULL) {
633 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
634 continue;
635 }
636
637 // Since we don't create the backing store files in directories
638 // pointed to by symbolic links, we also don't follow them when
639 // looking for the files. We check for a symbolic link after the
640 // call to opendir in order to eliminate a small window where the
641 // symlink can be exploited.
642 //
643 if (!is_directory_secure(usrdir_name)) {
644 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
645 os::closedir(subdirp);
646 continue;
647 }
648
649 struct dirent* udentry;
650 errno = 0;
651 while ((udentry = os::readdir(subdirp)) != NULL) {
652
653 if (filename_to_pid(udentry->d_name) == vmid) {
654 struct stat statbuf;
655 int result;
656
657 char* filename = NEW_C_HEAP_ARRAY(char,
658 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
659
660 strcpy(filename, usrdir_name);
661 strcat(filename, "/");
662 strcat(filename, udentry->d_name);
663
664 // don't follow symbolic links for the file
665 RESTARTABLE(::lstat(filename, &statbuf), result);
666 if (result == OS_ERR) {
667 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
668 continue;
669 }
670
671 // skip over files that are not regular files.
672 if (!S_ISREG(statbuf.st_mode)) {
673 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
674 continue;
675 }
676
677 // compare and save filename with latest creation time
678 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
679
680 if (statbuf.st_ctime > oldest_ctime) {
681 char* user = strchr(dentry->d_name, '_') + 1;
682
683 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user, mtInternal);
684 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
685
686 strcpy(oldest_user, user);
687 oldest_ctime = statbuf.st_ctime;
688 }
689 }
690
691 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
692 }
693 }
694 os::closedir(subdirp);
695 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
696 }
697 os::closedir(tmpdirp);
698
699 return(oldest_user);
700 }
701
702 // return the name of the user that owns the JVM indicated by the given vmid.
703 //
get_user_name(int vmid,TRAPS)704 static char* get_user_name(int vmid, TRAPS) {
705 return get_user_name_slow(vmid, THREAD);
706 }
707
708 // return the file name of the backing store file for the named
709 // shared memory region for the given user name and vmid.
710 //
711 // the caller is expected to free the allocated memory.
712 //
get_sharedmem_filename(const char * dirname,int vmid)713 static char* get_sharedmem_filename(const char* dirname, int vmid) {
714
715 // add 2 for the file separator and a null terminator.
716 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
717
718 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
719 snprintf(name, nbytes, "%s/%d", dirname, vmid);
720
721 return name;
722 }
723
724
725 // remove file
726 //
727 // this method removes the file specified by the given path
728 //
remove_file(const char * path)729 static void remove_file(const char* path) {
730
731 int result;
732
733 // if the file is a directory, the following unlink will fail. since
734 // we don't expect to find directories in the user temp directory, we
735 // won't try to handle this situation. even if accidentially or
736 // maliciously planted, the directory's presence won't hurt anything.
737 //
738 RESTARTABLE(::unlink(path), result);
739 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
740 if (errno != ENOENT) {
741 warning("Could not unlink shared memory backing"
742 " store file %s : %s\n", path, strerror(errno));
743 }
744 }
745 }
746
747 // Cleanup stale shared memory resources
748 //
749 // This method attempts to remove all stale shared memory files in
750 // the named user temporary directory. It scans the named directory
751 // for files matching the pattern ^$[0-9]*$. For each file found, the
752 // process id is extracted from the file name and a test is run to
753 // determine if the process is alive. If the process is not alive,
754 // any stale file resources are removed.
cleanup_sharedmem_resources(const char * dirname)755 static void cleanup_sharedmem_resources(const char* dirname) {
756
757 int saved_cwd_fd;
758 // Open the directory.
759 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
760 if (dirp == NULL) {
761 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
762 return;
763 }
764
765 // For each entry in the directory that matches the expected file
766 // name pattern, determine if the file resources are stale and if
767 // so, remove the file resources. Note, instrumented HotSpot processes
768 // for this user may start and/or terminate during this search and
769 // remove or create new files in this directory. The behavior of this
770 // loop under these conditions is dependent upon the implementation of
771 // opendir/readdir.
772 struct dirent* entry;
773 errno = 0;
774 while ((entry = os::readdir(dirp)) != NULL) {
775
776 pid_t pid = filename_to_pid(entry->d_name);
777
778 if (pid == 0) {
779
780 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
781
782 // Attempt to remove all unexpected files, except "." and "..".
783 unlink(entry->d_name);
784 }
785
786 errno = 0;
787 continue;
788 }
789
790 // We now have a file name that converts to a valid integer
791 // that could represent a process id . if this process id
792 // matches the current process id or the process is not running,
793 // then remove the stale file resources.
794 //
795 // Process liveness is detected by sending signal number 0 to
796 // the process id (see kill(2)). if kill determines that the
797 // process does not exist, then the file resources are removed.
798 // if kill determines that that we don't have permission to
799 // signal the process, then the file resources are assumed to
800 // be stale and are removed because the resources for such a
801 // process should be in a different user specific directory.
802 if ((pid == os::current_process_id()) ||
803 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
804
805 unlink(entry->d_name);
806 }
807 errno = 0;
808 }
809
810 // Close the directory and reset the current working directory.
811 close_directory_secure_cwd(dirp, saved_cwd_fd);
812
813 }
814
815 // Make the user specific temporary directory. Returns true if
816 // the directory exists and is secure upon return. Returns false
817 // if the directory exists but is either a symlink, is otherwise
818 // insecure, or if an error occurred.
make_user_tmp_dir(const char * dirname)819 static bool make_user_tmp_dir(const char* dirname) {
820
821 // Create the directory with 0755 permissions. note that the directory
822 // will be owned by euid::egid, which may not be the same as uid::gid.
823 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
824 if (errno == EEXIST) {
825 // The directory already exists and was probably created by another
826 // JVM instance. However, this could also be the result of a
827 // deliberate symlink. Verify that the existing directory is safe.
828 if (!is_directory_secure(dirname)) {
829 // Directory is not secure.
830 if (PrintMiscellaneous && Verbose) {
831 warning("%s directory is insecure\n", dirname);
832 }
833 return false;
834 }
835 }
836 else {
837 // we encountered some other failure while attempting
838 // to create the directory
839 //
840 if (PrintMiscellaneous && Verbose) {
841 warning("could not create directory %s: %s\n",
842 dirname, strerror(errno));
843 }
844 return false;
845 }
846 }
847 return true;
848 }
849
850 // create the shared memory file resources
851 //
852 // This method creates the shared memory file with the given size
853 // This method also creates the user specific temporary directory, if
854 // it does not yet exist.
855 //
create_sharedmem_resources(const char * dirname,const char * filename,size_t size)856 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
857
858 // make the user temporary directory
859 if (!make_user_tmp_dir(dirname)) {
860 // could not make/find the directory or the found directory
861 // was not secure
862 return -1;
863 }
864
865 int saved_cwd_fd;
866 // Open the directory and set the current working directory to it.
867 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
868 if (dirp == NULL) {
869 // Directory doesn't exist or is insecure, so cannot create shared
870 // memory file.
871 return -1;
872 }
873
874 // Open the filename in the current directory.
875 // Cannot use O_TRUNC here; truncation of an existing file has to happen
876 // after the is_file_secure() check below.
877 int result;
878
879 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
880 // so provide a workaround in this case.
881 #ifdef O_NOFOLLOW
882 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
883 #else
884 // workaround function (jdk6 code)
885 RESTARTABLE(::open_o_nofollow(filename, O_RDWR|O_CREAT, S_IREAD|S_IWRITE), result);
886 #endif
887
888 if (result == OS_ERR) {
889 if (PrintMiscellaneous && Verbose) {
890 if (errno == ELOOP) {
891 warning("file %s is a symlink and is not secure\n", filename);
892 } else {
893 warning("could not create file %s: %s\n", filename, strerror(errno));
894 }
895 }
896 // Close the directory and reset the current working directory.
897 close_directory_secure_cwd(dirp, saved_cwd_fd);
898
899 return -1;
900 }
901 // Close the directory and reset the current working directory.
902 close_directory_secure_cwd(dirp, saved_cwd_fd);
903
904 // save the file descriptor
905 int fd = result;
906
907 // Check to see if the file is secure.
908 if (!is_file_secure(fd, filename)) {
909 ::close(fd);
910 return -1;
911 }
912
913 // Truncate the file to get rid of any existing data.
914 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
915 if (result == OS_ERR) {
916 if (PrintMiscellaneous && Verbose) {
917 warning("could not truncate shared memory file: %s\n", strerror(errno));
918 }
919 ::close(fd);
920 return -1;
921 }
922 // set the file size
923 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
924 if (result == OS_ERR) {
925 if (PrintMiscellaneous && Verbose) {
926 warning("could not set shared memory file size: %s\n", strerror(errno));
927 }
928 RESTARTABLE(::close(fd), result);
929 return -1;
930 }
931
932 return fd;
933 }
934
935 // open the shared memory file for the given user and vmid. returns
936 // the file descriptor for the open file or -1 if the file could not
937 // be opened.
938 //
open_sharedmem_file(const char * filename,int oflags,TRAPS)939 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
940
941 // open the file
942 int result;
943 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
944 // so provide a workaround in this case
945 #ifdef O_NOFOLLOW
946 RESTARTABLE(::open(filename, oflags), result);
947 #else
948 RESTARTABLE(::open_o_nofollow(filename, oflags), result);
949 #endif
950
951 if (result == OS_ERR) {
952 if (errno == ENOENT) {
953 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
954 "Process not found");
955 }
956 else if (errno == EACCES) {
957 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
958 "Permission denied");
959 }
960 else {
961 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
962 }
963 }
964 int fd = result;
965
966 // Check to see if the file is secure.
967 if (!is_file_secure(fd, filename)) {
968 ::close(fd);
969 return -1;
970 }
971
972 return fd;
973 }
974
975 // create a named shared memory region. returns the address of the
976 // memory region on success or NULL on failure. A return value of
977 // NULL will ultimately disable the shared memory feature.
978 //
979 // On Solaris and Linux, the name space for shared memory objects
980 // is the file system name space.
981 //
982 // A monitoring application attaching to a JVM does not need to know
983 // the file system name of the shared memory object. However, it may
984 // be convenient for applications to discover the existence of newly
985 // created and terminating JVMs by watching the file system name space
986 // for files being created or removed.
987 //
mmap_create_shared(size_t size)988 static char* mmap_create_shared(size_t size) {
989
990 int result;
991 int fd;
992 char* mapAddress;
993
994 int vmid = os::current_process_id();
995
996 char* user_name = get_user_name(geteuid());
997
998 if (user_name == NULL)
999 return NULL;
1000
1001 char* dirname = get_user_tmp_dir(user_name);
1002 char* filename = get_sharedmem_filename(dirname, vmid);
1003
1004 // Get the short filename.
1005 char* short_filename = strrchr(filename, '/');
1006 if (short_filename == NULL) {
1007 short_filename = filename;
1008 } else {
1009 short_filename++;
1010 }
1011
1012 // cleanup any stale shared memory files
1013 cleanup_sharedmem_resources(dirname);
1014
1015 assert(((size > 0) && (size % os::vm_page_size() == 0)),
1016 "unexpected PerfMemory region size");
1017
1018 fd = create_sharedmem_resources(dirname, short_filename, size);
1019
1020 FREE_C_HEAP_ARRAY(char, user_name, mtInternal);
1021 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1022
1023 if (fd == -1) {
1024 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1025 return NULL;
1026 }
1027
1028 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
1029
1030 // attempt to close the file - restart it if it was interrupted,
1031 // but ignore other failures
1032 RESTARTABLE(::close(fd), result);
1033 assert(result != OS_ERR, "could not close file");
1034
1035 if (mapAddress == MAP_FAILED) {
1036 if (PrintMiscellaneous && Verbose) {
1037 warning("mmap failed - %s\n", strerror(errno));
1038 }
1039 remove_file(filename);
1040 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1041 return NULL;
1042 }
1043
1044 // save the file name for use in delete_shared_memory()
1045 backing_store_file_name = filename;
1046
1047 // clear the shared memory region
1048 (void)::memset((void*) mapAddress, 0, size);
1049
1050 // It does not go through os api, the operation has to record from here.
1051 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, CURRENT_PC, mtInternal);
1052
1053 return mapAddress;
1054 }
1055
1056 // release a named shared memory region
1057 //
unmap_shared(char * addr,size_t bytes)1058 static void unmap_shared(char* addr, size_t bytes) {
1059 // Do not rely on os::reserve_memory/os::release_memory to use mmap.
1060 // Use os::reserve_memory/os::release_memory for PerfDisableSharedMem=1, mmap/munmap for PerfDisableSharedMem=0
1061 if (::munmap(addr, bytes) == -1) {
1062 warning("perfmemory: munmap failed (%d)\n", errno);
1063 }
1064 }
1065
1066 // create the PerfData memory region in shared memory.
1067 //
create_shared_memory(size_t size)1068 static char* create_shared_memory(size_t size) {
1069
1070 // create the shared memory region.
1071 return mmap_create_shared(size);
1072 }
1073
1074 // delete the shared PerfData memory region
1075 //
delete_shared_memory(char * addr,size_t size)1076 static void delete_shared_memory(char* addr, size_t size) {
1077
1078 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1079 // not support unloading of the JVM, unmapping of the memory resource is
1080 // not performed. The memory will be reclaimed by the OS upon termination of
1081 // the process. The backing store file is deleted from the file system.
1082
1083 assert(!PerfDisableSharedMem, "shouldn't be here");
1084
1085 if (backing_store_file_name != NULL) {
1086 remove_file(backing_store_file_name);
1087 // Don't.. Free heap memory could deadlock os::abort() if it is called
1088 // from signal handler. OS will reclaim the heap memory.
1089 // FREE_C_HEAP_ARRAY(char, backing_store_file_name, mtInternal);
1090 backing_store_file_name = NULL;
1091 }
1092 }
1093
1094 // return the size of the file for the given file descriptor
1095 // or 0 if it is not a valid size for a shared memory file
1096 //
sharedmem_filesize(int fd,TRAPS)1097 static size_t sharedmem_filesize(int fd, TRAPS) {
1098
1099 struct stat statbuf;
1100 int result;
1101
1102 RESTARTABLE(::fstat(fd, &statbuf), result);
1103 if (result == OS_ERR) {
1104 if (PrintMiscellaneous && Verbose) {
1105 warning("fstat failed: %s\n", strerror(errno));
1106 }
1107 THROW_MSG_0(vmSymbols::java_io_IOException(),
1108 "Could not determine PerfMemory size");
1109 }
1110
1111 if ((statbuf.st_size == 0) ||
1112 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1113 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1114 "Invalid PerfMemory size");
1115 }
1116
1117 return (size_t)statbuf.st_size;
1118 }
1119
1120 // attach to a named shared memory region.
1121 //
mmap_attach_shared(const char * user,int vmid,PerfMemory::PerfMemoryMode mode,char ** addr,size_t * sizep,TRAPS)1122 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1123
1124 char* mapAddress;
1125 int result;
1126 int fd;
1127 size_t size = 0;
1128 const char* luser = NULL;
1129
1130 int mmap_prot;
1131 int file_flags;
1132
1133 ResourceMark rm;
1134
1135 // map the high level access mode to the appropriate permission
1136 // constructs for the file and the shared memory mapping.
1137 if (mode == PerfMemory::PERF_MODE_RO) {
1138 mmap_prot = PROT_READ;
1139
1140 // No O_NOFOLLOW defined at buildtime, and it is not documented for open.
1141 #ifdef O_NOFOLLOW
1142 file_flags = O_RDONLY | O_NOFOLLOW;
1143 #else
1144 file_flags = O_RDONLY;
1145 #endif
1146 }
1147 else if (mode == PerfMemory::PERF_MODE_RW) {
1148 #ifdef LATER
1149 mmap_prot = PROT_READ | PROT_WRITE;
1150 file_flags = O_RDWR | O_NOFOLLOW;
1151 #else
1152 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1153 "Unsupported access mode");
1154 #endif
1155 }
1156 else {
1157 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1158 "Illegal access mode");
1159 }
1160
1161 if (user == NULL || strlen(user) == 0) {
1162 luser = get_user_name(vmid, CHECK);
1163 }
1164 else {
1165 luser = user;
1166 }
1167
1168 if (luser == NULL) {
1169 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1170 "Could not map vmid to user Name");
1171 }
1172
1173 char* dirname = get_user_tmp_dir(luser);
1174
1175 // since we don't follow symbolic links when creating the backing
1176 // store file, we don't follow them when attaching either.
1177 //
1178 if (!is_directory_secure(dirname)) {
1179 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1180 if (luser != user) {
1181 FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1182 }
1183 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1184 "Process not found");
1185 }
1186
1187 char* filename = get_sharedmem_filename(dirname, vmid);
1188
1189 // copy heap memory to resource memory. the open_sharedmem_file
1190 // method below need to use the filename, but could throw an
1191 // exception. using a resource array prevents the leak that
1192 // would otherwise occur.
1193 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1194 strcpy(rfilename, filename);
1195
1196 // free the c heap resources that are no longer needed
1197 if (luser != user) FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1198 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1199 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1200
1201 // open the shared memory file for the give vmid
1202 fd = open_sharedmem_file(rfilename, file_flags, CHECK);
1203 assert(fd != OS_ERR, "unexpected value");
1204
1205 if (*sizep == 0) {
1206 size = sharedmem_filesize(fd, CHECK);
1207 assert(size != 0, "unexpected size");
1208 } else {
1209 size = *sizep;
1210 }
1211
1212 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1213
1214 // attempt to close the file - restart if it gets interrupted,
1215 // but ignore other failures
1216 RESTARTABLE(::close(fd), result);
1217 assert(result != OS_ERR, "could not close file");
1218
1219 if (mapAddress == MAP_FAILED) {
1220 if (PrintMiscellaneous && Verbose) {
1221 warning("mmap failed: %s\n", strerror(errno));
1222 }
1223 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1224 "Could not map PerfMemory");
1225 }
1226
1227 // It does not go through os api, the operation has to record from here.
1228 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, CURRENT_PC, mtInternal);
1229
1230 *addr = mapAddress;
1231 *sizep = size;
1232
1233 if (PerfTraceMemOps) {
1234 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1235 INTPTR_FORMAT "\n", size, vmid, (void*)mapAddress);
1236 }
1237 }
1238
1239
1240
1241
1242 // create the PerfData memory region
1243 //
1244 // This method creates the memory region used to store performance
1245 // data for the JVM. The memory may be created in standard or
1246 // shared memory.
1247 //
create_memory_region(size_t size)1248 void PerfMemory::create_memory_region(size_t size) {
1249
1250 if (PerfDisableSharedMem) {
1251 // do not share the memory for the performance data.
1252 _start = create_standard_memory(size);
1253 }
1254 else {
1255 _start = create_shared_memory(size);
1256 if (_start == NULL) {
1257
1258 // creation of the shared memory region failed, attempt
1259 // to create a contiguous, non-shared memory region instead.
1260 //
1261 if (PrintMiscellaneous && Verbose) {
1262 warning("Reverting to non-shared PerfMemory region.\n");
1263 }
1264 PerfDisableSharedMem = true;
1265 _start = create_standard_memory(size);
1266 }
1267 }
1268
1269 if (_start != NULL) _capacity = size;
1270
1271 }
1272
1273 // delete the PerfData memory region
1274 //
1275 // This method deletes the memory region used to store performance
1276 // data for the JVM. The memory region indicated by the <address, size>
1277 // tuple will be inaccessible after a call to this method.
1278 //
delete_memory_region()1279 void PerfMemory::delete_memory_region() {
1280
1281 assert((start() != NULL && capacity() > 0), "verify proper state");
1282
1283 // If user specifies PerfDataSaveFile, it will save the performance data
1284 // to the specified file name no matter whether PerfDataSaveToFile is specified
1285 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1286 // -XX:+PerfDataSaveToFile.
1287 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1288 save_memory_to_file(start(), capacity());
1289 }
1290
1291 if (PerfDisableSharedMem) {
1292 delete_standard_memory(start(), capacity());
1293 }
1294 else {
1295 delete_shared_memory(start(), capacity());
1296 }
1297 }
1298
1299 // attach to the PerfData memory region for another JVM
1300 //
1301 // This method returns an <address, size> tuple that points to
1302 // a memory buffer that is kept reasonably synchronized with
1303 // the PerfData memory region for the indicated JVM. This
1304 // buffer may be kept in synchronization via shared memory
1305 // or some other mechanism that keeps the buffer updated.
1306 //
1307 // If the JVM chooses not to support the attachability feature,
1308 // this method should throw an UnsupportedOperation exception.
1309 //
1310 // This implementation utilizes named shared memory to map
1311 // the indicated process's PerfData memory region into this JVMs
1312 // address space.
1313 //
attach(const char * user,int vmid,PerfMemoryMode mode,char ** addrp,size_t * sizep,TRAPS)1314 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1315
1316 if (vmid == 0 || vmid == os::current_process_id()) {
1317 *addrp = start();
1318 *sizep = capacity();
1319 return;
1320 }
1321
1322 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1323 }
1324
1325 // detach from the PerfData memory region of another JVM
1326 //
1327 // This method detaches the PerfData memory region of another
1328 // JVM, specified as an <address, size> tuple of a buffer
1329 // in this process's address space. This method may perform
1330 // arbitrary actions to accomplish the detachment. The memory
1331 // region specified by <address, size> will be inaccessible after
1332 // a call to this method.
1333 //
1334 // If the JVM chooses not to support the attachability feature,
1335 // this method should throw an UnsupportedOperation exception.
1336 //
1337 // This implementation utilizes named shared memory to detach
1338 // the indicated process's PerfData memory region from this
1339 // process's address space.
1340 //
detach(char * addr,size_t bytes,TRAPS)1341 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1342
1343 assert(addr != 0, "address sanity check");
1344 assert(bytes > 0, "capacity sanity check");
1345
1346 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1347 // prevent accidental detachment of this process's PerfMemory region
1348 return;
1349 }
1350
1351 unmap_shared(addr, bytes);
1352 }
1353
backing_store_filename()1354 char* PerfMemory::backing_store_filename() {
1355 return backing_store_file_name;
1356 }
1357