1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/vmSymbols.hpp"
27 #include "logging/log.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "os_linux.inline.hpp"
32 #include "runtime/handles.inline.hpp"
33 #include "runtime/os.hpp"
34 #include "runtime/perfMemory.hpp"
35 #include "services/memTracker.hpp"
36 #include "utilities/exceptions.hpp"
37
38 // put OS-includes here
39 # include <sys/types.h>
40 # include <sys/mman.h>
41 # include <errno.h>
42 # include <stdio.h>
43 # include <unistd.h>
44 # include <sys/stat.h>
45 # include <signal.h>
46 # include <pwd.h>
47
48 static char* backing_store_file_name = NULL; // name of the backing store
49 // file, if successfully created.
50
51 // Standard Memory Implementation Details
52
53 // create the PerfData memory region in standard memory.
54 //
55 static char* create_standard_memory(size_t size) {
56
57 // allocate an aligned chuck of memory
58 char* mapAddress = os::reserve_memory(size);
59
60 if (mapAddress == NULL) {
61 return NULL;
62 }
63
64 // commit memory
65 if (!os::commit_memory(mapAddress, size, !ExecMem)) {
66 if (PrintMiscellaneous && Verbose) {
67 warning("Could not commit PerfData memory\n");
68 }
69 os::release_memory(mapAddress, size);
70 return NULL;
71 }
72
73 return mapAddress;
74 }
75
76 // delete the PerfData memory region
77 //
78 static void delete_standard_memory(char* addr, size_t size) {
79
80 // there are no persistent external resources to cleanup for standard
81 // memory. since DestroyJavaVM does not support unloading of the JVM,
82 // cleanup of the memory resource is not performed. The memory will be
83 // reclaimed by the OS upon termination of the process.
84 //
85 return;
86 }
87
88 // save the specified memory region to the given file
89 //
90 // Note: this function might be called from signal handler (by os::abort()),
91 // don't allocate heap memory.
92 //
93 static void save_memory_to_file(char* addr, size_t size) {
94
95 const char* destfile = PerfMemory::get_perfdata_file_path();
96 assert(destfile[0] != '\0', "invalid PerfData file path");
97
98 int result;
99
100 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
101 result);;
102 if (result == OS_ERR) {
103 if (PrintMiscellaneous && Verbose) {
104 warning("Could not create Perfdata save file: %s: %s\n",
105 destfile, os::strerror(errno));
106 }
107 } else {
108 int fd = result;
109
110 for (size_t remaining = size; remaining > 0;) {
111
112 RESTARTABLE(::write(fd, addr, remaining), result);
113 if (result == OS_ERR) {
114 if (PrintMiscellaneous && Verbose) {
115 warning("Could not write Perfdata save file: %s: %s\n",
116 destfile, os::strerror(errno));
117 }
118 break;
119 }
120
121 remaining -= (size_t)result;
122 addr += result;
123 }
124
125 result = ::close(fd);
126 if (PrintMiscellaneous && Verbose) {
127 if (result == OS_ERR) {
128 warning("Could not close %s: %s\n", destfile, os::strerror(errno));
129 }
130 }
131 }
132 FREE_C_HEAP_ARRAY(char, destfile);
133 }
134
135
136 // Shared Memory Implementation Details
137
138 // Note: the solaris and linux shared memory implementation uses the mmap
139 // interface with a backing store file to implement named shared memory.
140 // Using the file system as the name space for shared memory allows a
141 // common name space to be supported across a variety of platforms. It
142 // also provides a name space that Java applications can deal with through
143 // simple file apis.
144 //
145 // The solaris and linux implementations store the backing store file in
146 // a user specific temporary directory located in the /tmp file system,
147 // which is always a local file system and is sometimes a RAM based file
148 // system.
149
150
151 // return the user specific temporary directory name.
152 //
153 // If containerized process, get dirname of
154 // /proc/{vmid}/root/tmp/{PERFDATA_NAME_user}
155 // otherwise /tmp/{PERFDATA_NAME_user}
156 //
157 // the caller is expected to free the allocated memory.
158 //
159 #define TMP_BUFFER_LEN (4+22)
160 static char* get_user_tmp_dir(const char* user, int vmid, int nspid) {
161 char buffer[TMP_BUFFER_LEN];
162 char* tmpdir = (char *)os::get_temp_directory();
163 assert(strlen(tmpdir) == 4, "No longer using /tmp - update buffer size");
164
165 if (nspid != -1) {
166 jio_snprintf(buffer, TMP_BUFFER_LEN, "/proc/%d/root%s", vmid, tmpdir);
167 tmpdir = buffer;
168 }
169
170 const char* perfdir = PERFDATA_NAME;
171 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
172 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
173
174 // construct the path name to user specific tmp directory
175 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
176
177 return dirname;
178 }
179
180 // convert the given file name into a process id. if the file
181 // does not meet the file naming constraints, return 0.
182 //
183 static pid_t filename_to_pid(const char* filename) {
184
185 // a filename that doesn't begin with a digit is not a
186 // candidate for conversion.
187 //
188 if (!isdigit(*filename)) {
189 return 0;
190 }
191
192 // check if file name can be converted to an integer without
193 // any leftover characters.
194 //
195 char* remainder = NULL;
196 errno = 0;
197 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
198
199 if (errno != 0) {
200 return 0;
201 }
202
203 // check for left over characters. If any, then the filename is
204 // not a candidate for conversion.
205 //
206 if (remainder != NULL && *remainder != '\0') {
207 return 0;
208 }
209
210 // successful conversion, return the pid
211 return pid;
212 }
213
214
215 // Check if the given statbuf is considered a secure directory for
216 // the backing store files. Returns true if the directory is considered
217 // a secure location. Returns false if the statbuf is a symbolic link or
218 // if an error occurred.
219 //
220 static bool is_statbuf_secure(struct stat *statp) {
221 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
222 // The path represents a link or some non-directory file type,
223 // which is not what we expected. Declare it insecure.
224 //
225 return false;
226 }
227 // We have an existing directory, check if the permissions are safe.
228 //
229 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
230 // The directory is open for writing and could be subjected
231 // to a symlink or a hard link attack. Declare it insecure.
232 //
233 return false;
234 }
235 // If user is not root then see if the uid of the directory matches the effective uid of the process.
236 uid_t euid = geteuid();
237 if ((euid != 0) && (statp->st_uid != euid)) {
238 // The directory was not created by this user, declare it insecure.
239 //
240 return false;
241 }
242 return true;
243 }
244
245
246 // Check if the given path is considered a secure directory for
247 // the backing store files. Returns true if the directory exists
248 // and is considered a secure location. Returns false if the path
249 // is a symbolic link or if an error occurred.
250 //
251 static bool is_directory_secure(const char* path) {
252 struct stat statbuf;
253 int result = 0;
254
255 RESTARTABLE(::lstat(path, &statbuf), result);
256 if (result == OS_ERR) {
257 return false;
258 }
259
260 // The path exists, see if it is secure.
261 return is_statbuf_secure(&statbuf);
262 }
263
264
265 // Check if the given directory file descriptor is considered a secure
266 // directory for the backing store files. Returns true if the directory
267 // exists and is considered a secure location. Returns false if the path
268 // is a symbolic link or if an error occurred.
269 //
270 static bool is_dirfd_secure(int dir_fd) {
271 struct stat statbuf;
272 int result = 0;
273
274 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
275 if (result == OS_ERR) {
276 return false;
277 }
278
279 // The path exists, now check its mode.
280 return is_statbuf_secure(&statbuf);
281 }
282
283
284 // Check to make sure fd1 and fd2 are referencing the same file system object.
285 //
286 static bool is_same_fsobject(int fd1, int fd2) {
287 struct stat statbuf1;
288 struct stat statbuf2;
289 int result = 0;
290
291 RESTARTABLE(::fstat(fd1, &statbuf1), result);
292 if (result == OS_ERR) {
293 return false;
294 }
295 RESTARTABLE(::fstat(fd2, &statbuf2), result);
296 if (result == OS_ERR) {
297 return false;
298 }
299
300 if ((statbuf1.st_ino == statbuf2.st_ino) &&
301 (statbuf1.st_dev == statbuf2.st_dev)) {
302 return true;
303 } else {
304 return false;
305 }
306 }
307
308
309 // Open the directory of the given path and validate it.
310 // Return a DIR * of the open directory.
311 //
312 static DIR *open_directory_secure(const char* dirname) {
313 // Open the directory using open() so that it can be verified
314 // to be secure by calling is_dirfd_secure(), opendir() and then check
315 // to see if they are the same file system object. This method does not
316 // introduce a window of opportunity for the directory to be attacked that
317 // calling opendir() and is_directory_secure() does.
318 int result;
319 DIR *dirp = NULL;
320 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
321 if (result == OS_ERR) {
322 if (PrintMiscellaneous && Verbose) {
323 if (errno == ELOOP) {
324 warning("directory %s is a symlink and is not secure\n", dirname);
325 } else {
326 warning("could not open directory %s: %s\n", dirname, os::strerror(errno));
327 }
328 }
329 return dirp;
330 }
331 int fd = result;
332
333 // Determine if the open directory is secure.
334 if (!is_dirfd_secure(fd)) {
335 // The directory is not a secure directory.
336 os::close(fd);
337 return dirp;
338 }
339
340 // Open the directory.
341 dirp = ::opendir(dirname);
342 if (dirp == NULL) {
343 // The directory doesn't exist, close fd and return.
344 os::close(fd);
345 return dirp;
346 }
347
348 // Check to make sure fd and dirp are referencing the same file system object.
349 if (!is_same_fsobject(fd, dirfd(dirp))) {
350 // The directory is not secure.
351 os::close(fd);
352 os::closedir(dirp);
353 dirp = NULL;
354 return dirp;
355 }
356
357 // Close initial open now that we know directory is secure
358 os::close(fd);
359
360 return dirp;
361 }
362
363 // NOTE: The code below uses fchdir(), open() and unlink() because
364 // fdopendir(), openat() and unlinkat() are not supported on all
365 // versions. Once the support for fdopendir(), openat() and unlinkat()
366 // is available on all supported versions the code can be changed
367 // to use these functions.
368
369 // Open the directory of the given path, validate it and set the
370 // current working directory to it.
371 // Return a DIR * of the open directory and the saved cwd fd.
372 //
373 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
374
375 // Open the directory.
376 DIR* dirp = open_directory_secure(dirname);
377 if (dirp == NULL) {
378 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
379 return dirp;
380 }
381 int fd = dirfd(dirp);
382
383 // Open a fd to the cwd and save it off.
384 int result;
385 RESTARTABLE(::open(".", O_RDONLY), result);
386 if (result == OS_ERR) {
387 *saved_cwd_fd = -1;
388 } else {
389 *saved_cwd_fd = result;
390 }
391
392 // Set the current directory to dirname by using the fd of the directory and
393 // handle errors, otherwise shared memory files will be created in cwd.
394 result = fchdir(fd);
395 if (result == OS_ERR) {
396 if (PrintMiscellaneous && Verbose) {
397 warning("could not change to directory %s", dirname);
398 }
399 if (*saved_cwd_fd != -1) {
400 ::close(*saved_cwd_fd);
401 *saved_cwd_fd = -1;
402 }
403 // Close the directory.
404 os::closedir(dirp);
405 return NULL;
406 } else {
407 return dirp;
408 }
409 }
410
411 // Close the directory and restore the current working directory.
412 //
413 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
414
415 int result;
416 // If we have a saved cwd change back to it and close the fd.
417 if (saved_cwd_fd != -1) {
418 result = fchdir(saved_cwd_fd);
419 ::close(saved_cwd_fd);
420 }
421
422 // Close the directory.
423 os::closedir(dirp);
424 }
425
426 // Check if the given file descriptor is considered a secure.
427 //
428 static bool is_file_secure(int fd, const char *filename) {
429
430 int result;
431 struct stat statbuf;
432
433 // Determine if the file is secure.
434 RESTARTABLE(::fstat(fd, &statbuf), result);
435 if (result == OS_ERR) {
436 if (PrintMiscellaneous && Verbose) {
437 warning("fstat failed on %s: %s\n", filename, os::strerror(errno));
438 }
439 return false;
440 }
441 if (statbuf.st_nlink > 1) {
442 // A file with multiple links is not expected.
443 if (PrintMiscellaneous && Verbose) {
444 warning("file %s has multiple links\n", filename);
445 }
446 return false;
447 }
448 return true;
449 }
450
451
452 // return the user name for the given user id
453 //
454 // the caller is expected to free the allocated memory.
455 //
456 static char* get_user_name(uid_t uid) {
457
458 struct passwd pwent;
459
460 // determine the max pwbuf size from sysconf, and hardcode
461 // a default if this not available through sysconf.
462 //
463 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
464 if (bufsize == -1)
465 bufsize = 1024;
466
467 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
468
469 // POSIX interface to getpwuid_r is used on LINUX
470 struct passwd* p;
471 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
472
473 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
474 if (PrintMiscellaneous && Verbose) {
475 if (result != 0) {
476 warning("Could not retrieve passwd entry: %s\n",
477 os::strerror(result));
478 }
479 else if (p == NULL) {
480 // this check is added to protect against an observed problem
481 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
482 // indicating success, but has p == NULL. This was observed when
483 // inserting a file descriptor exhaustion fault prior to the call
484 // getpwuid_r() call. In this case, error is set to the appropriate
485 // error condition, but this is undocumented behavior. This check
486 // is safe under any condition, but the use of errno in the output
487 // message may result in an erroneous message.
488 // Bug Id 89052 was opened with RedHat.
489 //
490 warning("Could not retrieve passwd entry: %s\n",
491 os::strerror(errno));
492 }
493 else {
494 warning("Could not determine user name: %s\n",
495 p->pw_name == NULL ? "pw_name = NULL" :
496 "pw_name zero length");
497 }
498 }
499 FREE_C_HEAP_ARRAY(char, pwbuf);
500 return NULL;
501 }
502
503 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
504 strcpy(user_name, p->pw_name);
505
506 FREE_C_HEAP_ARRAY(char, pwbuf);
507 return user_name;
508 }
509
510 // return the name of the user that owns the process identified by vmid.
511 //
512 // This method uses a slow directory search algorithm to find the backing
513 // store file for the specified vmid and returns the user name, as determined
514 // by the user name suffix of the hsperfdata_<username> directory name.
515 //
516 // the caller is expected to free the allocated memory.
517 //
518 // If nspid != -1, look in /proc/{vmid}/root/tmp for directories
519 // containing nspid, otherwise just look for vmid in /tmp
520 //
521 static char* get_user_name_slow(int vmid, int nspid, TRAPS) {
522
523 // short circuit the directory search if the process doesn't even exist.
524 if (kill(vmid, 0) == OS_ERR) {
525 if (errno == ESRCH) {
526 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
527 "Process not found");
528 }
529 else /* EPERM */ {
530 THROW_MSG_0(vmSymbols::java_io_IOException(), os::strerror(errno));
531 }
532 }
533
534 // directory search
535 char* oldest_user = NULL;
536 time_t oldest_ctime = 0;
537 char buffer[TMP_BUFFER_LEN];
538 int searchpid;
539 char* tmpdirname = (char *)os::get_temp_directory();
540 assert(strlen(tmpdirname) == 4, "No longer using /tmp - update buffer size");
541
542 if (nspid == -1) {
543 searchpid = vmid;
544 }
545 else {
546 jio_snprintf(buffer, MAXPATHLEN, "/proc/%d/root%s", vmid, tmpdirname);
547 tmpdirname = buffer;
548 searchpid = nspid;
549 }
550
551 // open the temp directory
552 DIR* tmpdirp = os::opendir(tmpdirname);
553
554 if (tmpdirp == NULL) {
555 // Cannot open the directory to get the user name, return.
556 return NULL;
557 }
558
559 // for each entry in the directory that matches the pattern hsperfdata_*,
560 // open the directory and check if the file for the given vmid or nspid exists.
561 // The file with the expected name and the latest creation date is used
562 // to determine the user name for the process id.
563 //
564 struct dirent* dentry;
565 errno = 0;
566 while ((dentry = os::readdir(tmpdirp, NULL)) != NULL) {
567
568 // check if the directory entry is a hsperfdata file
569 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
570 continue;
571 }
572
573 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
574 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
575 strcpy(usrdir_name, tmpdirname);
576 strcat(usrdir_name, "/");
577 strcat(usrdir_name, dentry->d_name);
578
579 // open the user directory
580 DIR* subdirp = open_directory_secure(usrdir_name);
581
582 if (subdirp == NULL) {
583 FREE_C_HEAP_ARRAY(char, usrdir_name);
584 continue;
585 }
586
587 // Since we don't create the backing store files in directories
588 // pointed to by symbolic links, we also don't follow them when
589 // looking for the files. We check for a symbolic link after the
590 // call to opendir in order to eliminate a small window where the
591 // symlink can be exploited.
592 //
593 if (!is_directory_secure(usrdir_name)) {
594 FREE_C_HEAP_ARRAY(char, usrdir_name);
595 os::closedir(subdirp);
596 continue;
597 }
598
599 struct dirent* udentry;
600 errno = 0;
601 while ((udentry = os::readdir(subdirp, NULL)) != NULL) {
602
603 if (filename_to_pid(udentry->d_name) == searchpid) {
604 struct stat statbuf;
605 int result;
606
607 char* filename = NEW_C_HEAP_ARRAY(char,
608 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
609
610 strcpy(filename, usrdir_name);
611 strcat(filename, "/");
612 strcat(filename, udentry->d_name);
613
614 // don't follow symbolic links for the file
615 RESTARTABLE(::lstat(filename, &statbuf), result);
616 if (result == OS_ERR) {
617 FREE_C_HEAP_ARRAY(char, filename);
618 continue;
619 }
620
621 // skip over files that are not regular files.
622 if (!S_ISREG(statbuf.st_mode)) {
623 FREE_C_HEAP_ARRAY(char, filename);
624 continue;
625 }
626
627 // compare and save filename with latest creation time
628 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
629
630 if (statbuf.st_ctime > oldest_ctime) {
631 char* user = strchr(dentry->d_name, '_') + 1;
632
633 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
634 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
635
636 strcpy(oldest_user, user);
637 oldest_ctime = statbuf.st_ctime;
638 }
639 }
640
641 FREE_C_HEAP_ARRAY(char, filename);
642 }
643 }
644 os::closedir(subdirp);
645 FREE_C_HEAP_ARRAY(char, usrdir_name);
646 }
647 os::closedir(tmpdirp);
648
649 return(oldest_user);
650 }
651
652 // Determine if the vmid is the parent pid
653 // for a child in a PID namespace.
654 // return the namespace pid if so, otherwise -1
655 static int get_namespace_pid(int vmid) {
656 char fname[24];
657 int retpid = -1;
658
659 snprintf(fname, sizeof(fname), "/proc/%d/status", vmid);
660 FILE *fp = fopen(fname, "r");
661
662 if (fp) {
663 int pid, nspid;
664 int ret;
665 while (!feof(fp)) {
666 ret = fscanf(fp, "NSpid: %d %d", &pid, &nspid);
667 if (ret == 1) {
668 break;
669 }
670 if (ret == 2) {
671 retpid = nspid;
672 break;
673 }
674 for (;;) {
675 int ch = fgetc(fp);
676 if (ch == EOF || ch == (int)'\n') break;
677 }
678 }
679 fclose(fp);
680 }
681 return retpid;
682 }
683
684 // return the name of the user that owns the JVM indicated by the given vmid.
685 //
686 static char* get_user_name(int vmid, int *nspid, TRAPS) {
687 char *result = get_user_name_slow(vmid, *nspid, THREAD);
688
689 // If we are examining a container process without PID namespaces enabled
690 // we need to use /proc/{pid}/root/tmp to find hsperfdata files.
691 if (result == NULL) {
692 result = get_user_name_slow(vmid, vmid, THREAD);
693 // Enable nspid logic going forward
694 if (result != NULL) *nspid = vmid;
695 }
696 return result;
697 }
698
699 // return the file name of the backing store file for the named
700 // shared memory region for the given user name and vmid.
701 //
702 // the caller is expected to free the allocated memory.
703 //
704 static char* get_sharedmem_filename(const char* dirname, int vmid, int nspid) {
705
706 int pid = (nspid == -1) ? vmid : nspid;
707
708 // add 2 for the file separator and a null terminator.
709 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
710
711 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
712 snprintf(name, nbytes, "%s/%d", dirname, pid);
713
714 return name;
715 }
716
717
718 // remove file
719 //
720 // this method removes the file specified by the given path
721 //
722 static void remove_file(const char* path) {
723
724 int result;
725
726 // if the file is a directory, the following unlink will fail. since
727 // we don't expect to find directories in the user temp directory, we
728 // won't try to handle this situation. even if accidentially or
729 // maliciously planted, the directory's presence won't hurt anything.
730 //
731 RESTARTABLE(::unlink(path), result);
732 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
733 if (errno != ENOENT) {
734 warning("Could not unlink shared memory backing"
735 " store file %s : %s\n", path, os::strerror(errno));
736 }
737 }
738 }
739
740
741 // cleanup stale shared memory resources
742 //
743 // This method attempts to remove all stale shared memory files in
744 // the named user temporary directory. It scans the named directory
745 // for files matching the pattern ^$[0-9]*$. For each file found, the
746 // process id is extracted from the file name and a test is run to
747 // determine if the process is alive. If the process is not alive,
748 // any stale file resources are removed.
749 //
750 static void cleanup_sharedmem_resources(const char* dirname) {
751
752 int saved_cwd_fd;
753 // open the directory
754 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
755 if (dirp == NULL) {
756 // directory doesn't exist or is insecure, so there is nothing to cleanup
757 return;
758 }
759
760 // for each entry in the directory that matches the expected file
761 // name pattern, determine if the file resources are stale and if
762 // so, remove the file resources. Note, instrumented HotSpot processes
763 // for this user may start and/or terminate during this search and
764 // remove or create new files in this directory. The behavior of this
765 // loop under these conditions is dependent upon the implementation of
766 // opendir/readdir.
767 //
768 struct dirent* entry;
769
770 errno = 0;
771 while ((entry = os::readdir(dirp, NULL)) != NULL) {
772
773 pid_t pid = filename_to_pid(entry->d_name);
774
775 if (pid == 0) {
776
777 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
778 // attempt to remove all unexpected files, except "." and ".."
779 unlink(entry->d_name);
780 }
781
782 errno = 0;
783 continue;
784 }
785
786 // we now have a file name that converts to a valid integer
787 // that could represent a process id . if this process id
788 // matches the current process id or the process is not running,
789 // then remove the stale file resources.
790 //
791 // process liveness is detected by sending signal number 0 to
792 // the process id (see kill(2)). if kill determines that the
793 // process does not exist, then the file resources are removed.
794 // if kill determines that that we don't have permission to
795 // signal the process, then the file resources are assumed to
796 // be stale and are removed because the resources for such a
797 // process should be in a different user specific directory.
798 //
799 if ((pid == os::current_process_id()) ||
800 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
801 unlink(entry->d_name);
802 }
803 errno = 0;
804 }
805
806 // close the directory and reset the current working directory
807 close_directory_secure_cwd(dirp, saved_cwd_fd);
808 }
809
810 // make the user specific temporary directory. Returns true if
811 // the directory exists and is secure upon return. Returns false
812 // if the directory exists but is either a symlink, is otherwise
813 // insecure, or if an error occurred.
814 //
815 static bool make_user_tmp_dir(const char* dirname) {
816
817 // create the directory with 0755 permissions. note that the directory
818 // will be owned by euid::egid, which may not be the same as uid::gid.
819 //
820 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
821 if (errno == EEXIST) {
822 // The directory already exists and was probably created by another
823 // JVM instance. However, this could also be the result of a
824 // deliberate symlink. Verify that the existing directory is safe.
825 //
826 if (!is_directory_secure(dirname)) {
827 // directory is not secure
828 if (PrintMiscellaneous && Verbose) {
829 warning("%s directory is insecure\n", dirname);
830 }
831 return false;
832 }
833 }
834 else {
835 // we encountered some other failure while attempting
836 // to create the directory
837 //
838 if (PrintMiscellaneous && Verbose) {
839 warning("could not create directory %s: %s\n",
840 dirname, os::strerror(errno));
841 }
842 return false;
843 }
844 }
845 return true;
846 }
847
848 // create the shared memory file resources
849 //
850 // This method creates the shared memory file with the given size
851 // This method also creates the user specific temporary directory, if
852 // it does not yet exist.
853 //
854 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
855
856 // make the user temporary directory
857 if (!make_user_tmp_dir(dirname)) {
858 // could not make/find the directory or the found directory
859 // was not secure
860 return -1;
861 }
862
863 int saved_cwd_fd;
864 // open the directory and set the current working directory to it
865 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
866 if (dirp == NULL) {
867 // Directory doesn't exist or is insecure, so cannot create shared
868 // memory file.
869 return -1;
870 }
871
872 // Open the filename in the current directory.
873 // Cannot use O_TRUNC here; truncation of an existing file has to happen
874 // after the is_file_secure() check below.
875 int result;
876 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
877 if (result == OS_ERR) {
878 if (PrintMiscellaneous && Verbose) {
879 if (errno == ELOOP) {
880 warning("file %s is a symlink and is not secure\n", filename);
881 } else {
882 warning("could not create file %s: %s\n", filename, os::strerror(errno));
883 }
884 }
885 // close the directory and reset the current working directory
886 close_directory_secure_cwd(dirp, saved_cwd_fd);
887
888 return -1;
889 }
890 // close the directory and reset the current working directory
891 close_directory_secure_cwd(dirp, saved_cwd_fd);
892
893 // save the file descriptor
894 int fd = result;
895
896 // check to see if the file is secure
897 if (!is_file_secure(fd, filename)) {
898 ::close(fd);
899 return -1;
900 }
901
902 // truncate the file to get rid of any existing data
903 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
904 if (result == OS_ERR) {
905 if (PrintMiscellaneous && Verbose) {
906 warning("could not truncate shared memory file: %s\n", os::strerror(errno));
907 }
908 ::close(fd);
909 return -1;
910 }
911 // set the file size
912 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
913 if (result == OS_ERR) {
914 if (PrintMiscellaneous && Verbose) {
915 warning("could not set shared memory file size: %s\n", os::strerror(errno));
916 }
917 ::close(fd);
918 return -1;
919 }
920
921 // Verify that we have enough disk space for this file.
922 // We'll get random SIGBUS crashes on memory accesses if
923 // we don't.
924
925 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
926 int zero_int = 0;
927 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
928 if (result == -1 ) break;
929 RESTARTABLE(::write(fd, &zero_int, 1), result);
930 if (result != 1) {
931 if (errno == ENOSPC) {
932 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
933 }
934 break;
935 }
936 }
937
938 if (result != -1) {
939 return fd;
940 } else {
941 ::close(fd);
942 return -1;
943 }
944 }
945
946 // open the shared memory file for the given user and vmid. returns
947 // the file descriptor for the open file or -1 if the file could not
948 // be opened.
949 //
950 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
951
952 // open the file
953 int result;
954 RESTARTABLE(::open(filename, oflags), result);
955 if (result == OS_ERR) {
956 if (errno == ENOENT) {
957 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
958 "Process not found", OS_ERR);
959 }
960 else if (errno == EACCES) {
961 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
962 "Permission denied", OS_ERR);
963 }
964 else {
965 THROW_MSG_(vmSymbols::java_io_IOException(),
966 os::strerror(errno), OS_ERR);
967 }
968 }
969 int fd = result;
970
971 // check to see if the file is secure
972 if (!is_file_secure(fd, filename)) {
973 ::close(fd);
974 return -1;
975 }
976
977 return fd;
978 }
979
980 // create a named shared memory region. returns the address of the
981 // memory region on success or NULL on failure. A return value of
982 // NULL will ultimately disable the shared memory feature.
983 //
984 // On Linux, the name space for shared memory objects
985 // is the file system name space.
986 //
987 // A monitoring application attaching to a JVM does not need to know
988 // the file system name of the shared memory object. However, it may
989 // be convenient for applications to discover the existence of newly
990 // created and terminating JVMs by watching the file system name space
991 // for files being created or removed.
992 //
993 static char* mmap_create_shared(size_t size) {
994
995 int result;
996 int fd;
997 char* mapAddress;
998
999 int vmid = os::current_process_id();
1000
1001 char* user_name = get_user_name(geteuid());
1002
1003 if (user_name == NULL)
1004 return NULL;
1005
1006 char* dirname = get_user_tmp_dir(user_name, vmid, -1);
1007 char* filename = get_sharedmem_filename(dirname, vmid, -1);
1008
1009 // get the short filename
1010 char* short_filename = strrchr(filename, '/');
1011 if (short_filename == NULL) {
1012 short_filename = filename;
1013 } else {
1014 short_filename++;
1015 }
1016
1017 // cleanup any stale shared memory files
1018 cleanup_sharedmem_resources(dirname);
1019
1020 assert(((size > 0) && (size % os::vm_page_size() == 0)),
1021 "unexpected PerfMemory region size");
1022
1023 fd = create_sharedmem_resources(dirname, short_filename, size);
1024
1025 FREE_C_HEAP_ARRAY(char, user_name);
1026 FREE_C_HEAP_ARRAY(char, dirname);
1027
1028 if (fd == -1) {
1029 FREE_C_HEAP_ARRAY(char, filename);
1030 return NULL;
1031 }
1032
1033 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
1034
1035 result = ::close(fd);
1036 assert(result != OS_ERR, "could not close file");
1037
1038 if (mapAddress == MAP_FAILED) {
1039 if (PrintMiscellaneous && Verbose) {
1040 warning("mmap failed - %s\n", os::strerror(errno));
1041 }
1042 remove_file(filename);
1043 FREE_C_HEAP_ARRAY(char, filename);
1044 return NULL;
1045 }
1046
1047 // save the file name for use in delete_shared_memory()
1048 backing_store_file_name = filename;
1049
1050 // clear the shared memory region
1051 (void)::memset((void*) mapAddress, 0, size);
1052
1053 // it does not go through os api, the operation has to record from here
1054 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1055
1056 return mapAddress;
1057 }
1058
1059 // release a named shared memory region
1060 //
1061 static void unmap_shared(char* addr, size_t bytes) {
1062 os::release_memory(addr, bytes);
1063 }
1064
1065 // create the PerfData memory region in shared memory.
1066 //
1067 static char* create_shared_memory(size_t size) {
1068
1069 // create the shared memory region.
1070 return mmap_create_shared(size);
1071 }
1072
1073 // delete the shared PerfData memory region
1074 //
1075 static void delete_shared_memory(char* addr, size_t size) {
1076
1077 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1078 // not support unloading of the JVM, unmapping of the memory resource is
1079 // not performed. The memory will be reclaimed by the OS upon termination of
1080 // the process. The backing store file is deleted from the file system.
1081
1082 assert(!PerfDisableSharedMem, "shouldn't be here");
1083
1084 if (backing_store_file_name != NULL) {
1085 remove_file(backing_store_file_name);
1086 // Don't.. Free heap memory could deadlock os::abort() if it is called
1087 // from signal handler. OS will reclaim the heap memory.
1088 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1089 backing_store_file_name = NULL;
1090 }
1091 }
1092
1093 // return the size of the file for the given file descriptor
1094 // or 0 if it is not a valid size for a shared memory file
1095 //
1096 static size_t sharedmem_filesize(int fd, TRAPS) {
1097
1098 struct stat statbuf;
1099 int result;
1100
1101 RESTARTABLE(::fstat(fd, &statbuf), result);
1102 if (result == OS_ERR) {
1103 if (PrintMiscellaneous && Verbose) {
1104 warning("fstat failed: %s\n", os::strerror(errno));
1105 }
1106 THROW_MSG_0(vmSymbols::java_io_IOException(),
1107 "Could not determine PerfMemory size");
1108 }
1109
1110 if ((statbuf.st_size == 0) ||
1111 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1112 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1113 "Invalid PerfMemory size");
1114 }
1115
1116 return (size_t)statbuf.st_size;
1117 }
1118
1119 // attach to a named shared memory region.
1120 //
1121 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1122
1123 char* mapAddress;
1124 int result;
1125 int fd;
1126 size_t size = 0;
1127 const char* luser = NULL;
1128
1129 int mmap_prot;
1130 int file_flags;
1131
1132 ResourceMark rm;
1133
1134 // map the high level access mode to the appropriate permission
1135 // constructs for the file and the shared memory mapping.
1136 if (mode == PerfMemory::PERF_MODE_RO) {
1137 mmap_prot = PROT_READ;
1138 file_flags = O_RDONLY | O_NOFOLLOW;
1139 }
1140 else if (mode == PerfMemory::PERF_MODE_RW) {
1141 #ifdef LATER
1142 mmap_prot = PROT_READ | PROT_WRITE;
1143 file_flags = O_RDWR | O_NOFOLLOW;
1144 #else
1145 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1146 "Unsupported access mode");
1147 #endif
1148 }
1149 else {
1150 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1151 "Illegal access mode");
1152 }
1153
1154 // determine if vmid is for a containerized process
1155 int nspid = get_namespace_pid(vmid);
1156
1157 if (user == NULL || strlen(user) == 0) {
1158 luser = get_user_name(vmid, &nspid, CHECK);
1159 }
1160 else {
1161 luser = user;
1162 }
1163
1164 if (luser == NULL) {
1165 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1166 "Could not map vmid to user Name");
1167 }
1168
1169 char* dirname = get_user_tmp_dir(luser, vmid, nspid);
1170
1171 // since we don't follow symbolic links when creating the backing
1172 // store file, we don't follow them when attaching either.
1173 //
1174 if (!is_directory_secure(dirname)) {
1175 FREE_C_HEAP_ARRAY(char, dirname);
1176 if (luser != user) {
1177 FREE_C_HEAP_ARRAY(char, luser);
1178 }
1179 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1180 "Process not found");
1181 }
1182
1183 char* filename = get_sharedmem_filename(dirname, vmid, nspid);
1184
1185 // copy heap memory to resource memory. the open_sharedmem_file
1186 // method below need to use the filename, but could throw an
1187 // exception. using a resource array prevents the leak that
1188 // would otherwise occur.
1189 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1190 strcpy(rfilename, filename);
1191
1192 // free the c heap resources that are no longer needed
1193 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
1194 FREE_C_HEAP_ARRAY(char, dirname);
1195 FREE_C_HEAP_ARRAY(char, filename);
1196
1197 // open the shared memory file for the give vmid
1198 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1199
1200 if (fd == OS_ERR) {
1201 return;
1202 }
1203
1204 if (HAS_PENDING_EXCEPTION) {
1205 ::close(fd);
1206 return;
1207 }
1208
1209 if (*sizep == 0) {
1210 size = sharedmem_filesize(fd, CHECK);
1211 } else {
1212 size = *sizep;
1213 }
1214
1215 assert(size > 0, "unexpected size <= 0");
1216
1217 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1218
1219 result = ::close(fd);
1220 assert(result != OS_ERR, "could not close file");
1221
1222 if (mapAddress == MAP_FAILED) {
1223 if (PrintMiscellaneous && Verbose) {
1224 warning("mmap failed: %s\n", os::strerror(errno));
1225 }
1226 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1227 "Could not map PerfMemory");
1228 }
1229
1230 // it does not go through os api, the operation has to record from here
1231 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1232
1233 *addr = mapAddress;
1234 *sizep = size;
1235
1236 log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at "
1237 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress));
1238 }
1239
1240 // create the PerfData memory region
1241 //
1242 // This method creates the memory region used to store performance
1243 // data for the JVM. The memory may be created in standard or
1244 // shared memory.
1245 //
1246 void PerfMemory::create_memory_region(size_t size) {
1247
1248 if (PerfDisableSharedMem) {
1249 // do not share the memory for the performance data.
1250 _start = create_standard_memory(size);
1251 }
1252 else {
1253 _start = create_shared_memory(size);
1254 if (_start == NULL) {
1255
1256 // creation of the shared memory region failed, attempt
1257 // to create a contiguous, non-shared memory region instead.
1258 //
1259 if (PrintMiscellaneous && Verbose) {
1260 warning("Reverting to non-shared PerfMemory region.\n");
1261 }
1262 PerfDisableSharedMem = true;
1263 _start = create_standard_memory(size);
1264 }
1265 }
1266
1267 if (_start != NULL) _capacity = size;
1268
1269 }
1270
1271 // delete the PerfData memory region
1272 //
1273 // This method deletes the memory region used to store performance
1274 // data for the JVM. The memory region indicated by the <address, size>
1275 // tuple will be inaccessible after a call to this method.
1276 //
1277 void PerfMemory::delete_memory_region() {
1278
1279 assert((start() != NULL && capacity() > 0), "verify proper state");
1280
1281 // If user specifies PerfDataSaveFile, it will save the performance data
1282 // to the specified file name no matter whether PerfDataSaveToFile is specified
1283 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1284 // -XX:+PerfDataSaveToFile.
1285 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1286 save_memory_to_file(start(), capacity());
1287 }
1288
1289 if (PerfDisableSharedMem) {
1290 delete_standard_memory(start(), capacity());
1291 }
1292 else {
1293 delete_shared_memory(start(), capacity());
1294 }
1295 }
1296
1297 // attach to the PerfData memory region for another JVM
1298 //
1299 // This method returns an <address, size> tuple that points to
1300 // a memory buffer that is kept reasonably synchronized with
1301 // the PerfData memory region for the indicated JVM. This
1302 // buffer may be kept in synchronization via shared memory
1303 // or some other mechanism that keeps the buffer updated.
1304 //
1305 // If the JVM chooses not to support the attachability feature,
1306 // this method should throw an UnsupportedOperation exception.
1307 //
1308 // This implementation utilizes named shared memory to map
1309 // the indicated process's PerfData memory region into this JVMs
1310 // address space.
1311 //
1312 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1313
1314 if (vmid == 0 || vmid == os::current_process_id()) {
1315 *addrp = start();
1316 *sizep = capacity();
1317 return;
1318 }
1319
1320 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1321 }
1322
1323 // detach from the PerfData memory region of another JVM
1324 //
1325 // This method detaches the PerfData memory region of another
1326 // JVM, specified as an <address, size> tuple of a buffer
1327 // in this process's address space. This method may perform
1328 // arbitrary actions to accomplish the detachment. The memory
1329 // region specified by <address, size> will be inaccessible after
1330 // a call to this method.
1331 //
1332 // If the JVM chooses not to support the attachability feature,
1333 // this method should throw an UnsupportedOperation exception.
1334 //
1335 // This implementation utilizes named shared memory to detach
1336 // the indicated process's PerfData memory region from this
1337 // process's address space.
1338 //
1339 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1340
1341 assert(addr != 0, "address sanity check");
1342 assert(bytes > 0, "capacity sanity check");
1343
1344 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1345 // prevent accidental detachment of this process's PerfMemory region
1346 return;
1347 }
1348
1349 unmap_shared(addr, bytes);
1350 }