1/*
2 * Copyright (c) 2001, 2019, 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
48static 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//
55static 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//
78static 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//
93static 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(os::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR),
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)
160static 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//
183static 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//
220static 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//
251static 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//
270static 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//
286static 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//
312static 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//
373static 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//
413static 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//
428static 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//
456static 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//
521static 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[MAXPATHLEN + 1];
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 } else {
545 jio_snprintf(buffer, MAXPATHLEN, "/proc/%d/root%s", vmid, tmpdirname);
546 tmpdirname = buffer;
547 searchpid = nspid;
548 }
549
550 // open the temp directory
551 DIR* tmpdirp = os::opendir(tmpdirname);
552
553 if (tmpdirp == NULL) {
554 // Cannot open the directory to get the user name, return.
555 return NULL;
556 }
557
558 // for each entry in the directory that matches the pattern hsperfdata_*,
559 // open the directory and check if the file for the given vmid or nspid exists.
560 // The file with the expected name and the latest creation date is used
561 // to determine the user name for the process id.
562 //
563 struct dirent* dentry;
564 errno = 0;
565 while ((dentry = os::readdir(tmpdirp)) != NULL) {
566
567 // check if the directory entry is a hsperfdata file
568 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
569 continue;
570 }
571
572 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
573 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
574 strcpy(usrdir_name, tmpdirname);
575 strcat(usrdir_name, "/");
576 strcat(usrdir_name, dentry->d_name);
577
578 // open the user directory
579 DIR* subdirp = open_directory_secure(usrdir_name);
580
581 if (subdirp == NULL) {
582 FREE_C_HEAP_ARRAY(char, usrdir_name);
583 continue;
584 }
585
586 // Since we don't create the backing store files in directories
587 // pointed to by symbolic links, we also don't follow them when
588 // looking for the files. We check for a symbolic link after the
589 // call to opendir in order to eliminate a small window where the
590 // symlink can be exploited.
591 //
592 if (!is_directory_secure(usrdir_name)) {
593 FREE_C_HEAP_ARRAY(char, usrdir_name);
594 os::closedir(subdirp);
595 continue;
596 }
597
598 struct dirent* udentry;
599 errno = 0;
600 while ((udentry = os::readdir(subdirp)) != NULL) {
601
602 if (filename_to_pid(udentry->d_name) == searchpid) {
603 struct stat statbuf;
604 int result;
605
606 char* filename = NEW_C_HEAP_ARRAY(char,
607 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
608
609 strcpy(filename, usrdir_name);
610 strcat(filename, "/");
611 strcat(filename, udentry->d_name);
612
613 // don't follow symbolic links for the file
614 RESTARTABLE(::lstat(filename, &statbuf), result);
615 if (result == OS_ERR) {
616 FREE_C_HEAP_ARRAY(char, filename);
617 continue;
618 }
619
620 // skip over files that are not regular files.
621 if (!S_ISREG(statbuf.st_mode)) {
622 FREE_C_HEAP_ARRAY(char, filename);
623 continue;
624 }
625
626 // compare and save filename with latest creation time
627 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
628
629 if (statbuf.st_ctime > oldest_ctime) {
630 char* user = strchr(dentry->d_name, '_') + 1;
631
632 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
633 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
634
635 strcpy(oldest_user, user);
636 oldest_ctime = statbuf.st_ctime;
637 }
638 }
639
640 FREE_C_HEAP_ARRAY(char, filename);
641 }
642 }
643 os::closedir(subdirp);
644 FREE_C_HEAP_ARRAY(char, usrdir_name);
645 }
646 os::closedir(tmpdirp);
647
648 return(oldest_user);
649}
650
651// Determine if the vmid is the parent pid
652// for a child in a PID namespace.
653// return the namespace pid if so, otherwise -1
654static int get_namespace_pid(int vmid) {
655 char fname[24];
656 int retpid = -1;
657
658 snprintf(fname, sizeof(fname), "/proc/%d/status", vmid);
659 FILE *fp = fopen(fname, "r");
660
661 if (fp) {
662 int pid, nspid;
663 int ret;
664 while (!feof(fp) && !ferror(fp)) {
665 ret = fscanf(fp, "NSpid: %d %d", &pid, &nspid);
666 if (ret == 1) {
667 break;
668 }
669 if (ret == 2) {
670 retpid = nspid;
671 break;
672 }
673 for (;;) {
674 int ch = fgetc(fp);
675 if (ch == EOF || ch == (int)'\n') break;
676 }
677 }
678 fclose(fp);
679 }
680 return retpid;
681}
682
683// return the name of the user that owns the JVM indicated by the given vmid.
684//
685static char* get_user_name(int vmid, int *nspid, TRAPS) {
686 char *result = get_user_name_slow(vmid, *nspid, THREAD);
687
688 // If we are examining a container process without PID namespaces enabled
689 // we need to use /proc/{pid}/root/tmp to find hsperfdata files.
690 if (result == NULL) {
691 result = get_user_name_slow(vmid, vmid, THREAD);
692 // Enable nspid logic going forward
693 if (result != NULL) *nspid = vmid;
694 }
695 return result;
696}
697
698// return the file name of the backing store file for the named
699// shared memory region for the given user name and vmid.
700//
701// the caller is expected to free the allocated memory.
702//
703static char* get_sharedmem_filename(const char* dirname, int vmid, int nspid) {
704
705 int pid = (nspid == -1) ? vmid : nspid;
706
707 // add 2 for the file separator and a null terminator.
708 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
709
710 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
711 snprintf(name, nbytes, "%s/%d", dirname, pid);
712
713 return name;
714}
715
716
717// remove file
718//
719// this method removes the file specified by the given path
720//
721static void remove_file(const char* path) {
722
723 int result;
724
725 // if the file is a directory, the following unlink will fail. since
726 // we don't expect to find directories in the user temp directory, we
727 // won't try to handle this situation. even if accidentially or
728 // maliciously planted, the directory's presence won't hurt anything.
729 //
730 RESTARTABLE(::unlink(path), result);
731 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
732 if (errno != ENOENT) {
733 warning("Could not unlink shared memory backing"
734 " store file %s : %s\n", path, os::strerror(errno));
735 }
736 }
737}
738
739
740// cleanup stale shared memory resources
741//
742// This method attempts to remove all stale shared memory files in
743// the named user temporary directory. It scans the named directory
744// for files matching the pattern ^$[0-9]*$. For each file found, the
745// process id is extracted from the file name and a test is run to
746// determine if the process is alive. If the process is not alive,
747// any stale file resources are removed.
748//
749static void cleanup_sharedmem_resources(const char* dirname) {
750
751 int saved_cwd_fd;
752 // open the directory
753 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
754 if (dirp == NULL) {
755 // directory doesn't exist or is insecure, so there is nothing to cleanup
756 return;
757 }
758
759 // for each entry in the directory that matches the expected file
760 // name pattern, determine if the file resources are stale and if
761 // so, remove the file resources. Note, instrumented HotSpot processes
762 // for this user may start and/or terminate during this search and
763 // remove or create new files in this directory. The behavior of this
764 // loop under these conditions is dependent upon the implementation of
765 // opendir/readdir.
766 //
767 struct dirent* entry;
768 errno = 0;
769 while ((entry = os::readdir(dirp)) != NULL) {
770
771 pid_t pid = filename_to_pid(entry->d_name);
772
773 if (pid == 0) {
774
775 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
776 // attempt to remove all unexpected files, except "." and ".."
777 unlink(entry->d_name);
778 }
779
780 errno = 0;
781 continue;
782 }
783
784 // we now have a file name that converts to a valid integer
785 // that could represent a process id . if this process id
786 // matches the current process id or the process is not running,
787 // then remove the stale file resources.
788 //
789 // process liveness is detected by sending signal number 0 to
790 // the process id (see kill(2)). if kill determines that the
791 // process does not exist, then the file resources are removed.
792 // if kill determines that that we don't have permission to
793 // signal the process, then the file resources are assumed to
794 // be stale and are removed because the resources for such a
795 // process should be in a different user specific directory.
796 //
797 if ((pid == os::current_process_id()) ||
798 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
799 unlink(entry->d_name);
800 }
801 errno = 0;
802 }
803
804 // close the directory and reset the current working directory
805 close_directory_secure_cwd(dirp, saved_cwd_fd);
806}
807
808// make the user specific temporary directory. Returns true if
809// the directory exists and is secure upon return. Returns false
810// if the directory exists but is either a symlink, is otherwise
811// insecure, or if an error occurred.
812//
813static bool make_user_tmp_dir(const char* dirname) {
814
815 // create the directory with 0755 permissions. note that the directory
816 // will be owned by euid::egid, which may not be the same as uid::gid.
817 //
818 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
819 if (errno == EEXIST) {
820 // The directory already exists and was probably created by another
821 // JVM instance. However, this could also be the result of a
822 // deliberate symlink. Verify that the existing directory is safe.
823 //
824 if (!is_directory_secure(dirname)) {
825 // directory is not secure
826 if (PrintMiscellaneous && Verbose) {
827 warning("%s directory is insecure\n", dirname);
828 }
829 return false;
830 }
831 }
832 else {
833 // we encountered some other failure while attempting
834 // to create the directory
835 //
836 if (PrintMiscellaneous && Verbose) {
837 warning("could not create directory %s: %s\n",
838 dirname, os::strerror(errno));
839 }
840 return false;
841 }
842 }
843 return true;
844}
845
846// create the shared memory file resources
847//
848// This method creates the shared memory file with the given size
849// This method also creates the user specific temporary directory, if
850// it does not yet exist.
851//
852static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
853
854 // make the user temporary directory
855 if (!make_user_tmp_dir(dirname)) {
856 // could not make/find the directory or the found directory
857 // was not secure
858 return -1;
859 }
860
861 int saved_cwd_fd;
862 // open the directory and set the current working directory to it
863 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
864 if (dirp == NULL) {
865 // Directory doesn't exist or is insecure, so cannot create shared
866 // memory file.
867 return -1;
868 }
869
870 // Open the filename in the current directory.
871 // Cannot use O_TRUNC here; truncation of an existing file has to happen
872 // after the is_file_secure() check below.
873 int result;
874 RESTARTABLE(os::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IRUSR|S_IWUSR), result);
875 if (result == OS_ERR) {
876 if (PrintMiscellaneous && Verbose) {
877 if (errno == ELOOP) {
878 warning("file %s is a symlink and is not secure\n", filename);
879 } else {
880 warning("could not create file %s: %s\n", filename, os::strerror(errno));
881 }
882 }
883 // close the directory and reset the current working directory
884 close_directory_secure_cwd(dirp, saved_cwd_fd);
885
886 return -1;
887 }
888 // close the directory and reset the current working directory
889 close_directory_secure_cwd(dirp, saved_cwd_fd);
890
891 // save the file descriptor
892 int fd = result;
893
894 // check to see if the file is secure
895 if (!is_file_secure(fd, filename)) {
896 ::close(fd);
897 return -1;
898 }
899
900 // truncate the file to get rid of any existing data
901 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
902 if (result == OS_ERR) {
903 if (PrintMiscellaneous && Verbose) {
904 warning("could not truncate shared memory file: %s\n", os::strerror(errno));
905 }
906 ::close(fd);
907 return -1;
908 }
909 // set the file size
910 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
911 if (result == OS_ERR) {
912 if (PrintMiscellaneous && Verbose) {
913 warning("could not set shared memory file size: %s\n", os::strerror(errno));
914 }
915 ::close(fd);
916 return -1;
917 }
918
919 // Verify that we have enough disk space for this file.
920 // We'll get random SIGBUS crashes on memory accesses if
921 // we don't.
922
923 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
924 int zero_int = 0;
925 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
926 if (result == -1 ) break;
927 RESTARTABLE(::write(fd, &zero_int, 1), result);
928 if (result != 1) {
929 if (errno == ENOSPC) {
930 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
931 }
932 break;
933 }
934 }
935
936 if (result != -1) {
937 return fd;
938 } else {
939 ::close(fd);
940 return -1;
941 }
942}
943
944// open the shared memory file for the given user and vmid. returns
945// the file descriptor for the open file or -1 if the file could not
946// be opened.
947//
948static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
949
950 // open the file
951 int result;
952 RESTARTABLE(os::open(filename, oflags, 0), result);
953 if (result == OS_ERR) {
954 if (errno == ENOENT) {
955 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
956 "Process not found", OS_ERR);
957 }
958 else if (errno == EACCES) {
959 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
960 "Permission denied", OS_ERR);
961 }
962 else {
963 THROW_MSG_(vmSymbols::java_io_IOException(),
964 os::strerror(errno), OS_ERR);
965 }
966 }
967 int fd = result;
968
969 // check to see if the file is secure
970 if (!is_file_secure(fd, filename)) {
971 ::close(fd);
972 return -1;
973 }
974
975 return fd;
976}
977
978// create a named shared memory region. returns the address of the
979// memory region on success or NULL on failure. A return value of
980// NULL will ultimately disable the shared memory feature.
981//
982// On Linux, the name space for shared memory objects
983// is the file system name space.
984//
985// A monitoring application attaching to a JVM does not need to know
986// the file system name of the shared memory object. However, it may
987// be convenient for applications to discover the existence of newly
988// created and terminating JVMs by watching the file system name space
989// for files being created or removed.
990//
991static char* mmap_create_shared(size_t size) {
992
993 int result;
994 int fd;
995 char* mapAddress;
996
997 int vmid = os::current_process_id();
998
999 char* user_name = get_user_name(geteuid());
1000
1001 if (user_name == NULL)
1002 return NULL;
1003
1004 char* dirname = get_user_tmp_dir(user_name, vmid, -1);
1005 char* filename = get_sharedmem_filename(dirname, vmid, -1);
1006
1007 // get the short filename
1008 char* short_filename = strrchr(filename, '/');
1009 if (short_filename == NULL) {
1010 short_filename = filename;
1011 } else {
1012 short_filename++;
1013 }
1014
1015 // cleanup any stale shared memory files
1016 cleanup_sharedmem_resources(dirname);
1017
1018 assert(((size > 0) && (size % os::vm_page_size() == 0)),
1019 "unexpected PerfMemory region size");
1020
1021 fd = create_sharedmem_resources(dirname, short_filename, size);
1022
1023 FREE_C_HEAP_ARRAY(char, user_name);
1024 FREE_C_HEAP_ARRAY(char, dirname);
1025
1026 if (fd == -1) {
1027 FREE_C_HEAP_ARRAY(char, filename);
1028 return NULL;
1029 }
1030
1031 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
1032
1033 result = ::close(fd);
1034 assert(result != OS_ERR, "could not close file");
1035
1036 if (mapAddress == MAP_FAILED) {
1037 if (PrintMiscellaneous && Verbose) {
1038 warning("mmap failed - %s\n", os::strerror(errno));
1039 }
1040 remove_file(filename);
1041 FREE_C_HEAP_ARRAY(char, filename);
1042 return NULL;
1043 }
1044
1045 // save the file name for use in delete_shared_memory()
1046 backing_store_file_name = filename;
1047
1048 // clear the shared memory region
1049 (void)::memset((void*) mapAddress, 0, size);
1050
1051 // it does not go through os api, the operation has to record from here
1052 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1053
1054 return mapAddress;
1055}
1056
1057// release a named shared memory region
1058//
1059static void unmap_shared(char* addr, size_t bytes) {
1060 os::release_memory(addr, bytes);
1061}
1062
1063// create the PerfData memory region in shared memory.
1064//
1065static char* create_shared_memory(size_t size) {
1066
1067 // create the shared memory region.
1068 return mmap_create_shared(size);
1069}
1070
1071// delete the shared PerfData memory region
1072//
1073static void delete_shared_memory(char* addr, size_t size) {
1074
1075 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1076 // not support unloading of the JVM, unmapping of the memory resource is
1077 // not performed. The memory will be reclaimed by the OS upon termination of
1078 // the process. The backing store file is deleted from the file system.
1079
1080 assert(!PerfDisableSharedMem, "shouldn't be here");
1081
1082 if (backing_store_file_name != NULL) {
1083 remove_file(backing_store_file_name);
1084 // Don't.. Free heap memory could deadlock os::abort() if it is called
1085 // from signal handler. OS will reclaim the heap memory.
1086 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1087 backing_store_file_name = NULL;
1088 }
1089}
1090
1091// return the size of the file for the given file descriptor
1092// or 0 if it is not a valid size for a shared memory file
1093//
1094static size_t sharedmem_filesize(int fd, TRAPS) {
1095
1096 struct stat statbuf;
1097 int result;
1098
1099 RESTARTABLE(::fstat(fd, &statbuf), result);
1100 if (result == OS_ERR) {
1101 if (PrintMiscellaneous && Verbose) {
1102 warning("fstat failed: %s\n", os::strerror(errno));
1103 }
1104 THROW_MSG_0(vmSymbols::java_io_IOException(),
1105 "Could not determine PerfMemory size");
1106 }
1107
1108 if ((statbuf.st_size == 0) ||
1109 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1110 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1111 "Invalid PerfMemory size");
1112 }
1113
1114 return (size_t)statbuf.st_size;
1115}
1116
1117// attach to a named shared memory region.
1118//
1119static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1120
1121 char* mapAddress;
1122 int result;
1123 int fd;
1124 size_t size = 0;
1125 const char* luser = NULL;
1126
1127 int mmap_prot;
1128 int file_flags;
1129
1130 ResourceMark rm;
1131
1132 // map the high level access mode to the appropriate permission
1133 // constructs for the file and the shared memory mapping.
1134 if (mode == PerfMemory::PERF_MODE_RO) {
1135 mmap_prot = PROT_READ;
1136 file_flags = O_RDONLY | O_NOFOLLOW;
1137 }
1138 else if (mode == PerfMemory::PERF_MODE_RW) {
1139#ifdef LATER
1140 mmap_prot = PROT_READ | PROT_WRITE;
1141 file_flags = O_RDWR | O_NOFOLLOW;
1142#else
1143 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1144 "Unsupported access mode");
1145#endif
1146 }
1147 else {
1148 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1149 "Illegal access mode");
1150 }
1151
1152 // determine if vmid is for a containerized process
1153 int nspid = get_namespace_pid(vmid);
1154
1155 if (user == NULL || strlen(user) == 0) {
1156 luser = get_user_name(vmid, &nspid, CHECK);
1157 }
1158 else {
1159 luser = user;
1160 }
1161
1162 if (luser == NULL) {
1163 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1164 "Could not map vmid to user Name");
1165 }
1166
1167 char* dirname = get_user_tmp_dir(luser, vmid, nspid);
1168
1169 // since we don't follow symbolic links when creating the backing
1170 // store file, we don't follow them when attaching either.
1171 //
1172 if (!is_directory_secure(dirname)) {
1173 FREE_C_HEAP_ARRAY(char, dirname);
1174 if (luser != user) {
1175 FREE_C_HEAP_ARRAY(char, luser);
1176 }
1177 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1178 "Process not found");
1179 }
1180
1181 char* filename = get_sharedmem_filename(dirname, vmid, nspid);
1182
1183 // copy heap memory to resource memory. the open_sharedmem_file
1184 // method below need to use the filename, but could throw an
1185 // exception. using a resource array prevents the leak that
1186 // would otherwise occur.
1187 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1188 strcpy(rfilename, filename);
1189
1190 // free the c heap resources that are no longer needed
1191 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
1192 FREE_C_HEAP_ARRAY(char, dirname);
1193 FREE_C_HEAP_ARRAY(char, filename);
1194
1195 // open the shared memory file for the give vmid
1196 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1197
1198 if (fd == OS_ERR) {
1199 return;
1200 }
1201
1202 if (HAS_PENDING_EXCEPTION) {
1203 ::close(fd);
1204 return;
1205 }
1206
1207 if (*sizep == 0) {
1208 size = sharedmem_filesize(fd, CHECK);
1209 } else {
1210 size = *sizep;
1211 }
1212
1213 assert(size > 0, "unexpected size <= 0");
1214
1215 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1216
1217 result = ::close(fd);
1218 assert(result != OS_ERR, "could not close file");
1219
1220 if (mapAddress == MAP_FAILED) {
1221 if (PrintMiscellaneous && Verbose) {
1222 warning("mmap failed: %s\n", os::strerror(errno));
1223 }
1224 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1225 "Could not map PerfMemory");
1226 }
1227
1228 // it does not go through os api, the operation has to record from here
1229 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1230
1231 *addr = mapAddress;
1232 *sizep = size;
1233
1234 log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at "
1235 INTPTR_FORMAT, size, vmid, p2i((void*)mapAddress));
1236}
1237
1238// create the PerfData memory region
1239//
1240// This method creates the memory region used to store performance
1241// data for the JVM. The memory may be created in standard or
1242// shared memory.
1243//
1244void PerfMemory::create_memory_region(size_t size) {
1245
1246 if (PerfDisableSharedMem) {
1247 // do not share the memory for the performance data.
1248 _start = create_standard_memory(size);
1249 }
1250 else {
1251 _start = create_shared_memory(size);
1252 if (_start == NULL) {
1253
1254 // creation of the shared memory region failed, attempt
1255 // to create a contiguous, non-shared memory region instead.
1256 //
1257 if (PrintMiscellaneous && Verbose) {
1258 warning("Reverting to non-shared PerfMemory region.\n");
1259 }
1260 PerfDisableSharedMem = true;
1261 _start = create_standard_memory(size);
1262 }
1263 }
1264
1265 if (_start != NULL) _capacity = size;
1266
1267}
1268
1269// delete the PerfData memory region
1270//
1271// This method deletes the memory region used to store performance
1272// data for the JVM. The memory region indicated by the <address, size>
1273// tuple will be inaccessible after a call to this method.
1274//
1275void PerfMemory::delete_memory_region() {
1276
1277 assert((start() != NULL && capacity() > 0), "verify proper state");
1278
1279 // If user specifies PerfDataSaveFile, it will save the performance data
1280 // to the specified file name no matter whether PerfDataSaveToFile is specified
1281 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1282 // -XX:+PerfDataSaveToFile.
1283 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1284 save_memory_to_file(start(), capacity());
1285 }
1286
1287 if (PerfDisableSharedMem) {
1288 delete_standard_memory(start(), capacity());
1289 }
1290 else {
1291 delete_shared_memory(start(), capacity());
1292 }
1293}
1294
1295// attach to the PerfData memory region for another JVM
1296//
1297// This method returns an <address, size> tuple that points to
1298// a memory buffer that is kept reasonably synchronized with
1299// the PerfData memory region for the indicated JVM. This
1300// buffer may be kept in synchronization via shared memory
1301// or some other mechanism that keeps the buffer updated.
1302//
1303// If the JVM chooses not to support the attachability feature,
1304// this method should throw an UnsupportedOperation exception.
1305//
1306// This implementation utilizes named shared memory to map
1307// the indicated process's PerfData memory region into this JVMs
1308// address space.
1309//
1310void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1311
1312 if (vmid == 0 || vmid == os::current_process_id()) {
1313 *addrp = start();
1314 *sizep = capacity();
1315 return;
1316 }
1317
1318 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1319}
1320
1321// detach from the PerfData memory region of another JVM
1322//
1323// This method detaches the PerfData memory region of another
1324// JVM, specified as an <address, size> tuple of a buffer
1325// in this process's address space. This method may perform
1326// arbitrary actions to accomplish the detachment. The memory
1327// region specified by <address, size> will be inaccessible after
1328// a call to this method.
1329//
1330// If the JVM chooses not to support the attachability feature,
1331// this method should throw an UnsupportedOperation exception.
1332//
1333// This implementation utilizes named shared memory to detach
1334// the indicated process's PerfData memory region from this
1335// process's address space.
1336//
1337void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1338
1339 assert(addr != 0, "address sanity check");
1340 assert(bytes > 0, "capacity sanity check");
1341
1342 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1343 // prevent accidental detachment of this process's PerfMemory region
1344 return;
1345 }
1346
1347 unmap_shared(addr, bytes);
1348}
1349