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 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
566 errno = 0;
567 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
568
569 // check if the directory entry is a hsperfdata file
570 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
571 continue;
572 }
573
574 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
575 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
576 strcpy(usrdir_name, tmpdirname);
577 strcat(usrdir_name, "/");
578 strcat(usrdir_name, dentry->d_name);
579
580 // open the user directory
581 DIR* subdirp = open_directory_secure(usrdir_name);
582
583 if (subdirp == NULL) {
584 FREE_C_HEAP_ARRAY(char, usrdir_name);
585 continue;
586 }
587
588 // Since we don't create the backing store files in directories
589 // pointed to by symbolic links, we also don't follow them when
590 // looking for the files. We check for a symbolic link after the
591 // call to opendir in order to eliminate a small window where the
592 // symlink can be exploited.
593 //
594 if (!is_directory_secure(usrdir_name)) {
595 FREE_C_HEAP_ARRAY(char, usrdir_name);
596 os::closedir(subdirp);
597 continue;
598 }
599
600 struct dirent* udentry;
601 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
602 errno = 0;
603 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
604
605 if (filename_to_pid(udentry->d_name) == searchpid) {
606 struct stat statbuf;
607 int result;
608
609 char* filename = NEW_C_HEAP_ARRAY(char,
610 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
611
612 strcpy(filename, usrdir_name);
613 strcat(filename, "/");
614 strcat(filename, udentry->d_name);
615
616 // don't follow symbolic links for the file
617 RESTARTABLE(::lstat(filename, &statbuf), result);
618 if (result == OS_ERR) {
619 FREE_C_HEAP_ARRAY(char, filename);
620 continue;
621 }
622
623 // skip over files that are not regular files.
624 if (!S_ISREG(statbuf.st_mode)) {
625 FREE_C_HEAP_ARRAY(char, filename);
626 continue;
627 }
628
629 // compare and save filename with latest creation time
630 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
631
632 if (statbuf.st_ctime > oldest_ctime) {
633 char* user = strchr(dentry->d_name, '_') + 1;
634
635 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);
636 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
637
638 strcpy(oldest_user, user);
639 oldest_ctime = statbuf.st_ctime;
640 }
641 }
642
643 FREE_C_HEAP_ARRAY(char, filename);
644 }
645 }
646 os::closedir(subdirp);
647 FREE_C_HEAP_ARRAY(char, udbuf);
648 FREE_C_HEAP_ARRAY(char, usrdir_name);
649 }
650 os::closedir(tmpdirp);
651 FREE_C_HEAP_ARRAY(char, tdbuf);
652
653 return(oldest_user);
654 }
655
656 // Determine if the vmid is the parent pid
657 // for a child in a PID namespace.
658 // return the namespace pid if so, otherwise -1
659 static int get_namespace_pid(int vmid) {
660 char fname[24];
661 int retpid = -1;
662
663 snprintf(fname, sizeof(fname), "/proc/%d/status", vmid);
664 FILE *fp = fopen(fname, "r");
665
666 if (fp) {
667 int pid, nspid;
668 int ret;
669 while (!feof(fp)) {
670 ret = fscanf(fp, "NSpid: %d %d", &pid, &nspid);
671 if (ret == 1) {
672 break;
673 }
674 if (ret == 2) {
675 retpid = nspid;
676 break;
677 }
678 for (;;) {
679 int ch = fgetc(fp);
680 if (ch == EOF || ch == (int)'\n') break;
681 }
682 }
683 fclose(fp);
684 }
685 return retpid;
686 }
687
688 // return the name of the user that owns the JVM indicated by the given vmid.
689 //
690 static char* get_user_name(int vmid, int *nspid, TRAPS) {
691 char *result = get_user_name_slow(vmid, *nspid, THREAD);
692
693 // If we are examining a container process without PID namespaces enabled
694 // we need to use /proc/{pid}/root/tmp to find hsperfdata files.
695 if (result == NULL) {
696 result = get_user_name_slow(vmid, vmid, THREAD);
697 // Enable nspid logic going forward
698 if (result != NULL) *nspid = vmid;
699 }
700 return result;
701 }
702
703 // return the file name of the backing store file for the named
704 // shared memory region for the given user name and vmid.
705 //
706 // the caller is expected to free the allocated memory.
707 //
708 static char* get_sharedmem_filename(const char* dirname, int vmid, int nspid) {
709
710 int pid = (nspid == -1) ? vmid : nspid;
711
712 // add 2 for the file separator and a null terminator.
713 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
714
715 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
716 snprintf(name, nbytes, "%s/%d", dirname, pid);
717
718 return name;
719 }
720
721
722 // remove file
723 //
724 // this method removes the file specified by the given path
725 //
726 static void remove_file(const char* path) {
727
728 int result;
729
730 // if the file is a directory, the following unlink will fail. since
731 // we don't expect to find directories in the user temp directory, we
732 // won't try to handle this situation. even if accidentially or
733 // maliciously planted, the directory's presence won't hurt anything.
734 //
735 RESTARTABLE(::unlink(path), result);
736 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
737 if (errno != ENOENT) {
738 warning("Could not unlink shared memory backing"
739 " store file %s : %s\n", path, os::strerror(errno));
740 }
741 }
742 }
743
744
745 // cleanup stale shared memory resources
746 //
747 // This method attempts to remove all stale shared memory files in
748 // the named user temporary directory. It scans the named directory
749 // for files matching the pattern ^$[0-9]*$. For each file found, the
750 // process id is extracted from the file name and a test is run to
751 // determine if the process is alive. If the process is not alive,
752 // any stale file resources are removed.
753 //
754 static void cleanup_sharedmem_resources(const char* dirname) {
755
756 int saved_cwd_fd;
757 // open the directory
758 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
759 if (dirp == NULL) {
760 // directory doesn't exist or is insecure, so there is nothing to cleanup
761 return;
762 }
763
764 // for each entry in the directory that matches the expected file
765 // name pattern, determine if the file resources are stale and if
766 // so, remove the file resources. Note, instrumented HotSpot processes
767 // for this user may start and/or terminate during this search and
768 // remove or create new files in this directory. The behavior of this
769 // loop under these conditions is dependent upon the implementation of
770 // opendir/readdir.
771 //
772 struct dirent* entry;
773 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
774
775 errno = 0;
776 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
777
778 pid_t pid = filename_to_pid(entry->d_name);
779
780 if (pid == 0) {
781
782 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
783 // attempt to remove all unexpected files, except "." and ".."
784 unlink(entry->d_name);
785 }
786
787 errno = 0;
788 continue;
789 }
790
791 // we now have a file name that converts to a valid integer
792 // that could represent a process id . if this process id
793 // matches the current process id or the process is not running,
794 // then remove the stale file resources.
795 //
796 // process liveness is detected by sending signal number 0 to
797 // the process id (see kill(2)). if kill determines that the
798 // process does not exist, then the file resources are removed.
799 // if kill determines that that we don't have permission to
800 // signal the process, then the file resources are assumed to
801 // be stale and are removed because the resources for such a
802 // process should be in a different user specific directory.
803 //
804 if ((pid == os::current_process_id()) ||
805 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
806 unlink(entry->d_name);
807 }
808 errno = 0;
809 }
810
811 // close the directory and reset the current working directory
812 close_directory_secure_cwd(dirp, saved_cwd_fd);
813
814 FREE_C_HEAP_ARRAY(char, dbuf);
815 }
816
817 // make the user specific temporary directory. Returns true if
818 // the directory exists and is secure upon return. Returns false
819 // if the directory exists but is either a symlink, is otherwise
820 // insecure, or if an error occurred.
821 //
822 static bool make_user_tmp_dir(const char* dirname) {
823
824 // create the directory with 0755 permissions. note that the directory
825 // will be owned by euid::egid, which may not be the same as uid::gid.
826 //
827 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
828 if (errno == EEXIST) {
829 // The directory already exists and was probably created by another
830 // JVM instance. However, this could also be the result of a
831 // deliberate symlink. Verify that the existing directory is safe.
832 //
833 if (!is_directory_secure(dirname)) {
834 // directory is not secure
835 if (PrintMiscellaneous && Verbose) {
836 warning("%s directory is insecure\n", dirname);
837 }
838 return false;
839 }
840 }
841 else {
842 // we encountered some other failure while attempting
843 // to create the directory
844 //
845 if (PrintMiscellaneous && Verbose) {
846 warning("could not create directory %s: %s\n",
847 dirname, os::strerror(errno));
848 }
849 return false;
850 }
851 }
852 return true;
853 }
854
855 // create the shared memory file resources
856 //
857 // This method creates the shared memory file with the given size
858 // This method also creates the user specific temporary directory, if
859 // it does not yet exist.
860 //
861 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
862
863 // make the user temporary directory
864 if (!make_user_tmp_dir(dirname)) {
865 // could not make/find the directory or the found directory
866 // was not secure
867 return -1;
868 }
869
870 int saved_cwd_fd;
871 // open the directory and set the current working directory to it
872 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
873 if (dirp == NULL) {
874 // Directory doesn't exist or is insecure, so cannot create shared
875 // memory file.
876 return -1;
877 }
878
879 // Open the filename in the current directory.
880 // Cannot use O_TRUNC here; truncation of an existing file has to happen
881 // after the is_file_secure() check below.
882 int result;
883 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
884 if (result == OS_ERR) {
885 if (PrintMiscellaneous && Verbose) {
886 if (errno == ELOOP) {
887 warning("file %s is a symlink and is not secure\n", filename);
888 } else {
889 warning("could not create file %s: %s\n", filename, os::strerror(errno));
890 }
891 }
892 // close the directory and reset the current working directory
893 close_directory_secure_cwd(dirp, saved_cwd_fd);
894
895 return -1;
896 }
897 // close the directory and reset the current working directory
898 close_directory_secure_cwd(dirp, saved_cwd_fd);
899
900 // save the file descriptor
901 int fd = result;
902
903 // check to see if the file is secure
904 if (!is_file_secure(fd, filename)) {
905 ::close(fd);
906 return -1;
907 }
908
909 // truncate the file to get rid of any existing data
910 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
911 if (result == OS_ERR) {
912 if (PrintMiscellaneous && Verbose) {
913 warning("could not truncate shared memory file: %s\n", os::strerror(errno));
914 }
915 ::close(fd);
916 return -1;
917 }
918 // set the file size
919 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
920 if (result == OS_ERR) {
921 if (PrintMiscellaneous && Verbose) {
922 warning("could not set shared memory file size: %s\n", os::strerror(errno));
923 }
924 ::close(fd);
925 return -1;
926 }
927
928 // Verify that we have enough disk space for this file.
929 // We'll get random SIGBUS crashes on memory accesses if
930 // we don't.
931
932 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) {
933 int zero_int = 0;
934 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos));
935 if (result == -1 ) break;
936 RESTARTABLE(::write(fd, &zero_int, 1), result);
937 if (result != 1) {
938 if (errno == ENOSPC) {
939 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
940 }
941 break;
942 }
943 }
944
945 if (result != -1) {
946 return fd;
947 } else {
948 ::close(fd);
949 return -1;
950 }
951 }
952
953 // open the shared memory file for the given user and vmid. returns
954 // the file descriptor for the open file or -1 if the file could not
955 // be opened.
956 //
957 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
958
959 // open the file
960 int result;
961 RESTARTABLE(::open(filename, oflags), result);
962 if (result == OS_ERR) {
963 if (errno == ENOENT) {
964 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
965 "Process not found", OS_ERR);
966 }
967 else if (errno == EACCES) {
968 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
969 "Permission denied", OS_ERR);
970 }
971 else {
972 THROW_MSG_(vmSymbols::java_io_IOException(),
973 os::strerror(errno), OS_ERR);
974 }
975 }
976 int fd = result;
977
978 // check to see if the file is secure
979 if (!is_file_secure(fd, filename)) {
980 ::close(fd);
981 return -1;
982 }
983
984 return fd;
985 }
986
987 // create a named shared memory region. returns the address of the
988 // memory region on success or NULL on failure. A return value of
989 // NULL will ultimately disable the shared memory feature.
990 //
991 // On Linux, the name space for shared memory objects
992 // is the file system name space.
993 //
994 // A monitoring application attaching to a JVM does not need to know
995 // the file system name of the shared memory object. However, it may
996 // be convenient for applications to discover the existence of newly
997 // created and terminating JVMs by watching the file system name space
998 // for files being created or removed.
999 //
1000 static char* mmap_create_shared(size_t size) {
1001
1002 int result;
1003 int fd;
1004 char* mapAddress;
1005
1006 int vmid = os::current_process_id();
1007
1008 char* user_name = get_user_name(geteuid());
1009
1010 if (user_name == NULL)
1011 return NULL;
1012
1013 char* dirname = get_user_tmp_dir(user_name, vmid, -1);
1014 char* filename = get_sharedmem_filename(dirname, vmid, -1);
1015
1016 // get the short filename
1017 char* short_filename = strrchr(filename, '/');
1018 if (short_filename == NULL) {
1019 short_filename = filename;
1020 } else {
1021 short_filename++;
1022 }
1023
1024 // cleanup any stale shared memory files
1025 cleanup_sharedmem_resources(dirname);
1026
1027 assert(((size > 0) && (size % os::vm_page_size() == 0)),
1028 "unexpected PerfMemory region size");
1029
1030 fd = create_sharedmem_resources(dirname, short_filename, size);
1031
1032 FREE_C_HEAP_ARRAY(char, user_name);
1033 FREE_C_HEAP_ARRAY(char, dirname);
1034
1035 if (fd == -1) {
1036 FREE_C_HEAP_ARRAY(char, filename);
1037 return NULL;
1038 }
1039
1040 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
1041
1042 result = ::close(fd);
1043 assert(result != OS_ERR, "could not close file");
1044
1045 if (mapAddress == MAP_FAILED) {
1046 if (PrintMiscellaneous && Verbose) {
1047 warning("mmap failed - %s\n", os::strerror(errno));
1048 }
1049 remove_file(filename);
1050 FREE_C_HEAP_ARRAY(char, filename);
1051 return NULL;
1052 }
1053
1054 // save the file name for use in delete_shared_memory()
1055 backing_store_file_name = filename;
1056
1057 // clear the shared memory region
1058 (void)::memset((void*) mapAddress, 0, size);
1059
1060 // it does not go through os api, the operation has to record from here
1061 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1062
1063 return mapAddress;
1064 }
1065
1066 // release a named shared memory region
1067 //
1068 static void unmap_shared(char* addr, size_t bytes) {
1069 os::release_memory(addr, bytes);
1070 }
1071
1072 // create the PerfData memory region in shared memory.
1073 //
1074 static char* create_shared_memory(size_t size) {
1075
1076 // create the shared memory region.
1077 return mmap_create_shared(size);
1078 }
1079
1080 // delete the shared PerfData memory region
1081 //
1082 static void delete_shared_memory(char* addr, size_t size) {
1083
1084 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1085 // not support unloading of the JVM, unmapping of the memory resource is
1086 // not performed. The memory will be reclaimed by the OS upon termination of
1087 // the process. The backing store file is deleted from the file system.
1088
1089 assert(!PerfDisableSharedMem, "shouldn't be here");
1090
1091 if (backing_store_file_name != NULL) {
1092 remove_file(backing_store_file_name);
1093 // Don't.. Free heap memory could deadlock os::abort() if it is called
1094 // from signal handler. OS will reclaim the heap memory.
1095 // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
1096 backing_store_file_name = NULL;
1097 }
1098 }
1099
1100 // return the size of the file for the given file descriptor
1101 // or 0 if it is not a valid size for a shared memory file
1102 //
1103 static size_t sharedmem_filesize(int fd, TRAPS) {
1104
1105 struct stat statbuf;
1106 int result;
1107
1108 RESTARTABLE(::fstat(fd, &statbuf), result);
1109 if (result == OS_ERR) {
1110 if (PrintMiscellaneous && Verbose) {
1111 warning("fstat failed: %s\n", os::strerror(errno));
1112 }
1113 THROW_MSG_0(vmSymbols::java_io_IOException(),
1114 "Could not determine PerfMemory size");
1115 }
1116
1117 if ((statbuf.st_size == 0) ||
1118 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1119 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1120 "Invalid PerfMemory size");
1121 }
1122
1123 return (size_t)statbuf.st_size;
1124 }
1125
1126 // attach to a named shared memory region.
1127 //
1128 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1129
1130 char* mapAddress;
1131 int result;
1132 int fd;
1133 size_t size = 0;
1134 const char* luser = NULL;
1135
1136 int mmap_prot;
1137 int file_flags;
1138
1139 ResourceMark rm;
1140
1141 // map the high level access mode to the appropriate permission
1142 // constructs for the file and the shared memory mapping.
1143 if (mode == PerfMemory::PERF_MODE_RO) {
1144 mmap_prot = PROT_READ;
1145 file_flags = O_RDONLY | O_NOFOLLOW;
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 // determine if vmid is for a containerized process
1162 int nspid = get_namespace_pid(vmid);
1163
1164 if (user == NULL || strlen(user) == 0) {
1165 luser = get_user_name(vmid, &nspid, CHECK);
1166 }
1167 else {
1168 luser = user;
1169 }
1170
1171 if (luser == NULL) {
1172 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1173 "Could not map vmid to user Name");
1174 }
1175
1176 char* dirname = get_user_tmp_dir(luser, vmid, nspid);
1177
1178 // since we don't follow symbolic links when creating the backing
1179 // store file, we don't follow them when attaching either.
1180 //
1181 if (!is_directory_secure(dirname)) {
1182 FREE_C_HEAP_ARRAY(char, dirname);
1183 if (luser != user) {
1184 FREE_C_HEAP_ARRAY(char, luser);
1185 }
1186 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1187 "Process not found");
1188 }
1189
1190 char* filename = get_sharedmem_filename(dirname, vmid, nspid);
1191
1192 // copy heap memory to resource memory. the open_sharedmem_file
1193 // method below need to use the filename, but could throw an
1194 // exception. using a resource array prevents the leak that
1195 // would otherwise occur.
1196 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1197 strcpy(rfilename, filename);
1198
1199 // free the c heap resources that are no longer needed
1200 if (luser != user) FREE_C_HEAP_ARRAY(char, luser);
1201 FREE_C_HEAP_ARRAY(char, dirname);
1202 FREE_C_HEAP_ARRAY(char, filename);
1203
1204 // open the shared memory file for the give vmid
1205 fd = open_sharedmem_file(rfilename, file_flags, THREAD);
1206
1207 if (fd == OS_ERR) {
1208 return;
1209 }
1210
1211 if (HAS_PENDING_EXCEPTION) {
1212 ::close(fd);
1213 return;
1214 }
1215
1216 if (*sizep == 0) {
1217 size = sharedmem_filesize(fd, CHECK);
1218 } else {
1219 size = *sizep;
1220 }
1221
1222 assert(size > 0, "unexpected size <= 0");
1223
1224 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1225
1226 result = ::close(fd);
1227 assert(result != OS_ERR, "could not close file");
1228
1229 if (mapAddress == MAP_FAILED) {
1230 if (PrintMiscellaneous && Verbose) {
1231 warning("mmap failed: %s\n", os::strerror(errno));
1232 }
1233 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1234 "Could not map PerfMemory");
1235 }
1236
1237 // it does not go through os api, the operation has to record from here
1238 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
1239
1240 *addr = mapAddress;
1241 *sizep = size;
1242
1243 log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at "
1244 INTPTR_FORMAT, size, vmid, p2i((void*)mapAddress));
1245 }
1246
1247 // create the PerfData memory region
1248 //
1249 // This method creates the memory region used to store performance
1250 // data for the JVM. The memory may be created in standard or
1251 // shared memory.
1252 //
1253 void PerfMemory::create_memory_region(size_t size) {
1254
1255 if (PerfDisableSharedMem) {
1256 // do not share the memory for the performance data.
1257 _start = create_standard_memory(size);
1258 }
1259 else {
1260 _start = create_shared_memory(size);
1261 if (_start == NULL) {
1262
1263 // creation of the shared memory region failed, attempt
1264 // to create a contiguous, non-shared memory region instead.
1265 //
1266 if (PrintMiscellaneous && Verbose) {
1267 warning("Reverting to non-shared PerfMemory region.\n");
1268 }
1269 PerfDisableSharedMem = true;
1270 _start = create_standard_memory(size);
1271 }
1272 }
1273
1274 if (_start != NULL) _capacity = size;
1275
1276 }
1277
1278 // delete the PerfData memory region
1279 //
1280 // This method deletes the memory region used to store performance
1281 // data for the JVM. The memory region indicated by the <address, size>
1282 // tuple will be inaccessible after a call to this method.
1283 //
1284 void PerfMemory::delete_memory_region() {
1285
1286 assert((start() != NULL && capacity() > 0), "verify proper state");
1287
1288 // If user specifies PerfDataSaveFile, it will save the performance data
1289 // to the specified file name no matter whether PerfDataSaveToFile is specified
1290 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1291 // -XX:+PerfDataSaveToFile.
1292 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1293 save_memory_to_file(start(), capacity());
1294 }
1295
1296 if (PerfDisableSharedMem) {
1297 delete_standard_memory(start(), capacity());
1298 }
1299 else {
1300 delete_shared_memory(start(), capacity());
1301 }
1302 }
1303
1304 // attach to the PerfData memory region for another JVM
1305 //
1306 // This method returns an <address, size> tuple that points to
1307 // a memory buffer that is kept reasonably synchronized with
1308 // the PerfData memory region for the indicated JVM. This
1309 // buffer may be kept in synchronization via shared memory
1310 // or some other mechanism that keeps the buffer updated.
1311 //
1312 // If the JVM chooses not to support the attachability feature,
1313 // this method should throw an UnsupportedOperation exception.
1314 //
1315 // This implementation utilizes named shared memory to map
1316 // the indicated process's PerfData memory region into this JVMs
1317 // address space.
1318 //
1319 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1320
1321 if (vmid == 0 || vmid == os::current_process_id()) {
1322 *addrp = start();
1323 *sizep = capacity();
1324 return;
1325 }
1326
1327 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1328 }
1329
1330 // detach from the PerfData memory region of another JVM
1331 //
1332 // This method detaches the PerfData memory region of another
1333 // JVM, specified as an <address, size> tuple of a buffer
1334 // in this process's address space. This method may perform
1335 // arbitrary actions to accomplish the detachment. The memory
1336 // region specified by <address, size> will be inaccessible after
1337 // a call to this method.
1338 //
1339 // If the JVM chooses not to support the attachability feature,
1340 // this method should throw an UnsupportedOperation exception.
1341 //
1342 // This implementation utilizes named shared memory to detach
1343 // the indicated process's PerfData memory region from this
1344 // process's address space.
1345 //
1346 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1347
1348 assert(addr != 0, "address sanity check");
1349 assert(bytes > 0, "capacity sanity check");
1350
1351 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1352 // prevent accidental detachment of this process's PerfMemory region
1353 return;
1354 }
1355
1356 unmap_shared(addr, bytes);
1357 }