1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2012, 2018 SAP SE. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #include "precompiled.hpp" 27 #include "classfile/vmSymbols.hpp" 28 #include "logging/log.hpp" 29 #include "memory/allocation.inline.hpp" 30 #include "memory/resourceArea.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "os_aix.inline.hpp" 33 #include "runtime/handles.inline.hpp" 34 #include "runtime/os.hpp" 35 #include "runtime/perfMemory.hpp" 36 #include "services/memTracker.hpp" 37 #include "utilities/exceptions.hpp" 38 39 // put OS-includes here 40 # include <sys/types.h> 41 # include <sys/mman.h> 42 # include <errno.h> 43 # include <stdio.h> 44 # include <unistd.h> 45 # include <sys/stat.h> 46 # include <signal.h> 47 # include <pwd.h> 48 49 static char* backing_store_file_name = NULL; // name of the backing store 50 // file, if successfully created. 51 52 // Standard Memory Implementation Details 53 54 // create the PerfData memory region in standard memory. 55 // 56 static char* create_standard_memory(size_t size) { 57 58 // allocate an aligned chuck of memory 59 char* mapAddress = os::reserve_memory(size); 60 61 if (mapAddress == NULL) { 62 return NULL; 63 } 64 65 // commit memory 66 if (!os::commit_memory(mapAddress, size, !ExecMem)) { 67 if (PrintMiscellaneous && Verbose) { 68 warning("Could not commit PerfData memory\n"); 69 } 70 os::release_memory(mapAddress, size); 71 return NULL; 72 } 73 74 return mapAddress; 75 } 76 77 // delete the PerfData memory region 78 // 79 static void delete_standard_memory(char* addr, size_t size) { 80 81 // there are no persistent external resources to cleanup for standard 82 // memory. since DestroyJavaVM does not support unloading of the JVM, 83 // cleanup of the memory resource is not performed. The memory will be 84 // reclaimed by the OS upon termination of the process. 85 // 86 return; 87 } 88 89 // save the specified memory region to the given file 90 // 91 // Note: this function might be called from signal handler (by os::abort()), 92 // don't allocate heap memory. 93 // 94 static void save_memory_to_file(char* addr, size_t size) { 95 96 const char* destfile = PerfMemory::get_perfdata_file_path(); 97 assert(destfile[0] != '\0', "invalid PerfData file path"); 98 99 int result; 100 101 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE), 102 result);; 103 if (result == OS_ERR) { 104 if (PrintMiscellaneous && Verbose) { 105 warning("Could not create Perfdata save file: %s: %s\n", 106 destfile, os::strerror(errno)); 107 } 108 } else { 109 int fd = result; 110 111 for (size_t remaining = size; remaining > 0;) { 112 113 RESTARTABLE(::write(fd, addr, remaining), result); 114 if (result == OS_ERR) { 115 if (PrintMiscellaneous && Verbose) { 116 warning("Could not write Perfdata save file: %s: %s\n", 117 destfile, os::strerror(errno)); 118 } 119 break; 120 } 121 122 remaining -= (size_t)result; 123 addr += result; 124 } 125 126 result = ::close(fd); 127 if (PrintMiscellaneous && Verbose) { 128 if (result == OS_ERR) { 129 warning("Could not close %s: %s\n", destfile, os::strerror(errno)); 130 } 131 } 132 } 133 FREE_C_HEAP_ARRAY(char, destfile); 134 } 135 136 137 // Shared Memory Implementation Details 138 139 // Note: the solaris and linux shared memory implementation uses the mmap 140 // interface with a backing store file to implement named shared memory. 141 // Using the file system as the name space for shared memory allows a 142 // common name space to be supported across a variety of platforms. It 143 // also provides a name space that Java applications can deal with through 144 // simple file apis. 145 // 146 // The solaris and linux implementations store the backing store file in 147 // a user specific temporary directory located in the /tmp file system, 148 // which is always a local file system and is sometimes a RAM based file 149 // system. 150 151 // return the user specific temporary directory name. 152 // 153 // the caller is expected to free the allocated memory. 154 // 155 static char* get_user_tmp_dir(const char* user) { 156 157 const char* tmpdir = os::get_temp_directory(); 158 const char* perfdir = PERFDATA_NAME; 159 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3; 160 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal); 161 162 // construct the path name to user specific tmp directory 163 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user); 164 165 return dirname; 166 } 167 168 // convert the given file name into a process id. if the file 169 // does not meet the file naming constraints, return 0. 170 // 171 static pid_t filename_to_pid(const char* filename) { 172 173 // a filename that doesn't begin with a digit is not a 174 // candidate for conversion. 175 // 176 if (!isdigit(*filename)) { 177 return 0; 178 } 179 180 // check if file name can be converted to an integer without 181 // any leftover characters. 182 // 183 char* remainder = NULL; 184 errno = 0; 185 pid_t pid = (pid_t)strtol(filename, &remainder, 10); 186 187 if (errno != 0) { 188 return 0; 189 } 190 191 // check for left over characters. If any, then the filename is 192 // not a candidate for conversion. 193 // 194 if (remainder != NULL && *remainder != '\0') { 195 return 0; 196 } 197 198 // successful conversion, return the pid 199 return pid; 200 } 201 202 // Check if the given statbuf is considered a secure directory for 203 // the backing store files. Returns true if the directory is considered 204 // a secure location. Returns false if the statbuf is a symbolic link or 205 // if an error occurred. 206 // 207 static bool is_statbuf_secure(struct stat *statp) { 208 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) { 209 // The path represents a link or some non-directory file type, 210 // which is not what we expected. Declare it insecure. 211 // 212 return false; 213 } 214 // We have an existing directory, check if the permissions are safe. 215 // 216 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) { 217 // The directory is open for writing and could be subjected 218 // to a symlink or a hard link attack. Declare it insecure. 219 // 220 return false; 221 } 222 // If user is not root then see if the uid of the directory matches the effective uid of the process. 223 uid_t euid = geteuid(); 224 if ((euid != 0) && (statp->st_uid != euid)) { 225 // The directory was not created by this user, declare it insecure. 226 // 227 return false; 228 } 229 return true; 230 } 231 232 233 // Check if the given path is considered a secure directory for 234 // the backing store files. Returns true if the directory exists 235 // and is considered a secure location. Returns false if the path 236 // is a symbolic link or if an error occurred. 237 // 238 static bool is_directory_secure(const char* path) { 239 struct stat statbuf; 240 int result = 0; 241 242 RESTARTABLE(::lstat(path, &statbuf), result); 243 if (result == OS_ERR) { 244 return false; 245 } 246 247 // The path exists, see if it is secure. 248 return is_statbuf_secure(&statbuf); 249 } 250 251 // (Taken over from Solaris to support the O_NOFOLLOW case on AIX.) 252 // Check if the given directory file descriptor is considered a secure 253 // directory for the backing store files. Returns true if the directory 254 // exists and is considered a secure location. Returns false if the path 255 // is a symbolic link or if an error occurred. 256 static bool is_dirfd_secure(int dir_fd) { 257 struct stat statbuf; 258 int result = 0; 259 260 RESTARTABLE(::fstat(dir_fd, &statbuf), result); 261 if (result == OS_ERR) { 262 return false; 263 } 264 265 // The path exists, now check its mode. 266 return is_statbuf_secure(&statbuf); 267 } 268 269 270 // Check to make sure fd1 and fd2 are referencing the same file system object. 271 static bool is_same_fsobject(int fd1, int fd2) { 272 struct stat statbuf1; 273 struct stat statbuf2; 274 int result = 0; 275 276 RESTARTABLE(::fstat(fd1, &statbuf1), result); 277 if (result == OS_ERR) { 278 return false; 279 } 280 RESTARTABLE(::fstat(fd2, &statbuf2), result); 281 if (result == OS_ERR) { 282 return false; 283 } 284 285 if ((statbuf1.st_ino == statbuf2.st_ino) && 286 (statbuf1.st_dev == statbuf2.st_dev)) { 287 return true; 288 } else { 289 return false; 290 } 291 } 292 293 // Helper functions for open without O_NOFOLLOW which is not present on AIX 5.3/6.1. 294 // We use the jdk6 implementation here. 295 #ifndef O_NOFOLLOW 296 // The O_NOFOLLOW oflag doesn't exist before solaris 5.10, this is to simulate that behaviour 297 // was done in jdk 5/6 hotspot by Oracle this way 298 static int open_o_nofollow_impl(const char* path, int oflag, mode_t mode, bool use_mode) { 299 struct stat orig_st; 300 struct stat new_st; 301 bool create; 302 int error; 303 int fd; 304 int result; 305 306 create = false; 307 308 RESTARTABLE(::lstat(path, &orig_st), result); 309 310 if (result == OS_ERR) { 311 if (errno == ENOENT && (oflag & O_CREAT) != 0) { 312 // File doesn't exist, but_we want to create it, add O_EXCL flag 313 // to make sure no-one creates it (or a symlink) before us 314 // This works as we expect with symlinks, from posix man page: 315 // 'If O_EXCL and O_CREAT are set, and path names a symbolic 316 // link, open() shall fail and set errno to [EEXIST]'. 317 oflag |= O_EXCL; 318 create = true; 319 } else { 320 // File doesn't exist, and we are not creating it. 321 return OS_ERR; 322 } 323 } else { 324 // lstat success, check if existing file is a link. 325 if ((orig_st.st_mode & S_IFMT) == S_IFLNK) { 326 // File is a symlink. 327 errno = ELOOP; 328 return OS_ERR; 329 } 330 } 331 332 if (use_mode == true) { 333 RESTARTABLE(::open(path, oflag, mode), fd); 334 } else { 335 RESTARTABLE(::open(path, oflag), fd); 336 } 337 338 if (fd == OS_ERR) { 339 return fd; 340 } 341 342 // Can't do inode checks on before/after if we created the file. 343 if (create == false) { 344 RESTARTABLE(::fstat(fd, &new_st), result); 345 if (result == OS_ERR) { 346 // Keep errno from fstat, in case close also fails. 347 error = errno; 348 ::close(fd); 349 errno = error; 350 return OS_ERR; 351 } 352 353 if (orig_st.st_dev != new_st.st_dev || orig_st.st_ino != new_st.st_ino) { 354 // File was tampered with during race window. 355 ::close(fd); 356 errno = EEXIST; 357 if (PrintMiscellaneous && Verbose) { 358 warning("possible file tampering attempt detected when opening %s", path); 359 } 360 return OS_ERR; 361 } 362 } 363 364 return fd; 365 } 366 367 static int open_o_nofollow(const char* path, int oflag, mode_t mode) { 368 return open_o_nofollow_impl(path, oflag, mode, true); 369 } 370 371 static int open_o_nofollow(const char* path, int oflag) { 372 return open_o_nofollow_impl(path, oflag, 0, false); 373 } 374 #endif 375 376 // Open the directory of the given path and validate it. 377 // Return a DIR * of the open directory. 378 static DIR *open_directory_secure(const char* dirname) { 379 // Open the directory using open() so that it can be verified 380 // to be secure by calling is_dirfd_secure(), opendir() and then check 381 // to see if they are the same file system object. This method does not 382 // introduce a window of opportunity for the directory to be attacked that 383 // calling opendir() and is_directory_secure() does. 384 int result; 385 DIR *dirp = NULL; 386 387 // No O_NOFOLLOW defined at buildtime, and it is not documented for open; 388 // so provide a workaround in this case. 389 #ifdef O_NOFOLLOW 390 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result); 391 #else 392 // workaround (jdk6 coding) 393 result = open_o_nofollow(dirname, O_RDONLY); 394 #endif 395 396 if (result == OS_ERR) { 397 // Directory doesn't exist or is a symlink, so there is nothing to cleanup. 398 if (PrintMiscellaneous && Verbose) { 399 if (errno == ELOOP) { 400 warning("directory %s is a symlink and is not secure\n", dirname); 401 } else { 402 warning("could not open directory %s: %s\n", dirname, os::strerror(errno)); 403 } 404 } 405 return dirp; 406 } 407 int fd = result; 408 409 // Determine if the open directory is secure. 410 if (!is_dirfd_secure(fd)) { 411 // The directory is not a secure directory. 412 os::close(fd); 413 return dirp; 414 } 415 416 // Open the directory. 417 dirp = ::opendir(dirname); 418 if (dirp == NULL) { 419 // The directory doesn't exist, close fd and return. 420 os::close(fd); 421 return dirp; 422 } 423 424 // Check to make sure fd and dirp are referencing the same file system object. 425 if (!is_same_fsobject(fd, dirp->dd_fd)) { 426 // The directory is not secure. 427 os::close(fd); 428 os::closedir(dirp); 429 dirp = NULL; 430 return dirp; 431 } 432 433 // Close initial open now that we know directory is secure 434 os::close(fd); 435 436 return dirp; 437 } 438 439 // NOTE: The code below uses fchdir(), open() and unlink() because 440 // fdopendir(), openat() and unlinkat() are not supported on all 441 // versions. Once the support for fdopendir(), openat() and unlinkat() 442 // is available on all supported versions the code can be changed 443 // to use these functions. 444 445 // Open the directory of the given path, validate it and set the 446 // current working directory to it. 447 // Return a DIR * of the open directory and the saved cwd fd. 448 // 449 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) { 450 451 // Open the directory. 452 DIR* dirp = open_directory_secure(dirname); 453 if (dirp == NULL) { 454 // Directory doesn't exist or is insecure, so there is nothing to cleanup. 455 return dirp; 456 } 457 int fd = dirp->dd_fd; 458 459 // Open a fd to the cwd and save it off. 460 int result; 461 RESTARTABLE(::open(".", O_RDONLY), result); 462 if (result == OS_ERR) { 463 *saved_cwd_fd = -1; 464 } else { 465 *saved_cwd_fd = result; 466 } 467 468 // Set the current directory to dirname by using the fd of the directory and 469 // handle errors, otherwise shared memory files will be created in cwd. 470 result = fchdir(fd); 471 if (result == OS_ERR) { 472 if (PrintMiscellaneous && Verbose) { 473 warning("could not change to directory %s", dirname); 474 } 475 if (*saved_cwd_fd != -1) { 476 ::close(*saved_cwd_fd); 477 *saved_cwd_fd = -1; 478 } 479 // Close the directory. 480 os::closedir(dirp); 481 return NULL; 482 } else { 483 return dirp; 484 } 485 } 486 487 // Close the directory and restore the current working directory. 488 // 489 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) { 490 491 int result; 492 // If we have a saved cwd change back to it and close the fd. 493 if (saved_cwd_fd != -1) { 494 result = fchdir(saved_cwd_fd); 495 ::close(saved_cwd_fd); 496 } 497 498 // Close the directory. 499 os::closedir(dirp); 500 } 501 502 // Check if the given file descriptor is considered a secure. 503 static bool is_file_secure(int fd, const char *filename) { 504 505 int result; 506 struct stat statbuf; 507 508 // Determine if the file is secure. 509 RESTARTABLE(::fstat(fd, &statbuf), result); 510 if (result == OS_ERR) { 511 if (PrintMiscellaneous && Verbose) { 512 warning("fstat failed on %s: %s\n", filename, os::strerror(errno)); 513 } 514 return false; 515 } 516 if (statbuf.st_nlink > 1) { 517 // A file with multiple links is not expected. 518 if (PrintMiscellaneous && Verbose) { 519 warning("file %s has multiple links\n", filename); 520 } 521 return false; 522 } 523 return true; 524 } 525 526 // Return the user name for the given user id. 527 // 528 // The caller is expected to free the allocated memory. 529 static char* get_user_name(uid_t uid) { 530 531 struct passwd pwent; 532 533 // Determine the max pwbuf size from sysconf, and hardcode 534 // a default if this not available through sysconf. 535 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); 536 if (bufsize == -1) 537 bufsize = 1024; 538 539 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal); 540 541 struct passwd* p; 542 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p); 543 544 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') { 545 if (PrintMiscellaneous && Verbose) { 546 if (result != 0) { 547 warning("Could not retrieve passwd entry: %s\n", 548 os::strerror(result)); 549 } 550 else if (p == NULL) { 551 // this check is added to protect against an observed problem 552 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0, 553 // indicating success, but has p == NULL. This was observed when 554 // inserting a file descriptor exhaustion fault prior to the call 555 // getpwuid_r() call. In this case, error is set to the appropriate 556 // error condition, but this is undocumented behavior. This check 557 // is safe under any condition, but the use of errno in the output 558 // message may result in an erroneous message. 559 // Bug Id 89052 was opened with RedHat. 560 // 561 warning("Could not retrieve passwd entry: %s\n", 562 os::strerror(errno)); 563 } 564 else { 565 warning("Could not determine user name: %s\n", 566 p->pw_name == NULL ? "pw_name = NULL" : 567 "pw_name zero length"); 568 } 569 } 570 FREE_C_HEAP_ARRAY(char, pwbuf); 571 return NULL; 572 } 573 574 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal); 575 strcpy(user_name, p->pw_name); 576 577 FREE_C_HEAP_ARRAY(char, pwbuf); 578 return user_name; 579 } 580 581 // return the name of the user that owns the process identified by vmid. 582 // 583 // This method uses a slow directory search algorithm to find the backing 584 // store file for the specified vmid and returns the user name, as determined 585 // by the user name suffix of the hsperfdata_<username> directory name. 586 // 587 // the caller is expected to free the allocated memory. 588 // 589 static char* get_user_name_slow(int vmid, TRAPS) { 590 591 // short circuit the directory search if the process doesn't even exist. 592 if (kill(vmid, 0) == OS_ERR) { 593 if (errno == ESRCH) { 594 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), 595 "Process not found"); 596 } 597 else /* EPERM */ { 598 THROW_MSG_0(vmSymbols::java_io_IOException(), os::strerror(errno)); 599 } 600 } 601 602 // directory search 603 char* oldest_user = NULL; 604 time_t oldest_ctime = 0; 605 606 const char* tmpdirname = os::get_temp_directory(); 607 608 DIR* tmpdirp = os::opendir(tmpdirname); 609 610 if (tmpdirp == NULL) { 611 return NULL; 612 } 613 614 // for each entry in the directory that matches the pattern hsperfdata_*, 615 // open the directory and check if the file for the given vmid exists. 616 // The file with the expected name and the latest creation date is used 617 // to determine the user name for the process id. 618 // 619 struct dirent* dentry; 620 errno = 0; 621 while ((dentry = os::readdir(tmpdirp)) != NULL) { 622 623 // check if the directory entry is a hsperfdata file 624 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) { 625 continue; 626 } 627 628 char* usrdir_name = NEW_C_HEAP_ARRAY(char, 629 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal); 630 strcpy(usrdir_name, tmpdirname); 631 strcat(usrdir_name, "/"); 632 strcat(usrdir_name, dentry->d_name); 633 634 // Open the user directory. 635 DIR* subdirp = open_directory_secure(usrdir_name); 636 637 if (subdirp == NULL) { 638 FREE_C_HEAP_ARRAY(char, usrdir_name); 639 continue; 640 } 641 642 // Since we don't create the backing store files in directories 643 // pointed to by symbolic links, we also don't follow them when 644 // looking for the files. We check for a symbolic link after the 645 // call to opendir in order to eliminate a small window where the 646 // symlink can be exploited. 647 // 648 if (!is_directory_secure(usrdir_name)) { 649 FREE_C_HEAP_ARRAY(char, usrdir_name); 650 os::closedir(subdirp); 651 continue; 652 } 653 654 struct dirent* udentry; 655 errno = 0; 656 while ((udentry = os::readdir(subdirp)) != NULL) { 657 658 if (filename_to_pid(udentry->d_name) == vmid) { 659 struct stat statbuf; 660 int result; 661 662 char* filename = NEW_C_HEAP_ARRAY(char, 663 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal); 664 665 strcpy(filename, usrdir_name); 666 strcat(filename, "/"); 667 strcat(filename, udentry->d_name); 668 669 // don't follow symbolic links for the file 670 RESTARTABLE(::lstat(filename, &statbuf), result); 671 if (result == OS_ERR) { 672 FREE_C_HEAP_ARRAY(char, filename); 673 continue; 674 } 675 676 // skip over files that are not regular files. 677 if (!S_ISREG(statbuf.st_mode)) { 678 FREE_C_HEAP_ARRAY(char, filename); 679 continue; 680 } 681 682 // compare and save filename with latest creation time 683 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) { 684 685 if (statbuf.st_ctime > oldest_ctime) { 686 char* user = strchr(dentry->d_name, '_') + 1; 687 688 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user); 689 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal); 690 691 strcpy(oldest_user, user); 692 oldest_ctime = statbuf.st_ctime; 693 } 694 } 695 696 FREE_C_HEAP_ARRAY(char, filename); 697 } 698 } 699 os::closedir(subdirp); 700 FREE_C_HEAP_ARRAY(char, usrdir_name); 701 } 702 os::closedir(tmpdirp); 703 704 return(oldest_user); 705 } 706 707 // return the name of the user that owns the JVM indicated by the given vmid. 708 // 709 static char* get_user_name(int vmid, TRAPS) { 710 return get_user_name_slow(vmid, THREAD); 711 } 712 713 // return the file name of the backing store file for the named 714 // shared memory region for the given user name and vmid. 715 // 716 // the caller is expected to free the allocated memory. 717 // 718 static char* get_sharedmem_filename(const char* dirname, int vmid) { 719 720 // add 2 for the file separator and a null terminator. 721 size_t nbytes = strlen(dirname) + UINT_CHARS + 2; 722 723 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal); 724 snprintf(name, nbytes, "%s/%d", dirname, vmid); 725 726 return name; 727 } 728 729 730 // remove file 731 // 732 // this method removes the file specified by the given path 733 // 734 static void remove_file(const char* path) { 735 736 int result; 737 738 // if the file is a directory, the following unlink will fail. since 739 // we don't expect to find directories in the user temp directory, we 740 // won't try to handle this situation. even if accidentially or 741 // maliciously planted, the directory's presence won't hurt anything. 742 // 743 RESTARTABLE(::unlink(path), result); 744 if (PrintMiscellaneous && Verbose && result == OS_ERR) { 745 if (errno != ENOENT) { 746 warning("Could not unlink shared memory backing" 747 " store file %s : %s\n", path, os::strerror(errno)); 748 } 749 } 750 } 751 752 // Cleanup stale shared memory resources 753 // 754 // This method attempts to remove all stale shared memory files in 755 // the named user temporary directory. It scans the named directory 756 // for files matching the pattern ^$[0-9]*$. For each file found, the 757 // process id is extracted from the file name and a test is run to 758 // determine if the process is alive. If the process is not alive, 759 // any stale file resources are removed. 760 static void cleanup_sharedmem_resources(const char* dirname) { 761 762 int saved_cwd_fd; 763 // Open the directory. 764 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); 765 if (dirp == NULL) { 766 // Directory doesn't exist or is insecure, so there is nothing to cleanup. 767 return; 768 } 769 770 // For each entry in the directory that matches the expected file 771 // name pattern, determine if the file resources are stale and if 772 // so, remove the file resources. Note, instrumented HotSpot processes 773 // for this user may start and/or terminate during this search and 774 // remove or create new files in this directory. The behavior of this 775 // loop under these conditions is dependent upon the implementation of 776 // opendir/readdir. 777 struct dirent* entry; 778 errno = 0; 779 while ((entry = os::readdir(dirp)) != NULL) { 780 781 pid_t pid = filename_to_pid(entry->d_name); 782 783 if (pid == 0) { 784 785 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) { 786 787 // Attempt to remove all unexpected files, except "." and "..". 788 unlink(entry->d_name); 789 } 790 791 errno = 0; 792 continue; 793 } 794 795 // We now have a file name that converts to a valid integer 796 // that could represent a process id . if this process id 797 // matches the current process id or the process is not running, 798 // then remove the stale file resources. 799 // 800 // Process liveness is detected by sending signal number 0 to 801 // the process id (see kill(2)). if kill determines that the 802 // process does not exist, then the file resources are removed. 803 // if kill determines that that we don't have permission to 804 // signal the process, then the file resources are assumed to 805 // be stale and are removed because the resources for such a 806 // process should be in a different user specific directory. 807 if ((pid == os::current_process_id()) || 808 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) { 809 810 unlink(entry->d_name); 811 } 812 errno = 0; 813 } 814 815 // Close the directory and reset the current working directory. 816 close_directory_secure_cwd(dirp, saved_cwd_fd); 817 } 818 819 // Make the user specific temporary directory. Returns true if 820 // the directory exists and is secure upon return. Returns false 821 // if the directory exists but is either a symlink, is otherwise 822 // insecure, or if an error occurred. 823 static bool make_user_tmp_dir(const char* dirname) { 824 825 // Create the directory with 0755 permissions. note that the directory 826 // will be owned by euid::egid, which may not be the same as uid::gid. 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 if (!is_directory_secure(dirname)) { 833 // Directory is not secure. 834 if (PrintMiscellaneous && Verbose) { 835 warning("%s directory is insecure\n", dirname); 836 } 837 return false; 838 } 839 } 840 else { 841 // we encountered some other failure while attempting 842 // to create the directory 843 // 844 if (PrintMiscellaneous && Verbose) { 845 warning("could not create directory %s: %s\n", 846 dirname, os::strerror(errno)); 847 } 848 return false; 849 } 850 } 851 return true; 852 } 853 854 // create the shared memory file resources 855 // 856 // This method creates the shared memory file with the given size 857 // This method also creates the user specific temporary directory, if 858 // it does not yet exist. 859 // 860 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) { 861 862 // make the user temporary directory 863 if (!make_user_tmp_dir(dirname)) { 864 // could not make/find the directory or the found directory 865 // was not secure 866 return -1; 867 } 868 869 int saved_cwd_fd; 870 // Open the directory and set the current working directory to it. 871 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); 872 if (dirp == NULL) { 873 // Directory doesn't exist or is insecure, so cannot create shared 874 // memory file. 875 return -1; 876 } 877 878 // Open the filename in the current directory. 879 // Cannot use O_TRUNC here; truncation of an existing file has to happen 880 // after the is_file_secure() check below. 881 int result; 882 883 // No O_NOFOLLOW defined at buildtime, and it is not documented for open; 884 // so provide a workaround in this case. 885 #ifdef O_NOFOLLOW 886 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result); 887 #else 888 // workaround function (jdk6 code) 889 result = open_o_nofollow(filename, O_RDWR|O_CREAT, S_IREAD|S_IWRITE); 890 #endif 891 892 if (result == OS_ERR) { 893 if (PrintMiscellaneous && Verbose) { 894 if (errno == ELOOP) { 895 warning("file %s is a symlink and is not secure\n", filename); 896 } else { 897 warning("could not create file %s: %s\n", filename, os::strerror(errno)); 898 } 899 } 900 // Close the directory and reset the current working directory. 901 close_directory_secure_cwd(dirp, saved_cwd_fd); 902 903 return -1; 904 } 905 // Close the directory and reset the current working directory. 906 close_directory_secure_cwd(dirp, saved_cwd_fd); 907 908 // save the file descriptor 909 int fd = result; 910 911 // Check to see if the file is secure. 912 if (!is_file_secure(fd, filename)) { 913 ::close(fd); 914 return -1; 915 } 916 917 // Truncate the file to get rid of any existing data. 918 RESTARTABLE(::ftruncate(fd, (off_t)0), result); 919 if (result == OS_ERR) { 920 if (PrintMiscellaneous && Verbose) { 921 warning("could not truncate shared memory file: %s\n", os::strerror(errno)); 922 } 923 ::close(fd); 924 return -1; 925 } 926 // set the file size 927 RESTARTABLE(::ftruncate(fd, (off_t)size), result); 928 if (result == OS_ERR) { 929 if (PrintMiscellaneous && Verbose) { 930 warning("could not set shared memory file size: %s\n", os::strerror(errno)); 931 } 932 ::close(fd); 933 return -1; 934 } 935 936 return fd; 937 } 938 939 // open the shared memory file for the given user and vmid. returns 940 // the file descriptor for the open file or -1 if the file could not 941 // be opened. 942 // 943 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) { 944 945 // open the file 946 int result; 947 // provide a workaround in case no O_NOFOLLOW is defined at buildtime 948 #ifdef O_NOFOLLOW 949 RESTARTABLE(::open(filename, oflags), result); 950 #else 951 result = open_o_nofollow(filename, oflags); 952 #endif 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 AIX, 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 // 991 static 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); 1005 char* filename = get_sharedmem_filename(dirname, vmid); 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((address)mapAddress, size, CURRENT_PC, mtInternal); 1053 1054 return mapAddress; 1055 } 1056 1057 // release a named shared memory region 1058 // 1059 static void unmap_shared(char* addr, size_t bytes) { 1060 // Do not rely on os::reserve_memory/os::release_memory to use mmap. 1061 // Use os::reserve_memory/os::release_memory for PerfDisableSharedMem=1, mmap/munmap for PerfDisableSharedMem=0 1062 if (::munmap(addr, bytes) == -1) { 1063 warning("perfmemory: munmap failed (%d)\n", errno); 1064 } 1065 } 1066 1067 // create the PerfData memory region in shared memory. 1068 // 1069 static char* create_shared_memory(size_t size) { 1070 1071 // create the shared memory region. 1072 return mmap_create_shared(size); 1073 } 1074 1075 // delete the shared PerfData memory region 1076 // 1077 static void delete_shared_memory(char* addr, size_t size) { 1078 1079 // cleanup the persistent shared memory resources. since DestroyJavaVM does 1080 // not support unloading of the JVM, unmapping of the memory resource is 1081 // not performed. The memory will be reclaimed by the OS upon termination of 1082 // the process. The backing store file is deleted from the file system. 1083 1084 assert(!PerfDisableSharedMem, "shouldn't be here"); 1085 1086 if (backing_store_file_name != NULL) { 1087 remove_file(backing_store_file_name); 1088 // Don't.. Free heap memory could deadlock os::abort() if it is called 1089 // from signal handler. OS will reclaim the heap memory. 1090 // FREE_C_HEAP_ARRAY(char, backing_store_file_name); 1091 backing_store_file_name = NULL; 1092 } 1093 } 1094 1095 // return the size of the file for the given file descriptor 1096 // or 0 if it is not a valid size for a shared memory file 1097 // 1098 static size_t sharedmem_filesize(int fd, TRAPS) { 1099 1100 struct stat statbuf; 1101 int result; 1102 1103 RESTARTABLE(::fstat(fd, &statbuf), result); 1104 if (result == OS_ERR) { 1105 if (PrintMiscellaneous && Verbose) { 1106 warning("fstat failed: %s\n", os::strerror(errno)); 1107 } 1108 THROW_MSG_0(vmSymbols::java_io_IOException(), 1109 "Could not determine PerfMemory size"); 1110 } 1111 1112 if ((statbuf.st_size == 0) || 1113 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) { 1114 THROW_MSG_0(vmSymbols::java_lang_Exception(), 1115 "Invalid PerfMemory size"); 1116 } 1117 1118 return (size_t)statbuf.st_size; 1119 } 1120 1121 // attach to a named shared memory region. 1122 // 1123 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) { 1124 1125 char* mapAddress; 1126 int result; 1127 int fd; 1128 size_t size = 0; 1129 const char* luser = NULL; 1130 1131 int mmap_prot; 1132 int file_flags; 1133 1134 ResourceMark rm; 1135 1136 // map the high level access mode to the appropriate permission 1137 // constructs for the file and the shared memory mapping. 1138 if (mode == PerfMemory::PERF_MODE_RO) { 1139 mmap_prot = PROT_READ; 1140 // No O_NOFOLLOW defined at buildtime, and it is not documented for open. 1141 #ifdef O_NOFOLLOW 1142 file_flags = O_RDONLY | O_NOFOLLOW; 1143 #else 1144 file_flags = O_RDONLY; 1145 #endif 1146 } 1147 else if (mode == PerfMemory::PERF_MODE_RW) { 1148 #ifdef LATER 1149 mmap_prot = PROT_READ | PROT_WRITE; 1150 file_flags = O_RDWR | O_NOFOLLOW; 1151 #else 1152 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1153 "Unsupported access mode"); 1154 #endif 1155 } 1156 else { 1157 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1158 "Illegal access mode"); 1159 } 1160 1161 if (user == NULL || strlen(user) == 0) { 1162 luser = get_user_name(vmid, CHECK); 1163 } 1164 else { 1165 luser = user; 1166 } 1167 1168 if (luser == NULL) { 1169 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1170 "Could not map vmid to user Name"); 1171 } 1172 1173 char* dirname = get_user_tmp_dir(luser); 1174 1175 // since we don't follow symbolic links when creating the backing 1176 // store file, we don't follow them when attaching either. 1177 // 1178 if (!is_directory_secure(dirname)) { 1179 FREE_C_HEAP_ARRAY(char, dirname); 1180 if (luser != user) { 1181 FREE_C_HEAP_ARRAY(char, luser); 1182 } 1183 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1184 "Process not found"); 1185 } 1186 1187 char* filename = get_sharedmem_filename(dirname, vmid); 1188 1189 // copy heap memory to resource memory. the open_sharedmem_file 1190 // method below need to use the filename, but could throw an 1191 // exception. using a resource array prevents the leak that 1192 // would otherwise occur. 1193 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1); 1194 strcpy(rfilename, filename); 1195 1196 // free the c heap resources that are no longer needed 1197 if (luser != user) FREE_C_HEAP_ARRAY(char, luser); 1198 FREE_C_HEAP_ARRAY(char, dirname); 1199 FREE_C_HEAP_ARRAY(char, filename); 1200 1201 // open the shared memory file for the give vmid 1202 fd = open_sharedmem_file(rfilename, file_flags, THREAD); 1203 1204 if (fd == OS_ERR) { 1205 return; 1206 } 1207 1208 if (HAS_PENDING_EXCEPTION) { 1209 ::close(fd); 1210 return; 1211 } 1212 1213 if (*sizep == 0) { 1214 size = sharedmem_filesize(fd, CHECK); 1215 } else { 1216 size = *sizep; 1217 } 1218 1219 assert(size > 0, "unexpected size <= 0"); 1220 1221 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0); 1222 1223 result = ::close(fd); 1224 assert(result != OS_ERR, "could not close file"); 1225 1226 if (mapAddress == MAP_FAILED) { 1227 if (PrintMiscellaneous && Verbose) { 1228 warning("mmap failed: %s\n", os::strerror(errno)); 1229 } 1230 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(), 1231 "Could not map PerfMemory"); 1232 } 1233 1234 // it does not go through os api, the operation has to record from here. 1235 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, CURRENT_PC, mtInternal); 1236 1237 *addr = mapAddress; 1238 *sizep = size; 1239 1240 log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at " 1241 INTPTR_FORMAT, size, vmid, p2i((void*)mapAddress)); 1242 } 1243 1244 // create the PerfData memory region 1245 // 1246 // This method creates the memory region used to store performance 1247 // data for the JVM. The memory may be created in standard or 1248 // shared memory. 1249 // 1250 void PerfMemory::create_memory_region(size_t size) { 1251 1252 if (PerfDisableSharedMem) { 1253 // do not share the memory for the performance data. 1254 _start = create_standard_memory(size); 1255 } 1256 else { 1257 _start = create_shared_memory(size); 1258 if (_start == NULL) { 1259 1260 // creation of the shared memory region failed, attempt 1261 // to create a contiguous, non-shared memory region instead. 1262 // 1263 if (PrintMiscellaneous && Verbose) { 1264 warning("Reverting to non-shared PerfMemory region.\n"); 1265 } 1266 PerfDisableSharedMem = true; 1267 _start = create_standard_memory(size); 1268 } 1269 } 1270 1271 if (_start != NULL) _capacity = size; 1272 1273 } 1274 1275 // delete the PerfData memory region 1276 // 1277 // This method deletes the memory region used to store performance 1278 // data for the JVM. The memory region indicated by the <address, size> 1279 // tuple will be inaccessible after a call to this method. 1280 // 1281 void PerfMemory::delete_memory_region() { 1282 1283 assert((start() != NULL && capacity() > 0), "verify proper state"); 1284 1285 // If user specifies PerfDataSaveFile, it will save the performance data 1286 // to the specified file name no matter whether PerfDataSaveToFile is specified 1287 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag 1288 // -XX:+PerfDataSaveToFile. 1289 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) { 1290 save_memory_to_file(start(), capacity()); 1291 } 1292 1293 if (PerfDisableSharedMem) { 1294 delete_standard_memory(start(), capacity()); 1295 } 1296 else { 1297 delete_shared_memory(start(), capacity()); 1298 } 1299 } 1300 1301 // attach to the PerfData memory region for another JVM 1302 // 1303 // This method returns an <address, size> tuple that points to 1304 // a memory buffer that is kept reasonably synchronized with 1305 // the PerfData memory region for the indicated JVM. This 1306 // buffer may be kept in synchronization via shared memory 1307 // or some other mechanism that keeps the buffer updated. 1308 // 1309 // If the JVM chooses not to support the attachability feature, 1310 // this method should throw an UnsupportedOperation exception. 1311 // 1312 // This implementation utilizes named shared memory to map 1313 // the indicated process's PerfData memory region into this JVMs 1314 // address space. 1315 // 1316 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) { 1317 1318 if (vmid == 0 || vmid == os::current_process_id()) { 1319 *addrp = start(); 1320 *sizep = capacity(); 1321 return; 1322 } 1323 1324 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK); 1325 } 1326 1327 // detach from the PerfData memory region of another JVM 1328 // 1329 // This method detaches the PerfData memory region of another 1330 // JVM, specified as an <address, size> tuple of a buffer 1331 // in this process's address space. This method may perform 1332 // arbitrary actions to accomplish the detachment. The memory 1333 // region specified by <address, size> will be inaccessible after 1334 // a call to this method. 1335 // 1336 // If the JVM chooses not to support the attachability feature, 1337 // this method should throw an UnsupportedOperation exception. 1338 // 1339 // This implementation utilizes named shared memory to detach 1340 // the indicated process's PerfData memory region from this 1341 // process's address space. 1342 // 1343 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) { 1344 1345 assert(addr != 0, "address sanity check"); 1346 assert(bytes > 0, "capacity sanity check"); 1347 1348 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) { 1349 // prevent accidental detachment of this process's PerfMemory region 1350 return; 1351 } 1352 1353 unmap_shared(addr, bytes); 1354 }