perfMemory_linux.cpp revision 8875:efc17f03e5d4
1/* 2 * Copyright (c) 2001, 2015, 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 "memory/allocation.inline.hpp" 28#include "memory/resourceArea.hpp" 29#include "oops/oop.inline.hpp" 30#include "os_linux.inline.hpp" 31#include "runtime/handles.inline.hpp" 32#include "runtime/perfMemory.hpp" 33#include "services/memTracker.hpp" 34#include "utilities/exceptions.hpp" 35 36// put OS-includes here 37# include <sys/types.h> 38# include <sys/mman.h> 39# include <errno.h> 40# include <stdio.h> 41# include <unistd.h> 42# include <sys/stat.h> 43# include <signal.h> 44# include <pwd.h> 45 46static char* backing_store_file_name = NULL; // name of the backing store 47 // file, if successfully created. 48 49// Standard Memory Implementation Details 50 51// create the PerfData memory region in standard memory. 52// 53static char* create_standard_memory(size_t size) { 54 55 // allocate an aligned chuck of memory 56 char* mapAddress = os::reserve_memory(size); 57 58 if (mapAddress == NULL) { 59 return NULL; 60 } 61 62 // commit memory 63 if (!os::commit_memory(mapAddress, size, !ExecMem)) { 64 if (PrintMiscellaneous && Verbose) { 65 warning("Could not commit PerfData memory\n"); 66 } 67 os::release_memory(mapAddress, size); 68 return NULL; 69 } 70 71 return mapAddress; 72} 73 74// delete the PerfData memory region 75// 76static void delete_standard_memory(char* addr, size_t size) { 77 78 // there are no persistent external resources to cleanup for standard 79 // memory. since DestroyJavaVM does not support unloading of the JVM, 80 // cleanup of the memory resource is not performed. The memory will be 81 // reclaimed by the OS upon termination of the process. 82 // 83 return; 84} 85 86// save the specified memory region to the given file 87// 88// Note: this function might be called from signal handler (by os::abort()), 89// don't allocate heap memory. 90// 91static void save_memory_to_file(char* addr, size_t size) { 92 93 const char* destfile = PerfMemory::get_perfdata_file_path(); 94 assert(destfile[0] != '\0', "invalid PerfData file path"); 95 96 int result; 97 98 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE), 99 result);; 100 if (result == OS_ERR) { 101 if (PrintMiscellaneous && Verbose) { 102 warning("Could not create Perfdata save file: %s: %s\n", 103 destfile, strerror(errno)); 104 } 105 } else { 106 int fd = result; 107 108 for (size_t remaining = size; remaining > 0;) { 109 110 RESTARTABLE(::write(fd, addr, remaining), result); 111 if (result == OS_ERR) { 112 if (PrintMiscellaneous && Verbose) { 113 warning("Could not write Perfdata save file: %s: %s\n", 114 destfile, strerror(errno)); 115 } 116 break; 117 } 118 119 remaining -= (size_t)result; 120 addr += result; 121 } 122 123 result = ::close(fd); 124 if (PrintMiscellaneous && Verbose) { 125 if (result == OS_ERR) { 126 warning("Could not close %s: %s\n", destfile, strerror(errno)); 127 } 128 } 129 } 130 FREE_C_HEAP_ARRAY(char, destfile); 131} 132 133 134// Shared Memory Implementation Details 135 136// Note: the solaris and linux shared memory implementation uses the mmap 137// interface with a backing store file to implement named shared memory. 138// Using the file system as the name space for shared memory allows a 139// common name space to be supported across a variety of platforms. It 140// also provides a name space that Java applications can deal with through 141// simple file apis. 142// 143// The solaris and linux implementations store the backing store file in 144// a user specific temporary directory located in the /tmp file system, 145// which is always a local file system and is sometimes a RAM based file 146// system. 147 148// return the user specific temporary directory name. 149// 150// the caller is expected to free the allocated memory. 151// 152static char* get_user_tmp_dir(const char* user) { 153 154 const char* tmpdir = os::get_temp_directory(); 155 const char* perfdir = PERFDATA_NAME; 156 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3; 157 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal); 158 159 // construct the path name to user specific tmp directory 160 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user); 161 162 return dirname; 163} 164 165// convert the given file name into a process id. if the file 166// does not meet the file naming constraints, return 0. 167// 168static pid_t filename_to_pid(const char* filename) { 169 170 // a filename that doesn't begin with a digit is not a 171 // candidate for conversion. 172 // 173 if (!isdigit(*filename)) { 174 return 0; 175 } 176 177 // check if file name can be converted to an integer without 178 // any leftover characters. 179 // 180 char* remainder = NULL; 181 errno = 0; 182 pid_t pid = (pid_t)strtol(filename, &remainder, 10); 183 184 if (errno != 0) { 185 return 0; 186 } 187 188 // check for left over characters. If any, then the filename is 189 // not a candidate for conversion. 190 // 191 if (remainder != NULL && *remainder != '\0') { 192 return 0; 193 } 194 195 // successful conversion, return the pid 196 return pid; 197} 198 199 200// Check if the given statbuf is considered a secure directory for 201// the backing store files. Returns true if the directory is considered 202// a secure location. Returns false if the statbuf is a symbolic link or 203// if an error occurred. 204// 205static bool is_statbuf_secure(struct stat *statp) { 206 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) { 207 // The path represents a link or some non-directory file type, 208 // which is not what we expected. Declare it insecure. 209 // 210 return false; 211 } 212 // We have an existing directory, check if the permissions are safe. 213 // 214 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) { 215 // The directory is open for writing and could be subjected 216 // to a symlink or a hard link attack. Declare it insecure. 217 // 218 return false; 219 } 220 // If user is not root then see if the uid of the directory matches the effective uid of the process. 221 uid_t euid = geteuid(); 222 if ((euid != 0) && (statp->st_uid != euid)) { 223 // The directory was not created by this user, declare it insecure. 224 // 225 return false; 226 } 227 return true; 228} 229 230 231// Check if the given path is considered a secure directory for 232// the backing store files. Returns true if the directory exists 233// and is considered a secure location. Returns false if the path 234// is a symbolic link or if an error occurred. 235// 236static bool is_directory_secure(const char* path) { 237 struct stat statbuf; 238 int result = 0; 239 240 RESTARTABLE(::lstat(path, &statbuf), result); 241 if (result == OS_ERR) { 242 return false; 243 } 244 245 // The path exists, see if it is secure. 246 return is_statbuf_secure(&statbuf); 247} 248 249 250// Check if the given directory file descriptor is considered a secure 251// directory for the backing store files. Returns true if the directory 252// exists and is considered a secure location. Returns false if the path 253// is a symbolic link or if an error occurred. 254// 255static bool is_dirfd_secure(int dir_fd) { 256 struct stat statbuf; 257 int result = 0; 258 259 RESTARTABLE(::fstat(dir_fd, &statbuf), result); 260 if (result == OS_ERR) { 261 return false; 262 } 263 264 // The path exists, now check its mode. 265 return is_statbuf_secure(&statbuf); 266} 267 268 269// Check to make sure fd1 and fd2 are referencing the same file system object. 270// 271static 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} 292 293 294// Open the directory of the given path and validate it. 295// Return a DIR * of the open directory. 296// 297static DIR *open_directory_secure(const char* dirname) { 298 // Open the directory using open() so that it can be verified 299 // to be secure by calling is_dirfd_secure(), opendir() and then check 300 // to see if they are the same file system object. This method does not 301 // introduce a window of opportunity for the directory to be attacked that 302 // calling opendir() and is_directory_secure() does. 303 int result; 304 DIR *dirp = NULL; 305 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result); 306 if (result == OS_ERR) { 307 if (PrintMiscellaneous && Verbose) { 308 if (errno == ELOOP) { 309 warning("directory %s is a symlink and is not secure\n", dirname); 310 } else { 311 warning("could not open directory %s: %s\n", dirname, strerror(errno)); 312 } 313 } 314 return dirp; 315 } 316 int fd = result; 317 318 // Determine if the open directory is secure. 319 if (!is_dirfd_secure(fd)) { 320 // The directory is not a secure directory. 321 os::close(fd); 322 return dirp; 323 } 324 325 // Open the directory. 326 dirp = ::opendir(dirname); 327 if (dirp == NULL) { 328 // The directory doesn't exist, close fd and return. 329 os::close(fd); 330 return dirp; 331 } 332 333 // Check to make sure fd and dirp are referencing the same file system object. 334 if (!is_same_fsobject(fd, dirfd(dirp))) { 335 // The directory is not secure. 336 os::close(fd); 337 os::closedir(dirp); 338 dirp = NULL; 339 return dirp; 340 } 341 342 // Close initial open now that we know directory is secure 343 os::close(fd); 344 345 return dirp; 346} 347 348// NOTE: The code below uses fchdir(), open() and unlink() because 349// fdopendir(), openat() and unlinkat() are not supported on all 350// versions. Once the support for fdopendir(), openat() and unlinkat() 351// is available on all supported versions the code can be changed 352// to use these functions. 353 354// Open the directory of the given path, validate it and set the 355// current working directory to it. 356// Return a DIR * of the open directory and the saved cwd fd. 357// 358static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) { 359 360 // Open the directory. 361 DIR* dirp = open_directory_secure(dirname); 362 if (dirp == NULL) { 363 // Directory doesn't exist or is insecure, so there is nothing to cleanup. 364 return dirp; 365 } 366 int fd = dirfd(dirp); 367 368 // Open a fd to the cwd and save it off. 369 int result; 370 RESTARTABLE(::open(".", O_RDONLY), result); 371 if (result == OS_ERR) { 372 *saved_cwd_fd = -1; 373 } else { 374 *saved_cwd_fd = result; 375 } 376 377 // Set the current directory to dirname by using the fd of the directory and 378 // handle errors, otherwise shared memory files will be created in cwd. 379 result = fchdir(fd); 380 if (result == OS_ERR) { 381 if (PrintMiscellaneous && Verbose) { 382 warning("could not change to directory %s", dirname); 383 } 384 if (*saved_cwd_fd != -1) { 385 ::close(*saved_cwd_fd); 386 *saved_cwd_fd = -1; 387 } 388 // Close the directory. 389 os::closedir(dirp); 390 return NULL; 391 } else { 392 return dirp; 393 } 394} 395 396// Close the directory and restore the current working directory. 397// 398static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) { 399 400 int result; 401 // If we have a saved cwd change back to it and close the fd. 402 if (saved_cwd_fd != -1) { 403 result = fchdir(saved_cwd_fd); 404 ::close(saved_cwd_fd); 405 } 406 407 // Close the directory. 408 os::closedir(dirp); 409} 410 411// Check if the given file descriptor is considered a secure. 412// 413static bool is_file_secure(int fd, const char *filename) { 414 415 int result; 416 struct stat statbuf; 417 418 // Determine if the file is secure. 419 RESTARTABLE(::fstat(fd, &statbuf), result); 420 if (result == OS_ERR) { 421 if (PrintMiscellaneous && Verbose) { 422 warning("fstat failed on %s: %s\n", filename, strerror(errno)); 423 } 424 return false; 425 } 426 if (statbuf.st_nlink > 1) { 427 // A file with multiple links is not expected. 428 if (PrintMiscellaneous && Verbose) { 429 warning("file %s has multiple links\n", filename); 430 } 431 return false; 432 } 433 return true; 434} 435 436 437// return the user name for the given user id 438// 439// the caller is expected to free the allocated memory. 440// 441static char* get_user_name(uid_t uid) { 442 443 struct passwd pwent; 444 445 // determine the max pwbuf size from sysconf, and hardcode 446 // a default if this not available through sysconf. 447 // 448 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); 449 if (bufsize == -1) 450 bufsize = 1024; 451 452 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal); 453 454 // POSIX interface to getpwuid_r is used on LINUX 455 struct passwd* p; 456 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p); 457 458 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') { 459 if (PrintMiscellaneous && Verbose) { 460 if (result != 0) { 461 warning("Could not retrieve passwd entry: %s\n", 462 strerror(result)); 463 } 464 else if (p == NULL) { 465 // this check is added to protect against an observed problem 466 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0, 467 // indicating success, but has p == NULL. This was observed when 468 // inserting a file descriptor exhaustion fault prior to the call 469 // getpwuid_r() call. In this case, error is set to the appropriate 470 // error condition, but this is undocumented behavior. This check 471 // is safe under any condition, but the use of errno in the output 472 // message may result in an erroneous message. 473 // Bug Id 89052 was opened with RedHat. 474 // 475 warning("Could not retrieve passwd entry: %s\n", 476 strerror(errno)); 477 } 478 else { 479 warning("Could not determine user name: %s\n", 480 p->pw_name == NULL ? "pw_name = NULL" : 481 "pw_name zero length"); 482 } 483 } 484 FREE_C_HEAP_ARRAY(char, pwbuf); 485 return NULL; 486 } 487 488 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal); 489 strcpy(user_name, p->pw_name); 490 491 FREE_C_HEAP_ARRAY(char, pwbuf); 492 return user_name; 493} 494 495// return the name of the user that owns the process identified by vmid. 496// 497// This method uses a slow directory search algorithm to find the backing 498// store file for the specified vmid and returns the user name, as determined 499// by the user name suffix of the hsperfdata_<username> directory name. 500// 501// the caller is expected to free the allocated memory. 502// 503static char* get_user_name_slow(int vmid, TRAPS) { 504 505 // short circuit the directory search if the process doesn't even exist. 506 if (kill(vmid, 0) == OS_ERR) { 507 if (errno == ESRCH) { 508 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), 509 "Process not found"); 510 } 511 else /* EPERM */ { 512 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno)); 513 } 514 } 515 516 // directory search 517 char* oldest_user = NULL; 518 time_t oldest_ctime = 0; 519 520 const char* tmpdirname = os::get_temp_directory(); 521 522 // open the temp directory 523 DIR* tmpdirp = os::opendir(tmpdirname); 524 525 if (tmpdirp == NULL) { 526 // Cannot open the directory to get the user name, return. 527 return NULL; 528 } 529 530 // for each entry in the directory that matches the pattern hsperfdata_*, 531 // open the directory and check if the file for the given vmid exists. 532 // The file with the expected name and the latest creation date is used 533 // to determine the user name for the process id. 534 // 535 struct dirent* dentry; 536 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal); 537 errno = 0; 538 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) { 539 540 // check if the directory entry is a hsperfdata file 541 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) { 542 continue; 543 } 544 545 char* usrdir_name = NEW_C_HEAP_ARRAY(char, 546 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal); 547 strcpy(usrdir_name, tmpdirname); 548 strcat(usrdir_name, "/"); 549 strcat(usrdir_name, dentry->d_name); 550 551 // open the user directory 552 DIR* subdirp = open_directory_secure(usrdir_name); 553 554 if (subdirp == NULL) { 555 FREE_C_HEAP_ARRAY(char, usrdir_name); 556 continue; 557 } 558 559 // Since we don't create the backing store files in directories 560 // pointed to by symbolic links, we also don't follow them when 561 // looking for the files. We check for a symbolic link after the 562 // call to opendir in order to eliminate a small window where the 563 // symlink can be exploited. 564 // 565 if (!is_directory_secure(usrdir_name)) { 566 FREE_C_HEAP_ARRAY(char, usrdir_name); 567 os::closedir(subdirp); 568 continue; 569 } 570 571 struct dirent* udentry; 572 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal); 573 errno = 0; 574 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) { 575 576 if (filename_to_pid(udentry->d_name) == vmid) { 577 struct stat statbuf; 578 int result; 579 580 char* filename = NEW_C_HEAP_ARRAY(char, 581 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal); 582 583 strcpy(filename, usrdir_name); 584 strcat(filename, "/"); 585 strcat(filename, udentry->d_name); 586 587 // don't follow symbolic links for the file 588 RESTARTABLE(::lstat(filename, &statbuf), result); 589 if (result == OS_ERR) { 590 FREE_C_HEAP_ARRAY(char, filename); 591 continue; 592 } 593 594 // skip over files that are not regular files. 595 if (!S_ISREG(statbuf.st_mode)) { 596 FREE_C_HEAP_ARRAY(char, filename); 597 continue; 598 } 599 600 // compare and save filename with latest creation time 601 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) { 602 603 if (statbuf.st_ctime > oldest_ctime) { 604 char* user = strchr(dentry->d_name, '_') + 1; 605 606 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user); 607 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal); 608 609 strcpy(oldest_user, user); 610 oldest_ctime = statbuf.st_ctime; 611 } 612 } 613 614 FREE_C_HEAP_ARRAY(char, filename); 615 } 616 } 617 os::closedir(subdirp); 618 FREE_C_HEAP_ARRAY(char, udbuf); 619 FREE_C_HEAP_ARRAY(char, usrdir_name); 620 } 621 os::closedir(tmpdirp); 622 FREE_C_HEAP_ARRAY(char, tdbuf); 623 624 return(oldest_user); 625} 626 627// return the name of the user that owns the JVM indicated by the given vmid. 628// 629static char* get_user_name(int vmid, TRAPS) { 630 return get_user_name_slow(vmid, THREAD); 631} 632 633// return the file name of the backing store file for the named 634// shared memory region for the given user name and vmid. 635// 636// the caller is expected to free the allocated memory. 637// 638static char* get_sharedmem_filename(const char* dirname, int vmid) { 639 640 // add 2 for the file separator and a null terminator. 641 size_t nbytes = strlen(dirname) + UINT_CHARS + 2; 642 643 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal); 644 snprintf(name, nbytes, "%s/%d", dirname, vmid); 645 646 return name; 647} 648 649 650// remove file 651// 652// this method removes the file specified by the given path 653// 654static void remove_file(const char* path) { 655 656 int result; 657 658 // if the file is a directory, the following unlink will fail. since 659 // we don't expect to find directories in the user temp directory, we 660 // won't try to handle this situation. even if accidentially or 661 // maliciously planted, the directory's presence won't hurt anything. 662 // 663 RESTARTABLE(::unlink(path), result); 664 if (PrintMiscellaneous && Verbose && result == OS_ERR) { 665 if (errno != ENOENT) { 666 warning("Could not unlink shared memory backing" 667 " store file %s : %s\n", path, strerror(errno)); 668 } 669 } 670} 671 672 673// cleanup stale shared memory resources 674// 675// This method attempts to remove all stale shared memory files in 676// the named user temporary directory. It scans the named directory 677// for files matching the pattern ^$[0-9]*$. For each file found, the 678// process id is extracted from the file name and a test is run to 679// determine if the process is alive. If the process is not alive, 680// any stale file resources are removed. 681// 682static void cleanup_sharedmem_resources(const char* dirname) { 683 684 int saved_cwd_fd; 685 // open the directory 686 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); 687 if (dirp == NULL) { 688 // directory doesn't exist or is insecure, so there is nothing to cleanup 689 return; 690 } 691 692 // for each entry in the directory that matches the expected file 693 // name pattern, determine if the file resources are stale and if 694 // so, remove the file resources. Note, instrumented HotSpot processes 695 // for this user may start and/or terminate during this search and 696 // remove or create new files in this directory. The behavior of this 697 // loop under these conditions is dependent upon the implementation of 698 // opendir/readdir. 699 // 700 struct dirent* entry; 701 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal); 702 703 errno = 0; 704 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) { 705 706 pid_t pid = filename_to_pid(entry->d_name); 707 708 if (pid == 0) { 709 710 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) { 711 // attempt to remove all unexpected files, except "." and ".." 712 unlink(entry->d_name); 713 } 714 715 errno = 0; 716 continue; 717 } 718 719 // we now have a file name that converts to a valid integer 720 // that could represent a process id . if this process id 721 // matches the current process id or the process is not running, 722 // then remove the stale file resources. 723 // 724 // process liveness is detected by sending signal number 0 to 725 // the process id (see kill(2)). if kill determines that the 726 // process does not exist, then the file resources are removed. 727 // if kill determines that that we don't have permission to 728 // signal the process, then the file resources are assumed to 729 // be stale and are removed because the resources for such a 730 // process should be in a different user specific directory. 731 // 732 if ((pid == os::current_process_id()) || 733 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) { 734 unlink(entry->d_name); 735 } 736 errno = 0; 737 } 738 739 // close the directory and reset the current working directory 740 close_directory_secure_cwd(dirp, saved_cwd_fd); 741 742 FREE_C_HEAP_ARRAY(char, dbuf); 743} 744 745// make the user specific temporary directory. Returns true if 746// the directory exists and is secure upon return. Returns false 747// if the directory exists but is either a symlink, is otherwise 748// insecure, or if an error occurred. 749// 750static bool make_user_tmp_dir(const char* dirname) { 751 752 // create the directory with 0755 permissions. note that the directory 753 // will be owned by euid::egid, which may not be the same as uid::gid. 754 // 755 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) { 756 if (errno == EEXIST) { 757 // The directory already exists and was probably created by another 758 // JVM instance. However, this could also be the result of a 759 // deliberate symlink. Verify that the existing directory is safe. 760 // 761 if (!is_directory_secure(dirname)) { 762 // directory is not secure 763 if (PrintMiscellaneous && Verbose) { 764 warning("%s directory is insecure\n", dirname); 765 } 766 return false; 767 } 768 } 769 else { 770 // we encountered some other failure while attempting 771 // to create the directory 772 // 773 if (PrintMiscellaneous && Verbose) { 774 warning("could not create directory %s: %s\n", 775 dirname, strerror(errno)); 776 } 777 return false; 778 } 779 } 780 return true; 781} 782 783// create the shared memory file resources 784// 785// This method creates the shared memory file with the given size 786// This method also creates the user specific temporary directory, if 787// it does not yet exist. 788// 789static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) { 790 791 // make the user temporary directory 792 if (!make_user_tmp_dir(dirname)) { 793 // could not make/find the directory or the found directory 794 // was not secure 795 return -1; 796 } 797 798 int saved_cwd_fd; 799 // open the directory and set the current working directory to it 800 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); 801 if (dirp == NULL) { 802 // Directory doesn't exist or is insecure, so cannot create shared 803 // memory file. 804 return -1; 805 } 806 807 // Open the filename in the current directory. 808 // Cannot use O_TRUNC here; truncation of an existing file has to happen 809 // after the is_file_secure() check below. 810 int result; 811 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result); 812 if (result == OS_ERR) { 813 if (PrintMiscellaneous && Verbose) { 814 if (errno == ELOOP) { 815 warning("file %s is a symlink and is not secure\n", filename); 816 } else { 817 warning("could not create file %s: %s\n", filename, strerror(errno)); 818 } 819 } 820 // close the directory and reset the current working directory 821 close_directory_secure_cwd(dirp, saved_cwd_fd); 822 823 return -1; 824 } 825 // close the directory and reset the current working directory 826 close_directory_secure_cwd(dirp, saved_cwd_fd); 827 828 // save the file descriptor 829 int fd = result; 830 831 // check to see if the file is secure 832 if (!is_file_secure(fd, filename)) { 833 ::close(fd); 834 return -1; 835 } 836 837 // truncate the file to get rid of any existing data 838 RESTARTABLE(::ftruncate(fd, (off_t)0), result); 839 if (result == OS_ERR) { 840 if (PrintMiscellaneous && Verbose) { 841 warning("could not truncate shared memory file: %s\n", strerror(errno)); 842 } 843 ::close(fd); 844 return -1; 845 } 846 // set the file size 847 RESTARTABLE(::ftruncate(fd, (off_t)size), result); 848 if (result == OS_ERR) { 849 if (PrintMiscellaneous && Verbose) { 850 warning("could not set shared memory file size: %s\n", strerror(errno)); 851 } 852 ::close(fd); 853 return -1; 854 } 855 856 // Verify that we have enough disk space for this file. 857 // We'll get random SIGBUS crashes on memory accesses if 858 // we don't. 859 860 for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) { 861 int zero_int = 0; 862 result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos)); 863 if (result == -1 ) break; 864 RESTARTABLE(::write(fd, &zero_int, 1), result); 865 if (result != 1) { 866 if (errno == ENOSPC) { 867 warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename); 868 } 869 break; 870 } 871 } 872 873 if (result != -1) { 874 return fd; 875 } else { 876 ::close(fd); 877 return -1; 878 } 879} 880 881// open the shared memory file for the given user and vmid. returns 882// the file descriptor for the open file or -1 if the file could not 883// be opened. 884// 885static int open_sharedmem_file(const char* filename, int oflags, TRAPS) { 886 887 // open the file 888 int result; 889 RESTARTABLE(::open(filename, oflags), result); 890 if (result == OS_ERR) { 891 if (errno == ENOENT) { 892 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(), 893 "Process not found", OS_ERR); 894 } 895 else if (errno == EACCES) { 896 THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(), 897 "Permission denied", OS_ERR); 898 } 899 else { 900 THROW_MSG_(vmSymbols::java_io_IOException(), strerror(errno), OS_ERR); 901 } 902 } 903 int fd = result; 904 905 // check to see if the file is secure 906 if (!is_file_secure(fd, filename)) { 907 ::close(fd); 908 return -1; 909 } 910 911 return fd; 912} 913 914// create a named shared memory region. returns the address of the 915// memory region on success or NULL on failure. A return value of 916// NULL will ultimately disable the shared memory feature. 917// 918// On Solaris and Linux, the name space for shared memory objects 919// is the file system name space. 920// 921// A monitoring application attaching to a JVM does not need to know 922// the file system name of the shared memory object. However, it may 923// be convenient for applications to discover the existence of newly 924// created and terminating JVMs by watching the file system name space 925// for files being created or removed. 926// 927static char* mmap_create_shared(size_t size) { 928 929 int result; 930 int fd; 931 char* mapAddress; 932 933 int vmid = os::current_process_id(); 934 935 char* user_name = get_user_name(geteuid()); 936 937 if (user_name == NULL) 938 return NULL; 939 940 char* dirname = get_user_tmp_dir(user_name); 941 char* filename = get_sharedmem_filename(dirname, vmid); 942 // get the short filename 943 char* short_filename = strrchr(filename, '/'); 944 if (short_filename == NULL) { 945 short_filename = filename; 946 } else { 947 short_filename++; 948 } 949 950 // cleanup any stale shared memory files 951 cleanup_sharedmem_resources(dirname); 952 953 assert(((size > 0) && (size % os::vm_page_size() == 0)), 954 "unexpected PerfMemory region size"); 955 956 fd = create_sharedmem_resources(dirname, short_filename, size); 957 958 FREE_C_HEAP_ARRAY(char, user_name); 959 FREE_C_HEAP_ARRAY(char, dirname); 960 961 if (fd == -1) { 962 FREE_C_HEAP_ARRAY(char, filename); 963 return NULL; 964 } 965 966 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); 967 968 result = ::close(fd); 969 assert(result != OS_ERR, "could not close file"); 970 971 if (mapAddress == MAP_FAILED) { 972 if (PrintMiscellaneous && Verbose) { 973 warning("mmap failed - %s\n", strerror(errno)); 974 } 975 remove_file(filename); 976 FREE_C_HEAP_ARRAY(char, filename); 977 return NULL; 978 } 979 980 // save the file name for use in delete_shared_memory() 981 backing_store_file_name = filename; 982 983 // clear the shared memory region 984 (void)::memset((void*) mapAddress, 0, size); 985 986 // it does not go through os api, the operation has to record from here 987 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal); 988 989 return mapAddress; 990} 991 992// release a named shared memory region 993// 994static void unmap_shared(char* addr, size_t bytes) { 995 os::release_memory(addr, bytes); 996} 997 998// create the PerfData memory region in shared memory. 999// 1000static char* create_shared_memory(size_t size) { 1001 1002 // create the shared memory region. 1003 return mmap_create_shared(size); 1004} 1005 1006// delete the shared PerfData memory region 1007// 1008static void delete_shared_memory(char* addr, size_t size) { 1009 1010 // cleanup the persistent shared memory resources. since DestroyJavaVM does 1011 // not support unloading of the JVM, unmapping of the memory resource is 1012 // not performed. The memory will be reclaimed by the OS upon termination of 1013 // the process. The backing store file is deleted from the file system. 1014 1015 assert(!PerfDisableSharedMem, "shouldn't be here"); 1016 1017 if (backing_store_file_name != NULL) { 1018 remove_file(backing_store_file_name); 1019 // Don't.. Free heap memory could deadlock os::abort() if it is called 1020 // from signal handler. OS will reclaim the heap memory. 1021 // FREE_C_HEAP_ARRAY(char, backing_store_file_name); 1022 backing_store_file_name = NULL; 1023 } 1024} 1025 1026// return the size of the file for the given file descriptor 1027// or 0 if it is not a valid size for a shared memory file 1028// 1029static size_t sharedmem_filesize(int fd, TRAPS) { 1030 1031 struct stat statbuf; 1032 int result; 1033 1034 RESTARTABLE(::fstat(fd, &statbuf), result); 1035 if (result == OS_ERR) { 1036 if (PrintMiscellaneous && Verbose) { 1037 warning("fstat failed: %s\n", strerror(errno)); 1038 } 1039 THROW_MSG_0(vmSymbols::java_io_IOException(), 1040 "Could not determine PerfMemory size"); 1041 } 1042 1043 if ((statbuf.st_size == 0) || 1044 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) { 1045 THROW_MSG_0(vmSymbols::java_lang_Exception(), 1046 "Invalid PerfMemory size"); 1047 } 1048 1049 return (size_t)statbuf.st_size; 1050} 1051 1052// attach to a named shared memory region. 1053// 1054static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) { 1055 1056 char* mapAddress; 1057 int result; 1058 int fd; 1059 size_t size = 0; 1060 const char* luser = NULL; 1061 1062 int mmap_prot; 1063 int file_flags; 1064 1065 ResourceMark rm; 1066 1067 // map the high level access mode to the appropriate permission 1068 // constructs for the file and the shared memory mapping. 1069 if (mode == PerfMemory::PERF_MODE_RO) { 1070 mmap_prot = PROT_READ; 1071 file_flags = O_RDONLY | O_NOFOLLOW; 1072 } 1073 else if (mode == PerfMemory::PERF_MODE_RW) { 1074#ifdef LATER 1075 mmap_prot = PROT_READ | PROT_WRITE; 1076 file_flags = O_RDWR | O_NOFOLLOW; 1077#else 1078 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1079 "Unsupported access mode"); 1080#endif 1081 } 1082 else { 1083 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1084 "Illegal access mode"); 1085 } 1086 1087 if (user == NULL || strlen(user) == 0) { 1088 luser = get_user_name(vmid, CHECK); 1089 } 1090 else { 1091 luser = user; 1092 } 1093 1094 if (luser == NULL) { 1095 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1096 "Could not map vmid to user Name"); 1097 } 1098 1099 char* dirname = get_user_tmp_dir(luser); 1100 1101 // since we don't follow symbolic links when creating the backing 1102 // store file, we don't follow them when attaching either. 1103 // 1104 if (!is_directory_secure(dirname)) { 1105 FREE_C_HEAP_ARRAY(char, dirname); 1106 if (luser != user) { 1107 FREE_C_HEAP_ARRAY(char, luser); 1108 } 1109 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 1110 "Process not found"); 1111 } 1112 1113 char* filename = get_sharedmem_filename(dirname, vmid); 1114 1115 // copy heap memory to resource memory. the open_sharedmem_file 1116 // method below need to use the filename, but could throw an 1117 // exception. using a resource array prevents the leak that 1118 // would otherwise occur. 1119 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1); 1120 strcpy(rfilename, filename); 1121 1122 // free the c heap resources that are no longer needed 1123 if (luser != user) FREE_C_HEAP_ARRAY(char, luser); 1124 FREE_C_HEAP_ARRAY(char, dirname); 1125 FREE_C_HEAP_ARRAY(char, filename); 1126 1127 // open the shared memory file for the give vmid 1128 fd = open_sharedmem_file(rfilename, file_flags, THREAD); 1129 1130 if (fd == OS_ERR) { 1131 return; 1132 } 1133 1134 if (HAS_PENDING_EXCEPTION) { 1135 ::close(fd); 1136 return; 1137 } 1138 1139 if (*sizep == 0) { 1140 size = sharedmem_filesize(fd, CHECK); 1141 } else { 1142 size = *sizep; 1143 } 1144 1145 assert(size > 0, "unexpected size <= 0"); 1146 1147 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0); 1148 1149 result = ::close(fd); 1150 assert(result != OS_ERR, "could not close file"); 1151 1152 if (mapAddress == MAP_FAILED) { 1153 if (PrintMiscellaneous && Verbose) { 1154 warning("mmap failed: %s\n", strerror(errno)); 1155 } 1156 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(), 1157 "Could not map PerfMemory"); 1158 } 1159 1160 // it does not go through os api, the operation has to record from here 1161 MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal); 1162 1163 *addr = mapAddress; 1164 *sizep = size; 1165 1166 if (PerfTraceMemOps) { 1167 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at " 1168 INTPTR_FORMAT "\n", size, vmid, p2i((void*)mapAddress)); 1169 } 1170} 1171 1172 1173 1174 1175// create the PerfData memory region 1176// 1177// This method creates the memory region used to store performance 1178// data for the JVM. The memory may be created in standard or 1179// shared memory. 1180// 1181void PerfMemory::create_memory_region(size_t size) { 1182 1183 if (PerfDisableSharedMem) { 1184 // do not share the memory for the performance data. 1185 _start = create_standard_memory(size); 1186 } 1187 else { 1188 _start = create_shared_memory(size); 1189 if (_start == NULL) { 1190 1191 // creation of the shared memory region failed, attempt 1192 // to create a contiguous, non-shared memory region instead. 1193 // 1194 if (PrintMiscellaneous && Verbose) { 1195 warning("Reverting to non-shared PerfMemory region.\n"); 1196 } 1197 PerfDisableSharedMem = true; 1198 _start = create_standard_memory(size); 1199 } 1200 } 1201 1202 if (_start != NULL) _capacity = size; 1203 1204} 1205 1206// delete the PerfData memory region 1207// 1208// This method deletes the memory region used to store performance 1209// data for the JVM. The memory region indicated by the <address, size> 1210// tuple will be inaccessible after a call to this method. 1211// 1212void PerfMemory::delete_memory_region() { 1213 1214 assert((start() != NULL && capacity() > 0), "verify proper state"); 1215 1216 // If user specifies PerfDataSaveFile, it will save the performance data 1217 // to the specified file name no matter whether PerfDataSaveToFile is specified 1218 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag 1219 // -XX:+PerfDataSaveToFile. 1220 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) { 1221 save_memory_to_file(start(), capacity()); 1222 } 1223 1224 if (PerfDisableSharedMem) { 1225 delete_standard_memory(start(), capacity()); 1226 } 1227 else { 1228 delete_shared_memory(start(), capacity()); 1229 } 1230} 1231 1232// attach to the PerfData memory region for another JVM 1233// 1234// This method returns an <address, size> tuple that points to 1235// a memory buffer that is kept reasonably synchronized with 1236// the PerfData memory region for the indicated JVM. This 1237// buffer may be kept in synchronization via shared memory 1238// or some other mechanism that keeps the buffer updated. 1239// 1240// If the JVM chooses not to support the attachability feature, 1241// this method should throw an UnsupportedOperation exception. 1242// 1243// This implementation utilizes named shared memory to map 1244// the indicated process's PerfData memory region into this JVMs 1245// address space. 1246// 1247void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) { 1248 1249 if (vmid == 0 || vmid == os::current_process_id()) { 1250 *addrp = start(); 1251 *sizep = capacity(); 1252 return; 1253 } 1254 1255 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK); 1256} 1257 1258// detach from the PerfData memory region of another JVM 1259// 1260// This method detaches the PerfData memory region of another 1261// JVM, specified as an <address, size> tuple of a buffer 1262// in this process's address space. This method may perform 1263// arbitrary actions to accomplish the detachment. The memory 1264// region specified by <address, size> will be inaccessible after 1265// a call to this method. 1266// 1267// If the JVM chooses not to support the attachability feature, 1268// this method should throw an UnsupportedOperation exception. 1269// 1270// This implementation utilizes named shared memory to detach 1271// the indicated process's PerfData memory region from this 1272// process's address space. 1273// 1274void PerfMemory::detach(char* addr, size_t bytes, TRAPS) { 1275 1276 assert(addr != 0, "address sanity check"); 1277 assert(bytes > 0, "capacity sanity check"); 1278 1279 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) { 1280 // prevent accidental detachment of this process's PerfMemory region 1281 return; 1282 } 1283 1284 unmap_shared(addr, bytes); 1285} 1286