perfMemory_linux.cpp revision 0:a61af66fc99e
1/* 2 * Copyright 2001-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25# include "incls/_precompiled.incl" 26# include "incls/_perfMemory_linux.cpp.incl" 27 28// put OS-includes here 29# include <sys/types.h> 30# include <sys/mman.h> 31# include <errno.h> 32# include <stdio.h> 33# include <unistd.h> 34# include <sys/stat.h> 35# include <signal.h> 36# include <pwd.h> 37 38static char* backing_store_file_name = NULL; // name of the backing store 39 // file, if successfully created. 40 41// Standard Memory Implementation Details 42 43// create the PerfData memory region in standard memory. 44// 45static char* create_standard_memory(size_t size) { 46 47 // allocate an aligned chuck of memory 48 char* mapAddress = os::reserve_memory(size); 49 50 if (mapAddress == NULL) { 51 return NULL; 52 } 53 54 // commit memory 55 if (!os::commit_memory(mapAddress, size)) { 56 if (PrintMiscellaneous && Verbose) { 57 warning("Could not commit PerfData memory\n"); 58 } 59 os::release_memory(mapAddress, size); 60 return NULL; 61 } 62 63 return mapAddress; 64} 65 66// delete the PerfData memory region 67// 68static void delete_standard_memory(char* addr, size_t size) { 69 70 // there are no persistent external resources to cleanup for standard 71 // memory. since DestroyJavaVM does not support unloading of the JVM, 72 // cleanup of the memory resource is not performed. The memory will be 73 // reclaimed by the OS upon termination of the process. 74 // 75 return; 76} 77 78// save the specified memory region to the given file 79// 80// Note: this function might be called from signal handler (by os::abort()), 81// don't allocate heap memory. 82// 83static void save_memory_to_file(char* addr, size_t size) { 84 85 const char* destfile = PerfMemory::get_perfdata_file_path(); 86 assert(destfile[0] != '\0', "invalid PerfData file path"); 87 88 int result; 89 90 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE), 91 result);; 92 if (result == OS_ERR) { 93 if (PrintMiscellaneous && Verbose) { 94 warning("Could not create Perfdata save file: %s: %s\n", 95 destfile, strerror(errno)); 96 } 97 } else { 98 int fd = result; 99 100 for (size_t remaining = size; remaining > 0;) { 101 102 RESTARTABLE(::write(fd, addr, remaining), result); 103 if (result == OS_ERR) { 104 if (PrintMiscellaneous && Verbose) { 105 warning("Could not write Perfdata save file: %s: %s\n", 106 destfile, strerror(errno)); 107 } 108 break; 109 } 110 111 remaining -= (size_t)result; 112 addr += result; 113 } 114 115 RESTARTABLE(::close(fd), result); 116 if (PrintMiscellaneous && Verbose) { 117 if (result == OS_ERR) { 118 warning("Could not close %s: %s\n", destfile, strerror(errno)); 119 } 120 } 121 } 122 FREE_C_HEAP_ARRAY(char, destfile); 123} 124 125 126// Shared Memory Implementation Details 127 128// Note: the solaris and linux shared memory implementation uses the mmap 129// interface with a backing store file to implement named shared memory. 130// Using the file system as the name space for shared memory allows a 131// common name space to be supported across a variety of platforms. It 132// also provides a name space that Java applications can deal with through 133// simple file apis. 134// 135// The solaris and linux implementations store the backing store file in 136// a user specific temporary directory located in the /tmp file system, 137// which is always a local file system and is sometimes a RAM based file 138// system. 139 140// return the user specific temporary directory name. 141// 142// the caller is expected to free the allocated memory. 143// 144static char* get_user_tmp_dir(const char* user) { 145 146 const char* tmpdir = os::get_temp_directory(); 147 const char* perfdir = PERFDATA_NAME; 148 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 2; 149 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes); 150 151 // construct the path name to user specific tmp directory 152 snprintf(dirname, nbytes, "%s%s_%s", tmpdir, perfdir, user); 153 154 return dirname; 155} 156 157// convert the given file name into a process id. if the file 158// does not meet the file naming constraints, return 0. 159// 160static pid_t filename_to_pid(const char* filename) { 161 162 // a filename that doesn't begin with a digit is not a 163 // candidate for conversion. 164 // 165 if (!isdigit(*filename)) { 166 return 0; 167 } 168 169 // check if file name can be converted to an integer without 170 // any leftover characters. 171 // 172 char* remainder = NULL; 173 errno = 0; 174 pid_t pid = (pid_t)strtol(filename, &remainder, 10); 175 176 if (errno != 0) { 177 return 0; 178 } 179 180 // check for left over characters. If any, then the filename is 181 // not a candidate for conversion. 182 // 183 if (remainder != NULL && *remainder != '\0') { 184 return 0; 185 } 186 187 // successful conversion, return the pid 188 return pid; 189} 190 191 192// check if the given path is considered a secure directory for 193// the backing store files. Returns true if the directory exists 194// and is considered a secure location. Returns false if the path 195// is a symbolic link or if an error occured. 196// 197static bool is_directory_secure(const char* path) { 198 struct stat statbuf; 199 int result = 0; 200 201 RESTARTABLE(::lstat(path, &statbuf), result); 202 if (result == OS_ERR) { 203 return false; 204 } 205 206 // the path exists, now check it's mode 207 if (S_ISLNK(statbuf.st_mode) || !S_ISDIR(statbuf.st_mode)) { 208 // the path represents a link or some non-directory file type, 209 // which is not what we expected. declare it insecure. 210 // 211 return false; 212 } 213 else { 214 // we have an existing directory, check if the permissions are safe. 215 // 216 if ((statbuf.st_mode & (S_IWGRP|S_IWOTH)) != 0) { 217 // the directory is open for writing and could be subjected 218 // to a symlnk attack. declare it insecure. 219 // 220 return false; 221 } 222 } 223 return true; 224} 225 226 227// return the user name for the given user id 228// 229// the caller is expected to free the allocated memory. 230// 231static char* get_user_name(uid_t uid) { 232 233 struct passwd pwent; 234 235 // determine the max pwbuf size from sysconf, and hardcode 236 // a default if this not available through sysconf. 237 // 238 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); 239 if (bufsize == -1) 240 bufsize = 1024; 241 242 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize); 243 244 // POSIX interface to getpwuid_r is used on LINUX 245 struct passwd* p; 246 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p); 247 248 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') { 249 if (PrintMiscellaneous && Verbose) { 250 if (result != 0) { 251 warning("Could not retrieve passwd entry: %s\n", 252 strerror(result)); 253 } 254 else if (p == NULL) { 255 // this check is added to protect against an observed problem 256 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0, 257 // indicating success, but has p == NULL. This was observed when 258 // inserting a file descriptor exhaustion fault prior to the call 259 // getpwuid_r() call. In this case, error is set to the appropriate 260 // error condition, but this is undocumented behavior. This check 261 // is safe under any condition, but the use of errno in the output 262 // message may result in an erroneous message. 263 // Bug Id 89052 was opened with RedHat. 264 // 265 warning("Could not retrieve passwd entry: %s\n", 266 strerror(errno)); 267 } 268 else { 269 warning("Could not determine user name: %s\n", 270 p->pw_name == NULL ? "pw_name = NULL" : 271 "pw_name zero length"); 272 } 273 } 274 FREE_C_HEAP_ARRAY(char, pwbuf); 275 return NULL; 276 } 277 278 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1); 279 strcpy(user_name, p->pw_name); 280 281 FREE_C_HEAP_ARRAY(char, pwbuf); 282 return user_name; 283} 284 285// return the name of the user that owns the process identified by vmid. 286// 287// This method uses a slow directory search algorithm to find the backing 288// store file for the specified vmid and returns the user name, as determined 289// by the user name suffix of the hsperfdata_<username> directory name. 290// 291// the caller is expected to free the allocated memory. 292// 293static char* get_user_name_slow(int vmid, TRAPS) { 294 295 // short circuit the directory search if the process doesn't even exist. 296 if (kill(vmid, 0) == OS_ERR) { 297 if (errno == ESRCH) { 298 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), 299 "Process not found"); 300 } 301 else /* EPERM */ { 302 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno)); 303 } 304 } 305 306 // directory search 307 char* oldest_user = NULL; 308 time_t oldest_ctime = 0; 309 310 const char* tmpdirname = os::get_temp_directory(); 311 312 DIR* tmpdirp = os::opendir(tmpdirname); 313 314 if (tmpdirp == NULL) { 315 return NULL; 316 } 317 318 // for each entry in the directory that matches the pattern hsperfdata_*, 319 // open the directory and check if the file for the given vmid exists. 320 // The file with the expected name and the latest creation date is used 321 // to determine the user name for the process id. 322 // 323 struct dirent* dentry; 324 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname)); 325 errno = 0; 326 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) { 327 328 // check if the directory entry is a hsperfdata file 329 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) { 330 continue; 331 } 332 333 char* usrdir_name = NEW_C_HEAP_ARRAY(char, 334 strlen(tmpdirname) + strlen(dentry->d_name) + 1); 335 strcpy(usrdir_name, tmpdirname); 336 strcat(usrdir_name, dentry->d_name); 337 338 DIR* subdirp = os::opendir(usrdir_name); 339 340 if (subdirp == NULL) { 341 FREE_C_HEAP_ARRAY(char, usrdir_name); 342 continue; 343 } 344 345 // Since we don't create the backing store files in directories 346 // pointed to by symbolic links, we also don't follow them when 347 // looking for the files. We check for a symbolic link after the 348 // call to opendir in order to eliminate a small window where the 349 // symlink can be exploited. 350 // 351 if (!is_directory_secure(usrdir_name)) { 352 FREE_C_HEAP_ARRAY(char, usrdir_name); 353 os::closedir(subdirp); 354 continue; 355 } 356 357 struct dirent* udentry; 358 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name)); 359 errno = 0; 360 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) { 361 362 if (filename_to_pid(udentry->d_name) == vmid) { 363 struct stat statbuf; 364 int result; 365 366 char* filename = NEW_C_HEAP_ARRAY(char, 367 strlen(usrdir_name) + strlen(udentry->d_name) + 2); 368 369 strcpy(filename, usrdir_name); 370 strcat(filename, "/"); 371 strcat(filename, udentry->d_name); 372 373 // don't follow symbolic links for the file 374 RESTARTABLE(::lstat(filename, &statbuf), result); 375 if (result == OS_ERR) { 376 FREE_C_HEAP_ARRAY(char, filename); 377 continue; 378 } 379 380 // skip over files that are not regular files. 381 if (!S_ISREG(statbuf.st_mode)) { 382 FREE_C_HEAP_ARRAY(char, filename); 383 continue; 384 } 385 386 // compare and save filename with latest creation time 387 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) { 388 389 if (statbuf.st_ctime > oldest_ctime) { 390 char* user = strchr(dentry->d_name, '_') + 1; 391 392 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user); 393 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1); 394 395 strcpy(oldest_user, user); 396 oldest_ctime = statbuf.st_ctime; 397 } 398 } 399 400 FREE_C_HEAP_ARRAY(char, filename); 401 } 402 } 403 os::closedir(subdirp); 404 FREE_C_HEAP_ARRAY(char, udbuf); 405 FREE_C_HEAP_ARRAY(char, usrdir_name); 406 } 407 os::closedir(tmpdirp); 408 FREE_C_HEAP_ARRAY(char, tdbuf); 409 410 return(oldest_user); 411} 412 413// return the name of the user that owns the JVM indicated by the given vmid. 414// 415static char* get_user_name(int vmid, TRAPS) { 416 return get_user_name_slow(vmid, CHECK_NULL); 417} 418 419// return the file name of the backing store file for the named 420// shared memory region for the given user name and vmid. 421// 422// the caller is expected to free the allocated memory. 423// 424static char* get_sharedmem_filename(const char* dirname, int vmid) { 425 426 // add 2 for the file separator and a null terminator. 427 size_t nbytes = strlen(dirname) + UINT_CHARS + 2; 428 429 char* name = NEW_C_HEAP_ARRAY(char, nbytes); 430 snprintf(name, nbytes, "%s/%d", dirname, vmid); 431 432 return name; 433} 434 435 436// remove file 437// 438// this method removes the file specified by the given path 439// 440static void remove_file(const char* path) { 441 442 int result; 443 444 // if the file is a directory, the following unlink will fail. since 445 // we don't expect to find directories in the user temp directory, we 446 // won't try to handle this situation. even if accidentially or 447 // maliciously planted, the directory's presence won't hurt anything. 448 // 449 RESTARTABLE(::unlink(path), result); 450 if (PrintMiscellaneous && Verbose && result == OS_ERR) { 451 if (errno != ENOENT) { 452 warning("Could not unlink shared memory backing" 453 " store file %s : %s\n", path, strerror(errno)); 454 } 455 } 456} 457 458 459// remove file 460// 461// this method removes the file with the given file name in the 462// named directory. 463// 464static void remove_file(const char* dirname, const char* filename) { 465 466 size_t nbytes = strlen(dirname) + strlen(filename) + 2; 467 char* path = NEW_C_HEAP_ARRAY(char, nbytes); 468 469 strcpy(path, dirname); 470 strcat(path, "/"); 471 strcat(path, filename); 472 473 remove_file(path); 474 475 FREE_C_HEAP_ARRAY(char, path); 476} 477 478 479// cleanup stale shared memory resources 480// 481// This method attempts to remove all stale shared memory files in 482// the named user temporary directory. It scans the named directory 483// for files matching the pattern ^$[0-9]*$. For each file found, the 484// process id is extracted from the file name and a test is run to 485// determine if the process is alive. If the process is not alive, 486// any stale file resources are removed. 487// 488static void cleanup_sharedmem_resources(const char* dirname) { 489 490 // open the user temp directory 491 DIR* dirp = os::opendir(dirname); 492 493 if (dirp == NULL) { 494 // directory doesn't exist, so there is nothing to cleanup 495 return; 496 } 497 498 if (!is_directory_secure(dirname)) { 499 // the directory is not a secure directory 500 return; 501 } 502 503 // for each entry in the directory that matches the expected file 504 // name pattern, determine if the file resources are stale and if 505 // so, remove the file resources. Note, instrumented HotSpot processes 506 // for this user may start and/or terminate during this search and 507 // remove or create new files in this directory. The behavior of this 508 // loop under these conditions is dependent upon the implementation of 509 // opendir/readdir. 510 // 511 struct dirent* entry; 512 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname)); 513 errno = 0; 514 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) { 515 516 pid_t pid = filename_to_pid(entry->d_name); 517 518 if (pid == 0) { 519 520 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) { 521 522 // attempt to remove all unexpected files, except "." and ".." 523 remove_file(dirname, entry->d_name); 524 } 525 526 errno = 0; 527 continue; 528 } 529 530 // we now have a file name that converts to a valid integer 531 // that could represent a process id . if this process id 532 // matches the current process id or the process is not running, 533 // then remove the stale file resources. 534 // 535 // process liveness is detected by sending signal number 0 to 536 // the process id (see kill(2)). if kill determines that the 537 // process does not exist, then the file resources are removed. 538 // if kill determines that that we don't have permission to 539 // signal the process, then the file resources are assumed to 540 // be stale and are removed because the resources for such a 541 // process should be in a different user specific directory. 542 // 543 if ((pid == os::current_process_id()) || 544 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) { 545 546 remove_file(dirname, entry->d_name); 547 } 548 errno = 0; 549 } 550 os::closedir(dirp); 551 FREE_C_HEAP_ARRAY(char, dbuf); 552} 553 554// make the user specific temporary directory. Returns true if 555// the directory exists and is secure upon return. Returns false 556// if the directory exists but is either a symlink, is otherwise 557// insecure, or if an error occurred. 558// 559static bool make_user_tmp_dir(const char* dirname) { 560 561 // create the directory with 0755 permissions. note that the directory 562 // will be owned by euid::egid, which may not be the same as uid::gid. 563 // 564 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) { 565 if (errno == EEXIST) { 566 // The directory already exists and was probably created by another 567 // JVM instance. However, this could also be the result of a 568 // deliberate symlink. Verify that the existing directory is safe. 569 // 570 if (!is_directory_secure(dirname)) { 571 // directory is not secure 572 if (PrintMiscellaneous && Verbose) { 573 warning("%s directory is insecure\n", dirname); 574 } 575 return false; 576 } 577 } 578 else { 579 // we encountered some other failure while attempting 580 // to create the directory 581 // 582 if (PrintMiscellaneous && Verbose) { 583 warning("could not create directory %s: %s\n", 584 dirname, strerror(errno)); 585 } 586 return false; 587 } 588 } 589 return true; 590} 591 592// create the shared memory file resources 593// 594// This method creates the shared memory file with the given size 595// This method also creates the user specific temporary directory, if 596// it does not yet exist. 597// 598static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) { 599 600 // make the user temporary directory 601 if (!make_user_tmp_dir(dirname)) { 602 // could not make/find the directory or the found directory 603 // was not secure 604 return -1; 605 } 606 607 int result; 608 609 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_TRUNC, S_IREAD|S_IWRITE), result); 610 if (result == OS_ERR) { 611 if (PrintMiscellaneous && Verbose) { 612 warning("could not create file %s: %s\n", filename, strerror(errno)); 613 } 614 return -1; 615 } 616 617 // save the file descriptor 618 int fd = result; 619 620 // set the file size 621 RESTARTABLE(::ftruncate(fd, (off_t)size), result); 622 if (result == OS_ERR) { 623 if (PrintMiscellaneous && Verbose) { 624 warning("could not set shared memory file size: %s\n", strerror(errno)); 625 } 626 RESTARTABLE(::close(fd), result); 627 return -1; 628 } 629 630 return fd; 631} 632 633// open the shared memory file for the given user and vmid. returns 634// the file descriptor for the open file or -1 if the file could not 635// be opened. 636// 637static int open_sharedmem_file(const char* filename, int oflags, TRAPS) { 638 639 // open the file 640 int result; 641 RESTARTABLE(::open(filename, oflags), result); 642 if (result == OS_ERR) { 643 if (errno == ENOENT) { 644 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), 645 "Process not found"); 646 } 647 else if (errno == EACCES) { 648 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), 649 "Permission denied"); 650 } 651 else { 652 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno)); 653 } 654 } 655 656 return result; 657} 658 659// create a named shared memory region. returns the address of the 660// memory region on success or NULL on failure. A return value of 661// NULL will ultimately disable the shared memory feature. 662// 663// On Solaris and Linux, the name space for shared memory objects 664// is the file system name space. 665// 666// A monitoring application attaching to a JVM does not need to know 667// the file system name of the shared memory object. However, it may 668// be convenient for applications to discover the existence of newly 669// created and terminating JVMs by watching the file system name space 670// for files being created or removed. 671// 672static char* mmap_create_shared(size_t size) { 673 674 int result; 675 int fd; 676 char* mapAddress; 677 678 int vmid = os::current_process_id(); 679 680 char* user_name = get_user_name(geteuid()); 681 682 if (user_name == NULL) 683 return NULL; 684 685 char* dirname = get_user_tmp_dir(user_name); 686 char* filename = get_sharedmem_filename(dirname, vmid); 687 688 // cleanup any stale shared memory files 689 cleanup_sharedmem_resources(dirname); 690 691 assert(((size > 0) && (size % os::vm_page_size() == 0)), 692 "unexpected PerfMemory region size"); 693 694 fd = create_sharedmem_resources(dirname, filename, size); 695 696 FREE_C_HEAP_ARRAY(char, user_name); 697 FREE_C_HEAP_ARRAY(char, dirname); 698 699 if (fd == -1) { 700 FREE_C_HEAP_ARRAY(char, filename); 701 return NULL; 702 } 703 704 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); 705 706 // attempt to close the file - restart it if it was interrupted, 707 // but ignore other failures 708 RESTARTABLE(::close(fd), result); 709 assert(result != OS_ERR, "could not close file"); 710 711 if (mapAddress == MAP_FAILED) { 712 if (PrintMiscellaneous && Verbose) { 713 warning("mmap failed - %s\n", strerror(errno)); 714 } 715 remove_file(filename); 716 FREE_C_HEAP_ARRAY(char, filename); 717 return NULL; 718 } 719 720 // save the file name for use in delete_shared_memory() 721 backing_store_file_name = filename; 722 723 // clear the shared memory region 724 (void)::memset((void*) mapAddress, 0, size); 725 726 return mapAddress; 727} 728 729// release a named shared memory region 730// 731static void unmap_shared(char* addr, size_t bytes) { 732 os::release_memory(addr, bytes); 733} 734 735// create the PerfData memory region in shared memory. 736// 737static char* create_shared_memory(size_t size) { 738 739 // create the shared memory region. 740 return mmap_create_shared(size); 741} 742 743// delete the shared PerfData memory region 744// 745static void delete_shared_memory(char* addr, size_t size) { 746 747 // cleanup the persistent shared memory resources. since DestroyJavaVM does 748 // not support unloading of the JVM, unmapping of the memory resource is 749 // not performed. The memory will be reclaimed by the OS upon termination of 750 // the process. The backing store file is deleted from the file system. 751 752 assert(!PerfDisableSharedMem, "shouldn't be here"); 753 754 if (backing_store_file_name != NULL) { 755 remove_file(backing_store_file_name); 756 // Don't.. Free heap memory could deadlock os::abort() if it is called 757 // from signal handler. OS will reclaim the heap memory. 758 // FREE_C_HEAP_ARRAY(char, backing_store_file_name); 759 backing_store_file_name = NULL; 760 } 761} 762 763// return the size of the file for the given file descriptor 764// or 0 if it is not a valid size for a shared memory file 765// 766static size_t sharedmem_filesize(int fd, TRAPS) { 767 768 struct stat statbuf; 769 int result; 770 771 RESTARTABLE(::fstat(fd, &statbuf), result); 772 if (result == OS_ERR) { 773 if (PrintMiscellaneous && Verbose) { 774 warning("fstat failed: %s\n", strerror(errno)); 775 } 776 THROW_MSG_0(vmSymbols::java_io_IOException(), 777 "Could not determine PerfMemory size"); 778 } 779 780 if ((statbuf.st_size == 0) || 781 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) { 782 THROW_MSG_0(vmSymbols::java_lang_Exception(), 783 "Invalid PerfMemory size"); 784 } 785 786 return (size_t)statbuf.st_size; 787} 788 789// attach to a named shared memory region. 790// 791static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) { 792 793 char* mapAddress; 794 int result; 795 int fd; 796 size_t size; 797 const char* luser = NULL; 798 799 int mmap_prot; 800 int file_flags; 801 802 ResourceMark rm; 803 804 // map the high level access mode to the appropriate permission 805 // constructs for the file and the shared memory mapping. 806 if (mode == PerfMemory::PERF_MODE_RO) { 807 mmap_prot = PROT_READ; 808 file_flags = O_RDONLY; 809 } 810 else if (mode == PerfMemory::PERF_MODE_RW) { 811#ifdef LATER 812 mmap_prot = PROT_READ | PROT_WRITE; 813 file_flags = O_RDWR; 814#else 815 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 816 "Unsupported access mode"); 817#endif 818 } 819 else { 820 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 821 "Illegal access mode"); 822 } 823 824 if (user == NULL || strlen(user) == 0) { 825 luser = get_user_name(vmid, CHECK); 826 } 827 else { 828 luser = user; 829 } 830 831 if (luser == NULL) { 832 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 833 "Could not map vmid to user Name"); 834 } 835 836 char* dirname = get_user_tmp_dir(luser); 837 838 // since we don't follow symbolic links when creating the backing 839 // store file, we don't follow them when attaching either. 840 // 841 if (!is_directory_secure(dirname)) { 842 FREE_C_HEAP_ARRAY(char, dirname); 843 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), 844 "Process not found"); 845 } 846 847 char* filename = get_sharedmem_filename(dirname, vmid); 848 849 // copy heap memory to resource memory. the open_sharedmem_file 850 // method below need to use the filename, but could throw an 851 // exception. using a resource array prevents the leak that 852 // would otherwise occur. 853 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1); 854 strcpy(rfilename, filename); 855 856 // free the c heap resources that are no longer needed 857 if (luser != user) FREE_C_HEAP_ARRAY(char, luser); 858 FREE_C_HEAP_ARRAY(char, dirname); 859 FREE_C_HEAP_ARRAY(char, filename); 860 861 // open the shared memory file for the give vmid 862 fd = open_sharedmem_file(rfilename, file_flags, CHECK); 863 assert(fd != OS_ERR, "unexpected value"); 864 865 if (*sizep == 0) { 866 size = sharedmem_filesize(fd, CHECK); 867 assert(size != 0, "unexpected size"); 868 } 869 870 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0); 871 872 // attempt to close the file - restart if it gets interrupted, 873 // but ignore other failures 874 RESTARTABLE(::close(fd), result); 875 assert(result != OS_ERR, "could not close file"); 876 877 if (mapAddress == MAP_FAILED) { 878 if (PrintMiscellaneous && Verbose) { 879 warning("mmap failed: %s\n", strerror(errno)); 880 } 881 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(), 882 "Could not map PerfMemory"); 883 } 884 885 *addr = mapAddress; 886 *sizep = size; 887 888 if (PerfTraceMemOps) { 889 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at " 890 INTPTR_FORMAT "\n", size, vmid, (void*)mapAddress); 891 } 892} 893 894 895 896 897// create the PerfData memory region 898// 899// This method creates the memory region used to store performance 900// data for the JVM. The memory may be created in standard or 901// shared memory. 902// 903void PerfMemory::create_memory_region(size_t size) { 904 905 if (PerfDisableSharedMem) { 906 // do not share the memory for the performance data. 907 _start = create_standard_memory(size); 908 } 909 else { 910 _start = create_shared_memory(size); 911 if (_start == NULL) { 912 913 // creation of the shared memory region failed, attempt 914 // to create a contiguous, non-shared memory region instead. 915 // 916 if (PrintMiscellaneous && Verbose) { 917 warning("Reverting to non-shared PerfMemory region.\n"); 918 } 919 PerfDisableSharedMem = true; 920 _start = create_standard_memory(size); 921 } 922 } 923 924 if (_start != NULL) _capacity = size; 925 926} 927 928// delete the PerfData memory region 929// 930// This method deletes the memory region used to store performance 931// data for the JVM. The memory region indicated by the <address, size> 932// tuple will be inaccessible after a call to this method. 933// 934void PerfMemory::delete_memory_region() { 935 936 assert((start() != NULL && capacity() > 0), "verify proper state"); 937 938 // If user specifies PerfDataSaveFile, it will save the performance data 939 // to the specified file name no matter whether PerfDataSaveToFile is specified 940 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag 941 // -XX:+PerfDataSaveToFile. 942 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) { 943 save_memory_to_file(start(), capacity()); 944 } 945 946 if (PerfDisableSharedMem) { 947 delete_standard_memory(start(), capacity()); 948 } 949 else { 950 delete_shared_memory(start(), capacity()); 951 } 952} 953 954// attach to the PerfData memory region for another JVM 955// 956// This method returns an <address, size> tuple that points to 957// a memory buffer that is kept reasonably synchronized with 958// the PerfData memory region for the indicated JVM. This 959// buffer may be kept in synchronization via shared memory 960// or some other mechanism that keeps the buffer updated. 961// 962// If the JVM chooses not to support the attachability feature, 963// this method should throw an UnsupportedOperation exception. 964// 965// This implementation utilizes named shared memory to map 966// the indicated process's PerfData memory region into this JVMs 967// address space. 968// 969void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) { 970 971 if (vmid == 0 || vmid == os::current_process_id()) { 972 *addrp = start(); 973 *sizep = capacity(); 974 return; 975 } 976 977 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK); 978} 979 980// detach from the PerfData memory region of another JVM 981// 982// This method detaches the PerfData memory region of another 983// JVM, specified as an <address, size> tuple of a buffer 984// in this process's address space. This method may perform 985// arbitrary actions to accomplish the detachment. The memory 986// region specified by <address, size> will be inaccessible after 987// a call to this method. 988// 989// If the JVM chooses not to support the attachability feature, 990// this method should throw an UnsupportedOperation exception. 991// 992// This implementation utilizes named shared memory to detach 993// the indicated process's PerfData memory region from this 994// process's address space. 995// 996void PerfMemory::detach(char* addr, size_t bytes, TRAPS) { 997 998 assert(addr != 0, "address sanity check"); 999 assert(bytes > 0, "capacity sanity check"); 1000 1001 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) { 1002 // prevent accidental detachment of this process's PerfMemory region 1003 return; 1004 } 1005 1006 unmap_shared(addr, bytes); 1007} 1008 1009char* PerfMemory::backing_store_filename() { 1010 return backing_store_file_name; 1011} 1012