Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_perfMemory_windows.cpp.incl"

 #include <windows.h>

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <errno.h>

 #include <lmcons.h>

 typedef BOOL (WINAPI *SetSecurityDescriptorControlFnPtr)(

    IN PSECURITY_DESCRIPTOR pSecurityDescriptor,

    IN SECURITY_DESCRIPTOR_CONTROL ControlBitsOfInterest,

    IN SECURITY_DESCRIPTOR_CONTROL ControlBitsToSet);

 // Standard Memory Implementation Details

 // create the PerfData memory region in standard memory.

 //

 static char* create_standard_memory(size_t size) {

   // allocate an aligned chuck of memory

   char* mapAddress = os::reserve_memory(size);

   if (mapAddress == NULL) {

     return NULL;

   }

   // commit memory

   if (!os::commit_memory(mapAddress, size)) {

     if (PrintMiscellaneous && Verbose) {

       warning("Could not commit PerfData memory\n");

     }

     os::release_memory(mapAddress, size);

     return NULL;

   }

   return mapAddress;

 }

 // delete the PerfData memory region

 //

 static void delete_standard_memory(char* addr, size_t size) {

   // there are no persistent external resources to cleanup for standard

   // memory. since DestroyJavaVM does not support unloading of the JVM,

   // cleanup of the memory resource is not performed. The memory will be

   // reclaimed by the OS upon termination of the process.

   //

   return;

 }

 // save the specified memory region to the given file

 //

 static void save_memory_to_file(char* addr, size_t size) {

   const char* destfile = PerfMemory::get_perfdata_file_path();

   assert(destfile[0] != '\0', "invalid Perfdata file path");

   int fd = ::_open(destfile, _O_BINARY|_O_CREAT|_O_WRONLY|_O_TRUNC,

                    _S_IREAD|_S_IWRITE);

   if (fd == OS_ERR) {

     if (PrintMiscellaneous && Verbose) {

       warning("Could not create Perfdata save file: %s: %s\n",

               destfile, strerror(errno));

     }

   } else {

     for (size_t remaining = size; remaining > 0;) {

       int nbytes = ::_write(fd, addr, (unsigned int)remaining);

       if (nbytes == OS_ERR) {

         if (PrintMiscellaneous && Verbose) {

           warning("Could not write Perfdata save file: %s: %s\n",

                   destfile, strerror(errno));

         }

         break;

       }

       remaining -= (size_t)nbytes;

       addr += nbytes;

     }

     int result = ::_close(fd);

     if (PrintMiscellaneous && Verbose) {

       if (result == OS_ERR) {

         warning("Could not close %s: %s\n", destfile, strerror(errno));

       }

     }

   }

   FREE_C_HEAP_ARRAY(char, destfile);

 }

 // Shared Memory Implementation Details

 // Note: the win32 shared memory implementation uses two objects to represent

 // the shared memory: a windows kernel based file mapping object and a backing

 // store file. On windows, the name space for shared memory is a kernel

 // based name space that is disjoint from other win32 name spaces. Since Java

 // is unaware of this name space, a parallel file system based name space is

 // maintained, which provides a common file system based shared memory name

 // space across the supported platforms and one that Java apps can deal with

 // through simple file apis.

 //

 // For performance and resource cleanup reasons, it is recommended that the

 // user specific directory and the backing store file be stored in either a

 // RAM based file system or a local disk based file system. Network based

 // file systems are not recommended for performance reasons. In addition,

 // use of SMB network based file systems may result in unsuccesful cleanup

 // of the disk based resource on exit of the VM. The Windows TMP and TEMP

 // environement variables, as used by the GetTempPath() Win32 API (see

 // os::get_temp_directory() in os_win32.cpp), control the location of the

 // user specific directory and the shared memory backing store file.

 static HANDLE sharedmem_fileMapHandle = NULL;

 static HANDLE sharedmem_fileHandle = INVALID_HANDLE_VALUE;

 static char*  sharedmem_fileName = NULL;

 // return the user specific temporary directory name.

 //

 // the caller is expected to free the allocated memory.

 //

 static char* get_user_tmp_dir(const char* user) {

   const char* tmpdir = os::get_temp_directory();

   const char* perfdir = PERFDATA_NAME;

   size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 2;

   char* dirname = NEW_C_HEAP_ARRAY(char, nbytes);

   // construct the path name to user specific tmp directory

   _snprintf(dirname, nbytes, "%s%s_%s", tmpdir, perfdir, user);

   return dirname;

 }

 // convert the given file name into a process id. if the file

 // does not meet the file naming constraints, return 0.

 //

 static int filename_to_pid(const char* filename) {

   // a filename that doesn't begin with a digit is not a

   // candidate for conversion.

   //

   if (!isdigit(*filename)) {

     return 0;

   }

   // check if file name can be converted to an integer without

   // any leftover characters.

   //

   char* remainder = NULL;

   errno = 0;

   int pid = (int)strtol(filename, &remainder, 10);

   if (errno != 0) {

     return 0;

   }

   // check for left over characters. If any, then the filename is

   // not a candidate for conversion.

   //

   if (remainder != NULL && *remainder != '\0') {

     return 0;

   }

   // successful conversion, return the pid

   return pid;

 }

 // check if the given path is considered a secure directory for

 // the backing store files. Returns true if the directory exists

 // and is considered a secure location. Returns false if the path

 // is a symbolic link or if an error occurred.

 //

 static bool is_directory_secure(const char* path) {

   DWORD fa;

   fa = GetFileAttributes(path);

   if (fa == 0xFFFFFFFF) {

     DWORD lasterror = GetLastError();

     if (lasterror == ERROR_FILE_NOT_FOUND) {

       return false;

     }

     else {

       // unexpected error, declare the path insecure

       if (PrintMiscellaneous && Verbose) {

         warning("could not get attributes for file %s: ",

                 " lasterror = %d\n", path, lasterror);

       }

       return false;

     }

   }

   if (fa & FILE_ATTRIBUTE_REPARSE_POINT) {

     // we don't accept any redirection for the user specific directory

     // so declare the path insecure. This may be too conservative,

     // as some types of reparse points might be acceptable, but it

     // is probably more secure to avoid these conditions.

     //

     if (PrintMiscellaneous && Verbose) {

       warning("%s is a reparse point\n", path);

     }

     return false;

   }

   if (fa & FILE_ATTRIBUTE_DIRECTORY) {

     // this is the expected case. Since windows supports symbolic

     // links to directories only, not to files, there is no need

     // to check for open write permissions on the directory. If the

     // directory has open write permissions, any files deposited that

     // are not expected will be removed by the cleanup code.

     //

     return true;

   }

   else {

     // this is either a regular file or some other type of file,

     // any of which are unexpected and therefore insecure.

     //

     if (PrintMiscellaneous && Verbose) {

       warning("%s is not a directory, file attributes = "

               INTPTR_FORMAT "\n", path, fa);

     }

     return false;

   }

 }

 // return the user name for the owner of this process

 //

 // the caller is expected to free the allocated memory.

 //

 static char* get_user_name() {

   /* get the user name. This code is adapted from code found in

    * the jdk in src/windows/native/java/lang/java_props_md.c

    * java_props_md.c  1.29 02/02/06. According to the original

    * source, the call to GetUserName is avoided because of a resulting

    * increase in footprint of 100K.

    */

   char* user = getenv("USERNAME");

   char buf[UNLEN+1];

   DWORD buflen = sizeof(buf);

   if (user == NULL || strlen(user) == 0) {

     if (GetUserName(buf, &buflen)) {

       user = buf;

     }

     else {

       return NULL;

     }

   }

   char* user_name = NEW_C_HEAP_ARRAY(char, strlen(user)+1);

   strcpy(user_name, user);

   return user_name;

 }

 // return the name of the user that owns the process identified by vmid.

 //

 // This method uses a slow directory search algorithm to find the backing

 // store file for the specified vmid and returns the user name, as determined

 // by the user name suffix of the hsperfdata_<username> directory name.

 //

 // the caller is expected to free the allocated memory.

 //

 static char* get_user_name_slow(int vmid) {

   // directory search

   char* oldest_user = NULL;

   time_t oldest_ctime = 0;

   const char* tmpdirname = os::get_temp_directory();

   DIR* tmpdirp = os::opendir(tmpdirname);

   if (tmpdirp == NULL) {

     return NULL;

   }

   // for each entry in the directory that matches the pattern hsperfdata_*,

   // open the directory and check if the file for the given vmid exists.

   // The file with the expected name and the latest creation date is used

   // to determine the user name for the process id.

   //

   struct dirent* dentry;

   char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname));

   errno = 0;

   while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {

     // check if the directory entry is a hsperfdata file

     if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {

       continue;

     }

     char* usrdir_name = NEW_C_HEAP_ARRAY(char,

                               strlen(tmpdirname) + strlen(dentry->d_name) + 1);

     strcpy(usrdir_name, tmpdirname);

     strcat(usrdir_name, dentry->d_name);

     DIR* subdirp = os::opendir(usrdir_name);

     if (subdirp == NULL) {

       FREE_C_HEAP_ARRAY(char, usrdir_name);

       continue;

     }

     // Since we don't create the backing store files in directories

     // pointed to by symbolic links, we also don't follow them when

     // looking for the files. We check for a symbolic link after the

     // call to opendir in order to eliminate a small window where the

     // symlink can be exploited.

     //

     if (!is_directory_secure(usrdir_name)) {

       FREE_C_HEAP_ARRAY(char, usrdir_name);

       os::closedir(subdirp);

       continue;

     }

     struct dirent* udentry;

     char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name));

     errno = 0;

     while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {

       if (filename_to_pid(udentry->d_name) == vmid) {

         struct stat statbuf;

         char* filename = NEW_C_HEAP_ARRAY(char,

                             strlen(usrdir_name) + strlen(udentry->d_name) + 2);

         strcpy(filename, usrdir_name);

         strcat(filename, "\\");

         strcat(filename, udentry->d_name);

         if (::stat(filename, &statbuf) == OS_ERR) {

            FREE_C_HEAP_ARRAY(char, filename);

            continue;

         }

         // skip over files that are not regular files.

         if ((statbuf.st_mode & S_IFMT) != S_IFREG) {

           FREE_C_HEAP_ARRAY(char, filename);

           continue;

         }

         // compare and save filename with latest creation time

         if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {

           if (statbuf.st_ctime > oldest_ctime) {

             char* user = strchr(dentry->d_name, '_') + 1;

             if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user);

             oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1);

             strcpy(oldest_user, user);

             oldest_ctime = statbuf.st_ctime;

           }

         }

         FREE_C_HEAP_ARRAY(char, filename);

       }

     }

     os::closedir(subdirp);

     FREE_C_HEAP_ARRAY(char, udbuf);

     FREE_C_HEAP_ARRAY(char, usrdir_name);

   }

   os::closedir(tmpdirp);

   FREE_C_HEAP_ARRAY(char, tdbuf);

   return(oldest_user);

 }

 // return the name of the user that owns the process identified by vmid.

 //

 // note: this method should only be used via the Perf native methods.

 // There are various costs to this method and limiting its use to the

 // Perf native methods limits the impact to monitoring applications only.

 //

 static char* get_user_name(int vmid) {

   // A fast implementation is not provided at this time. It's possible

   // to provide a fast process id to user name mapping function using

   // the win32 apis, but the default ACL for the process object only

   // allows processes with the same owner SID to acquire the process

   // handle (via OpenProcess(PROCESS_QUERY_INFORMATION)). It's possible

   // to have the JVM change the ACL for the process object to allow arbitrary

   // users to access the process handle and the process security token.

   // The security ramifications need to be studied before providing this

   // mechanism.

   //

   return get_user_name_slow(vmid);

 }

 // return the name of the shared memory file mapping object for the

 // named shared memory region for the given user name and vmid.

 //

 // The file mapping object's name is not the file name. It is a name

 // in a separate name space.

 //

 // the caller is expected to free the allocated memory.

 //

 static char *get_sharedmem_objectname(const char* user, int vmid) {

   // construct file mapping object's name, add 3 for two '_' and a

   // null terminator.

   int nbytes = (int)strlen(PERFDATA_NAME) + (int)strlen(user) + 3;

   // the id is converted to an unsigned value here because win32 allows

   // negative process ids. However, OpenFileMapping API complains

   // about a name containing a '-' characters.

   //

   nbytes += UINT_CHARS;

   char* name = NEW_C_HEAP_ARRAY(char, nbytes);

   _snprintf(name, nbytes, "%s_%s_%u", PERFDATA_NAME, user, vmid);

   return name;

 }

 // return the file name of the backing store file for the named

 // shared memory region for the given user name and vmid.

 //

 // the caller is expected to free the allocated memory.

 //

 static char* get_sharedmem_filename(const char* dirname, int vmid) {

   // add 2 for the file separator and a null terminator.

   size_t nbytes = strlen(dirname) + UINT_CHARS + 2;

   char* name = NEW_C_HEAP_ARRAY(char, nbytes);

   _snprintf(name, nbytes, "%s\\%d", dirname, vmid);

   return name;

 }

 // remove file

 //

 // this method removes the file with the given file name.

 //

 // Note: if the indicated file is on an SMB network file system, this

 // method may be unsuccessful in removing the file.

 //

 static void remove_file(const char* dirname, const char* filename) {

   size_t nbytes = strlen(dirname) + strlen(filename) + 2;

   char* path = NEW_C_HEAP_ARRAY(char, nbytes);

   strcpy(path, dirname);

   strcat(path, "\\");

   strcat(path, filename);

   if (::unlink(path) == OS_ERR) {

     if (PrintMiscellaneous && Verbose) {

       if (errno != ENOENT) {

         warning("Could not unlink shared memory backing"

                 " store file %s : %s\n", path, strerror(errno));

       }

     }

   }

   FREE_C_HEAP_ARRAY(char, path);

 }

 // returns true if the process represented by pid is alive, otherwise

 // returns false. the validity of the result is only accurate if the

 // target process is owned by the same principal that owns this process.

 // this method should not be used if to test the status of an otherwise

 // arbitrary process unless it is know that this process has the appropriate

 // privileges to guarantee a result valid.

 //

 static bool is_alive(int pid) {

   HANDLE ph = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);

   if (ph == NULL) {

     // the process does not exist.

     if (PrintMiscellaneous && Verbose) {

       DWORD lastError = GetLastError();

       if (lastError != ERROR_INVALID_PARAMETER) {

         warning("OpenProcess failed: %d\n", GetLastError());

       }

     }

     return false;

   }

   DWORD exit_status;

   if (!GetExitCodeProcess(ph, &exit_status)) {

     if (PrintMiscellaneous && Verbose) {

       warning("GetExitCodeProcess failed: %d\n", GetLastError());

     }

     CloseHandle(ph);

     return false;

   }

   CloseHandle(ph);

   return (exit_status == STILL_ACTIVE) ? true : false;

 }

 // check if the file system is considered secure for the backing store files

 //

 static bool is_filesystem_secure(const char* path) {

   char root_path[MAX_PATH];

   char fs_type[MAX_PATH];

   if (PerfBypassFileSystemCheck) {

     if (PrintMiscellaneous && Verbose) {

       warning("bypassing file system criteria checks for %s\n", path);

     }

     return true;

   }

   char* first_colon = strchr((char *)path, ':');

   if (first_colon == NULL) {

     if (PrintMiscellaneous && Verbose) {

       warning("expected device specifier in path: %s\n", path);

     }

     return false;

   }

   size_t len = (size_t)(first_colon - path);

   assert(len + 2 <= MAX_PATH, "unexpected device specifier length");

   strncpy(root_path, path, len + 1);

   root_path[len + 1] = '\\';

   root_path[len + 2] = '\0';

   // check that we have something like "C:\" or "AA:\"

   assert(strlen(root_path) >= 3, "device specifier too short");

   assert(strchr(root_path, ':') != NULL, "bad device specifier format");

   assert(strchr(root_path, '\\') != NULL, "bad device specifier format");

   DWORD maxpath;

   DWORD flags;

   if (!GetVolumeInformation(root_path, NULL, 0, NULL, &maxpath,

                             &flags, fs_type, MAX_PATH)) {

     // we can't get information about the volume, so assume unsafe.

     if (PrintMiscellaneous && Verbose) {

       warning("could not get device information for %s: "

               " path = %s: lasterror = %d\n",

               root_path, path, GetLastError());

     }

     return false;

   }

   if ((flags & FS_PERSISTENT_ACLS) == 0) {

     // file system doesn't support ACLs, declare file system unsafe

     if (PrintMiscellaneous && Verbose) {

       warning("file system type %s on device %s does not support"

               " ACLs\n", fs_type, root_path);

     }

     return false;

   }

   if ((flags & FS_VOL_IS_COMPRESSED) != 0) {

     // file system is compressed, declare file system unsafe

     if (PrintMiscellaneous && Verbose) {

       warning("file system type %s on device %s is compressed\n",

               fs_type, root_path);

     }

     return false;

   }

   return true;

 }

 // cleanup stale shared memory resources

 //

 // This method attempts to remove all stale shared memory files in

 // the named user temporary directory. It scans the named directory

 // for files matching the pattern ^$[0-9]*$. For each file found, the

 // process id is extracted from the file name and a test is run to

 // determine if the process is alive. If the process is not alive,

 // any stale file resources are removed.

 //

 static void cleanup_sharedmem_resources(const char* dirname) {

   // open the user temp directory

   DIR* dirp = os::opendir(dirname);

   if (dirp == NULL) {

     // directory doesn't exist, so there is nothing to cleanup

     return;

   }

   if (!is_directory_secure(dirname)) {

     // the directory is not secure, don't attempt any cleanup

     return;

   }

   // for each entry in the directory that matches the expected file

   // name pattern, determine if the file resources are stale and if

   // so, remove the file resources. Note, instrumented HotSpot processes

   // for this user may start and/or terminate during this search and

   // remove or create new files in this directory. The behavior of this

   // loop under these conditions is dependent upon the implementation of

   // opendir/readdir.

   //

   struct dirent* entry;

   char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname));

   errno = 0;

   while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {

     int pid = filename_to_pid(entry->d_name);

     if (pid == 0) {

       if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {

         // attempt to remove all unexpected files, except "." and ".."

         remove_file(dirname, entry->d_name);

       }

       errno = 0;

       continue;

     }

     // we now have a file name that converts to a valid integer

     // that could represent a process id . if this process id

     // matches the current process id or the process is not running,

     // then remove the stale file resources.

     //

     // process liveness is detected by checking the exit status

     // of the process. if the process id is valid and the exit status

     // indicates that it is still running, the file file resources

     // are not removed. If the process id is invalid, or if we don't

     // have permissions to check the process status, or if the process

     // id is valid and the process has terminated, the the file resources

     // are assumed to be stale and are removed.

     //

     if (pid == os::current_process_id() || !is_alive(pid)) {

       // we can only remove the file resources. Any mapped views

       // of the file can only be unmapped by the processes that

       // opened those views and the file mapping object will not

       // get removed until all views are unmapped.

       //

       remove_file(dirname, entry->d_name);

     }

     errno = 0;

   }

   os::closedir(dirp);

   FREE_C_HEAP_ARRAY(char, dbuf);

 }

 // create a file mapping object with the requested name, and size

 // from the file represented by the given Handle object

 //

 static HANDLE create_file_mapping(const char* name, HANDLE fh, LPSECURITY_ATTRIBUTES fsa, size_t size) {

   DWORD lowSize = (DWORD)size;

   DWORD highSize = 0;

   HANDLE fmh = NULL;

   // Create a file mapping object with the given name. This function

   // will grow the file to the specified size.

   //

   fmh = CreateFileMapping(

                fh,                 /* HANDLE file handle for backing store */

                fsa,                /* LPSECURITY_ATTRIBUTES Not inheritable */

                PAGE_READWRITE,     /* DWORD protections */

                highSize,           /* DWORD High word of max size */

                lowSize,            /* DWORD Low word of max size */

                name);              /* LPCTSTR name for object */

   if (fmh == NULL) {

     if (PrintMiscellaneous && Verbose) {

       warning("CreateFileMapping failed, lasterror = %d\n", GetLastError());

     }

     return NULL;

   }

   if (GetLastError() == ERROR_ALREADY_EXISTS) {

     // a stale file mapping object was encountered. This object may be

     // owned by this or some other user and cannot be removed until

     // the other processes either exit or close their mapping objects

     // and/or mapped views of this mapping object.

     //

     if (PrintMiscellaneous && Verbose) {

       warning("file mapping already exists, lasterror = %d\n", GetLastError());

     }

     CloseHandle(fmh);

     return NULL;

   }

   return fmh;

 }

 // method to free the given security descriptor and the contained

 // access control list.

 //

 static void free_security_desc(PSECURITY_DESCRIPTOR pSD) {

   BOOL success, exists, isdefault;

   PACL pACL;

   if (pSD != NULL) {

     // get the access control list from the security descriptor

     success = GetSecurityDescriptorDacl(pSD, &exists, &pACL, &isdefault);

     // if an ACL existed and it was not a default acl, then it must

     // be an ACL we enlisted. free the resources.

     //

     if (success && exists && pACL != NULL && !isdefault) {

       FREE_C_HEAP_ARRAY(char, pACL);

     }

     // free the security descriptor

     FREE_C_HEAP_ARRAY(char, pSD);

   }

 }

 // method to free up a security attributes structure and any

 // contained security descriptors and ACL

 //

 static void free_security_attr(LPSECURITY_ATTRIBUTES lpSA) {

   if (lpSA != NULL) {

     // free the contained security descriptor and the ACL

     free_security_desc(lpSA->lpSecurityDescriptor);

     lpSA->lpSecurityDescriptor = NULL;

     // free the security attributes structure

     FREE_C_HEAP_ARRAY(char, lpSA);

   }

 }

 // get the user SID for the process indicated by the process handle

 //

 static PSID get_user_sid(HANDLE hProcess) {

   HANDLE hAccessToken;

   PTOKEN_USER token_buf = NULL;

   DWORD rsize = 0;

   if (hProcess == NULL) {

     return NULL;

   }

   // get the process token

   if (!OpenProcessToken(hProcess, TOKEN_READ, &hAccessToken)) {

     if (PrintMiscellaneous && Verbose) {

       warning("OpenProcessToken failure: lasterror = %d \n", GetLastError());

     }

     return NULL;

   }

   // determine the size of the token structured needed to retrieve

   // the user token information from the access token.

   //

   if (!GetTokenInformation(hAccessToken, TokenUser, NULL, rsize, &rsize)) {

     DWORD lasterror = GetLastError();

     if (lasterror != ERROR_INSUFFICIENT_BUFFER) {

       if (PrintMiscellaneous && Verbose) {

         warning("GetTokenInformation failure: lasterror = %d,"

                 " rsize = %d\n", lasterror, rsize);

       }

       CloseHandle(hAccessToken);

       return NULL;

     }

   }

   token_buf = (PTOKEN_USER) NEW_C_HEAP_ARRAY(char, rsize);

   // get the user token information

   if (!GetTokenInformation(hAccessToken, TokenUser, token_buf, rsize, &rsize)) {

     if (PrintMiscellaneous && Verbose) {

       warning("GetTokenInformation failure: lasterror = %d,"

               " rsize = %d\n", GetLastError(), rsize);

     }

     FREE_C_HEAP_ARRAY(char, token_buf);

     CloseHandle(hAccessToken);

     return NULL;

   }

   DWORD nbytes = GetLengthSid(token_buf->User.Sid);

   PSID pSID = NEW_C_HEAP_ARRAY(char, nbytes);

   if (!CopySid(nbytes, pSID, token_buf->User.Sid)) {

     if (PrintMiscellaneous && Verbose) {

       warning("GetTokenInformation failure: lasterror = %d,"

               " rsize = %d\n", GetLastError(), rsize);

     }

     FREE_C_HEAP_ARRAY(char, token_buf);

     FREE_C_HEAP_ARRAY(char, pSID);

     CloseHandle(hAccessToken);

     return NULL;

   }

   // close the access token.

   CloseHandle(hAccessToken);

   FREE_C_HEAP_ARRAY(char, token_buf);

   return pSID;

 }

 // structure used to consolidate access control entry information

 //

 typedef struct ace_data {

   PSID pSid;      // SID of the ACE

   DWORD mask;     // mask for the ACE

 } ace_data_t;

 // method to add an allow access control entry with the access rights

 // indicated in mask for the principal indicated in SID to the given

 // security descriptor. Much of the DACL handling was adapted from

 // the example provided here:

 //      http://support.microsoft.com/kb/102102/EN-US/

 //

 static bool add_allow_aces(PSECURITY_DESCRIPTOR pSD,

                            ace_data_t aces[], int ace_count) {

   PACL newACL = NULL;

   PACL oldACL = NULL;

   if (pSD == NULL) {

     return false;

   }

   BOOL exists, isdefault;

   // retrieve any existing access control list.

   if (!GetSecurityDescriptorDacl(pSD, &exists, &oldACL, &isdefault)) {

     if (PrintMiscellaneous && Verbose) {

       warning("GetSecurityDescriptor failure: lasterror = %d \n",

               GetLastError());

     }

     return false;

   }

   // get the size of the DACL

   ACL_SIZE_INFORMATION aclinfo;

   // GetSecurityDescriptorDacl may return true value for exists (lpbDaclPresent)

   // while oldACL is NULL for some case.

   if (oldACL == NULL) {

     exists = FALSE;

   }

   if (exists) {

     if (!GetAclInformation(oldACL, &aclinfo,

                            sizeof(ACL_SIZE_INFORMATION),

                            AclSizeInformation)) {

       if (PrintMiscellaneous && Verbose) {

         warning("GetAclInformation failure: lasterror = %d \n", GetLastError());

         return false;

       }

     }

   } else {

     aclinfo.AceCount = 0; // assume NULL DACL

     aclinfo.AclBytesFree = 0;

     aclinfo.AclBytesInUse = sizeof(ACL);

   }

   // compute the size needed for the new ACL

   // initial size of ACL is sum of the following:

   //   * size of ACL structure.

   //   * size of each ACE structure that ACL is to contain minus the sid

   //     sidStart member (DWORD) of the ACE.

   //   * length of the SID that each ACE is to contain.

   DWORD newACLsize = aclinfo.AclBytesInUse +

                         (sizeof(ACCESS_ALLOWED_ACE) - sizeof(DWORD)) * ace_count;

   for (int i = 0; i < ace_count; i++) {

      newACLsize += GetLengthSid(aces[i].pSid);

   }

   // create the new ACL

   newACL = (PACL) NEW_C_HEAP_ARRAY(char, newACLsize);

   if (!InitializeAcl(newACL, newACLsize, ACL_REVISION)) {

     if (PrintMiscellaneous && Verbose) {

       warning("InitializeAcl failure: lasterror = %d \n", GetLastError());

     }

     FREE_C_HEAP_ARRAY(char, newACL);

     return false;

   }

   unsigned int ace_index = 0;

   // copy any existing ACEs from the old ACL (if any) to the new ACL.

   if (aclinfo.AceCount != 0) {

     while (ace_index < aclinfo.AceCount) {

       LPVOID ace;

       if (!GetAce(oldACL, ace_index, &ace)) {

         if (PrintMiscellaneous && Verbose) {

           warning("InitializeAcl failure: lasterror = %d \n", GetLastError());

         }

         FREE_C_HEAP_ARRAY(char, newACL);

         return false;

       }

       if (((ACCESS_ALLOWED_ACE *)ace)->Header.AceFlags && INHERITED_ACE) {

         // this is an inherited, allowed ACE; break from loop so we can

         // add the new access allowed, non-inherited ACE in the correct

         // position, immediately following all non-inherited ACEs.

         break;

       }

       // determine if the SID of this ACE matches any of the SIDs

       // for which we plan to set ACEs.

       int matches = 0;

       for (int i = 0; i < ace_count; i++) {

         if (EqualSid(aces[i].pSid, &(((ACCESS_ALLOWED_ACE *)ace)->SidStart))) {

           matches++;

           break;

         }

       }

       // if there are no SID matches, then add this existing ACE to the new ACL

       if (matches == 0) {

         if (!AddAce(newACL, ACL_REVISION, MAXDWORD, ace,

                     ((PACE_HEADER)ace)->AceSize)) {

           if (PrintMiscellaneous && Verbose) {

             warning("AddAce failure: lasterror = %d \n", GetLastError());

           }

           FREE_C_HEAP_ARRAY(char, newACL);

           return false;

         }

       }

       ace_index++;

     }

   }

   // add the passed-in access control entries to the new ACL

   for (int i = 0; i < ace_count; i++) {

     if (!AddAccessAllowedAce(newACL, ACL_REVISION,

                              aces[i].mask, aces[i].pSid)) {

       if (PrintMiscellaneous && Verbose) {

         warning("AddAccessAllowedAce failure: lasterror = %d \n",

                 GetLastError());

       }

       FREE_C_HEAP_ARRAY(char, newACL);

       return false;

     }

   }

   // now copy the rest of the inherited ACEs from the old ACL

   if (aclinfo.AceCount != 0) {

     // picking up at ace_index, where we left off in the

     // previous ace_index loop

     while (ace_index < aclinfo.AceCount) {

       LPVOID ace;

       if (!GetAce(oldACL, ace_index, &ace)) {

         if (PrintMiscellaneous && Verbose) {

           warning("InitializeAcl failure: lasterror = %d \n", GetLastError());

         }

         FREE_C_HEAP_ARRAY(char, newACL);

         return false;

       }

       if (!AddAce(newACL, ACL_REVISION, MAXDWORD, ace,

                   ((PACE_HEADER)ace)->AceSize)) {

         if (PrintMiscellaneous && Verbose) {

           warning("AddAce failure: lasterror = %d \n", GetLastError());

         }

         FREE_C_HEAP_ARRAY(char, newACL);

         return false;

       }

       ace_index++;

     }

   }

   // add the new ACL to the security descriptor.

   if (!SetSecurityDescriptorDacl(pSD, TRUE, newACL, FALSE)) {

     if (PrintMiscellaneous && Verbose) {

       warning("SetSecurityDescriptorDacl failure:"

               " lasterror = %d \n", GetLastError());

     }

     FREE_C_HEAP_ARRAY(char, newACL);

     return false;

   }

   // if running on windows 2000 or later, set the automatic inheritance

   // control flags.

   SetSecurityDescriptorControlFnPtr _SetSecurityDescriptorControl;

   _SetSecurityDescriptorControl = (SetSecurityDescriptorControlFnPtr)

        GetProcAddress(GetModuleHandle(TEXT("advapi32.dll")),

                       "SetSecurityDescriptorControl");

   if (_SetSecurityDescriptorControl != NULL) {

     // We do not want to further propagate inherited DACLs, so making them

     // protected prevents that.

     if (!_SetSecurityDescriptorControl(pSD, SE_DACL_PROTECTED,

                                             SE_DACL_PROTECTED)) {

       if (PrintMiscellaneous && Verbose) {

         warning("SetSecurityDescriptorControl failure:"

                 " lasterror = %d \n", GetLastError());

       }

       FREE_C_HEAP_ARRAY(char, newACL);

       return false;

     }

   }

    // Note, the security descriptor maintains a reference to the newACL, not

    // a copy of it. Therefore, the newACL is not freed here. It is freed when

    // the security descriptor containing its reference is freed.

    //

    return true;

 }

 // method to create a security attributes structure, which contains a

 // security descriptor and an access control list comprised of 0 or more

 // access control entries. The method take an array of ace_data structures

 // that indicate the ACE to be added to the security descriptor.

 //

 // the caller must free the resources associated with the security

 // attributes structure created by this method by calling the

 // free_security_attr() method.

 //

 static LPSECURITY_ATTRIBUTES make_security_attr(ace_data_t aces[], int count) {

   // allocate space for a security descriptor

   PSECURITY_DESCRIPTOR pSD = (PSECURITY_DESCRIPTOR)

                          NEW_C_HEAP_ARRAY(char, SECURITY_DESCRIPTOR_MIN_LENGTH);

   // initialize the security descriptor

   if (!InitializeSecurityDescriptor(pSD, SECURITY_DESCRIPTOR_REVISION)) {

     if (PrintMiscellaneous && Verbose) {

       warning("InitializeSecurityDescriptor failure: "

               "lasterror = %d \n", GetLastError());

     }

     free_security_desc(pSD);

     return NULL;

   }

   // add the access control entries

   if (!add_allow_aces(pSD, aces, count)) {

     free_security_desc(pSD);

     return NULL;

   }

   // allocate and initialize the security attributes structure and

   // return it to the caller.

   //

   LPSECURITY_ATTRIBUTES lpSA = (LPSECURITY_ATTRIBUTES)

                             NEW_C_HEAP_ARRAY(char, sizeof(SECURITY_ATTRIBUTES));

   lpSA->nLength = sizeof(SECURITY_ATTRIBUTES);

   lpSA->lpSecurityDescriptor = pSD;

   lpSA->bInheritHandle = FALSE;

   return(lpSA);

 }

 // method to create a security attributes structure with a restrictive

 // access control list that creates a set access rights for the user/owner

 // of the securable object and a separate set access rights for everyone else.

 // also provides for full access rights for the administrator group.

 //

 // the caller must free the resources associated with the security

 // attributes structure created by this method by calling the

 // free_security_attr() method.

 //

 static LPSECURITY_ATTRIBUTES make_user_everybody_admin_security_attr(

                                 DWORD umask, DWORD emask, DWORD amask) {

   ace_data_t aces[3];

   // initialize the user ace data

   aces[0].pSid = get_user_sid(GetCurrentProcess());

   aces[0].mask = umask;

   // get the well known SID for BUILTIN\Administrators

   PSID administratorsSid = NULL;

   SID_IDENTIFIER_AUTHORITY SIDAuthAdministrators = SECURITY_NT_AUTHORITY;

   if (!AllocateAndInitializeSid( &SIDAuthAdministrators, 2,

            SECURITY_BUILTIN_DOMAIN_RID,

            DOMAIN_ALIAS_RID_ADMINS,

            0, 0, 0, 0, 0, 0, &administratorsSid)) {

     if (PrintMiscellaneous && Verbose) {

       warning("AllocateAndInitializeSid failure: "

               "lasterror = %d \n", GetLastError());

     }

     return NULL;

   }

   // initialize the ace data for administrator group

   aces[1].pSid = administratorsSid;

   aces[1].mask = amask;

   // get the well known SID for the universal Everybody

   PSID everybodySid = NULL;

   SID_IDENTIFIER_AUTHORITY SIDAuthEverybody = SECURITY_WORLD_SID_AUTHORITY;

   if (!AllocateAndInitializeSid( &SIDAuthEverybody, 1, SECURITY_WORLD_RID,

            0, 0, 0, 0, 0, 0, 0, &everybodySid)) {

     if (PrintMiscellaneous && Verbose) {

       warning("AllocateAndInitializeSid failure: "

               "lasterror = %d \n", GetLastError());

     }

     return NULL;

   }

   // initialize the ace data for everybody else.

   aces[2].pSid = everybodySid;

   aces[2].mask = emask;

   // create a security attributes structure with access control

   // entries as initialized above.

   LPSECURITY_ATTRIBUTES lpSA = make_security_attr(aces, 3);

   FREE_C_HEAP_ARRAY(char, aces[0].pSid);

   FreeSid(everybodySid);

   FreeSid(administratorsSid);

   return(lpSA);

 }

 // method to create the security attributes structure for restricting

 // access to the user temporary directory.

 //

 // the caller must free the resources associated with the security

 // attributes structure created by this method by calling the

 // free_security_attr() method.

 //

 static LPSECURITY_ATTRIBUTES make_tmpdir_security_attr() {

   // create full access rights for the user/owner of the directory

   // and read-only access rights for everybody else. This is

   // effectively equivalent to UNIX 755 permissions on a directory.

   //

   DWORD umask = STANDARD_RIGHTS_REQUIRED | FILE_ALL_ACCESS;

   DWORD emask = GENERIC_READ | FILE_LIST_DIRECTORY | FILE_TRAVERSE;

   DWORD amask = STANDARD_RIGHTS_ALL | FILE_ALL_ACCESS;

   return make_user_everybody_admin_security_attr(umask, emask, amask);

 }

 // method to create the security attributes structure for restricting

 // access to the shared memory backing store file.

 //

 // the caller must free the resources associated with the security

 // attributes structure created by this method by calling the

 // free_security_attr() method.

 //

 static LPSECURITY_ATTRIBUTES make_file_security_attr() {

   // create extensive access rights for the user/owner of the file

   // and attribute read-only access rights for everybody else. This

   // is effectively equivalent to UNIX 600 permissions on a file.

   //

   DWORD umask = STANDARD_RIGHTS_ALL | FILE_ALL_ACCESS;

   DWORD emask = STANDARD_RIGHTS_READ | FILE_READ_ATTRIBUTES |

                  FILE_READ_EA | FILE_LIST_DIRECTORY | FILE_TRAVERSE;

   DWORD amask = STANDARD_RIGHTS_ALL | FILE_ALL_ACCESS;

   return make_user_everybody_admin_security_attr(umask, emask, amask);

 }

 // method to create the security attributes structure for restricting

 // access to the name shared memory file mapping object.

 //

 // the caller must free the resources associated with the security

 // attributes structure created by this method by calling the

 // free_security_attr() method.

 //

 static LPSECURITY_ATTRIBUTES make_smo_security_attr() {

   // create extensive access rights for the user/owner of the shared

   // memory object and attribute read-only access rights for everybody

   // else. This is effectively equivalent to UNIX 600 permissions on

   // on the shared memory object.

   //

   DWORD umask = STANDARD_RIGHTS_REQUIRED | FILE_MAP_ALL_ACCESS;

   DWORD emask = STANDARD_RIGHTS_READ; // attributes only

   DWORD amask = STANDARD_RIGHTS_ALL | FILE_MAP_ALL_ACCESS;

   return make_user_everybody_admin_security_attr(umask, emask, amask);

 }

 // make the user specific temporary directory

 //

 static bool make_user_tmp_dir(const char* dirname) {

   LPSECURITY_ATTRIBUTES pDirSA = make_tmpdir_security_attr();

   if (pDirSA == NULL) {

     return false;

   }

   // create the directory with the given security attributes

   if (!CreateDirectory(dirname, pDirSA)) {

     DWORD lasterror = GetLastError();

     if (lasterror == ERROR_ALREADY_EXISTS) {

       // The directory already exists and was probably created by another

       // JVM instance. However, this could also be the result of a

       // deliberate symlink. Verify that the existing directory is safe.

       //

       if (!is_directory_secure(dirname)) {

         // directory is not secure

         if (PrintMiscellaneous && Verbose) {

           warning("%s directory is insecure\n", dirname);

         }

         return false;

       }

       // The administrator should be able to delete this directory.

       // But the directory created by previous version of JVM may not

       // have permission for administrators to delete this directory.

       // So add full permission to the administrator. Also setting new

       // DACLs might fix the corrupted the DACLs.

       SECURITY_INFORMATION secInfo = DACL_SECURITY_INFORMATION;

       if (!SetFileSecurity(dirname, secInfo, pDirSA->lpSecurityDescriptor)) {

         if (PrintMiscellaneous && Verbose) {

           lasterror = GetLastError();

           warning("SetFileSecurity failed for %s directory.  lasterror %d \n",

                                                         dirname, lasterror);

         }

       }

     }

     else {

       if (PrintMiscellaneous && Verbose) {

         warning("CreateDirectory failed: %d\n", GetLastError());

       }

       return false;

     }

   }

   // free the security attributes structure

   free_security_attr(pDirSA);

   return true;

 }

 // create the shared memory resources

 //

 // This function creates the shared memory resources. This includes

 // the backing store file and the file mapping shared memory object.

 //

 static HANDLE create_sharedmem_resources(const char* dirname, const char* filename, const char* objectname, size_t size) {

   HANDLE fh = INVALID_HANDLE_VALUE;

   HANDLE fmh = NULL;

   // create the security attributes for the backing store file

   LPSECURITY_ATTRIBUTES lpFileSA = make_file_security_attr();

   if (lpFileSA == NULL) {

     return NULL;

   }

   // create the security attributes for the shared memory object

   LPSECURITY_ATTRIBUTES lpSmoSA = make_smo_security_attr();

   if (lpSmoSA == NULL) {

     free_security_attr(lpFileSA);

     return NULL;

   }

   // create the user temporary directory

   if (!make_user_tmp_dir(dirname)) {

     // could not make/find the directory or the found directory

     // was not secure

     return NULL;

   }

   // Create the file - the FILE_FLAG_DELETE_ON_CLOSE flag allows the

   // file to be deleted by the last process that closes its handle to

   // the file. This is important as the apis do not allow a terminating

   // JVM being monitored by another process to remove the file name.

   //

   // the FILE_SHARE_DELETE share mode is valid only in winnt

   //

   fh = CreateFile(

              filename,                   /* LPCTSTR file name */

              GENERIC_READ|GENERIC_WRITE, /* DWORD desired access */

              (os::win32::is_nt() ? FILE_SHARE_DELETE : 0)|

              FILE_SHARE_READ,            /* DWORD share mode, future READONLY

                                           * open operations allowed

                                           */

              lpFileSA,                   /* LPSECURITY security attributes */

              CREATE_ALWAYS,              /* DWORD creation disposition

                                           * create file, if it already

                                           * exists, overwrite it.

                                           */

              FILE_FLAG_DELETE_ON_CLOSE,  /* DWORD flags and attributes */

              NULL);                      /* HANDLE template file access */

   free_security_attr(lpFileSA);

   if (fh == INVALID_HANDLE_VALUE) {

     DWORD lasterror = GetLastError();

     if (PrintMiscellaneous && Verbose) {

       warning("could not create file %s: %d\n", filename, lasterror);

     }

     return NULL;

   }

   // try to create the file mapping

   fmh = create_file_mapping(objectname, fh, lpSmoSA, size);

   free_security_attr(lpSmoSA);

   if (fmh == NULL) {

     // closing the file handle here will decrement the reference count

     // on the file. When all processes accessing the file close their

     // handle to it, the reference count will decrement to 0 and the

     // OS will delete the file. These semantics are requested by the

     // FILE_FLAG_DELETE_ON_CLOSE flag in CreateFile call above.

     CloseHandle(fh);

     fh = NULL;

     return NULL;

   }

   // the file has been successfully created and the file mapping

   // object has been created.

   sharedmem_fileHandle = fh;

   sharedmem_fileName = strdup(filename);

   return fmh;

 }

 // open the shared memory object for the given vmid.

 //

 static HANDLE open_sharedmem_object(const char* objectname, DWORD ofm_access, TRAPS) {

   HANDLE fmh;

   // open the file mapping with the requested mode

   fmh = OpenFileMapping(

                ofm_access,       /* DWORD access mode */

                FALSE,            /* BOOL inherit flag - Do not allow inherit */

                objectname);      /* name for object */

   if (fmh == NULL) {

     if (PrintMiscellaneous && Verbose) {

       warning("OpenFileMapping failed for shared memory object %s:"

               " lasterror = %d\n", objectname, GetLastError());

     }

     THROW_MSG_(vmSymbols::java_lang_Exception(),

                "Could not open PerfMemory", INVALID_HANDLE_VALUE);

   }

   return fmh;;

 }

 // create a named shared memory region

 //

 // On Win32, a named shared memory object has a name space that

 // is independent of the file system name space. Shared memory object,

 // or more precisely, file mapping objects, provide no mechanism to

 // inquire the size of the memory region. There is also no api to

 // enumerate the memory regions for various processes.

 //

 // This implementation utilizes the shared memory name space in parallel

 // with the file system name space. This allows us to determine the

 // size of the shared memory region from the size of the file and it

 // allows us to provide a common, file system based name space for

 // shared memory across platforms.

 //

 static char* mapping_create_shared(size_t size) {

   void *mapAddress;

   int vmid = os::current_process_id();

   // get the name of the user associated with this process

   char* user = get_user_name();

   if (user == NULL) {

     return NULL;

   }

   // construct the name of the user specific temporary directory

   char* dirname = get_user_tmp_dir(user);

   // check that the file system is secure - i.e. it supports ACLs.

   if (!is_filesystem_secure(dirname)) {

     return NULL;

   }

   // create the names of the backing store files and for the

   // share memory object.

   //

   char* filename = get_sharedmem_filename(dirname, vmid);

   char* objectname = get_sharedmem_objectname(user, vmid);

   // cleanup any stale shared memory resources

   cleanup_sharedmem_resources(dirname);

   assert(((size != 0) && (size % os::vm_page_size() == 0)),

          "unexpected PerfMemry region size");

   FREE_C_HEAP_ARRAY(char, user);

   // create the shared memory resources

   sharedmem_fileMapHandle =

                create_sharedmem_resources(dirname, filename, objectname, size);

   FREE_C_HEAP_ARRAY(char, filename);

   FREE_C_HEAP_ARRAY(char, objectname);

   FREE_C_HEAP_ARRAY(char, dirname);

   if (sharedmem_fileMapHandle == NULL) {

     return NULL;

   }

   // map the file into the address space

   mapAddress = MapViewOfFile(

                    sharedmem_fileMapHandle, /* HANDLE = file mapping object */

                    FILE_MAP_ALL_ACCESS,     /* DWORD access flags */

                    0,                       /* DWORD High word of offset */

                    0,                       /* DWORD Low word of offset */

                    (DWORD)size);            /* DWORD Number of bytes to map */

   if (mapAddress == NULL) {

     if (PrintMiscellaneous && Verbose) {

       warning("MapViewOfFile failed, lasterror = %d\n", GetLastError());

     }

     CloseHandle(sharedmem_fileMapHandle);

     sharedmem_fileMapHandle = NULL;

     return NULL;

   }

   // clear the shared memory region

   (void)memset(mapAddress, '\0', size);

   return (char*) mapAddress;

 }

 // this method deletes the file mapping object.

 //

 static void delete_file_mapping(char* addr, size_t size) {

   // cleanup the persistent shared memory resources. since DestroyJavaVM does

   // not support unloading of the JVM, unmapping of the memory resource is not

   // performed. The memory will be reclaimed by the OS upon termination of all

   // processes mapping the resource. The file mapping handle and the file

   // handle are closed here to expedite the remove of the file by the OS. The

   // file is not removed directly because it was created with

   // FILE_FLAG_DELETE_ON_CLOSE semantics and any attempt to remove it would

   // be unsuccessful.

   // close the fileMapHandle. the file mapping will still be retained

   // by the OS as long as any other JVM processes has an open file mapping

   // handle or a mapped view of the file.

   //

   if (sharedmem_fileMapHandle != NULL) {

     CloseHandle(sharedmem_fileMapHandle);

     sharedmem_fileMapHandle = NULL;

   }

   // close the file handle. This will decrement the reference count on the

   // backing store file. When the reference count decrements to 0, the OS

   // will delete the file. These semantics apply because the file was

   // created with the FILE_FLAG_DELETE_ON_CLOSE flag.

   //

   if (sharedmem_fileHandle != INVALID_HANDLE_VALUE) {

     CloseHandle(sharedmem_fileHandle);

     sharedmem_fileHandle = INVALID_HANDLE_VALUE;

   }

 }

 // this method determines the size of the shared memory file

 //

 static size_t sharedmem_filesize(const char* filename, TRAPS) {

   struct stat statbuf;

   // get the file size

   //

   // on win95/98/me, _stat returns a file size of 0 bytes, but on

   // winnt/2k the appropriate file size is returned. support for

   // the sharable aspects of performance counters was abandonded

   // on the non-nt win32 platforms due to this and other api

   // inconsistencies

   //

   if (::stat(filename, &statbuf) == OS_ERR) {

     if (PrintMiscellaneous && Verbose) {

       warning("stat %s failed: %s\n", filename, strerror(errno));

     }

     THROW_MSG_0(vmSymbols::java_io_IOException(),

                 "Could not determine PerfMemory size");

   }

   if ((statbuf.st_size == 0) || (statbuf.st_size % os::vm_page_size() != 0)) {

     if (PrintMiscellaneous && Verbose) {

       warning("unexpected file size: size = " SIZE_FORMAT "\n",

               statbuf.st_size);

     }

     THROW_MSG_0(vmSymbols::java_lang_Exception(),

                 "Invalid PerfMemory size");

   }

   return statbuf.st_size;

 }

 // this method opens a file mapping object and maps the object

 // into the address space of the process

 //

 static void open_file_mapping(const char* user, int vmid,

                               PerfMemory::PerfMemoryMode mode,

                               char** addrp, size_t* sizep, TRAPS) {

   ResourceMark rm;

   void *mapAddress = 0;

   size_t size;

   HANDLE fmh;

   DWORD ofm_access;

   DWORD mv_access;

   const char* luser = NULL;

   if (mode == PerfMemory::PERF_MODE_RO) {

     ofm_access = FILE_MAP_READ;

     mv_access = FILE_MAP_READ;

   }

   else if (mode == PerfMemory::PERF_MODE_RW) {

 #ifdef LATER

     ofm_access = FILE_MAP_READ | FILE_MAP_WRITE;

     mv_access = FILE_MAP_READ | FILE_MAP_WRITE;

 #else

     THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),

               "Unsupported access mode");

 #endif

   }

   else {

     THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),

               "Illegal access mode");

   }

   // if a user name wasn't specified, then find the user name for

   // the owner of the target vm.

   if (user == NULL || strlen(user) == 0) {

     luser = get_user_name(vmid);

   }

   else {

     luser = user;

   }

   if (luser == NULL) {

     THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),

               "Could not map vmid to user name");

   }

   // get the names for the resources for the target vm

   char* dirname = get_user_tmp_dir(luser);

   // since we don't follow symbolic links when creating the backing

   // store file, we also don't following them when attaching

   //

   if (!is_directory_secure(dirname)) {

     FREE_C_HEAP_ARRAY(char, dirname);

     THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),

               "Process not found");

   }

   char* filename = get_sharedmem_filename(dirname, vmid);

   char* objectname = get_sharedmem_objectname(luser, vmid);

   // copy heap memory to resource memory. the objectname and

   // filename are passed to methods that may throw exceptions.

   // using resource arrays for these names prevents the leaks

   // that would otherwise occur.

   //

   char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);

   char* robjectname = NEW_RESOURCE_ARRAY(char, strlen(objectname) + 1);

   strcpy(rfilename, filename);

   strcpy(robjectname, objectname);

   // free the c heap resources that are no longer needed

   if (luser != user) FREE_C_HEAP_ARRAY(char, luser);

   FREE_C_HEAP_ARRAY(char, dirname);

   FREE_C_HEAP_ARRAY(char, filename);

   FREE_C_HEAP_ARRAY(char, objectname);

   if (*sizep == 0) {

     size = sharedmem_filesize(rfilename, CHECK);

     assert(size != 0, "unexpected size");

   }

   // Open the file mapping object with the given name

   fmh = open_sharedmem_object(robjectname, ofm_access, CHECK);

   assert(fmh != INVALID_HANDLE_VALUE, "unexpected handle value");

   // map the entire file into the address space

   mapAddress = MapViewOfFile(

                  fmh,             /* HANDLE Handle of file mapping object */

                  mv_access,       /* DWORD access flags */

                  0,               /* DWORD High word of offset */

                  0,               /* DWORD Low word of offset */

                  size);           /* DWORD Number of bytes to map */

   if (mapAddress == NULL) {

     if (PrintMiscellaneous && Verbose) {

       warning("MapViewOfFile failed, lasterror = %d\n", GetLastError());

     }

     CloseHandle(fmh);

     THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),

               "Could not map PerfMemory");

   }

   *addrp = (char*)mapAddress;

   *sizep = size;

   // File mapping object can be closed at this time without

   // invalidating the mapped view of the file

   CloseHandle(fmh);

   if (PerfTraceMemOps) {

     tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "

                INTPTR_FORMAT "\n", size, vmid, mapAddress);

   }

 }

 // this method unmaps the the mapped view of the the

 // file mapping object.

 //

 static void remove_file_mapping(char* addr) {

   // the file mapping object was closed in open_file_mapping()

   // after the file map view was created. We only need to

   // unmap the file view here.

   UnmapViewOfFile(addr);

 }

 // create the PerfData memory region in shared memory.

 static char* create_shared_memory(size_t size) {

   return mapping_create_shared(size);

 }

 // release a named, shared memory region

 //

 void delete_shared_memory(char* addr, size_t size) {

   delete_file_mapping(addr, size);

 }

 // create the PerfData memory region

 //

 // This method creates the memory region used to store performance

 // data for the JVM. The memory may be created in standard or

 // shared memory.

 //

 void PerfMemory::create_memory_region(size_t size) {

   if (PerfDisableSharedMem || !os::win32::is_nt()) {

     // do not share the memory for the performance data.

     PerfDisableSharedMem = true;

     _start = create_standard_memory(size);

   }

   else {

     _start = create_shared_memory(size);

     if (_start == NULL) {

       // creation of the shared memory region failed, attempt

       // to create a contiguous, non-shared memory region instead.

       //

       if (PrintMiscellaneous && Verbose) {

         warning("Reverting to non-shared PerfMemory region.\n");

       }

       PerfDisableSharedMem = true;

       _start = create_standard_memory(size);

     }

   }

   if (_start != NULL) _capacity = size;

 }

 // delete the PerfData memory region

 //

 // This method deletes the memory region used to store performance

 // data for the JVM. The memory region indicated by the <address, size>

 // tuple will be inaccessible after a call to this method.

 //

 void PerfMemory::delete_memory_region() {

   assert((start() != NULL && capacity() > 0), "verify proper state");

   // If user specifies PerfDataSaveFile, it will save the performance data

   // to the specified file name no matter whether PerfDataSaveToFile is specified

   // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag

   // -XX:+PerfDataSaveToFile.

   if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {

     save_memory_to_file(start(), capacity());

   }

   if (PerfDisableSharedMem) {

     delete_standard_memory(start(), capacity());

   }

   else {

     delete_shared_memory(start(), capacity());

   }

 }

 // attach to the PerfData memory region for another JVM

 //

 // This method returns an <address, size> tuple that points to

 // a memory buffer that is kept reasonably synchronized with

 // the PerfData memory region for the indicated JVM. This

 // buffer may be kept in synchronization via shared memory

 // or some other mechanism that keeps the buffer updated.

 //

 // If the JVM chooses not to support the attachability feature,

 // this method should throw an UnsupportedOperation exception.

 //

 // This implementation utilizes named shared memory to map

 // the indicated process's PerfData memory region into this JVMs

 // address space.

 //

 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode,

                         char** addrp, size_t* sizep, TRAPS) {

   if (vmid == 0 || vmid == os::current_process_id()) {

      *addrp = start();

      *sizep = capacity();

      return;

   }

   open_file_mapping(user, vmid, mode, addrp, sizep, CHECK);

 }

 // detach from the PerfData memory region of another JVM

 //

 // This method detaches the PerfData memory region of another

 // JVM, specified as an <address, size> tuple of a buffer

 // in this process's address space. This method may perform

 // arbitrary actions to accomplish the detachment. The memory

 // region specified by <address, size> will be inaccessible after

 // a call to this method.

 //

 // If the JVM chooses not to support the attachability feature,

 // this method should throw an UnsupportedOperation exception.

 //

 // This implementation utilizes named shared memory to detach

 // the indicated process's PerfData memory region from this

 // process's address space.

 //

 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {

   assert(addr != 0, "address sanity check");

   assert(bytes > 0, "capacity sanity check");

   if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {

     // prevent accidental detachment of this process's PerfMemory region

     return;

   }

   remove_file_mapping(addr);

 }

 char* PerfMemory::backing_store_filename() {

   return sharedmem_fileName;

 }