text: /*
   * Copyright (c) 2001, 2018, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   *
   */
  
  #include "precompiled.hpp"
  #include "classfile/vmSymbols.hpp"
  #include "logging/log.hpp"
  #include "memory/allocation.inline.hpp"
  #include "memory/resourceArea.hpp"
  #include "oops/oop.inline.hpp"
  #include "os_solaris.inline.hpp"
  #include "runtime/handles.inline.hpp"
  #include "runtime/perfMemory.hpp"
  #include "services/memTracker.hpp"
  #include "utilities/exceptions.hpp"
  
  // put OS-includes here
  #include <sys/types.h>
  #include <sys/mman.h>
  #include <errno.h>
  #include <stdio.h>
  #include <unistd.h>
  #include <sys/stat.h>
  #include <signal.h>
  #include <procfs.h>
  
  /* For POSIX-compliant getpwuid_r on Solaris */
  #define _POSIX_PTHREAD_SEMANTICS
  #include <pwd.h>
  
  static char* backing_store_file_name = NULL;  // name of the backing store
                                                // file, if successfully created.
  
  // 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, !ExecMem)) {
      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
  //
  // Note: this function might be called from signal handler (by os::abort()),
  // don't allocate heap memory.
  //
  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 result;
  
    RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
                result);;
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("Could not create Perfdata save file: %s: %s\n",
                destfile, os::strerror(errno));
      }
    } else {
  
      int fd = result;
  
      for (size_t remaining = size; remaining > 0;) {
  
        RESTARTABLE(::write(fd, addr, remaining), result);
        if (result == OS_ERR) {
          if (PrintMiscellaneous && Verbose) {
            warning("Could not write Perfdata save file: %s: %s\n",
                    destfile, os::strerror(errno));
          }
          break;
        }
        remaining -= (size_t)result;
        addr += result;
      }
  
      result = ::close(fd);
      if (PrintMiscellaneous && Verbose) {
        if (result == OS_ERR) {
          warning("Could not close %s: %s\n", destfile, os::strerror(errno));
        }
      }
    }
    FREE_C_HEAP_ARRAY(char, destfile);
  }
  
  
  // Shared Memory Implementation Details
  
  // Note: the solaris and linux shared memory implementation uses the mmap
  // interface with a backing store file to implement named shared memory.
  // Using the file system as the name space for shared memory allows a
  // common name space to be supported across a variety of platforms. It
  // also provides a name space that Java applications can deal with through
  // simple file apis.
  //
  // The solaris and linux implementations store the backing store file in
  // a user specific temporary directory located in the /tmp file system,
  // which is always a local file system and is sometimes a RAM based file
  // system.
  
  // 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) + 3;
    char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
  
    // 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 pid_t 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;
    pid_t pid = (pid_t)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 statbuf is considered a secure directory for
  // the backing store files. Returns true if the directory is considered
  // a secure location. Returns false if the statbuf is a symbolic link or
  // if an error occurred.
  //
  static bool is_statbuf_secure(struct stat *statp) {
    if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
      // The path represents a link or some non-directory file type,
      // which is not what we expected. Declare it insecure.
      //
      return false;
    }
    // We have an existing directory, check if the permissions are safe.
    //
    if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
      // The directory is open for writing and could be subjected
      // to a symlink or a hard link attack. Declare it insecure.
      //
      return false;
    }
    // If user is not root then see if the uid of the directory matches the effective uid of the process.
    uid_t euid = geteuid();
    if ((euid != 0) && (statp->st_uid != euid)) {
      // The directory was not created by this user, declare it insecure.
      //
      return false;
    }
    return true;
  }
  
  
  // 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) {
    struct stat statbuf;
    int result = 0;
  
    RESTARTABLE(::lstat(path, &statbuf), result);
    if (result == OS_ERR) {
      return false;
    }
  
    // The path exists, see if it is secure.
    return is_statbuf_secure(&statbuf);
  }
  
  
  // Check if the given directory file descriptor 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_dirfd_secure(int dir_fd) {
    struct stat statbuf;
    int result = 0;
  
    RESTARTABLE(::fstat(dir_fd, &statbuf), result);
    if (result == OS_ERR) {
      return false;
    }
  
    // The path exists, now check its mode.
    return is_statbuf_secure(&statbuf);
  }
  
  
  // Check to make sure fd1 and fd2 are referencing the same file system object.
  //
  static bool is_same_fsobject(int fd1, int fd2) {
    struct stat statbuf1;
    struct stat statbuf2;
    int result = 0;
  
    RESTARTABLE(::fstat(fd1, &statbuf1), result);
    if (result == OS_ERR) {
      return false;
    }
    RESTARTABLE(::fstat(fd2, &statbuf2), result);
    if (result == OS_ERR) {
      return false;
    }
  
    if ((statbuf1.st_ino == statbuf2.st_ino) &&
        (statbuf1.st_dev == statbuf2.st_dev)) {
      return true;
    } else {
      return false;
    }
  }
  
  
  // Open the directory of the given path and validate it.
  // Return a DIR * of the open directory.
  //
  static DIR *open_directory_secure(const char* dirname) {
    // Open the directory using open() so that it can be verified
    // to be secure by calling is_dirfd_secure(), opendir() and then check
    // to see if they are the same file system object.  This method does not
    // introduce a window of opportunity for the directory to be attacked that
    // calling opendir() and is_directory_secure() does.
    int result;
    DIR *dirp = NULL;
    RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
    if (result == OS_ERR) {
      // Directory doesn't exist or is a symlink, so there is nothing to cleanup.
      if (PrintMiscellaneous && Verbose) {
        if (errno == ELOOP) {
          warning("directory %s is a symlink and is not secure\n", dirname);
        } else {
          warning("could not open directory %s: %s\n", dirname, os::strerror(errno));
        }
      }
      return dirp;
    }
    int fd = result;
  
    // Determine if the open directory is secure.
    if (!is_dirfd_secure(fd)) {
      // The directory is not a secure directory.
      os::close(fd);
      return dirp;
    }
  
    // Open the directory.
    dirp = ::opendir(dirname);
    if (dirp == NULL) {
      // The directory doesn't exist, close fd and return.
      os::close(fd);
      return dirp;
    }
  
    // Check to make sure fd and dirp are referencing the same file system object.
    if (!is_same_fsobject(fd, dirp->d_fd)) {
      // The directory is not secure.
      os::close(fd);
      os::closedir(dirp);
      dirp = NULL;
      return dirp;
    }
  
    // Close initial open now that we know directory is secure
    os::close(fd);
  
    return dirp;
  }
  
  // NOTE: The code below uses fchdir(), open() and unlink() because
  // fdopendir(), openat() and unlinkat() are not supported on all
  // versions.  Once the support for fdopendir(), openat() and unlinkat()
  // is available on all supported versions the code can be changed
  // to use these functions.
  
  // Open the directory of the given path, validate it and set the
  // current working directory to it.
  // Return a DIR * of the open directory and the saved cwd fd.
  //
  static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
  
    // Open the directory.
    DIR* dirp = open_directory_secure(dirname);
    if (dirp == NULL) {
      // Directory doesn't exist or is insecure, so there is nothing to cleanup.
      return dirp;
    }
    int fd = dirp->d_fd;
  
    // Open a fd to the cwd and save it off.
    int result;
    RESTARTABLE(::open(".", O_RDONLY), result);
    if (result == OS_ERR) {
      *saved_cwd_fd = -1;
    } else {
      *saved_cwd_fd = result;
    }
  
    // Set the current directory to dirname by using the fd of the directory and
    // handle errors, otherwise shared memory files will be created in cwd.
    result = fchdir(fd);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("could not change to directory %s", dirname);
      }
      if (*saved_cwd_fd != -1) {
        ::close(*saved_cwd_fd);
        *saved_cwd_fd = -1;
      }
      // Close the directory.
      os::closedir(dirp);
      return NULL;
    } else {
      return dirp;
    }
  }
  
  // Close the directory and restore the current working directory.
  //
  static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
  
    int result;
    // If we have a saved cwd change back to it and close the fd.
    if (saved_cwd_fd != -1) {
      result = fchdir(saved_cwd_fd);
      ::close(saved_cwd_fd);
    }
  
    // Close the directory.
    os::closedir(dirp);
  }
  
  // Check if the given file descriptor is considered a secure.
  //
  static bool is_file_secure(int fd, const char *filename) {
  
    int result;
    struct stat statbuf;
  
    // Determine if the file is secure.
    RESTARTABLE(::fstat(fd, &statbuf), result);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("fstat failed on %s: %s\n", filename, os::strerror(errno));
      }
      return false;
    }
    if (statbuf.st_nlink > 1) {
      // A file with multiple links is not expected.
      if (PrintMiscellaneous && Verbose) {
        warning("file %s has multiple links\n", filename);
      }
      return false;
    }
    return true;
  }
  
  // return the user name for the given user id
  //
  // the caller is expected to free the allocated memory.
  //
  static char* get_user_name(uid_t uid) {
  
    struct passwd pwent;
  
    // determine the max pwbuf size from sysconf, and hardcode
    // a default if this not available through sysconf.
    //
    long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
    if (bufsize == -1)
      bufsize = 1024;
  
    char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
  
    struct passwd* p = NULL;
    int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
  
    if (p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
      if (PrintMiscellaneous && Verbose) {
        if (p == NULL) {
          warning("Could not retrieve passwd entry: %s\n",
                  os::strerror(errno));
        }
        else {
          warning("Could not determine user name: %s\n",
                  p->pw_name == NULL ? "pw_name = NULL" :
                                       "pw_name zero length");
        }
      }
      FREE_C_HEAP_ARRAY(char, pwbuf);
      return NULL;
    }
  
    char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
    strcpy(user_name, p->pw_name);
  
    FREE_C_HEAP_ARRAY(char, pwbuf);
    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, TRAPS) {
  
    // short circuit the directory search if the process doesn't even exist.
    if (kill(vmid, 0) == OS_ERR) {
      if (errno == ESRCH) {
        THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
                    "Process not found");
      }
      else /* EPERM */ {
        THROW_MSG_0(vmSymbols::java_io_IOException(), os::strerror(errno));
      }
    }
  
    // directory search
    char* oldest_user = NULL;
    time_t oldest_ctime = 0;
  
    const char* tmpdirname = os::get_temp_directory();
  
    // open the temp directory
    DIR* tmpdirp = os::opendir(tmpdirname);
  
    if (tmpdirp == NULL) {
      // Cannot open the directory to get the user name, return.
      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;
    errno = 0;
    while ((dentry = os::readdir(tmpdirp)) != 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) + 2, mtInternal);
      strcpy(usrdir_name, tmpdirname);
      strcat(usrdir_name, "/");
      strcat(usrdir_name, dentry->d_name);
  
      // open the user directory
      DIR* subdirp = open_directory_secure(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;
      errno = 0;
      while ((udentry = os::readdir(subdirp)) != NULL) {
  
        if (filename_to_pid(udentry->d_name) == vmid) {
          struct stat statbuf;
          int result;
  
          char* filename = NEW_C_HEAP_ARRAY(char,
                   strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
  
          strcpy(filename, usrdir_name);
          strcat(filename, "/");
          strcat(filename, udentry->d_name);
  
          // don't follow symbolic links for the file
          RESTARTABLE(::lstat(filename, &statbuf), result);
          if (result == OS_ERR) {
             FREE_C_HEAP_ARRAY(char, filename);
             continue;
          }
  
          // skip over files that are not regular files.
          if (!S_ISREG(statbuf.st_mode)) {
            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, mtInternal);
  
              strcpy(oldest_user, user);
              oldest_ctime = statbuf.st_ctime;
            }
          }
  
          FREE_C_HEAP_ARRAY(char, filename);
        }
      }
      os::closedir(subdirp);
      FREE_C_HEAP_ARRAY(char, usrdir_name);
    }
    os::closedir(tmpdirp);
  
    return(oldest_user);
  }
  
  // return the name of the user that owns the JVM indicated by the given vmid.
  //
  static char* get_user_name(int vmid, TRAPS) {
  
    char psinfo_name[PATH_MAX];
    int result;
  
    snprintf(psinfo_name, PATH_MAX, "/proc/%d/psinfo", vmid);
  
    RESTARTABLE(::open(psinfo_name, O_RDONLY), result);
  
    if (result != OS_ERR) {
      int fd = result;
  
      psinfo_t psinfo;
      char* addr = (char*)&psinfo;
  
      for (size_t remaining = sizeof(psinfo_t); remaining > 0;) {
  
        RESTARTABLE(::read(fd, addr, remaining), result);
        if (result == OS_ERR) {
          ::close(fd);
          THROW_MSG_0(vmSymbols::java_io_IOException(), "Read error");
        } else {
          remaining-=result;
          addr+=result;
        }
      }
  
      ::close(fd);
  
      // get the user name for the effective user id of the process
      char* user_name = get_user_name(psinfo.pr_euid);
  
      return user_name;
    }
  
    if (result == OS_ERR && errno == EACCES) {
  
      // In this case, the psinfo file for the process id existed,
      // but we didn't have permission to access it.
      THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
                  os::strerror(errno));
    }
  
    // at this point, we don't know if the process id itself doesn't
    // exist or if the psinfo file doesn't exit. If the psinfo file
    // doesn't exist, then we are running on Solaris 2.5.1 or earlier.
    // since the structured procfs and old procfs interfaces can't be
    // mixed, we attempt to find the file through a directory search.
  
    return get_user_name_slow(vmid, THREAD);
  }
  
  // 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, mtInternal);
    snprintf(name, nbytes, "%s/%d", dirname, vmid);
  
    return name;
  }
  
  
  // remove file
  //
  // this method removes the file specified by the given path
  //
  static void remove_file(const char* path) {
  
    int result;
  
    // if the file is a directory, the following unlink will fail. since
    // we don't expect to find directories in the user temp directory, we
    // won't try to handle this situation. even if accidentially or
    // maliciously planted, the directory's presence won't hurt anything.
    //
    RESTARTABLE(::unlink(path), result);
    if (PrintMiscellaneous && Verbose && result == OS_ERR) {
      if (errno != ENOENT) {
        warning("Could not unlink shared memory backing"
                " store file %s : %s\n", path, os::strerror(errno));
      }
    }
  }
  
  
  // 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) {
  
    int saved_cwd_fd;
    // open the directory
    DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
    if (dirp == NULL) {
      // directory doesn't exist or is insecure, so there is nothing to 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;
    errno = 0;
    while ((entry = os::readdir(dirp)) != NULL) {
  
      pid_t 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 ".."
          unlink(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 sending signal number 0 to
      // the process id (see kill(2)). if kill determines that the
      // process does not exist, then the file resources are removed.
      // if kill determines that that we don't have permission to
      // signal the process, then the file resources are assumed to
      // be stale and are removed because the resources for such a
      // process should be in a different user specific directory.
      //
      if ((pid == os::current_process_id()) ||
          (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
  
          unlink(entry->d_name);
      }
      errno = 0;
    }
  
    // close the directory and reset the current working directory
    close_directory_secure_cwd(dirp, saved_cwd_fd);
  }
  
  // make the user specific temporary directory. Returns true if
  // the directory exists and is secure upon return. Returns false
  // if the directory exists but is either a symlink, is otherwise
  // insecure, or if an error occurred.
  //
  static bool make_user_tmp_dir(const char* dirname) {
  
    // create the directory with 0755 permissions. note that the directory
    // will be owned by euid::egid, which may not be the same as uid::gid.
    //
    if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
      if (errno == EEXIST) {
        // 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;
        }
      }
      else {
        // we encountered some other failure while attempting
        // to create the directory
        //
        if (PrintMiscellaneous && Verbose) {
          warning("could not create directory %s: %s\n",
                  dirname, os::strerror(errno));
        }
        return false;
      }
    }
    return true;
  }
  
  // create the shared memory file resources
  //
  // This method creates the shared memory file with the given size
  // This method also creates the user specific temporary directory, if
  // it does not yet exist.
  //
  static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
  
    // make the user temporary directory
    if (!make_user_tmp_dir(dirname)) {
      // could not make/find the directory or the found directory
      // was not secure
      return -1;
    }
  
    int saved_cwd_fd;
    // open the directory and set the current working directory to it
    DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
    if (dirp == NULL) {
      // Directory doesn't exist or is insecure, so cannot create shared
      // memory file.
      return -1;
    }
  
    // Open the filename in the current directory.
    // Cannot use O_TRUNC here; truncation of an existing file has to happen
    // after the is_file_secure() check below.
    int result;
    RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        if (errno == ELOOP) {
          warning("file %s is a symlink and is not secure\n", filename);
        } else {
          warning("could not create file %s: %s\n", filename, os::strerror(errno));
        }
      }
      // close the directory and reset the current working directory
      close_directory_secure_cwd(dirp, saved_cwd_fd);
  
      return -1;
    }
    // close the directory and reset the current working directory
    close_directory_secure_cwd(dirp, saved_cwd_fd);
  
    // save the file descriptor
    int fd = result;
  
    // check to see if the file is secure
    if (!is_file_secure(fd, filename)) {
      ::close(fd);
      return -1;
    }
  
    // truncate the file to get rid of any existing data
    RESTARTABLE(::ftruncate(fd, (off_t)0), result);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("could not truncate shared memory file: %s\n", os::strerror(errno));
      }
      ::close(fd);
      return -1;
    }
    // set the file size
    RESTARTABLE(::ftruncate(fd, (off_t)size), result);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("could not set shared memory file size: %s\n", os::strerror(errno));
      }
      ::close(fd);
      return -1;
    }
  
    return fd;
  }
  
  // open the shared memory file for the given user and vmid. returns
  // the file descriptor for the open file or -1 if the file could not
  // be opened.
  //
  static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
  
    // open the file
    int result;
    RESTARTABLE(::open(filename, oflags), result);
    if (result == OS_ERR) {
      if (errno == ENOENT) {
        THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
                   "Process not found", OS_ERR);
      }
      else if (errno == EACCES) {
        THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(),
                   "Permission denied", OS_ERR);
      }
      else {
        THROW_MSG_(vmSymbols::java_io_IOException(),
                   os::strerror(errno), OS_ERR);
      }
    }
    int fd = result;
  
    // check to see if the file is secure
    if (!is_file_secure(fd, filename)) {
      ::close(fd);
      return -1;
    }
  
    return fd;
  }
  
  // create a named shared memory region. returns the address of the
  // memory region on success or NULL on failure. A return value of
  // NULL will ultimately disable the shared memory feature.
  //
  // On Solaris, the name space for shared memory objects
  // is the file system name space.
  //
  // A monitoring application attaching to a JVM does not need to know
  // the file system name of the shared memory object. However, it may
  // be convenient for applications to discover the existence of newly
  // created and terminating JVMs by watching the file system name space
  // for files being created or removed.
  //
  static char* mmap_create_shared(size_t size) {
  
    int result;
    int fd;
    char* mapAddress;
  
    int vmid = os::current_process_id();
  
    char* user_name = get_user_name(geteuid());
  
    if (user_name == NULL)
      return NULL;
  
    char* dirname = get_user_tmp_dir(user_name);
    char* filename = get_sharedmem_filename(dirname, vmid);
  
    // get the short filename
    char* short_filename = strrchr(filename, '/');
    if (short_filename == NULL) {
      short_filename = filename;
    } else {
      short_filename++;
    }
  
    // cleanup any stale shared memory files
    cleanup_sharedmem_resources(dirname);
  
    assert(((size > 0) && (size % os::vm_page_size() == 0)),
           "unexpected PerfMemory region size");
  
    fd = create_sharedmem_resources(dirname, short_filename, size);
  
    FREE_C_HEAP_ARRAY(char, user_name);
    FREE_C_HEAP_ARRAY(char, dirname);
  
    if (fd == -1) {
      FREE_C_HEAP_ARRAY(char, filename);
      return NULL;
    }
  
    mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
  
    result = ::close(fd);
    assert(result != OS_ERR, "could not close file");
  
    if (mapAddress == MAP_FAILED) {
      if (PrintMiscellaneous && Verbose) {
        warning("mmap failed -  %s\n", os::strerror(errno));
      }
      remove_file(filename);
      FREE_C_HEAP_ARRAY(char, filename);
      return NULL;
    }
  
    // save the file name for use in delete_shared_memory()
    backing_store_file_name = filename;
  
    // clear the shared memory region
    (void)::memset((void*) mapAddress, 0, size);
  
    // it does not go through os api, the operation has to record from here
    MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress,
      size, CURRENT_PC, mtInternal);
  
    return mapAddress;
  }
  
  // release a named shared memory region
  //
  static void unmap_shared(char* addr, size_t bytes) {
    os::release_memory(addr, bytes);
  }
  
  // create the PerfData memory region in shared memory.
  //
  static char* create_shared_memory(size_t size) {
  
    // create the shared memory region.
    return mmap_create_shared(size);
  }
  
  // delete the shared PerfData memory region
  //
  static void delete_shared_memory(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
    // the process. The backing store file is deleted from the file system.
  
    assert(!PerfDisableSharedMem, "shouldn't be here");
  
    if (backing_store_file_name != NULL) {
      remove_file(backing_store_file_name);
      // Don't.. Free heap memory could deadlock os::abort() if it is called
      // from signal handler. OS will reclaim the heap memory.
      // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
      backing_store_file_name = NULL;
    }
  }
  
  // return the size of the file for the given file descriptor
  // or 0 if it is not a valid size for a shared memory file
  //
  static size_t sharedmem_filesize(int fd, TRAPS) {
  
    struct stat statbuf;
    int result;
  
    RESTARTABLE(::fstat(fd, &statbuf), result);
    if (result == OS_ERR) {
      if (PrintMiscellaneous && Verbose) {
        warning("fstat failed: %s\n", os::strerror(errno));
      }
      THROW_MSG_0(vmSymbols::java_io_IOException(),
                  "Could not determine PerfMemory size");
    }
  
    if ((statbuf.st_size == 0) ||
       ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
      THROW_MSG_0(vmSymbols::java_lang_Exception(),
                  "Invalid PerfMemory size");
    }
  
    return (size_t)statbuf.st_size;
  }
  
  // attach to a named shared memory region.
  //
  static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
  
    char* mapAddress;
    int result;
    int fd;
    size_t size = 0;
    const char* luser = NULL;
  
    int mmap_prot;
    int file_flags;
  
    ResourceMark rm;
  
    // map the high level access mode to the appropriate permission
    // constructs for the file and the shared memory mapping.
    if (mode == PerfMemory::PERF_MODE_RO) {
      mmap_prot = PROT_READ;
      file_flags = O_RDONLY | O_NOFOLLOW;
    }
    else if (mode == PerfMemory::PERF_MODE_RW) {
  #ifdef LATER
      mmap_prot = PROT_READ | PROT_WRITE;
      file_flags = O_RDWR | O_NOFOLLOW;
  #else
      THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
                "Unsupported access mode");
  #endif
    }
    else {
      THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
                "Illegal access mode");
    }
  
    if (user == NULL || strlen(user) == 0) {
      luser = get_user_name(vmid, CHECK);
    }
    else {
      luser = user;
    }
  
    if (luser == NULL) {
      THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
                "Could not map vmid to user Name");
    }
  
    char* dirname = get_user_tmp_dir(luser);
  
    // since we don't follow symbolic links when creating the backing
    // store file, we don't follow them when attaching either.
    //
    if (!is_directory_secure(dirname)) {
      FREE_C_HEAP_ARRAY(char, dirname);
      if (luser != user) {
        FREE_C_HEAP_ARRAY(char, luser);
      }
      THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
                "Process not found");
    }
  
    char* filename = get_sharedmem_filename(dirname, vmid);
  
    // copy heap memory to resource memory. the open_sharedmem_file
    // method below need to use the filename, but could throw an
    // exception. using a resource array prevents the leak that
    // would otherwise occur.
    char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
    strcpy(rfilename, filename);
  
    // 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);
  
    // open the shared memory file for the give vmid
    fd = open_sharedmem_file(rfilename, file_flags, THREAD);
  
    if (fd == OS_ERR) {
      return;
    }
  
    if (HAS_PENDING_EXCEPTION) {
      ::close(fd);
      return;
    }
  
    if (*sizep == 0) {
      size = sharedmem_filesize(fd, CHECK);
    } else {
      size = *sizep;
    }
  
    assert(size > 0, "unexpected size <= 0");
  
    mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
  
    result = ::close(fd);
    assert(result != OS_ERR, "could not close file");
  
    if (mapAddress == MAP_FAILED) {
      if (PrintMiscellaneous && Verbose) {
        warning("mmap failed: %s\n", os::strerror(errno));
      }
      THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
                "Could not map PerfMemory");
    }
  
    // it does not go through os api, the operation has to record from here
    MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress,
      size, CURRENT_PC, mtInternal);
  
    *addr = mapAddress;
    *sizep = size;
  
    log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at "
                            INTPTR_FORMAT, size, vmid, (void*)mapAddress);
  }
  
  // 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) {
      // do not share the memory for the performance data.
      _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;
    }
  
    mmap_attach_shared(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;
    }
  
    unmap_shared(addr, bytes);
  }
  