text: /* provide a replacement openat function
     Copyright (C) 2004-2015 Free Software Foundation, Inc.
  
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program 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 for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  /* written by Jim Meyering */
  
  /* If the user's config.h happens to include <fcntl.h>, let it include only
     the system's <fcntl.h> here, so that orig_openat doesn't recurse to
     rpl_openat.  */
  #define __need_system_fcntl_h
  #include <config.h>
  
  /* Get the original definition of open.  It might be defined as a macro.  */
  #include <fcntl.h>
  #include <sys/types.h>
  #undef __need_system_fcntl_h
  
  #if HAVE_OPENAT
  static int
  orig_openat (int fd, char const *filename, int flags, mode_t mode)
  {
    return openat (fd, filename, flags, mode);
  }
  #endif
  
  /* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
     this include because of the preliminary #include <fcntl.h> above.  */
  #include "fcntl.h"
  
  #include "openat.h"
  
  #include <stdarg.h>
  #include <stdbool.h>
  #include <stddef.h>
  #include <string.h>
  #include <sys/stat.h>
  #include <errno.h>
  
  #if HAVE_OPENAT
  
  /* Like openat, but work around Solaris 9 bugs with trailing slash.  */
  int
  rpl_openat (int dfd, char const *filename, int flags, ...)
  {
    mode_t mode;
    int fd;
  
    mode = 0;
    if (flags & O_CREAT)
      {
        va_list arg;
        va_start (arg, flags);
  
        /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
           creates crashing code when 'mode_t' is smaller than 'int'.  */
        mode = va_arg (arg, PROMOTED_MODE_T);
  
        va_end (arg);
      }
  
  # if OPEN_TRAILING_SLASH_BUG
    /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
       is specified, then fail.
       Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
       says that
         "A pathname that contains at least one non-slash character and that
          ends with one or more trailing slashes shall be resolved as if a
          single dot character ( '.' ) were appended to the pathname."
       and
         "The special filename dot shall refer to the directory specified by
          its predecessor."
       If the named file already exists as a directory, then
         - if O_CREAT is specified, open() must fail because of the semantics
           of O_CREAT,
         - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
           <http://www.opengroup.org/susv3/functions/open.html> says that it
           fails with errno = EISDIR in this case.
       If the named file does not exist or does not name a directory, then
         - if O_CREAT is specified, open() must fail since open() cannot create
           directories,
         - if O_WRONLY or O_RDWR is specified, open() must fail because the
           file does not contain a '.' directory.  */
    if (flags & (O_CREAT | O_WRONLY | O_RDWR))
      {
        size_t len = strlen (filename);
        if (len > 0 && filename[len - 1] == '/')
          {
            errno = EISDIR;
            return -1;
          }
      }
  # endif
  
    fd = orig_openat (dfd, filename, flags, mode);
  
  # if OPEN_TRAILING_SLASH_BUG
    /* If the filename ends in a slash and fd does not refer to a directory,
       then fail.
       Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
       says that
         "A pathname that contains at least one non-slash character and that
          ends with one or more trailing slashes shall be resolved as if a
          single dot character ( '.' ) were appended to the pathname."
       and
         "The special filename dot shall refer to the directory specified by
          its predecessor."
       If the named file without the slash is not a directory, open() must fail
       with ENOTDIR.  */
    if (fd >= 0)
      {
        /* We know len is positive, since open did not fail with ENOENT.  */
        size_t len = strlen (filename);
        if (filename[len - 1] == '/')
          {
            struct stat statbuf;
  
            if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
              {
                close (fd);
                errno = ENOTDIR;
                return -1;
              }
          }
      }
  # endif
  
    return fd;
  }
  
  #else /* !HAVE_OPENAT */
  
  # include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
  # include "openat-priv.h"
  # include "save-cwd.h"
  
  /* Replacement for Solaris' openat function.
     <http://www.google.com/search?q=openat+site:docs.sun.com>
     First, try to simulate it via open ("/proc/self/fd/FD/FILE").
     Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
     If either the save_cwd or the restore_cwd fails (relatively unlikely),
     then give a diagnostic and exit nonzero.
     Otherwise, upon failure, set errno and return -1, as openat does.
     Upon successful completion, return a file descriptor.  */
  int
  openat (int fd, char const *file, int flags, ...)
  {
    mode_t mode = 0;
  
    if (flags & O_CREAT)
      {
        va_list arg;
        va_start (arg, flags);
  
        /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
           creates crashing code when 'mode_t' is smaller than 'int'.  */
        mode = va_arg (arg, PROMOTED_MODE_T);
  
        va_end (arg);
      }
  
    return openat_permissive (fd, file, flags, mode, NULL);
  }
  
  /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
     nonnull, set *CWD_ERRNO to an errno value if unable to save
     or restore the initial working directory.  This is needed only
     the first time remove.c's remove_dir opens a command-line
     directory argument.
  
     If a previous attempt to restore the current working directory
     failed, then we must not even try to access a '.'-relative name.
     It is the caller's responsibility not to call this function
     in that case.  */
  
  int
  openat_permissive (int fd, char const *file, int flags, mode_t mode,
                     int *cwd_errno)
  {
    struct saved_cwd saved_cwd;
    int saved_errno;
    int err;
    bool save_ok;
  
    if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
      return open (file, flags, mode);
  
    {
      char buf[OPENAT_BUFFER_SIZE];
      char *proc_file = openat_proc_name (buf, fd, file);
      if (proc_file)
        {
          int open_result = open (proc_file, flags, mode);
          int open_errno = errno;
          if (proc_file != buf)
            free (proc_file);
          /* If the syscall succeeds, or if it fails with an unexpected
             errno value, then return right away.  Otherwise, fall through
             and resort to using save_cwd/restore_cwd.  */
          if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
            {
              errno = open_errno;
              return open_result;
            }
        }
    }
  
    save_ok = (save_cwd (&saved_cwd) == 0);
    if (! save_ok)
      {
        if (! cwd_errno)
          openat_save_fail (errno);
        *cwd_errno = errno;
      }
    if (0 <= fd && fd == saved_cwd.desc)
      {
        /* If saving the working directory collides with the user's
           requested fd, then the user's fd must have been closed to
           begin with.  */
        free_cwd (&saved_cwd);
        errno = EBADF;
        return -1;
      }
  
    err = fchdir (fd);
    saved_errno = errno;
  
    if (! err)
      {
        err = open (file, flags, mode);
        saved_errno = errno;
        if (save_ok && restore_cwd (&saved_cwd) != 0)
          {
            if (! cwd_errno)
              {
                /* Don't write a message to just-created fd 2.  */
                saved_errno = errno;
                if (err == STDERR_FILENO)
                  close (err);
                openat_restore_fail (saved_errno);
              }
            *cwd_errno = errno;
          }
      }
  
    free_cwd (&saved_cwd);
    errno = saved_errno;
    return err;
  }
  
  /* Return true if our openat implementation must resort to
     using save_cwd and restore_cwd.  */
  bool
  openat_needs_fchdir (void)
  {
    bool needs_fchdir = true;
    int fd = open ("/", O_SEARCH);
  
    if (0 <= fd)
      {
        char buf[OPENAT_BUFFER_SIZE];
        char *proc_file = openat_proc_name (buf, fd, ".");
        if (proc_file)
          {
            needs_fchdir = false;
            if (proc_file != buf)
              free (proc_file);
          }
        close (fd);
      }
  
    return needs_fchdir;
  }
  
  #endif /* !HAVE_OPENAT */
  