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108429b83f
Idea and some code from Ulrich Drepper's glibc changes. (BUILD_PROC_NAME): New macro. Include <stdio.h>, <string.h>, "alloca.h" and "intprops.h". (rpl_openat): Emulate by trying to open /proc/self/fd/%d/%s, before falling back on save_cwd and restore_cwd. (fdopendir, fstatat, unlinkat): Likewise.
292 lines
8.3 KiB
C
292 lines
8.3 KiB
C
/* provide a replacement openat function
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Copyright (C) 2004, 2005 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* written by Jim Meyering */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "openat.h"
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#include <stdlib.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <fcntl.h>
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#include "alloca.h"
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#include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
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#include "intprops.h"
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#include "save-cwd.h"
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#include "gettext.h"
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#define _(msgid) gettext (msgid)
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/* Set PROC_FD_FILENAME to the expansion of "/proc/self/fd/%d/%s" in
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alloca'd memory, using FD and FILE, respectively for %d and %s. */
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#define BUILD_PROC_NAME(Proc_fd_filename, Fd, File) \
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do \
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{ \
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size_t filelen = strlen (File); \
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static const char procfd[] = "/proc/self/fd/%d/%s"; \
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/* Buffer for the file name we are going to use. It consists of \
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- the string /proc/self/fd/ \
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- the file descriptor number \
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- the file name provided. \
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The final NUL is included in the sizeof. \
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Subtract 4 to account for %d and %s. */ \
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size_t buflen = sizeof (procfd) - 4 + INT_STRLEN_BOUND (Fd) + filelen; \
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(Proc_fd_filename) = alloca (buflen); \
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snprintf ((Proc_fd_filename), buflen, procfd, (Fd), (File)); \
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} \
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while (0)
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/* Replacement for Solaris' openat function.
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<http://www.google.com/search?q=openat+site:docs.sun.com>
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Simulate it by doing save_cwd/fchdir/open/restore_cwd.
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If either the save_cwd or the restore_cwd fails (relatively unlikely,
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and usually indicative of a problem that deserves close attention),
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then give a diagnostic and exit nonzero.
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Otherwise, upon failure, set errno and return -1, as openat does.
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Upon successful completion, return a file descriptor. */
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int
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rpl_openat (int fd, char const *file, int flags, ...)
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{
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struct saved_cwd saved_cwd;
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int saved_errno;
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int err;
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mode_t mode = 0;
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if (flags & O_CREAT)
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{
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va_list arg;
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va_start (arg, flags);
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/* Use the promoted type (int), not mode_t, as second argument. */
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mode = (mode_t) va_arg (arg, int);
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va_end (arg);
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}
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if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
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return open (file, flags, mode);
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{
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char *proc_file;
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BUILD_PROC_NAME (proc_file, fd, file);
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err = open (proc_file, flags, mode);
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/* If the syscall succeeded, or if it failed for any reason other
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than ENOTDIR (i.e., /proc is not mounted), then return right away.
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Otherwise, fall through and resort to save_cwd/restore_cwd. */
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if (0 <= err || errno != ENOTDIR)
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return err;
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}
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if (save_cwd (&saved_cwd) != 0)
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openat_save_fail (errno);
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if (fchdir (fd) != 0)
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{
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saved_errno = errno;
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return -1;
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}
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err = open (file, flags, mode);
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saved_errno = errno;
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if (restore_cwd (&saved_cwd) != 0)
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openat_restore_fail (errno);
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return err;
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}
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#if !HAVE_FDOPENDIR
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/* Replacement for Solaris' function by the same name.
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<http://www.google.com/search?q=fdopendir+site:docs.sun.com>
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Simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
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If either the save_cwd or the restore_cwd fails (relatively unlikely,
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and usually indicative of a problem that deserves close attention),
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then give a diagnostic and exit nonzero.
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Otherwise, this function works just like Solaris' fdopendir.
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W A R N I N G:
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Unlike the other fd-related functions here, this one
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effectively consumes its FD parameter. The caller should not
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close or otherwise manipulate FD if this function returns successfully. */
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DIR *
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fdopendir (int fd)
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{
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struct saved_cwd saved_cwd;
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int saved_errno;
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DIR *dir;
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{
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char *proc_file;
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BUILD_PROC_NAME (proc_file, fd, ".");
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dir = opendir (proc_file);
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saved_errno = errno;
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/* If the syscall succeeded, or if it failed for any reason other
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than ENOTDIR (i.e., /proc is not mounted), then return right away.
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Otherwise, fall through and resort to save_cwd/restore_cwd. */
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if (dir != NULL || errno != ENOTDIR)
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goto close_and_return;
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}
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if (save_cwd (&saved_cwd) != 0)
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openat_save_fail (errno);
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if (fchdir (fd) != 0)
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{
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saved_errno = errno;
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return NULL;
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}
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dir = opendir (".");
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saved_errno = errno;
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if (restore_cwd (&saved_cwd) != 0)
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openat_restore_fail (errno);
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free_cwd (&saved_cwd);
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close_and_return:;
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if (dir)
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close (fd);
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errno = saved_errno;
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return dir;
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}
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#endif
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/* Replacement for Solaris' function by the same name.
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<http://www.google.com/search?q=fstatat+site:docs.sun.com>
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Simulate it by doing save_cwd/fchdir/(stat|lstat)/restore_cwd.
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If either the save_cwd or the restore_cwd fails (relatively unlikely,
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and usually indicative of a problem that deserves close attention),
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then give a diagnostic and exit nonzero.
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Otherwise, this function works just like Solaris' fstatat. */
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int
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fstatat (int fd, char const *file, struct stat *st, int flag)
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{
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struct saved_cwd saved_cwd;
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int saved_errno;
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int err;
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if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
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return (flag == AT_SYMLINK_NOFOLLOW
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? lstat (file, st)
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: stat (file, st));
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{
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char *proc_file;
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BUILD_PROC_NAME (proc_file, fd, file);
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err = (flag == AT_SYMLINK_NOFOLLOW
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? lstat (proc_file, st)
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: stat (proc_file, st));
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/* If the syscall succeeded, or if it failed for any reason other
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than ENOTDIR (i.e., /proc is not mounted), then return right away.
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Otherwise, fall through and resort to save_cwd/restore_cwd. */
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if (0 <= err || errno != ENOTDIR)
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return err;
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}
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if (save_cwd (&saved_cwd) != 0)
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openat_save_fail (errno);
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if (fchdir (fd) != 0)
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{
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saved_errno = errno;
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return -1;
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}
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err = (flag == AT_SYMLINK_NOFOLLOW
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? lstat (file, st)
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: stat (file, st));
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saved_errno = errno;
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if (restore_cwd (&saved_cwd) != 0)
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openat_restore_fail (errno);
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return err;
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}
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/* Replacement for Solaris' function by the same name.
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<http://www.google.com/search?q=unlinkat+site:docs.sun.com>
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Simulate it by doing save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
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If either the save_cwd or the restore_cwd fails (relatively unlikely,
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and usually indicative of a problem that deserves close attention),
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then give a diagnostic and exit nonzero.
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Otherwise, this function works just like Solaris' unlinkat. */
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int
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unlinkat (int fd, char const *file, int flag)
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{
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struct saved_cwd saved_cwd;
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int saved_errno;
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int err;
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if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
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return (flag == AT_REMOVEDIR ? rmdir (file) : unlink (file));
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{
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char *proc_file;
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BUILD_PROC_NAME (proc_file, fd, file);
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err = (flag == AT_REMOVEDIR ? rmdir (proc_file) : unlink (proc_file));
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/* If the syscall succeeded, or if it failed for any reason other
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than ENOTDIR (i.e., /proc is not mounted), then return right away.
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Otherwise, fall through and resort to save_cwd/restore_cwd. */
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if (0 <= err || errno != ENOTDIR)
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return err;
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}
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if (save_cwd (&saved_cwd) != 0)
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openat_save_fail (errno);
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if (fchdir (fd) != 0)
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{
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saved_errno = errno;
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return -1;
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}
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err = (flag == AT_REMOVEDIR ? rmdir (file) : unlink (file));
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saved_errno = errno;
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if (restore_cwd (&saved_cwd) != 0)
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openat_restore_fail (errno);
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free_cwd (&saved_cwd);
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errno = saved_errno;
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return err;
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}
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