287 lines
8.5 KiB
C
287 lines
8.5 KiB
C
/* provide a replacement openat function
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Copyright (C) 2004-2016 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 3 of the License, or
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(at your option) 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, see <http://www.gnu.org/licenses/>. */
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/* written by Jim Meyering */
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/* If the user's config.h happens to include <fcntl.h>, let it include only
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the system's <fcntl.h> here, so that orig_openat doesn't recurse to
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rpl_openat. */
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#define __need_system_fcntl_h
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#include <config.h>
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/* Get the original definition of open. It might be defined as a macro. */
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#include <fcntl.h>
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#include <sys/types.h>
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#undef __need_system_fcntl_h
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#if HAVE_OPENAT
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static int
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orig_openat (int fd, char const *filename, int flags, mode_t mode)
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{
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return openat (fd, filename, flags, mode);
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}
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#endif
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/* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
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this include because of the preliminary #include <fcntl.h> above. */
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#include "fcntl.h"
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#include "openat.h"
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#include <stdarg.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <errno.h>
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#if HAVE_OPENAT
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/* Like openat, but work around Solaris 9 bugs with trailing slash. */
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int
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rpl_openat (int dfd, char const *filename, int flags, ...)
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{
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mode_t mode;
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int fd;
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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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/* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
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creates crashing code when 'mode_t' is smaller than 'int'. */
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mode = va_arg (arg, PROMOTED_MODE_T);
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va_end (arg);
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}
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# if OPEN_TRAILING_SLASH_BUG
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/* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
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is specified, then fail.
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Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
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says that
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"A pathname that contains at least one non-slash character and that
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ends with one or more trailing slashes shall be resolved as if a
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single dot character ( '.' ) were appended to the pathname."
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and
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"The special filename dot shall refer to the directory specified by
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its predecessor."
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If the named file already exists as a directory, then
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- if O_CREAT is specified, open() must fail because of the semantics
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of O_CREAT,
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- if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
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<http://www.opengroup.org/susv3/functions/open.html> says that it
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fails with errno = EISDIR in this case.
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If the named file does not exist or does not name a directory, then
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- if O_CREAT is specified, open() must fail since open() cannot create
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directories,
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- if O_WRONLY or O_RDWR is specified, open() must fail because the
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file does not contain a '.' directory. */
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if (flags & (O_CREAT | O_WRONLY | O_RDWR))
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{
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size_t len = strlen (filename);
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if (len > 0 && filename[len - 1] == '/')
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{
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errno = EISDIR;
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return -1;
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}
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}
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# endif
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fd = orig_openat (dfd, filename, flags, mode);
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# if OPEN_TRAILING_SLASH_BUG
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/* If the filename ends in a slash and fd does not refer to a directory,
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then fail.
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Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
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says that
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"A pathname that contains at least one non-slash character and that
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ends with one or more trailing slashes shall be resolved as if a
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single dot character ( '.' ) were appended to the pathname."
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and
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"The special filename dot shall refer to the directory specified by
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its predecessor."
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If the named file without the slash is not a directory, open() must fail
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with ENOTDIR. */
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if (fd >= 0)
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{
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/* We know len is positive, since open did not fail with ENOENT. */
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size_t len = strlen (filename);
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if (filename[len - 1] == '/')
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{
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struct stat statbuf;
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if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
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{
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close (fd);
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errno = ENOTDIR;
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return -1;
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}
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}
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}
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# endif
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return fd;
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}
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#else /* !HAVE_OPENAT */
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# include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
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# include "openat-priv.h"
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# include "save-cwd.h"
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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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First, try to simulate it via open ("/proc/self/fd/FD/FILE").
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Failing that, 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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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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openat (int fd, char const *file, int flags, ...)
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{
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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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/* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
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creates crashing code when 'mode_t' is smaller than 'int'. */
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mode = va_arg (arg, PROMOTED_MODE_T);
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va_end (arg);
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}
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return openat_permissive (fd, file, flags, mode, NULL);
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}
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/* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
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nonnull, set *CWD_ERRNO to an errno value if unable to save
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or restore the initial working directory. This is needed only
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the first time remove.c's remove_dir opens a command-line
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directory argument.
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If a previous attempt to restore the current working directory
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failed, then we must not even try to access a '.'-relative name.
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It is the caller's responsibility not to call this function
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in that case. */
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int
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openat_permissive (int fd, char const *file, int flags, mode_t mode,
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int *cwd_errno)
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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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bool save_ok;
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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 buf[OPENAT_BUFFER_SIZE];
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char *proc_file = openat_proc_name (buf, fd, file);
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if (proc_file)
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{
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int open_result = open (proc_file, flags, mode);
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int open_errno = errno;
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if (proc_file != buf)
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free (proc_file);
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/* If the syscall succeeds, or if it fails with an unexpected
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errno value, then return right away. Otherwise, fall through
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and resort to using save_cwd/restore_cwd. */
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if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
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{
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errno = open_errno;
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return open_result;
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}
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}
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}
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save_ok = (save_cwd (&saved_cwd) == 0);
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if (! save_ok)
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{
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if (! cwd_errno)
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openat_save_fail (errno);
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*cwd_errno = errno;
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}
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if (0 <= fd && fd == saved_cwd.desc)
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{
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/* If saving the working directory collides with the user's
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requested fd, then the user's fd must have been closed to
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begin with. */
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free_cwd (&saved_cwd);
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errno = EBADF;
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return -1;
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}
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err = fchdir (fd);
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saved_errno = errno;
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if (! err)
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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 (save_ok && restore_cwd (&saved_cwd) != 0)
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{
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if (! cwd_errno)
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{
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/* Don't write a message to just-created fd 2. */
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saved_errno = errno;
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if (err == STDERR_FILENO)
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close (err);
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openat_restore_fail (saved_errno);
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}
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*cwd_errno = errno;
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}
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}
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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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/* Return true if our openat implementation must resort to
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using save_cwd and restore_cwd. */
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bool
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openat_needs_fchdir (void)
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{
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bool needs_fchdir = true;
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int fd = open ("/", O_SEARCH);
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if (0 <= fd)
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{
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char buf[OPENAT_BUFFER_SIZE];
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char *proc_file = openat_proc_name (buf, fd, ".");
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if (proc_file)
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{
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needs_fchdir = false;
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if (proc_file != buf)
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free (proc_file);
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}
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close (fd);
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}
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return needs_fchdir;
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}
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#endif /* !HAVE_OPENAT */
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