238 lines
6.2 KiB
C
238 lines
6.2 KiB
C
/* Copyright (C) 1991-2014 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <limits.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <string.h>
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#include <dirstream.h>
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#include <not-cancel.h>
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#include <kernel-features.h>
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/* The st_blksize value of the directory is used as a hint for the
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size of the buffer which receives struct dirent values from the
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kernel. st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the
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file system provides a bogus value. */
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#define MAX_DIR_BUFFER_SIZE 1048576U
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/* opendir() must not accidentally open something other than a directory.
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Some OS's have kernel support for that, some don't. In the worst
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case we have to stat() before the open() AND fstat() after.
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We have to test at runtime for kernel support since libc may have
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been compiled with different headers to the kernel it's running on.
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This test can't be done reliably in the general case. We'll use
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/dev/null, which if it's not a device lots of stuff will break, as
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a guinea pig. It may be missing in chroot environments, so we
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make sure to fail safe. */
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#ifdef O_DIRECTORY
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# ifdef O_DIRECTORY_WORKS
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# define o_directory_works 1
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# define tryopen_o_directory() while (1) /* This must not be called. */
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# else
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static int o_directory_works;
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static void
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tryopen_o_directory (void)
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{
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int serrno = errno;
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int x = open_not_cancel_2 ("/dev/null", O_RDONLY|O_NDELAY|O_DIRECTORY);
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if (x >= 0)
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{
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close_not_cancel_no_status (x);
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o_directory_works = -1;
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}
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else if (errno != ENOTDIR)
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o_directory_works = -1;
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else
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o_directory_works = 1;
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__set_errno (serrno);
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}
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# endif
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# define EXTRA_FLAGS O_DIRECTORY
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#else
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# define EXTRA_FLAGS 0
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#endif
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DIR *
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internal_function
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__opendirat (int dfd, const char *name)
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{
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struct stat64 statbuf;
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struct stat64 *statp = NULL;
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if (__builtin_expect (name[0], '\1') == '\0')
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{
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/* POSIX.1-1990 says an empty name gets ENOENT;
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but `open' might like it fine. */
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__set_errno (ENOENT);
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return NULL;
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}
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#ifdef O_DIRECTORY
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/* Test whether O_DIRECTORY works. */
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if (o_directory_works == 0)
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tryopen_o_directory ();
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/* We can skip the expensive `stat' call if O_DIRECTORY works. */
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if (o_directory_works < 0)
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#endif
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{
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/* We first have to check whether the name is for a directory. We
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cannot do this after the open() call since the open/close operation
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performed on, say, a tape device might have undesirable effects. */
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if (__builtin_expect (__xstat64 (_STAT_VER, name, &statbuf), 0) < 0)
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return NULL;
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if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))
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{
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__set_errno (ENOTDIR);
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return NULL;
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}
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}
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int flags = O_RDONLY|O_NDELAY|EXTRA_FLAGS|O_LARGEFILE;
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#ifdef O_CLOEXEC
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flags |= O_CLOEXEC;
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#endif
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int fd;
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#if IS_IN (rtld)
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assert (dfd == AT_FDCWD);
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fd = open_not_cancel_2 (name, flags);
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#else
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fd = openat_not_cancel_3 (dfd, name, flags);
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#endif
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if (__builtin_expect (fd, 0) < 0)
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return NULL;
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#ifdef O_DIRECTORY
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if (o_directory_works <= 0)
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#endif
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{
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/* Now make sure this really is a directory and nothing changed since
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the `stat' call. */
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if (__builtin_expect (__fxstat64 (_STAT_VER, fd, &statbuf), 0) < 0)
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goto lose;
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if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))
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{
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__set_errno (ENOTDIR);
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lose:
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close_not_cancel_no_status (fd);
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return NULL;
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}
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statp = &statbuf;
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}
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return __alloc_dir (fd, true, 0, statp);
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}
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/* Open a directory stream on NAME. */
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DIR *
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__opendir (const char *name)
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{
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return __opendirat (AT_FDCWD, name);
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}
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weak_alias (__opendir, opendir)
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#ifdef __ASSUME_O_CLOEXEC
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# define check_have_o_cloexec(fd) 1
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#else
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static int
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check_have_o_cloexec (int fd)
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{
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if (__have_o_cloexec == 0)
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__have_o_cloexec = (__fcntl (fd, F_GETFD, 0) & FD_CLOEXEC) == 0 ? -1 : 1;
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return __have_o_cloexec > 0;
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}
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#endif
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DIR *
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internal_function
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__alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp)
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{
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/* We always have to set the close-on-exit flag if the user provided
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the file descriptor. Otherwise only if we have no working
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O_CLOEXEC support. */
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#ifdef O_CLOEXEC
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if ((! close_fd && (flags & O_CLOEXEC) == 0)
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|| ! check_have_o_cloexec (fd))
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#endif
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{
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if (__builtin_expect (__fcntl (fd, F_SETFD, FD_CLOEXEC), 0) < 0)
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goto lose;
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}
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const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64)
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? sizeof (struct dirent64) : 4 * BUFSIZ);
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const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64)
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? sizeof (struct dirent64) : BUFSIZ);
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size_t allocation = default_allocation;
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#ifdef _STATBUF_ST_BLKSIZE
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/* Increase allocation if requested, but not if the value appears to
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be bogus. */
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if (statp != NULL)
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allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation),
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MAX_DIR_BUFFER_SIZE);
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#endif
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DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
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if (dirp == NULL)
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{
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allocation = small_allocation;
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dirp = (DIR *) malloc (sizeof (DIR) + allocation);
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if (dirp == NULL)
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lose:
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{
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if (close_fd)
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{
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int save_errno = errno;
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close_not_cancel_no_status (fd);
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__set_errno (save_errno);
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}
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return NULL;
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}
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}
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dirp->fd = fd;
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#if IS_IN (libc)
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__libc_lock_init (dirp->lock);
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#endif
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dirp->allocation = allocation;
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dirp->size = 0;
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dirp->offset = 0;
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dirp->filepos = 0;
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dirp->errcode = 0;
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return dirp;
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}
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