| /* Copyright (C) 1991-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library 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 |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <assert.h> |
| #include <errno.h> |
| #include <limits.h> |
| #include <stdbool.h> |
| #include <stddef.h> |
| #include <stdlib.h> |
| #include <dirent.h> |
| #include <fcntl.h> |
| #include <sys/param.h> |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| #include <stdio.h> |
| #include <string.h> |
| |
| #include <dirstream.h> |
| #include <not-cancel.h> |
| #include <kernel-features.h> |
| |
| /* The st_blksize value of the directory is used as a hint for the |
| size of the buffer which receives struct dirent values from the |
| kernel. st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the |
| file system provides a bogus value. */ |
| #define MAX_DIR_BUFFER_SIZE 1048576U |
| |
| /* opendir() must not accidentally open something other than a directory. |
| Some OS's have kernel support for that, some don't. In the worst |
| case we have to stat() before the open() AND fstat() after. |
| |
| We have to test at runtime for kernel support since libc may have |
| been compiled with different headers to the kernel it's running on. |
| This test can't be done reliably in the general case. We'll use |
| /dev/null, which if it's not a device lots of stuff will break, as |
| a guinea pig. It may be missing in chroot environments, so we |
| make sure to fail safe. */ |
| #ifdef O_DIRECTORY |
| # ifdef O_DIRECTORY_WORKS |
| # define o_directory_works 1 |
| # define tryopen_o_directory() while (1) /* This must not be called. */ |
| # else |
| static int o_directory_works; |
| |
| static void |
| tryopen_o_directory (void) |
| { |
| int serrno = errno; |
| int x = __open_nocancel ("/dev/null", O_RDONLY|O_NDELAY|O_DIRECTORY); |
| |
| if (x >= 0) |
| { |
| __close_nocancel_nostatus (x); |
| o_directory_works = -1; |
| } |
| else if (errno != ENOTDIR) |
| o_directory_works = -1; |
| else |
| o_directory_works = 1; |
| |
| __set_errno (serrno); |
| } |
| # endif |
| # define EXTRA_FLAGS O_DIRECTORY |
| #else |
| # define EXTRA_FLAGS 0 |
| #endif |
| |
| enum { |
| opendir_oflags = O_RDONLY|O_NDELAY|EXTRA_FLAGS|O_LARGEFILE|O_CLOEXEC |
| }; |
| |
| static bool |
| invalid_name (const char *name) |
| { |
| if (__glibc_unlikely (name[0] == '\0')) |
| { |
| /* POSIX.1-1990 says an empty name gets ENOENT; |
| but `open' might like it fine. */ |
| __set_errno (ENOENT); |
| return true; |
| } |
| return false; |
| } |
| |
| |
| static bool |
| need_isdir_precheck (void) |
| { |
| #ifdef O_DIRECTORY |
| /* Test whether O_DIRECTORY works. */ |
| if (o_directory_works == 0) |
| tryopen_o_directory (); |
| |
| /* We can skip the expensive `stat' call if O_DIRECTORY works. */ |
| return o_directory_works < 0; |
| #endif |
| return true; |
| } |
| |
| static DIR * |
| opendir_tail (int fd) |
| { |
| if (__glibc_unlikely (fd < 0)) |
| return NULL; |
| |
| /* Now make sure this really is a directory and nothing changed since the |
| `stat' call. The S_ISDIR check is superfluous if O_DIRECTORY works, |
| but it's cheap and we need the stat call for st_blksize anyway. */ |
| struct stat64 statbuf; |
| if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &statbuf) < 0)) |
| goto lose; |
| if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode))) |
| { |
| __set_errno (ENOTDIR); |
| lose: |
| __close_nocancel_nostatus (fd); |
| return NULL; |
| } |
| |
| return __alloc_dir (fd, true, 0, &statbuf); |
| } |
| |
| |
| #if IS_IN (libc) |
| DIR * |
| __opendirat (int dfd, const char *name) |
| { |
| if (__glibc_unlikely (invalid_name (name))) |
| return NULL; |
| |
| if (need_isdir_precheck ()) |
| { |
| /* We first have to check whether the name is for a directory. We |
| cannot do this after the open() call since the open/close operation |
| performed on, say, a tape device might have undesirable effects. */ |
| struct stat64 statbuf; |
| if (__glibc_unlikely (__fxstatat64 (_STAT_VER, dfd, name, |
| &statbuf, 0) < 0)) |
| return NULL; |
| if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode))) |
| { |
| __set_errno (ENOTDIR); |
| return NULL; |
| } |
| } |
| |
| return opendir_tail (__openat_nocancel (dfd, name, opendir_oflags)); |
| } |
| #endif |
| |
| |
| /* Open a directory stream on NAME. */ |
| DIR * |
| __opendir (const char *name) |
| { |
| if (__glibc_unlikely (invalid_name (name))) |
| return NULL; |
| |
| if (need_isdir_precheck ()) |
| { |
| /* We first have to check whether the name is for a directory. We |
| cannot do this after the open() call since the open/close operation |
| performed on, say, a tape device might have undesirable effects. */ |
| struct stat64 statbuf; |
| if (__glibc_unlikely (__xstat64 (_STAT_VER, name, &statbuf) < 0)) |
| return NULL; |
| if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode))) |
| { |
| __set_errno (ENOTDIR); |
| return NULL; |
| } |
| } |
| |
| return opendir_tail (__open_nocancel (name, opendir_oflags)); |
| } |
| weak_alias (__opendir, opendir) |
| |
| DIR * |
| __alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp) |
| { |
| /* We have to set the close-on-exit flag if the user provided the |
| file descriptor. */ |
| if (!close_fd |
| && __builtin_expect (__fcntl (fd, F_SETFD, FD_CLOEXEC), 0) < 0) |
| goto lose; |
| |
| const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64) |
| ? sizeof (struct dirent64) : 4 * BUFSIZ); |
| const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64) |
| ? sizeof (struct dirent64) : BUFSIZ); |
| size_t allocation = default_allocation; |
| #ifdef _STATBUF_ST_BLKSIZE |
| /* Increase allocation if requested, but not if the value appears to |
| be bogus. */ |
| if (statp != NULL) |
| allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation), |
| MAX_DIR_BUFFER_SIZE); |
| #endif |
| |
| DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation); |
| if (dirp == NULL) |
| { |
| allocation = small_allocation; |
| dirp = (DIR *) malloc (sizeof (DIR) + allocation); |
| |
| if (dirp == NULL) |
| lose: |
| { |
| if (close_fd) |
| { |
| int save_errno = errno; |
| __close_nocancel_nostatus (fd); |
| __set_errno (save_errno); |
| } |
| return NULL; |
| } |
| } |
| |
| dirp->fd = fd; |
| #if IS_IN (libc) |
| __libc_lock_init (dirp->lock); |
| #endif |
| dirp->allocation = allocation; |
| dirp->size = 0; |
| dirp->offset = 0; |
| dirp->filepos = 0; |
| dirp->errcode = 0; |
| |
| return dirp; |
| } |