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118 lines
3.8 KiB
C
118 lines
3.8 KiB
C
/* Get directory entries. Linux non-LFS version.
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Copyright (C) 1993-2024 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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<https://www.gnu.org/licenses/>. */
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#include <dirent.h>
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#if !_DIRENT_MATCHES_DIRENT64
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# include <unistd.h>
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# include <string.h>
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# include <errno.h>
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# ifndef DIRENT_SET_DP_INO
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# define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value)
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# endif
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/* Pack the dirent64 struct down into 32-bit offset/inode fields, and
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ensure that no overflow occurs. */
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ssize_t
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__getdents (int fd, void *buf0, size_t nbytes)
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{
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char *buf = buf0;
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union
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{
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/* For !_DIRENT_MATCHES_DIRENT64 kernel 'linux_dirent64' has the same
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layout of 'struct dirent64'. */
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struct dirent64 k;
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struct dirent u;
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char b[1];
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} *kbuf = (void *) buf, *outp, *inp;
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size_t kbytes = nbytes;
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off64_t last_offset = -1;
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ssize_t retval;
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# define size_diff (offsetof (struct dirent64, d_name) \
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- offsetof (struct dirent, d_name))
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char kbuftmp[sizeof (struct dirent) + size_diff];
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if (nbytes <= sizeof (struct dirent))
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kbuf = (void*) kbuftmp;
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retval = INLINE_SYSCALL_CALL (getdents64, fd, kbuf, kbytes);
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if (retval == -1)
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return -1;
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/* These two pointers might alias the same memory buffer.
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Standard C requires that we always use the same type for them,
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so we must use the union type. */
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inp = kbuf;
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outp = (void *) buf;
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while (&inp->b < &kbuf->b + retval)
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{
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const size_t alignment = _Alignof (struct dirent);
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/* Since inp->k.d_reclen is already aligned for the kernel
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structure this may compute a value that is bigger
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than necessary. */
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size_t old_reclen = inp->k.d_reclen;
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size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
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& ~(alignment - 1));
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/* Copy the data out of the old structure into temporary space.
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Then copy the name, which may overlap if BUF == KBUF. */
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const uint64_t d_ino = inp->k.d_ino;
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const int64_t d_off = inp->k.d_off;
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const uint8_t d_type = inp->k.d_type;
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memmove (outp->u.d_name, inp->k.d_name,
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old_reclen - offsetof (struct dirent64, d_name));
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/* Now we have copied the data from INP and access only OUTP. */
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DIRENT_SET_DP_INO (&outp->u, d_ino);
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outp->u.d_off = d_off;
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if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
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&& outp->u.d_ino != d_ino)
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|| (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
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&& outp->u.d_off != d_off))
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{
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/* Overflow. If there was at least one entry before this one,
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return them without error, otherwise signal overflow. */
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if (last_offset != -1)
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{
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__lseek64 (fd, last_offset, SEEK_SET);
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return outp->b - buf;
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}
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (EOVERFLOW);
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}
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last_offset = d_off;
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outp->u.d_reclen = new_reclen;
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outp->u.d_type = d_type;
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inp = (void *) inp + old_reclen;
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outp = (void *) outp + new_reclen;
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}
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return outp->b - buf;
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}
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# undef DIRENT_SET_DP_INO
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#endif /* _DIRENT_MATCHES_DIRENT64 */
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