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688903eb3e
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
272 lines
8.0 KiB
C
272 lines
8.0 KiB
C
/* Copyright (C) 1993-2018 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 <alloca.h>
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#include <assert.h>
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#include <errno.h>
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#include <dirent.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sysdep.h>
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#include <sys/syscall.h>
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#include <linux/posix_types.h>
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#include <kernel-features.h>
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/* For Linux we need a special version of this file since the
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definition of `struct dirent' is not the same for the kernel and
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the libc. There is one additional field which might be introduced
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in the kernel structure in the future.
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Here is the kernel definition of `struct dirent' as of 2.1.20: */
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struct kernel_dirent
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{
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long int d_ino;
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__kernel_off_t d_off;
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unsigned short int d_reclen;
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char d_name[256];
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};
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struct kernel_dirent64
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{
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uint64_t d_ino;
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int64_t d_off;
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unsigned short int d_reclen;
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unsigned char d_type;
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char d_name[256];
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};
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#ifndef __GETDENTS
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# define __GETDENTS __getdents
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#endif
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#ifndef DIRENT_TYPE
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# define DIRENT_TYPE struct dirent
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#endif
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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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/* The problem here is that we cannot simply read the next NBYTES
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bytes. We need to take the additional field into account. We use
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some heuristic. Assuming the directory contains names with 14
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characters on average we can compute an estimated number of entries
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which fit in the buffer. Taking this number allows us to specify a
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reasonable number of bytes to read. If we should be wrong, we can
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reset the file descriptor. In practice the kernel is limiting the
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amount of data returned much more then the reduced buffer size. */
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ssize_t
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__GETDENTS (int fd, char *buf, size_t nbytes)
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{
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ssize_t retval;
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/* The d_ino and d_off fields in kernel_dirent and dirent must have
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the same sizes and alignments. */
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if (sizeof (DIRENT_TYPE) == sizeof (struct dirent)
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&& (sizeof (((struct kernel_dirent *) 0)->d_ino)
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== sizeof (((struct dirent *) 0)->d_ino))
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&& (sizeof (((struct kernel_dirent *) 0)->d_off)
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== sizeof (((struct dirent *) 0)->d_off))
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&& (offsetof (struct kernel_dirent, d_off)
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== offsetof (struct dirent, d_off))
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&& (offsetof (struct kernel_dirent, d_reclen)
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== offsetof (struct dirent, d_reclen)))
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{
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retval = INLINE_SYSCALL (getdents, 3, fd, buf, nbytes);
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/* The kernel added the d_type value after the name. Change
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this now. */
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if (retval != -1)
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{
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union
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{
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struct kernel_dirent k;
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struct dirent u;
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} *kbuf = (void *) buf;
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while ((char *) kbuf < buf + retval)
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{
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char d_type = *((char *) kbuf + kbuf->k.d_reclen - 1);
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memmove (kbuf->u.d_name, kbuf->k.d_name,
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strlen (kbuf->k.d_name) + 1);
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kbuf->u.d_type = d_type;
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kbuf = (void *) ((char *) kbuf + kbuf->k.d_reclen);
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}
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}
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return retval;
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}
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off64_t last_offset = -1;
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#ifdef __NR_getdents64
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{
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union
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{
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struct kernel_dirent64 k;
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DIRENT_TYPE 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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if (offsetof (DIRENT_TYPE, d_name)
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< offsetof (struct kernel_dirent64, d_name)
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&& nbytes <= sizeof (DIRENT_TYPE))
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{
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kbytes = (nbytes + offsetof (struct kernel_dirent64, d_name)
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- offsetof (DIRENT_TYPE, d_name));
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kbuf = __alloca(kbytes);
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}
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retval = INLINE_SYSCALL (getdents64, 3, fd, kbuf, kbytes);
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const size_t size_diff = (offsetof (struct kernel_dirent64, d_name)
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- offsetof (DIRENT_TYPE, d_name));
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/* Return the error if encountered. */
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if (retval == -1)
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return -1;
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/* If the structure returned by the kernel is identical to what we
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need, don't do any conversions. */
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if (offsetof (DIRENT_TYPE, d_name)
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== offsetof (struct kernel_dirent64, d_name)
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&& sizeof (outp->u.d_ino) == sizeof (inp->k.d_ino)
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&& sizeof (outp->u.d_off) == sizeof (inp->k.d_off))
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return retval;
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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__ (DIRENT_TYPE);
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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 kernel_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
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before this one, return them without error,
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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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__set_errno (EOVERFLOW);
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return -1;
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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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#endif
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{
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size_t red_nbytes;
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struct kernel_dirent *skdp, *kdp;
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const size_t size_diff = (offsetof (DIRENT_TYPE, d_name)
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- offsetof (struct kernel_dirent, d_name));
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red_nbytes = MIN (nbytes
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- ((nbytes / (offsetof (DIRENT_TYPE, d_name) + 14))
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* size_diff),
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nbytes - size_diff);
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skdp = kdp = __alloca (red_nbytes);
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retval = INLINE_SYSCALL (getdents, 3, fd, (char *) kdp, red_nbytes);
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if (retval == -1)
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return -1;
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DIRENT_TYPE *dp = (DIRENT_TYPE *) buf;
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while ((char *) kdp < (char *) skdp + retval)
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{
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const size_t alignment = __alignof__ (DIRENT_TYPE);
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/* Since kdp->d_reclen is already aligned for the kernel structure
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this may compute a value that is bigger than necessary. */
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size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1)
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& ~(alignment - 1));
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if ((char *) dp + new_reclen > buf + nbytes)
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{
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/* Our heuristic failed. We read too many entries. Reset
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the stream. */
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assert (last_offset != -1);
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__lseek64 (fd, last_offset, SEEK_SET);
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if ((char *) dp == buf)
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{
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/* The buffer the user passed in is too small to hold even
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one entry. */
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__set_errno (EINVAL);
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return -1;
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}
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break;
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}
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last_offset = kdp->d_off;
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DIRENT_SET_DP_INO(dp, kdp->d_ino);
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dp->d_off = kdp->d_off;
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dp->d_reclen = new_reclen;
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dp->d_type = *((char *) kdp + kdp->d_reclen - 1);
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memcpy (dp->d_name, kdp->d_name,
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kdp->d_reclen - offsetof (struct kernel_dirent, d_name));
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dp = (DIRENT_TYPE *) ((char *) dp + new_reclen);
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kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
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}
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return (char *) dp - buf;
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}
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}
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