sysdeps/unix/sysv/linux/mips/mips64/getdents64.c

   1 /* Get directory entries.  Linux/MIPSn64 LFS version.
   2    Copyright (C) 2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library.  If not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <dirent.h>
  21 #include <errno.h>
  22 #include <assert.h>
  23 #include <sys/param.h>
  24 #include <unistd.h>
  25 #include <scratch_buffer.h>
  26
  27 ssize_t
  28 __getdents64 (int fd, char *buf, size_t nbytes)
  29 {
  30 #ifdef __NR_getdents64
  31   ssize_t ret = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
  32   if (ret != -1)
  33     return ret;
  34 #endif
  35
  36   /* Unfortunately getdents64 was only wire-up for MIPS n64 on Linux 3.10.
  37      If syscall is not available it need to fallback to non-LFS one.  */
  38
  39   struct kernel_dirent
  40     {
  41       unsigned long d_ino;
  42       unsigned long d_off;
  43       unsigned short int d_reclen;
  44       char d_name[256];
  45     };
  46
  47   const size_t size_diff = (offsetof (struct dirent64, d_name)
  48                            - offsetof (struct kernel_dirent, d_name));
  49
  50   size_t red_nbytes = MIN (nbytes
  51                            - ((nbytes / (offsetof (struct dirent64, d_name)
  52                                          + 14)) * size_diff),
  53                            nbytes - size_diff);
  54
  55   struct scratch_buffer tmpbuf;
  56   scratch_buffer_init (&tmpbuf);
  57   if (!scratch_buffer_set_array_size (&tmpbuf, red_nbytes, sizeof (uint8_t)))
  58     INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOMEM);
  59
  60   struct kernel_dirent *skdp, *kdp;
  61   skdp = kdp = tmpbuf.data;
  62
  63   ssize_t retval = INLINE_SYSCALL_CALL (getdents, fd, kdp, red_nbytes);
  64   if (retval == -1)
  65     {
  66       scratch_buffer_free (&tmpbuf);
  67       return -1;
  68     }
  69
  70   off64_t last_offset = -1;
  71   struct dirent64 *dp = (struct dirent64 *) buf;
  72   while ((char *) kdp < (char *) skdp + retval)
  73     {
  74       const size_t alignment = _Alignof (struct dirent64);
  75       /* Since kdp->d_reclen is already aligned for the kernel structure
  76          this may compute a value that is bigger than necessary.  */
  77       size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1)
  78                            & ~(alignment - 1));
  79       if ((char *) dp + new_reclen > buf + nbytes)
  80         {
  81           /* Our heuristic failed.  We read too many entries.  Reset
  82              the stream.  */
  83           assert (last_offset != -1);
  84           __lseek64 (fd, last_offset, SEEK_SET);
  85
  86           if ((char *) dp == buf)
  87             {
  88               scratch_buffer_free (&tmpbuf);
  89               return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
  90             }
  91
  92           break;
  93         }
  94
  95       last_offset = kdp->d_off;
  96       dp->d_ino = kdp->d_ino;
  97       dp->d_off = kdp->d_off;
  98       dp->d_reclen = new_reclen;
  99       dp->d_type = *((char *) kdp + kdp->d_reclen - 1);
 100       memcpy (dp->d_name, kdp->d_name,
 101               kdp->d_reclen - offsetof (struct kernel_dirent, d_name));
 102
 103       dp = (struct dirent64 *) ((char *) dp + new_reclen);
 104       kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
 105     }
 106
 107   scratch_buffer_free (&tmpbuf);
 108   return (char *) dp - buf;
 109 }
 110 #if _DIRENT_MATCHES_DIRENT64
 111 strong_alias (__getdents64, __getdents)
 112 #endif