disk-utils/cramfs_common.c

   1 /*
   2  * SPDX-License-Identifier: GPL-2.0-or-later
   3  *
   4  * cramfs_common - cramfs common code
   5  *
   6  * Copyright (c) 2008 Roy Peled, the.roy.peled  -at-  gmail.com
   7  * Copyright (c) 2004-2006 by Juliane Holzt, kju -at- fqdn.org
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  */
  20
  21 #include <string.h>
  22 #include "cramfs.h"
  23 #include "../include/bitops.h"
  24
  25 uint32_t u32_toggle_endianness(int big_endian, uint32_t what)
  26 {
  27         return big_endian == HOST_IS_BIG_ENDIAN ? what : swab32(what);
  28 }
  29
  30 void super_toggle_endianness(int big_endian, struct cramfs_super *super)
  31 {
  32         if (big_endian != HOST_IS_BIG_ENDIAN) {
  33                 super->magic = swab32(super->magic);
  34                 super->size = swab32(super->size);
  35                 super->flags = swab32(super->flags);
  36                 super->future = swab32(super->future);
  37                 super->fsid.crc = swab32(super->fsid.crc);
  38                 super->fsid.edition = swab32(super->fsid.edition);
  39                 super->fsid.blocks = swab32(super->fsid.blocks);
  40                 super->fsid.files = swab32(super->fsid.files);
  41         }
  42 }
  43
  44 static void inode_toggle_endianness(int input_big_endian, int output_big_endian,
  45                              struct cramfs_inode *inode_in,
  46                              struct cramfs_inode *inode_out)
  47 {
  48         if (input_big_endian == output_big_endian) {
  49                 memmove(inode_out, inode_in, sizeof(*inode_out));
  50         } else {
  51                 unsigned char inode_out_buf[sizeof(*inode_in)];
  52                 unsigned char *inode_in_buf = (unsigned char*)inode_in;
  53
  54                 inode_out_buf[0] = inode_in_buf[1]; /* 16 bit: mode */
  55                 inode_out_buf[1] = inode_in_buf[0];
  56
  57                 inode_out_buf[2] = inode_in_buf[3]; /* 16 bit: uid */
  58                 inode_out_buf[3] = inode_in_buf[2];
  59
  60                 inode_out_buf[4] = inode_in_buf[6]; /* 24 bit: size */
  61                 inode_out_buf[5] = inode_in_buf[5];
  62                 inode_out_buf[6] = inode_in_buf[4];
  63
  64                 inode_out_buf[7] = inode_in_buf[7]; /* 8 bit: gid width */
  65
  66                 /*
  67                  * Stop the madness! Outlaw C bitfields! They are unportable
  68                  * and nasty! See for yourself what a mess this is:
  69                  */
  70                 if (output_big_endian) {
  71                         inode_out_buf[ 8] = ( (inode_in_buf[ 8]&0x3F) << 2 ) |
  72                                 ( (inode_in_buf[11]&0xC0) >> 6 );
  73
  74                         inode_out_buf[ 9] = ( (inode_in_buf[11]&0x3F) << 2 ) |
  75                                 ( (inode_in_buf[10]&0xC0) >> 6 );
  76
  77                         inode_out_buf[10] = ( (inode_in_buf[10]&0x3F) << 2 ) |
  78                                 ( (inode_in_buf[ 9]&0xC0) >> 6 );
  79
  80                         inode_out_buf[11] = ( (inode_in_buf[ 9]&0x3F) << 2 ) |
  81                                 ( (inode_in_buf[ 8]&0xC0) >> 6 );
  82                 } else {
  83                         inode_out_buf[ 8] = ( (inode_in_buf[ 8]&0xFD) >> 2 ) |
  84                                 ( (inode_in_buf[11]&0x03) << 6 );
  85
  86                         inode_out_buf[ 9] = ( (inode_in_buf[11]&0xFD) >> 2 ) |
  87                                 ( (inode_in_buf[10]&0x03) << 6 );
  88
  89                         inode_out_buf[10] = ( (inode_in_buf[10]&0xFD) >> 2 ) |
  90                                 ( (inode_in_buf[ 9]&0x03) << 6 );
  91
  92                         inode_out_buf[11] = ( (inode_in_buf[ 9]&0xFD) >> 2 ) |
  93                                 ( (inode_in_buf[ 8]&0x03) << 6 );
  94                 }
  95                 memmove(inode_out, inode_out_buf, sizeof(*inode_out));
  96         }
  97 }
  98
  99 void inode_to_host(int from_big_endian, struct cramfs_inode *inode_in,
 100                    struct cramfs_inode *inode_out)
 101 {
 102         inode_toggle_endianness(from_big_endian, HOST_IS_BIG_ENDIAN, inode_in,
 103                                 inode_out);
 104 }
 105
 106 void inode_from_host(int to_big_endian, struct cramfs_inode *inode_in,
 107                      struct cramfs_inode *inode_out)
 108 {
 109         inode_toggle_endianness(HOST_IS_BIG_ENDIAN, to_big_endian, inode_in,
 110                                 inode_out);
 111 }