mirror of https://github.com/pbatard/rufus.git
127 lines
3.9 KiB
C
127 lines
3.9 KiB
C
/* ----------------------------------------------------------------------- *
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*
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* Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
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* Copyright 2009-2010 Intel Corporation; author H. Peter Anvin
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, Inc., 53 Temple Place Ste 330,
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* Boston MA 02111-1307, USA; either version 2 of the License, or
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* (at your option) any later version; incorporated herein by reference.
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*
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* ----------------------------------------------------------------------- */
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/*
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* fat.c - Initial sanity check for FAT-based installers
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*/
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#define _XOPEN_SOURCE 500 /* Required on glibc 2.x */
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#define _BSD_SOURCE
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#include <stdio.h>
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#include <inttypes.h>
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#include <string.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include "syslinux.h"
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#include "syslxint.h"
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void syslinux_make_bootsect(void *bs)
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{
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struct boot_sector *bootsect = bs;
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const struct boot_sector *sbs =
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(const struct boot_sector *)boot_sector;
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memcpy(&bootsect->bsHead, &sbs->bsHead, bsHeadLen);
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memcpy(&bootsect->bsCode, &sbs->bsCode, bsCodeLen);
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}
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/*
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* Check to see that what we got was indeed an MS-DOS boot sector/superblock;
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* Return NULL if OK and otherwise an error message;
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*/
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const char *syslinux_check_bootsect(const void *bs)
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{
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int sectorsize;
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long long sectors, fatsectors, dsectors;
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long long clusters;
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int rootdirents, clustersize;
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const struct boot_sector *sectbuf = bs;
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/* Must be 0xF0 or 0xF8..0xFF */
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if (get_8(§buf->bsMedia) != 0xF0 && get_8(§buf->bsMedia) < 0xF8)
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return "invalid media signature (not a FAT filesystem?)";
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sectorsize = get_16(§buf->bsBytesPerSec);
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if (sectorsize == SECTOR_SIZE)
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; /* ok */
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else if (sectorsize >= 512 && sectorsize <= 4096 &&
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(sectorsize & (sectorsize - 1)) == 0)
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return "unsupported sectors size";
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else
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return "impossible sector size";
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clustersize = get_8(§buf->bsSecPerClust);
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if (clustersize == 0 || (clustersize & (clustersize - 1)))
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return "impossible cluster size";
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sectors = get_16(§buf->bsSectors);
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sectors = sectors ? sectors : get_32(§buf->bsHugeSectors);
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dsectors = sectors - get_16(§buf->bsResSectors);
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fatsectors = get_16(§buf->bsFATsecs);
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fatsectors = fatsectors ? fatsectors : get_32(§buf->bs32.FATSz32);
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fatsectors *= get_8(§buf->bsFATs);
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dsectors -= fatsectors;
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rootdirents = get_16(§buf->bsRootDirEnts);
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dsectors -= (rootdirents + sectorsize / 32 - 1) / sectorsize;
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if (dsectors < 0)
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return "negative number of data sectors";
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if (fatsectors == 0)
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return "zero FAT sectors";
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clusters = dsectors / clustersize;
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if (clusters < 0xFFF5) {
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/* FAT12 or FAT16 */
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if (!get_16(§buf->bsFATsecs))
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return "zero FAT sectors (FAT12/16)";
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if (get_8(§buf->bs16.BootSignature) == 0x29) {
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if (!memcmp(§buf->bs16.FileSysType, "FAT12 ", 8)) {
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if (clusters >= 0xFF5)
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return "more than 4084 clusters but claims FAT12";
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} else if (!memcmp(§buf->bs16.FileSysType, "FAT16 ", 8)) {
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if (clusters < 0xFF5)
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return "less than 4084 clusters but claims FAT16";
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} else if (!memcmp(§buf->bs16.FileSysType, "FAT32 ", 8)) {
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return "less than 65525 clusters but claims FAT32";
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} else if (memcmp(§buf->bs16.FileSysType, "FAT ", 8)) {
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static char fserr[] =
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"filesystem type \"????????\" not supported";
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memcpy(fserr + 17, §buf->bs16.FileSysType, 8);
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return fserr;
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}
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}
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} else if (clusters < 0x0FFFFFF5) {
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/*
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* FAT32...
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*
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* Moving the FileSysType and BootSignature was a lovely stroke
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* of M$ idiocy...
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*/
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if (get_8(§buf->bs32.BootSignature) != 0x29 ||
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memcmp(§buf->bs32.FileSysType, "FAT32 ", 8))
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return "missing FAT32 signature";
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} else {
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return "impossibly large number of clusters";
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}
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return NULL;
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}
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