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#ident "$Id$"
/* ----------------------------------------------------------------------- *
*
* Copyright 1998-2003 H. Peter Anvin - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
* USA; either version 2 of the License, or (at your option) any later
* version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* syslxmod.c - Code to provide a SYSLINUX code set to an installer.
*/
#define _XOPEN_SOURCE 500 /* Required on glibc 2.x */
#define _BSD_SOURCE
#include <stdio.h>
#include <inttypes.h>
#include <string.h>
#include "syslinux.h"
enum bs_offsets {
bsJump = 0x00,
bsOemName = 0x03,
bsBytesPerSec = 0x0b,
bsSecPerClust = 0x0d,
bsResSectors = 0x0e,
bsFATs = 0x10,
bsRootDirEnts = 0x11,
bsSectors = 0x13,
bsMedia = 0x15,
bsFATsecs = 0x16,
bsSecPerTrack = 0x18,
bsHeads = 0x1a,
bsHiddenSecs = 0x1c,
bsHugeSectors = 0x20,
bsDriveNumber = 0x24,
bsReserved1 = 0x25,
bsBootSignature = 0x26,
bsVolumeID = 0x27,
bsVolumeLabel = 0x2b,
bsFileSysType = 0x36,
bsCode = 0x3e,
bsSignature = 0x1fe
};
#define bsHead bsJump
#define bsHeadLen (bsBytesPerSec-bsHead)
#define bsCodeLen (bsSignature-bsCode)
/*
* Access functions for littleendian numbers, possibly misaligned.
*/
static inline uint16_t get_16(const unsigned char *p)
{
#if defined(__i386__) || defined(__x86_64__)
/* Littleendian and unaligned-capable */
return *(uint16_t *)p;
#else
return (uint16_t)p[0] + ((uint16_t)p[1] << 8);
#endif
}
static inline uint32_t get_32(const unsigned char *p)
{
#if defined(__i386__) || defined(__x86_64__)
/* Littleendian and unaligned-capable */
return *(uint32_t *)p;
#else
return (uint32_t)p[0] + ((uint32_t)p[1] << 8) +
((uint32_t)p[2] << 16) + ((uint32_t)p[3] << 24);
#endif
}
static inline void set_16(unsigned char *p, uint16_t v)
{
p[0] = (v & 0xff);
p[1] = ((v >> 8) & 0xff);
}
#if 0 /* Not needed */
static inline void set_32(unsigned char *p, uint32_t v)
{
p[0] = (v & 0xff);
p[1] = ((v >> 8) & 0xff);
p[2] = ((v >> 16) & 0xff);
p[3] = ((v >> 24) & 0xff);
}
#endif
/* Patch the code so that we're running in stupid mode */
void syslinux_make_stupid(void)
{
/* Access only one sector at a time */
set_16(syslinux_ldlinux+PATCH_OFFSET, 1);
}
void syslinux_make_bootsect(void *bs)
{
unsigned char *bootsect = bs;
memcpy(bootsect+bsHead, syslinux_bootsect+bsHead, bsHeadLen);
memcpy(bootsect+bsCode, syslinux_bootsect+bsCode, bsCodeLen);
}
/*
* Check to see that what we got was indeed an MS-DOS boot sector/superblock
*/
int syslinux_check_bootsect(const void *bs, const char *device)
{
int veryold;
unsigned int sectors, clusters;
const unsigned char *sectbuf = bs;
if ( sectbuf[bsBootSignature] == 0x29 ) {
/* It's DOS, and it has all the new nice fields */
veryold = 0;
sectors = get_16(sectbuf+bsSectors);
sectors = sectors ? sectors : get_32(sectbuf+bsHugeSectors);
clusters = sectors / sectbuf[bsSecPerClust];
if ( !memcmp(sectbuf+bsFileSysType, "FAT12 ", 8) ) {
if ( clusters > 4086 ) {
fprintf(stderr, "%s: ERROR: FAT12 but claims more than 4086 clusters\n",
device);
return 0;
}
} else if ( !memcmp(sectbuf+bsFileSysType, "FAT16 ", 8) ) {
if ( clusters <= 4086 ) {
fprintf(stderr, "%s: ERROR: FAT16 but claims less than 4086 clusters\n",
device);
return 0;
}
} else if ( !memcmp(sectbuf+bsFileSysType, "FAT ", 8) ) {
/* OS/2 sets up the filesystem as just `FAT'. */
} else {
fprintf(stderr, "%s: filesystem type \"%8.8s\" not supported\n",
device, sectbuf+bsFileSysType);
return 0;
}
} else {
veryold = 1;
if ( sectbuf[bsSecPerClust] & (sectbuf[bsSecPerClust] - 1) ||
sectbuf[bsSecPerClust] == 0 ) {
fprintf(stderr, "%s: This doesn't look like a FAT filesystem\n",
device);
}
sectors = get_16(sectbuf+bsSectors);
sectors = sectors ? sectors : get_32(sectbuf+bsHugeSectors);
clusters = sectors / sectbuf[bsSecPerClust];
}
if ( get_16(sectbuf+bsBytesPerSec) != 512 ) {
fprintf(stderr, "%s: Sector sizes other than 512 not supported\n",
device);
return 0;
}
if ( sectbuf[bsSecPerClust] > 32 ) {
fprintf(stderr, "%s: Cluster sizes larger than 16K not supported\n",
device);
return 0;
}
return 1;
}
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