boot-parameters.c

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/*****************************************
 Copyright (c) 2001-2002  
 Sigma Designs, Inc. All Rights Reserved
 Proprietary and Confidential
 *****************************************/

/* This is file is part of the Jasper DVD boot loader */

/*
 * boot-parameters.c
 *
 * Utility to modify boot-cd ISO image parameters
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

//#include "config.h"
#define ELTORITO_PLATFORM_ID	85

static unsigned char sector[2048];

static unsigned short calc_check(unsigned short *buf)
{
	int i;
	unsigned short sum=0;
	for(i=0;i<16;i++) {
		sum+=buf[i];
	}
	return sum;
}

int main(int argc, char *argv[])
{
	int fd;
	unsigned long cat_addr; // boot catalog address

	if(argc<2) {
		fprintf(stderr,"Usage: %s <image.iso>\n", argv[0]);
		exit(1);
	}

	fd=open(argv[1],O_RDWR);
	if(fd==-1) {
		perror("Cannot open ISO image");
		exit(1);
	}
	
	// Seek to boot record
	lseek(fd, 2048*17, SEEK_SET);
	if(read(fd, sector, 2048)!=2048){
		perror("Couldnt read fully the boot sector");
		exit(1);
	}
	
	// test boot sector
	if(strcmp(sector+7,"EL TORITO SPECIFICATION")!=0) {
		printf("Not an EL TORITO boot image (%s)\n",sector+7);
		exit(1);
	}
	
	// Get the boot catalog address
	// -  Warning cast doesnt respect aligment
	cat_addr = *(unsigned long *)(sector+0x47); 
	
	printf("Boot catalog address: sector %ld (abs %lx)\n",
	       cat_addr, cat_addr*2048);

	// Seek to boot catalog
	lseek(fd, cat_addr*2048, SEEK_SET);
	if(read(fd, sector, 2048)!=2048){
		perror("Couldnt read fully the boot catalog");
		exit(1);
	}
	
	// check validation entry
	if(sector[0]!=1) {
		printf("Validation Entry invalid %d instead of 1\n",sector[0]);
		exit(1);
	}

	printf("Current platform ID: %d\n",sector[1]);
	printf("Current ID string : %s\n",sector+4);
	printf("Current checksum word: %04x (sum=%04x)\n",
	       *(unsigned short *)(sector+0x1c),
	       calc_check((unsigned short *)sector));
	
#ifdef	ELTORITO_PLATFORM_ID 
	sector[1]=ELTORITO_PLATFORM_ID;
	printf("Changed platform ID to %d\n",ELTORITO_PLATFORM_ID);
#endif
#ifdef ELTORITO_ID_STRING	
	memset(sector+4, 0, ELTORITO_ID_STRING_MAX_LENGTH);
	strncpy(sector+4, ELTORITO_ID_STRING, ELTORITO_ID_STRING_MAX_LENGTH);
	(sector+4)[ELTORITO_ID_STRING_MAX_LENGTH-1]=0;
	printf("Changed ID string to %s\n",sector+4);
#endif

	*(unsigned short *)(sector+0x1c) = 0;
	*(unsigned short *)(sector+0x1c) = 0 - calc_check((unsigned short *)sector);

	printf("New checksum word: %04x (sum=%04x)\n",
	       *(unsigned short *)(sector+0x1c),
	       calc_check((unsigned short *)sector));

	// check initial entry
	if(sector[0x20]!=0x88) {
		printf("Initial/Default entry not bootable.. abort\n");
		exit(1);
	}

#ifdef ELTORITO_EMULATION_TYPE	
	if(sector[0x21]!=ELTORITO_EMULATION_TYPE) {
		printf("Initial/Default entry emulation type set to %d, resetting to %d\n", sector[0x21], ELTORITO_EMULATION_TYPE);
		sector[0x21]=ELTORITO_EMULATION_TYPE;
	}
#endif

	lseek(fd, cat_addr*2048, SEEK_SET);
	write(fd, sector, 2048);
	close(fd);
	
	return 0;
}