/* * install new master boot record boot code on PC disk. */ #include <u.h>#include <libc.h>#include <disk.h> enum {	Toffset = 0x1BE	/* offset of partition table */}; /* * Default boot block prints an error message and reboots.  */static int ndefmbr = Toffset;static char defmbr[512] = {[0x000]	0xEB, 0x3C, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,[0x03E] 0xFA, 0xFC, 0x8C, 0xC8, 0x8E, 0xD8, 0x8E, 0xD0,	0xBC, 0x00, 0x7C, 0xBE, 0x77, 0x7C, 0xE8, 0x19,	0x00, 0x33, 0xC0, 0xCD, 0x16, 0xBB, 0x40, 0x00,	0x8E, 0xC3, 0xBB, 0x72, 0x00, 0xB8, 0x34, 0x12,	0x26, 0x89, 0x07, 0xEA, 0x00, 0x00, 0xFF, 0xFF,	0xEB, 0xD6, 0xAC, 0x0A, 0xC0, 0x74, 0x09, 0xB4,	0x0E, 0xBB, 0x07, 0x00, 0xCD, 0x10, 0xEB, 0xF2,	0xC3,  'N',  'o',  't',  ' ',  'a',  ' ',  'b',	 'o',  'o',  't',  'a',  'b',  'l',  'e',  ' ',	 'd',  'i',  's',  'c',  ' ',  'o',  'r',  ' ',	 'd',  'i',  's',  'c',  ' ',  'e',  'r',  'r',	 'o',  'r', '\r', '\n',  'P',  'r',  'e',  's',	 's',  ' ',  'a',  'l',  'm',  'o',  's',  't',	 ' ',  'a',  'n',  'y',  ' ',  'k',  'e',  'y',	 ' ',  't',  'o',  ' ',  'r',  'e',  'b',  'o',	 'o',  't',  '.',  '.',  '.', 0x00, 0x00, 0x00,}; voidusage(void){	fprint(2, "usage: disk/mbr [-m mbrfile] disk\n");	exits("usage");} voidfatal(char *fmt, ...){	char err[ERRMAX];	va_list arg; 	va_start(arg, fmt);	vsnprint(err, ERRMAX, fmt, arg);	va_end(arg);	fprint(2, "mbr: %s\n", err);	exits(err);} voidmain(int argc, char **argv){	Disk *disk;	uchar *mbr, *buf;	char *mbrfile;	ulong secsize;	int sysfd, nmbr; 	mbrfile = nil;	ARGBEGIN {	case 'm':		mbrfile = ARGF();		break;	default:		usage();	} ARGEND 	if(argc < 1)		usage(); 	disk = opendisk(argv[0], 0, 0);	if(disk == nil)		fatal("opendisk %s: %r", argv[0]); 	if(disk->type == Tfloppy)		fatal("will not install mbr on floppy");	if(disk->secsize != 512)		fatal("secsize %d invalid", disk->secsize); 	secsize = disk->secsize;	buf = malloc(secsize);	mbr = malloc(secsize);	if(buf == nil || mbr == nil)		fatal("out of memory"); 	/*	 * Start with initial sector from disk.	 */	if(seek(disk->fd, 0, 0) < 0)		fatal("seek to boot sector: %r\n");	if(read(disk->fd, mbr, secsize) != secsize)		fatal("reading boot sector: %r"); 	if(mbrfile == nil){		nmbr = ndefmbr;		memmove(mbr, defmbr, nmbr);	} else {		if((sysfd = open(mbrfile, OREAD)) < 0)			fatal("open %s: %r", mbrfile);		if((nmbr = read(sysfd, buf, secsize)) < 0)			fatal("read %s: %r", mbrfile);		if(nmbr > Toffset)			fatal("master boot record too large");		close(sysfd);		memmove(mbr, buf, nmbr);	} 	if(nmbr < Toffset)		memset(mbr+nmbr, 0, Toffset-nmbr); 	mbr[secsize-2] = 0x55;	mbr[secsize-1] = 0xAA; 	if(seek(disk->wfd, 0, 0) < 0)		fatal("seek to MBR sector: %r\n");	if(write(disk->wfd, mbr, secsize) != secsize)		fatal("writing MBR: %r");		exits(0);}