sysfix.c

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

/*
 * fix system image for I/D space
 *  Move data down to 0; move text to 4K.
 *  Also put the data at the start of the
 *  file and the text after it.
 */

int	tbuf[259];
int	rbuf[259];
int	obuf[259];
int	txtsiz;
int	datsiz;
int	bsssiz;
int	symsiz;

int	txtrel	8192;
int	datrel;


main(argc, argv)
char **argv;
{
	register word, rel, s;

	if (argc<3) {
		printf("Arg count\n");
		exit(1);
	}
	if ((tbuf[0] = open(argv[1], 0)) < 0) {
		printf("Input file\n");
		exit(1);
	}
	rbuf[0] = open(argv[1], 0);
	if ((fcreat(argv[2], obuf)) < 0) {
		printf("Output file\n");
		exit(1);
	}
	if (getw(tbuf) != 0407) {
		printf("Bad input format\n");
		exit(1);
	}
	putw(0407, obuf);
	txtsiz = getw(tbuf);
	datsiz = getw(tbuf);
	bsssiz = getw(tbuf);
	symsiz = getw(tbuf);
	getw(tbuf);
	getw(tbuf);
	if (getw(tbuf) != 0) {
		printf("No relocation bits\n");
		exit(1);
	}
	putw(txtsiz, obuf);
	putw(datsiz, obuf);
	putw(bsssiz, obuf);
	putw(symsiz, obuf);
	putw(0, obuf);
	putw(0, obuf);
	putw(1, obuf);
	datrel = -txtsiz;
/*
 *  Copy out data first
 */
	tbuf[1] = 0;
	seek(tbuf[0], 020+txtsiz, 0);
	seek(rbuf[0], 020+txtsiz, 0);
	seek(rbuf[0], txtsiz, 1);
	seek(rbuf[0], datsiz, 1);
	s = datsiz >> 1;
	while (s--) {
		word = getw(tbuf);
		rel = getw(rbuf);
		if (rel&01)
			word =- datrel;
		word =+ getrel(rel);
		putw(word, obuf);
	}
/*
 * Now to the text.
 */
	rbuf[1] = 0;
	tbuf[1] = 0;
	seek(rbuf[0], 020+txtsiz, 0);
	seek(rbuf[0], datsiz, 1);
	seek(tbuf[0], 020, 0);
	s = txtsiz >> 1;
	while(s--) {
		rel = getw(rbuf);
		word = getw(tbuf);
		if (rel&01)
			word =- txtrel;
		word =+ getrel(rel);
		putw(word, obuf);
	}
/*
 * The symbol table.
 */
	tbuf[1] = 0;
	seek(tbuf[0], 020+txtsiz, 0);
	seek(tbuf[0], txtsiz, 1);
	seek(tbuf[0], datsiz, 1);
	seek(tbuf[0], datsiz, 1);
	s = symsiz;
	while ((s =- 12) >= 0) {
		putw(getw(tbuf), obuf);
		putw(getw(tbuf), obuf);
		putw(getw(tbuf), obuf);
		putw(getw(tbuf), obuf);
		rel = getw(tbuf);
		putw(rel, obuf);
		word = getw(tbuf);
		switch(rel&07) {
			case 2:
				word =+ txtrel;
				break;

			case 3:
			case 4:
				word =+ datrel;
		}
		putw(word, obuf);
	}
	fflush(obuf);
	close(obuf[0]);
	exit(0);
}

getrel(r)
{
	switch (r&016) {

	case 02:	/* ref to text */
		return(txtrel);

	case 04:		/* ref to data */
	case 06:		/* ref to bss */
		return(datrel);

	case 0:
		return(0);

	default:
		printf("Bad relocation %o\n", r);
		return(0);
	}
}