crt0.c

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)crt0.c	8.1 (Berkeley) 6/1/93";
#endif /* not lint */

/*
 *	C start up routine.
 *	Robert Henry, UCB, 20 Oct 81
 *
 *	We make the following (true) assumptions:
 *	1) When the kernel calls start, it does a jump to location 2,
 *	and thus avoids the register save mask.  We are NOT called
 *	with a calls!
 *	2) The only register variable that we can trust is sp,
 *	which points to the base of the kernel calling frame.
 */

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

char **environ = (char **)0;
static char empty[1];
char *__progname = empty;
static int fd;

extern	unsigned char	etext;
extern	unsigned char	eprol asm ("eprol");
extern			start() asm("start");

/*
 * Some kluges: store sp at entry in environ, and
 * install 16 bits of 0 at location 0 (a zero register save mask).
 * These two hacks remove limits on the use of local
 * and register variables in start().
 * The reason for using 'moval (sp),...' is that 'movl sp,...' generates
 * a privileged instruction trap (argh).
 * XXX 'addl3 $start,$2,r0; jmp (r0)' should be replaced with
 * XXX 'jbr start+2' when we convert over to gas.
 */
asm(".text; .word 0; moval (sp),_environ; addl3 $start,$2,r0; jmp (r0)");

start()
{
	struct kframe {
		int	kargc;
		char	*kargv[1];	/* size depends on kargc */
		char	kargstr[1];	/* size varies */
		char	kenvstr[1];	/* size varies */
	};
	register struct kframe *kfp;
	register char **targv;
	register char **argv;
	extern int errno;

	kfp = (struct kframe *) environ;
	for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
		/* void */ ;
	if (targv >= (char **)(*argv))
		--targv;
	environ = targv;
asm("eprol:");

#ifdef MCRT0
	monstartup(&eprol, &etext);
#endif
	errno = 0;
	if (argv[0])
		if ((__progname = strrchr(argv[0], '/')) == NULL)
			__progname = argv[0];
		else
			++__progname;
	exit(main(kfp->kargc, argv, environ));
}

#ifdef MCRT0
/*ARGSUSED*/
exit(code)
	register int code;
{
	_mcleanup();
	_cleanup();
	_exit(code);
}
#endif

#ifdef CRT0
/*
 * null moncontrol, just in case some routine is compiled for profiling
 */
moncontrol(val)
	int val;
{

}
#endif