NetBSD/lib/csu/mips/crt0.c

/* $NetBSD: crt0.c,v 1.20 2009/12/14 01:04:02 matt Exp $ */

/*
 * Copyright (c) 1995 Christopher G. Demetriou
 * All rights reserved.
 *
 * Modifications for NetBSD/mips:
 *
 *	Jonathan Stone
 *	Jason R. Thorpe, Numerical Aerospace Simulation Facility,
 *	    NASA Ames Research Center
 *
 * 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 Christopher G. Demetriou
 *	for the NetBSD Project.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

#include "common.h"

/*
 *	C start-up.  Assumes kernel (or ld.so) passes the
 *	following parameters to user-space in registers:
 *
 *	a0	stack pointer (0 if setregs didn't fill this in)
 *	a1	cleanup
 *	a2	Obj_Entry
 *	a3	ps_strings
 *
 *	XXX Does this violate the ABI?
 *	as well as the usual registers (pc, sp, and t9 == pc for ABI).
 */

void __start(u_long, void (*)(void), const Obj_Entry *,
		struct ps_strings *);

__asm(".text; .align 4;  .globl _start; _start:");

void
__start(u_long sp,
    void (*cleanup)(void),		/* from shared loader */
    const Obj_Entry *obj,		/* from shared loader */
    struct ps_strings *ps_strings)
{
	char **ksp;
	char **argv, *namep;
	int argc;

	/*
	 * Grab the argc, argv, and envp set up by the kernel.
	 * Layout of stuff on the stack:
	 *
	 *	[ high ]
	 *	char	kenvstr[1];	// size varies
	 *	char	kargstr[1];	// size varies
	 *	char	*argv[1];	// varies on argc
	 *	int	argc;
	 *	[ low ] 		<--- kernel's SP points here
	 *	.
	 *	.
	 *	.
	 *	[ current stack pointer ]
	 *
	 * WARNING!  There is an implicit sizeof(int) == sizeof(char *) here!
	 */

#ifndef DYNAMIC
#ifdef _LP64
	__asm volatile("dla $28,_gp");
#else
	__asm volatile("la $28,_gp");
#endif
#endif

	ksp = (char**)sp;
#if defined(__mips_n32) || defined(__mips_n64)
	if (ksp == 0) {
		/*
		 * Uh, oh. We're running on a old kernel that passed
		 * us zero in $a0-$a3.  Try adjusting the current
		 * $sp for our own stack-frame size and see  what
		 * we find.
		 * WARNING!  The constants 56 and 64 below were determined
		 * by examining GCC assembler output of __start to find the
		 * frame size.  If you change the code or compiler,
		 * you _will_ lose!
		 */

#ifndef DYNAMIC
		/* XXX 56 is compiler and stackframe dependent */
		__asm volatile("	addiu	%0,$29,56" : "=r" (ksp));
#else
		/* XXX 64 is compiler and stackframe dependent */
		__asm volatile("	addiu	%0,$29,64" : "=r" (ksp));
#endif
	}
#endif


	argc = *(int *)ksp;
	argv = ksp + 1;
	environ = ksp + 2 + argc;	/* 2: argc + NULL ending argv */

	if ((namep = argv[0]) != NULL) {	/* NULL ptr if argc = 0 */
		if ((__progname = _strrchr(namep, '/')) == NULL)
			__progname = namep;
		else
			__progname++;
	}

	/*
	 * Deal with stuff that is only provided if setregs() did
	 * did the right thing.
	 */
	if (sp != 0) {
		if (ps_strings != (struct ps_strings *)0)
			__ps_strings = ps_strings;
#ifdef DYNAMIC
		/*
		 * XXX Old MIPS ld.so didn't do any of this at all.
		 * XXX If we were loaded by that loader, just abort
		 * XXX the rtld setup.
		 */
		if (&_DYNAMIC != NULL && cleanup != NULL && obj != NULL)
			_rtld_setup(cleanup, obj);
#endif
	}

#ifdef MCRT0
	atexit(_mcleanup);
	monstartup((u_long)&_eprol, (u_long)&_etext);
#endif

	atexit(_fini);
	_init();

	exit(main(argc, argv, environ));
}

/*
 * RCSid. Place after __start for programs that assume start of text
 *  is the entrypoint. (Only needed for old toolchains).
 */
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: crt0.c,v 1.20 2009/12/14 01:04:02 matt Exp $");
#endif /* LIBC_SCCS and not lint */

#include "common.c"