stand/libsa/SRT0.S

|	$NetBSD: SRT0.S,v 1.4 2009/10/21 23:12:09 snj Exp $

| Copyright (c) 1995 Gordon W. Ross
| 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.
|
| 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.

|	this is a pre-startup wrapper for bugcrt which relocates the
|	code to the correct place before exec()ing.

|	SRT0.S - Stand-alone Run-Time startup code, part 0

#include <m68k/asm.h>

	.file	"SRT0.S"
	.text
GLOBAL(_estack)

xstart:
| first, relocate code to correct place without touching critical regs
| (args are in: d0, d1, d4, a0, a1, a2, a3, a4, a5, a6)
| 	[a3 and a4 only when netbooting]
	movl	%a3, %d3		| SAVE a3 in d3
	movl	%a4, %d5		| SAVE a4 in d5
	lea	%pc@(xstart:w), %a3	| a3 = current addr (could be anywhere)
	lea	xstart:l, %a4		| a4 = desired location (LINKADDR)
	cmpl	%a3, %a4		| already there?
	beqs	restart			| short-circuit out

					| Relocate the code and data
	movl	#_C_LABEL(edata),%d2	| Desired end of program
	subl	%a4,%d2			| Calculate length, round up.
	lsrl	#2,%d2
Lcp:
	movl	%a3@+, %a4@+
	dbra	%d2, Lcp

| Force a long jump to the relocated code (not pc-relative)
	lea	restart:l, %a3
	jmp	%a3@

restart:
| now in the relocated code

| Set up stack (just before relocated text)
	lea	_C_LABEL(_estack):l, %a3
	movl	%a3, %sp

| now that we have relocated, call the bugcrt  (note we skip over the special
|	bug header which has a PC and SP in it)
	movl	%d3, %a3		| RESTORE a3
	movl	%d5, %a4		| RESTORE a4
	jmp	_start

| The end.