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      1 |	$NetBSD: SRT0.S,v 1.4 2009/10/21 23:12:09 snj Exp $
      2 
      3 | Copyright (c) 1995 Gordon W. Ross
      4 | All rights reserved.
      5 |
      6 | Redistribution and use in source and binary forms, with or without
      7 | modification, are permitted provided that the following conditions
      8 | are met:
      9 | 1. Redistributions of source code must retain the above copyright
     10 |    notice, this list of conditions and the following disclaimer.
     11 | 2. Redistributions in binary form must reproduce the above copyright
     12 |    notice, this list of conditions and the following disclaimer in the
     13 |    documentation and/or other materials provided with the distribution.
     14 |
     15 | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     16 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     17 | OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     18 | IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     19 | INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     20 | NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     21 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     22 | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     23 | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     24 | THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     25 
     26 |	this is a pre-startup wrapper for bugcrt which relocates the
     27 |	code to the correct place before exec()ing.
     28 
     29 |	SRT0.S - Stand-alone Run-Time startup code, part 0
     30 
     31 #include <m68k/asm.h>
     32 
     33 	.file	"SRT0.S"
     34 	.text
     35 GLOBAL(_estack)
     36 
     37 xstart:
     38 | first, relocate code to correct place without touching critical regs
     39 | (args are in: d0, d1, d4, a0, a1, a2, a3, a4, a5, a6)
     40 | 	[a3 and a4 only when netbooting]
     41 	movl	%a3, %d3		| SAVE a3 in d3
     42 	movl	%a4, %d5		| SAVE a4 in d5
     43 	lea	%pc@(xstart:w), %a3	| a3 = current addr (could be anywhere)
     44 	lea	xstart:l, %a4		| a4 = desired location (LINKADDR)
     45 	cmpl	%a3, %a4		| already there?
     46 	beqs	restart			| short-circuit out
     47 
     48 					| Relocate the code and data
     49 	movl	#_C_LABEL(edata),%d2	| Desired end of program
     50 	subl	%a4,%d2			| Calculate length, round up.
     51 	lsrl	#2,%d2
     52 Lcp:
     53 	movl	%a3@+, %a4@+
     54 	dbra	%d2, Lcp
     55 
     56 | Force a long jump to the relocated code (not pc-relative)
     57 	lea	restart:l, %a3
     58 	jmp	%a3@
     59 
     60 restart:
     61 | now in the relocated code
     62 
     63 | Set up stack (just before relocated text)
     64 	lea	_C_LABEL(_estack):l, %a3
     65 	movl	%a3, %sp
     66 
     67 | now that we have relocated, call the bugcrt  (note we skip over the special
     68 |	bug header which has a PC and SP in it)
     69 	movl	%d3, %a3		| RESTORE a3
     70 	movl	%d5, %a4		| RESTORE a4
     71 	jmp	_start
     72 
     73 | The end.
     74