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SRT0.S revision 1.2 
      1 |	$NetBSD: SRT0.S,v 1.2 1996/05/17 20:53:49 chuck 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 | 3. The name of the author may not be used to endorse or promote products
     15 |    derived from this software without specific prior written permission.
     16 | 4. All advertising materials mentioning features or use of this software
     17 |    must display the following acknowledgement:
     18 |      This product includes software developed by Gordon Ross
     19 |
     20 | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     21 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     22 | OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     23 | IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     24 | INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     25 | NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     26 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     27 | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     28 | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     29 | THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     30 
     31 |	this is a pre-startup wrapper for bugcrt which relocates the
     32 |	code to the correct place before exec()ing.
     33 
     34 |	SRT0.S - Stand-alone Run-Time startup code, part 0
     35 	.file	"SRT0.S"
     36 	.text
     37 	.globl	__estack
     38 __estack:
     39 	.globl	xstart
     40 xstart:
     41 | first, relocate code to correct place without touching critical regs
     42 | (args are in: d0, d1, d4, a0, a1, a2, a3, a4, a5, a6)
     43 | 	[a3 and a4 only when netbooting]
     44 	movl	a3, d3			| SAVE a3 in d3
     45 	movl	a4, d5			| SAVE a4 in d5
     46 	lea	pc@(xstart:w), a3	| a3 = current addr (could be anywhere)
     47 	lea	xstart:l, a4		| a4 = desired location (LINKADDR)
     48 	cmpl	a3, a4			| already there?
     49 	beqs	restart			| short-circuit out
     50 
     51 					| Relocate the code and data
     52 	movl	#_edata,d2		| Desired end of program
     53 	subl	a4,d2			| Calculate length, round up.
     54 	lsrl	#2,d2
     55 Lcp:
     56 	movl	a3@+, a4@+
     57 	dbra	d2, Lcp
     58 
     59 | Force a long jump to the relocated code (not pc-relative)
     60 	lea	restart:l, a3
     61 	jmp	a3@
     62 
     63 restart:
     64 | now in the relocated code
     65 
     66 | Set up stack (just before relocated text)
     67 	lea	__estack:l, a3
     68 	movl	a3, sp
     69 
     70 | now that we have relocated, call the bugcrt  (note we skip over the special
     71 |	bug header which has a PC and SP in it)
     72 	movl	d3, a3			| RESTORE a3
     73 	movl	d5, a4			| RESTORE a4
     74 	jmp	_start
     75 
     76 | The end.
     77