/* $NetBSD: bbstart.s,v 1.15 2022/04/29 07:12:41 rin Exp $ */
/*-
* Copyright (c) 1996 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Ignatios Souvatzis.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
.text
#if defined(_PRIMARY_BOOT) || defined(AUTOLOAD)
Lzero: .asciz "DOS" | "DOS type"
#else
Lzero: .ascii "BOOT" | Secondary Boot
#endif
/*
* We put the relocator version here, for elf2bb, which replaces
* it with the bootblock checksum.
*/
Chksum: .long RELVER_RELATIVE_BYTES_FORWARD
Filesz: .long 8192 | dummy
/*
* Entry point from Kickstart.
* A1 points to an IOrequest, A6 points to ExecBase, we have a stack.
* _must_ be at offset 12.
*/
ENTRY_NOPROFILE(start)
#ifdef AUTOLOAD
jra Lautoload
#else
jra Lrelocate
#endif
Lreltab:
.word 0 | elf2bb puts the reloc table address here
/*
* Relocate ourselves, at the same time clearing the relocation table
* (in case it overlaps with BSS).
*
* Register usage:
* A2: points into the reloc table, located at our end.
* A0: pointer to the longword to relocate.
* D0: word offset of longword to relocate
* D1: points to our start.
*
* Table has relative byte offsets, if a byte offset is zero, it is
* followed by an absolute word offset. If this is zero, too, table
* end is reached.
*/
Lrelocate:
lea %pc@(Lzero),%a0
movl %a0,%d1
/*
* Here, we cannot use
* movw %pc@(Lreltab),%a2
* "movw" against An is synonym for "movea.w", which carries out
* sign extension. This breaks things when reltab >= 0x8000.
*/
movq #0,%d0
movw %pc@(Lreltab),%d0
movl %d0,%a2
addl %d1,%a2
jra Loopend
Loopw:
clrw %a2@+
Loopb:
addl %d0,%a0
addl %d1,%a0@
Loopend:
movq #0,%d0
movb %a2@,%d0
clrb %a2@+ | bfclr %a2@+{0:8} is still two shorts
tstb %d0 | we could save one short by using casb %d0,d0,%a2@+
jne Loopb
