1/* $NetBSD: bbstart.s,v 1.15 2022/04/29 07:12:41 rin Exp $ */ 2 3/*- 4 * Copyright (c) 1996 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Ignatios Souvatzis. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32#include <machine/asm.h> 33#include "elf2bb.h" 34 35#define LVOAllocMem -0x0c6 36#define LVODoIO -0x1c8 37#define LVOCacheClearU -0x27c 38 39#define IOcmd 28 40#define IOerr 31 41#define IOlen 36 42#define IObuf 40 43#define IOoff 44 44 45#define Cmd_Rd 2 46 47 .text 48#if defined(_PRIMARY_BOOT) || defined(AUTOLOAD) 49Lzero: .asciz "DOS" | "DOS type" 50#else 51Lzero: .ascii "BOOT" | Secondary Boot 52#endif 53 /* 54 * We put the relocator version here, for elf2bb, which replaces 55 * it with the bootblock checksum. 56 */ 57Chksum: .long RELVER_RELATIVE_BYTES_FORWARD 58Filesz: .long 8192 | dummy 59 60/* 61 * Entry point from Kickstart. 62 * A1 points to an IOrequest, A6 points to ExecBase, we have a stack. 63 * _must_ be at offset 12. 64 */ 65ENTRY_NOPROFILE(start) 66#ifdef AUTOLOAD 67 jra Lautoload 68#else 69 jra Lrelocate 70#endif 71 72Lreltab: 73 .word 0 | elf2bb puts the reloc table address here 74 75 .globl _C_LABEL(default_command) 76_C_LABEL(default_command): 77 .asciz "netbsd -ASn2" 78 .org (_C_LABEL(default_command)+32) 79 80#ifdef AUTOLOAD 81/* 82 * autoload 83 */ 84Lautoload: 85 movl %a6,%sp@- |SysBase 86 movl %a1,%sp@- |IORequest 87 88 movl #AUTOLOAD,%d0 |Howmuch 89 movl %d0,%a1@(IOlen) | for the actual read... 90 movl #0x10001,%d1 |MEMF_CLEAR|MEMF_PUBLIC 91 jsr %a6@(LVOAllocMem) 92 movl %sp@+,%a1 |IORequest 93 movl %sp@+,%a6 |SysBase 94 orl %d0,%d0 95 jne Lgotmem 96 movql #1,%d0 97 rts 98 99Lgotmem: 100 movl %d0,%sp@- |Address 101 movl %a1@(IOoff),%sp@- |Old offset 102 movl %a1,%sp@- 103 movl %a6,%sp@- 104 105/* we've set IOlen above */ 106 movl %d0,%a1@(IObuf) 107 movw #Cmd_Rd,%a1@(IOcmd) 108 jsr %a6@(LVODoIO) 109 110 movl %sp@+,%a6 111 movl %sp@+,%a1 112 movl %sp@+,%a1@(IOoff) 113 114 tstb %a1@(IOerr) 115 jne Lioerr 116 addl #Lrelocate-Lzero,%sp@ 117 118 movl %a6,%sp@- 119 jsr %a6@(LVOCacheClearU) 120 movl %sp@+,%a6 121 rts 122Lioerr: 123 movql #1,%d0 124 addql #4,%sp 125 rts 126#endif 127 128/* 129 * Relocate ourselves, at the same time clearing the relocation table 130 * (in case it overlaps with BSS). 131 * 132 * Register usage: 133 * A2: points into the reloc table, located at our end. 134 * A0: pointer to the longword to relocate. 135 * D0: word offset of longword to relocate 136 * D1: points to our start. 137 * 138 * Table has relative byte offsets, if a byte offset is zero, it is 139 * followed by an absolute word offset. If this is zero, too, table 140 * end is reached. 141 */ 142 143Lrelocate: 144 lea %pc@(Lzero),%a0 145 movl %a0,%d1 146 147 /* 148 * Here, we cannot use 149 * movw %pc@(Lreltab),%a2 150 * "movw" against An is synonym for "movea.w", which carries out 151 * sign extension. This breaks things when reltab >= 0x8000. 152 */ 153 movq #0,%d0 154 movw %pc@(Lreltab),%d0 155 movl %d0,%a2 156 157 addl %d1,%a2 158 jra Loopend 159 160Loopw: 161 clrw %a2@+ 162Loopb: 163 addl %d0,%a0 164 addl %d1,%a0@ 165Loopend: 166 movq #0,%d0 167 movb %a2@,%d0 168 clrb %a2@+ | bfclr %a2@+{0:8} is still two shorts 169 tstb %d0 | we could save one short by using casb %d0,d0,%a2@+ 170 jne Loopb 171 172 movw %a2@,%d0 173 jne Loopw 174 175Lendtab: 176 movl %a6,%sp@- 177 jsr %a6@(LVOCacheClearU) 178 movl %sp@+,%a6 179 180/* We are relocated. Now it is safe to initialize _SysBase: */ 181 182 movl %a6,_C_LABEL(SysBase) 183 184#ifndef _PRIMARY_BOOT 185 movl %a5,%sp@- | Console info 186#endif 187 movl %a1,%sp@- 188 bsr _C_LABEL(pain) 189#ifdef _PRIMARY_BOOT 190 addql #4,%sp 191#else 192 addql #8,%sp 193#endif 194 195Lerr: 196 movq #1,%d0 197 rts 198 199 .comm _C_LABEL(SysBase),4 200