bbstart.s revision 1.4
1 /* $NetBSD: bbstart.s,v 1.4 1999/02/16 22:46:56 is Exp $ */ 2 3 /*- 4 * Copyright (c) 1999 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "aout2bb.h" 40 41 #define LVOAllocMem -0x0c6 42 #define LVODoIO -0x1c8 43 #define LVOCacheClearU -0x27c 44 45 #define IOcmd 28 46 #define IOerr 31 47 #define IOlen 36 48 #define IObuf 40 49 #define IOoff 44 50 51 #define Cmd_Rd 2 52 53 .globl _pain 54 55 .text 56 Lzero: .asciz "DOS" | "DOS type" 57 /* 58 * We put the relocator version here, for aout2bb, which replaces 59 * it with the bootblock checksum. 60 */ 61 Chksum: .long RELVER_RELATIVE_BYTES_FORWARD 62 Filesz: .long 8192 | dummy 63 64 /* 65 * Entry point from Kickstart. 66 * A1 points to an IOrequest, A6 points to ExecBase, we have a stack. 67 * _must_ be at offset 12. 68 */ 69 .globl _start 70 _start: 71 #ifdef AUTOLOAD 72 jra Lautoload 73 #else 74 jra Lrelocate 75 #endif 76 77 Lreltab: 78 .word 0 | aout2bb puts the reloc table address here 79 80 #ifdef AUTOLOAD 81 /* 82 * autoload 83 */ 84 Lautoload: 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 99 Lgotmem: 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 122 Lioerr: 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 */ 142 143 Lrelocate: 144 lea pc@(Lzero),a0 145 movl a0,d1 146 movw pc@(Lreltab),a2 147 addl d1,a2 148 jra Loopend 149 150 Loopw: 151 clrw a2@+ 152 movl d1,a0 | for a variant with relative words, erase this line 153 Loopb: 154 addl d0,a0 155 addl d1,a0@ 156 Loopend: 157 movq #0,d0 158 movb a2@,d0 159 clrb a2@+ | bfclr a2@+{0:8} is still two shorts 160 tstb d0 | we could save one short by using casb d0,d0,a2@+ 161 jne Loopb 162 163 movw a2@,d0 164 jne Loopw 165 166 Lendtab: 167 movl a6,sp@- 168 jsr a6@(LVOCacheClearU) 169 movl sp@+,a6 170 171 /* We are relocated. Now it is safe to initialize _SysBase: */ 172 173 movl a6,_SysBase 174 175 movl a1,sp@- 176 bsr _pain 177 178 Lerr: 179 movq #1,d0 180 rts 181 182 .comm _SysBase,4 183
Indexes created Wed Oct 29 12:09:47 GMT 2025