mbr.S revision 1.2
1 /* $NetBSD: mbr.S,v 1.2 2012/01/21 19:44:30 nonaka Exp $ */ 2 3 /*- 4 * Copyright (C) 2005 NONAKA Kimihiro <nonaka (at) netbsd.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include <machine/asm.h> 29 #include <sys/bootblock.h> 30 31 ENTRY(start) 32 mova mbr_end, r0 33 mov r0, r11 /* r11: relocate address */ 34 35 mov.w mbr_size, r2 36 sub r2, r0 37 mov r0, r10 /* r10: loaded address */ 38 39 mov.w stack_offset, r1 40 add r1, r0 41 mov r0, r15 /* r15: stack pointer */ 42 43 /* relocate code */ 44 mova jmp_start, r0 45 mov r0, r13 46 add r2, r13 /* calc jump address */ 47 48 mov r10, r0 49 mov r11, r1 50 1: mov.b @r0+, r3 51 dt r2 52 mov.b r3, @r1 53 bf/s 1b 54 add #1, r1 55 56 jmp @r13 57 nop 58 59 .align 2 60 jmp_start: 61 /* enable cache */ 62 mov #0, r4 63 mov #6, r0 64 trapa #0x3f 65 66 #ifndef NO_BANNER 67 /* print banner */ 68 mova banner, r0 69 bsr message_crlf 70 mov r0, r4 71 #endif 72 73 /* search bootable partition */ 74 mov.w part_offset, r12 75 add r11, r12 /* r12: pointer to partition entry */ 76 mov #MBR_PART_COUNT, r8 /* r8: partition loop counter */ 77 loop_part: 78 mov.b @(4, r12), r0 79 cmp/eq #MBR_PTYPE_UNUSED, r0 80 bt next_part 81 82 /* check active partition */ 83 mov.b @(0, r12), r0 84 cmp/eq #0x80, r0 85 bf next_part 86 87 /* found bootable partition */ 88 mov.w @(8, r12), r0 /* load unaligned 32bit data */ 89 mov r0, r1 90 mov.w @(10, r12), r0 91 extu.w r1, r1 92 shll16 r0 93 or r1, r0 94 95 mov r0, r3 96 mova found_sector, r0 97 bra boot_lba 98 mov.l r3, @r0 99 100 next_part: 101 dt r8 102 bf/s loop_part 103 add #16, r12 104 105 noos_error: 106 /* Not found bootable partition */ 107 mova ERR_NOOS, r0 108 error: 109 bsr message_crlf 110 mov r0, r4 111 99: bra 99b 112 nop 113 114 read_error: 115 bra error 116 mova ERR_READ, r0 117 118 message_crlf: 119 mov #32, r0 120 trapa #0x3f 121 mova crlf, r0 122 mov r0, r4 123 mov #32, r0 124 trapa #0x3f 125 rts 126 nop 127 128 read_sector_lba: 129 mov #1, r7 130 mov #2, r0 131 trapa #0x3f 132 tst r0, r0 133 bf read_error 134 rts 135 nop 136 137 boot_lba: 138 /* read PBR sector */ 139 mova found_sector, r0 140 mov #0x40, r4 141 mov.l @r0, r5 142 bsr read_sector_lba 143 mov r10, r6 144 145 /* flush cache */ 146 mov #0, r4 147 mov #6, r0 148 trapa #0x3f 149 150 /* check signature */ 151 mov.b @(0, r10), r0 152 tst r0, r0 153 bt noos_error /* first byte non-zero */ 154 mov.w magic_offset, r0 155 mov.w @(r0, r10), r1 156 mov.w magic, r2 157 cmp/eq r1, r2 158 bf noos_error /* magic */ 159 160 /* now jump to PBR */ 161 mov r10, r0 162 jmp @r10 163 nop 164 165 166 .align 1 167 mbr_size: .word mbr_end - _C_LABEL(start) 168 .align 1 169 stack_offset: .word 0x1000 170 .align 1 171 part_offset: .word MBR_PART_OFFSET 172 .align 1 173 magic_offset: .word MBR_MAGIC_OFFSET 174 175 .align 2 176 found_sector: .long 0 177 178 #ifndef NO_BANNER 179 .align 2 180 banner: .asciz "\r\nNetBSD MBR boot" 181 #endif 182 .align 2 183 crlf: .asciz "\r\n" 184 185 .align 2 186 ERR_INVPART: .asciz "No active partition" 187 .align 2 188 ERR_READ: .asciz "Disk read error" 189 .align 2 190 ERR_NOOS: .asciz "No operating system" 191 192 193 /* space for mbr_dsn */ 194 . = _C_LABEL(start) + MBR_DSN_OFFSET 195 .long 0 196 197 /* mbr_bootsel_magic */ 198 . = _C_LABEL(start) + MBR_BS_MAGIC_OFFSET 199 .word MBR_BS_MAGIC 200 201 /* 202 * MBR partition table 203 */ 204 . = _C_LABEL(start) + MBR_PART_OFFSET 205 _pbr_part0: 206 .byte 0, 0, 0, 0, 0, 0, 0, 0 207 .byte 0, 0, 0, 0, 0, 0, 0, 0 208 _pbr_part1: 209 .byte 0, 0, 0, 0, 0, 0, 0, 0 210 .byte 0, 0, 0, 0, 0, 0, 0, 0 211 _pbr_part2: 212 .byte 0, 0, 0, 0, 0, 0, 0, 0 213 .byte 0, 0, 0, 0, 0, 0, 0, 0 214 _pbr_part3: 215 .byte 0, 0, 0, 0, 0, 0, 0, 0 216 .byte 0, 0, 0, 0, 0, 0, 0, 0 217 218 . = _C_LABEL(start) + MBR_MAGIC_OFFSET 219 magic: 220 .word MBR_MAGIC 221 mbr_end: 222
Indexes created Tue Oct 14 01:09:49 GMT 2025