diff options
Diffstat (limited to 'grub-core/boot/i386/pc/cdboot.S')
| -rw-r--r-- | grub-core/boot/i386/pc/cdboot.S | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/grub-core/boot/i386/pc/cdboot.S b/grub-core/boot/i386/pc/cdboot.S new file mode 100644 index 0000000..de4f809 --- /dev/null +++ b/grub-core/boot/i386/pc/cdboot.S @@ -0,0 +1,173 @@ +/* -*-Asm-*- */ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2008,2009 Free Software Foundation, Inc. + * + * GRUB is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * GRUB is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <grub/symbol.h> +#include <grub/machine/boot.h> +#include <grub/machine/kernel.h> +#include <multiboot.h> + + .file "cdboot.S" + +#define CODE_ADDR 0x6000 +#define DATA_ADDR ((GRUB_BOOT_MACHINE_KERNEL_ADDR) + 0x200) + +#define CDSEC_SHIFT 11 +#define CDBLK_LENG 16 + + .text + + .code16 + + .globl start, _start + +start: +_start: + call LOCAL(next) + +LOCAL(next): + jmp 1f + + .org 8 + +bi_pvd: + .long 0 /* LBA of primary volume descriptor. */ +bi_file: + .long 0 /* LBA of boot file. */ +bi_length: + .long 0 /* Length of boot file. */ +bi_csum: + .long 0 /* Checksum of boot file */ +bi_reserved: + .space (10*4) /* Reserved */ + +1: + popw %bx + + /* Boot from CDROM. */ + + xorw %ax, %ax + movw %ax, %ss + movw $(CODE_ADDR), %sp + movw %ax, %ds + movw %ax, %es + + movw $(0x7C00 + err_noboot_msg - start), %si + movl %cs: bi_length - LOCAL(next)(%bx), %ecx + orl %ecx, %ecx + jz LOCAL(fail) + + addl $((1 << CDSEC_SHIFT) - 1), %ecx + shrl $CDSEC_SHIFT, %ecx + + movl %cs: bi_file - LOCAL(next)(%bx), %esi + + call LOCAL(read_cdrom) + + ljmp $(DATA_ADDR >> 4), $0 + +/* + * Parameters: + * esi: start sector + * ecx: number of sectors + */ +LOCAL(read_cdrom): + xorl %eax, %eax + + /* Number of blocks to read. */ + pushw $CDBLK_LENG + + /* Block number. */ + incl %esi + pushl %eax + pushl %esi + + /* Buffer address. */ + pushw $((DATA_ADDR - 0x200)>> 4) + pushl %eax + pushw $0x10 + + xorl %edi, %edi + movw %sp, %si + +1: + movw 0x10(%si), %di + cmpl %ecx, %edi + jbe 2f + movl %ecx, %edi + +2: + mov %di, 2(%si) + + pushl %ecx + + movb $0x42, %ah + int $0x13 + + jnc 3f + + movb $0x42, %ah /* Try again. */ + int $0x13 + + jnc 3f + +2: + shrw $1, %di /* Reduce transfer size. */ + jz LOCAL(cdrom_fail) + movw %di, 0x10(%si) + movw %di, 2(%si) + movb $0x42, %ah + int $0x13 + jc 2b + +3: + + movw %di, %ax + shlw $(CDSEC_SHIFT - 4), %ax + addw %ax, 6(%si) + addl %edi, 8(%si) + + popl %ecx + subl %edi, %ecx + jnz 1b + + addw $0x12, %sp + ret + +LOCAL(cdrom_fail): + movw $(0x7C00 + err_cdfail_msg - start), %si + +LOCAL(fail): + movb $0x0e, %ah + xorw %bx, %bx +1: + lodsb (%si), %al + int $0x10 + cmpb $0, %al + jne 1b +1: jmp 1b + +err_noboot_msg: + .ascii "no boot info\0" + +err_cdfail_msg: + .ascii "cdrom read fails\0" + + .org 0x7FF + + .byte 0 |