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bootacient.SのFDからの読み込み部分を先に書いた。
bootacient.S, bootmiddle.Sはそれぞれfirstboot, secondbootの役割でこれらは0x90000, 0x90200に置きkernelは0x1000に置く。
また、kernelのstack領域はとりあえず0x9f000としておいた。
/* * @File bootacient.S * @Brief The initial boot section of Sodex * * @Author Sodex * @Revision 0.1 * @License suspension * @Date create: 2007/04/05 update: 2007/04/05 * * Copyright (C) 2007 Sodex */ BOOTSEG = 0x07C0 INITSEG = 0x9000 KERNEL_SEG = 0x0100 KERNEL_STACK_SEG = 0x9000 KERNEL_STACK_OFFSET = 0xf000 # We won't have to increase the BOOT_SECTS to more 18 ACIENT_SECTS = 1 MIDDLE_SECTS = 1 KERNEL_SECTS = 46 BOOT_SECTS = ACIENT_SECTS + MIDDLE_SECTS KERNEL_FIRST = KERNEL_SECTS - BOOT_SECTS # This is the default size of general FD formatted at 1.44MB. SECTORS = 18 .code16 .text .global _start, printstr _start: jmpl $BOOTSEG, $start2 start2: xorw %si, %si xorw %di, %di movw $BOOTSEG, %ax movw %ax, %ds movw $INITSEG, %ax movw %ax, %es movw $0x100, %cx cld rep movsw jmpl $INITSEG, $next next: movw %ax, %ds movw $KERNEL_STACK_SEG, %ax movw %ax, %ss movw $KERNEL_STACK_OFFSET, %sp # Clear the display and the message is printed # before we load the boot_middle and kernel movb $0x3, %al # Clear the display movb $0, %ah int $0x10 movw $loader_mes, %si call printstr # Reset FD call reset_fd jmp read_middleboot /* Read next boot section from floppy drive. * The data is read from fd and It is set at ES:BX of the memory point. * The reserved memory at first is the parameter of FD. * "secotr:" is sectors of current track ( 1 <= sector <= 18 ) * "head:" is current head ( 0 <= head <= 1 ) * "track:" is current track ( 0 <= track <= 79 ) */ sector: .byte 1 track: .byte 0 head: .byte 0 dummy: .byte 0 read_middleboot: movw $0x200, %bx # "es" is already set at 0x9000 movb $0x2, %al # boot acient code spend a sect movw $sector, %si movb %al, (%si) movb $0x2, %ah # AH is BIOS COMMAND, The no.2 indicates # reading disk sectors movb $MIDDLE_SECTS, %al # AL is Num of sectors to read movb (%si), %cl # CL is the sector movb 1(%si), %ch # CH is the track movb 2(%si), %dh # DH is the head movb $0, %dl # DL is the drive(always 0) int $0x13 jc read_error incb (%si) call reset_fd /* Read the kernel section from FD. * The data is read from fd and It is set at ES:BX. */ xorw %bx, %bx movw $KERNEL_SEG, %ax movw %ax, %es # ES:BX = 0x0100:0x0000(0x1000) movw $KERNEL_SECTS, %di # set the num of kernel sects to di movb $0x2, %ah # AH is BIOS COMMAND, The no.2 indicates # reading disk sectors movb $KERNEL_FIRST, %al # The num sector must be between 1 and 18. movb (%si), %cl # CL is the sector movb 1(%si), %ch # CH is the track movb 2(%si), %dh # DH is the head movb $0, %dl # DL is the drive(always 0) int $0x13 jc read_error addb %al, %bh addb %al, %bh # bx += 2*al*256 (add reading bytes) movb %ah, %ah # al is no. of read sectors subw %ax, %di movb $0x0, (%si) # sector is 0 movb $0x1, 2(%si) # head is 1 read1: cmpw $SECTORS, %di ja left_sects_over18 movw %di, %ax xorb %ah, %ah call read_it jmp read_end left_sects_over18: movb $SECTORS, %al call read_it jmp read1 read_end: call reset_fd jmp middle_start /* Read FD's data * Before using this function, we must set the following parameter * ES:BX - sent address * AL - Num of read sectors * sector, track, head - FD parameter */ read_it: movb $0x2, %ah # AH is BIOS COMMAND, The no.2 indicates # reading disk sectors movb (%si), %cl # CL is the sector movb 1(%si), %ch # CH is the track movb 2(%si), %dh # DH is the head movb $0, %dl # DL is the drive(always 0) int $0x13 jc read_error addb %al, %bh addb %al, %bh # bx += 2*al*256 (add reading bytes) movb %ah, %ah # al is no. of read sectors subw %ax, %di # if head is 0, then we set head to 1 # else if head is 1, then we increment track and set head to 0 cmpb $0x0, 2(%si) jnz read_it_next movb $0x1, 2(%si) jmp read_it_end read_it_next: movb $0x0, 2(%si) incb 1(%si) read_it_end: ret /* Reset floppy drive * Set AH = 0, which indicate to reset drive * Set AL = 0, which indicate first floppy drive. * INT 0x13: BIOS Disk services */ reset_fd: xorw %ax, %ax xorb %dl, %dl # dl is num of drive int $0x13 jnc fd_reset_ok movw $fd_reset_error_mes, %si call printstr jmp halt fd_reset_ok: ret read_error: movw $fd_read_error_mes, %si call printstr jmp halt printstr: pushw %ax printstr_start: lodsb cmpb $0, %al jz printstr_end movb $0x0e, %ah movb $0, %bh int $0x10 jmp printstr_start printstr_end: popw %ax ret halt: # hlt jmp halt loader_mes: .ascii "Loading...\r\n" .byte 0 fd_reset_error_mes: .ascii "The floppy drive failed reset..\r\n" .byte 0 fd_read_error_mes: .ascii "read error at the floppy drive..\r\n" .byte 0 .org 510 .word 0xAA55
