Make kernel and fat.bs use BPB struct
This commit is contained in:
parent
303b1756e0
commit
9cd4c04c42
11
Makefile
11
Makefile
@ -1,4 +1,4 @@
|
||||
FLOPPY = 360
|
||||
FLOPPY = 1440
|
||||
|
||||
PROGRAMS = hello.com
|
||||
DISTFILES = $(PROGRAMS) kernel.bs
|
||||
@ -55,15 +55,6 @@ fat4.bs: boot/fat.asm
|
||||
fat6.bs: boot/fat.asm
|
||||
$(NASM) $(NASM_ARGS) -DFAT16 -DCHS -DLARGE -o $@ $<
|
||||
|
||||
fatb.bs: boot/fat.asm
|
||||
$(NASM) $(NASM_ARGS) -DFAT32 -DCHS -DLARGE -o $@ $<
|
||||
|
||||
fatc.bs: boot/fat.asm
|
||||
$(NASM) $(NASM_ARGS) -DFAT32 -DLBA -DLARGE -o $@ $<
|
||||
|
||||
fate.bs: boot/fat.asm
|
||||
$(NASM) $(NASM_ARGS) -DFAT16 -DLBA -DLARGE -o $@ $<
|
||||
|
||||
# BIOS option roms
|
||||
%.rom: rom/%.asm utils/fix-rom
|
||||
$(NASM) $(NASM_ARGS) -o $@ $< && utils/fix-rom $@
|
||||
|
||||
108
boot/fat.asm
108
boot/fat.asm
@ -1,11 +1,7 @@
|
||||
; Bootsector for FAT32 filesystems
|
||||
; Bootsector for FAT12/FAT16 filesystems
|
||||
; Takes defines:
|
||||
; FAT12 FAT has 1.5 bytes per entry
|
||||
; FAT16 FAT has WORD per entry
|
||||
; FAT32 FAT has DWORD per entry
|
||||
; CHS uses int13h/AH=02h
|
||||
; LARGE requires 32 bit sector numbers
|
||||
; LBA uses int13h/AH=42h
|
||||
cpu 8086
|
||||
|
||||
org 0x0800
|
||||
@ -14,14 +10,12 @@
|
||||
|
||||
%include "inc/bpb.asm"
|
||||
|
||||
bpb: equ 0x080B
|
||||
times ( 0x0B - ($-$$) ) db 0
|
||||
|
||||
params: times bpb_size db 0
|
||||
|
||||
; Area for BPB
|
||||
%ifdef FAT32
|
||||
times ( 0x5A - ($-$$) ) db 0
|
||||
%else
|
||||
times ( 0x3E - ($-$$) ) db 0
|
||||
%endif
|
||||
|
||||
init: xor ax, ax
|
||||
mov ss, ax
|
||||
@ -45,7 +39,7 @@ init: xor ax, ax
|
||||
; offsets relative to FS
|
||||
readd: ; add offset of cluster data area to DX:AX
|
||||
push cx
|
||||
mov di, [bp+bpb_rde]
|
||||
mov di, [bp+bpb.direntries]
|
||||
mov cl, 4
|
||||
shr di, cl ; 32 bytes per entry
|
||||
add ax, di
|
||||
@ -54,60 +48,20 @@ readd: ; add offset of cluster data area to DX:AX
|
||||
readr: ; add offset to rootdir to DX:AX (FAT12/FAT16 only)
|
||||
push cx
|
||||
xor ch, ch
|
||||
mov cl, byte [bp+bpb_fn]
|
||||
fatlp:
|
||||
%ifdef FAT32
|
||||
add ax, [bp+bpb7_lsf]
|
||||
adc dx, [bp+bpb7_lsf+2]
|
||||
%else
|
||||
add ax, [bp+bpb_sf]
|
||||
mov cl, byte [bp+bpb.fatnumber]
|
||||
fatlp: add ax, [bp+bpb.fatsectors]
|
||||
adc dx, 0
|
||||
%endif
|
||||
loop fatlp
|
||||
pop cx
|
||||
readf: ; add offset to FAT table to DX:AX
|
||||
add ax, word [bp+bpb_rsc]
|
||||
add ax, word [bp+bpb.reservedsects]
|
||||
adc dx, 0
|
||||
readp: ; read sector DX:AX from partition
|
||||
add ax, word [bp+bpb_po]
|
||||
adc dx, word [bp+bpb_po+2]
|
||||
add ax, word [bp+bpb.sectoroffset]
|
||||
adc dx, word [bp+bpb.sectoroffset+2]
|
||||
jnc ($+5)
|
||||
call errcll
|
||||
|
||||
%ifdef LBA
|
||||
read_: ; read sector DX:AX from disk
|
||||
; this uses the EBIOS extensions
|
||||
; qword sector number DX:AX
|
||||
push cs
|
||||
push cs
|
||||
push dx
|
||||
push ax
|
||||
|
||||
; dword target buffer: BX:0
|
||||
push bx
|
||||
push cs
|
||||
|
||||
; word sector number
|
||||
push cx
|
||||
|
||||
; size & passing
|
||||
mov di, 0x10
|
||||
push di
|
||||
|
||||
mov si, sp
|
||||
mov ah, 0x42
|
||||
mov dl, [bp+bpb7_dn]
|
||||
stc
|
||||
int 0x13
|
||||
jnc ($+5)
|
||||
call errcll
|
||||
|
||||
add sp, di
|
||||
|
||||
ret
|
||||
%endif
|
||||
|
||||
%ifdef CHS
|
||||
read_: ; read sector DX:AX from disk
|
||||
; uses basic CHS disk IO
|
||||
; this cant reliable read over track boundaries
|
||||
@ -118,15 +72,15 @@ chslp: push ax
|
||||
push bx
|
||||
|
||||
; calculate CHS data
|
||||
div word [bp+bpb_spt] ; ax:temp = (lba / spt)
|
||||
div word [bp+bpb.tracksectors] ; ax:temp = (lba / spt)
|
||||
inc dx ; dx:sector = (lba % spt) + 1
|
||||
mov cl, dl ; sector number
|
||||
xor dx, dx
|
||||
div word [bp+bpb_nos] ; ax:cylinder = (tmp / heads)
|
||||
div word [bp+bpb.heads] ; ax:cylinder = (tmp / heads)
|
||||
; dx:head = (tmp % heads)
|
||||
mov ch, al ; cylinder number
|
||||
mov dh, dl ; head number
|
||||
mov dl, [bp+bpb7_dn] ; drive number
|
||||
mov dl, [bp+bpb.drivenum] ; drive number
|
||||
|
||||
; set up read buffer
|
||||
mov es, bx
|
||||
@ -150,7 +104,6 @@ chslp: push ax
|
||||
; loop on CX
|
||||
loop chslp
|
||||
ret
|
||||
%endif
|
||||
|
||||
next: ; Advances DX:AX to next FAT entry
|
||||
push ax
|
||||
@ -205,18 +158,6 @@ shftl: clc
|
||||
xor dx, dx
|
||||
%endif
|
||||
|
||||
%ifdef FAT32
|
||||
; multiply with 4
|
||||
sal si, 1
|
||||
sal si, 1
|
||||
; make sure its within sector range
|
||||
and si, 0x1FF
|
||||
add si, buf
|
||||
; load dword
|
||||
lodsw
|
||||
mov dx, [si]
|
||||
%endif
|
||||
|
||||
ret
|
||||
|
||||
; reads current cluster into [dest]
|
||||
@ -230,7 +171,7 @@ readc: ; load cluster number
|
||||
|
||||
; convert cluster number to sector number
|
||||
; this is some cheapo multiplication with 2^n
|
||||
mov cl, [bp+bpb_sc]
|
||||
mov cl, [bp+bpb.clustersects]
|
||||
l02: shr cl, 1
|
||||
jz l02e
|
||||
clc
|
||||
@ -239,7 +180,7 @@ l02: shr cl, 1
|
||||
jmp l02
|
||||
l02e:
|
||||
; dx:ax is now sector num in data area
|
||||
mov cx, [bp+bpb_sc]
|
||||
mov cx, [bp+bpb.clustersects]
|
||||
xor ch, ch
|
||||
|
||||
call readd
|
||||
@ -255,13 +196,7 @@ l02e:
|
||||
ret
|
||||
|
||||
; Load root directory
|
||||
loadr:
|
||||
%ifdef FAT32
|
||||
mov ax, 2
|
||||
xor dx, dx
|
||||
jmp load
|
||||
%else
|
||||
mov ax, [bp+bpb_rde]
|
||||
loadr: mov ax, [bp+bpb.direntries]
|
||||
mov cl, 4
|
||||
shr ax, cl
|
||||
mov cx, ax
|
||||
@ -269,7 +204,6 @@ loadr:
|
||||
xor dx, dx
|
||||
mov bx, 0x07C0
|
||||
jmp readr
|
||||
%endif
|
||||
|
||||
; Load file identified by fsattr
|
||||
; Directory data is expected at 0x07C00
|
||||
@ -302,20 +236,18 @@ lloop: call readc
|
||||
%ifdef FAT16
|
||||
cmp word ax, 0xFFF8
|
||||
%endif
|
||||
%ifdef FAT32
|
||||
cmp word dx, 0x0FFF
|
||||
%endif
|
||||
jc lloop
|
||||
ret
|
||||
|
||||
main: ; Set up BP to point to BPB
|
||||
; Relative addressing saves one instruction byte per access
|
||||
mov bp, bpb
|
||||
mov bp, params
|
||||
; Save DL contents
|
||||
mov [bp+bpb7_dn], dl
|
||||
mov [bp+bpb.drivenum], dl
|
||||
|
||||
; load root directory
|
||||
call loadr
|
||||
|
||||
; search for first system directory
|
||||
mov ah, 0x14
|
||||
call loadf
|
||||
@ -324,7 +256,7 @@ main: ; Set up BP to point to BPB
|
||||
call loadf
|
||||
|
||||
; restore drive number
|
||||
mov dl, [bp+bpb7_dn]
|
||||
mov dl, [bp+bpb.drivenum]
|
||||
|
||||
; restore potential partition table
|
||||
pop si
|
||||
|
||||
46
inc/bpb.asm
46
inc/bpb.asm
@ -1,29 +1,17 @@
|
||||
; DOS 3.31 Bios Parameter Block
|
||||
bpb_ss: equ 0x00 ; WORD sector size
|
||||
bpb_sc: equ 0x02 ; BYTE sector / cluster
|
||||
bpb_rsc: equ 0x03 ; WORD reserved sector count
|
||||
bpb_fn: equ 0x05 ; BYTE fat number
|
||||
bpb_rde: equ 0x06 ; WORD root dir entries
|
||||
bpb_ts: equ 0x08 ; WORD total sectors
|
||||
bpb_md: equ 0x0A ; BYTE media descriptor
|
||||
bpb_sf: equ 0x0B ; WORD sectors / fat
|
||||
bpb_spt: equ 0x0D ; WORD sectors per track
|
||||
bpb_nos: equ 0x0F ; WORD number of sides
|
||||
bpb_po: equ 0x11 ; DWORD partition offset
|
||||
bpb_lts: equ 0x15 ; DWORD large total sectors
|
||||
|
||||
; DOS 4.0 Extended Bios Parameter Block
|
||||
bpb4_dn: equ 0x19 ; BYTE drive number
|
||||
bpb4_sig: equ 0x1B ; BYTE 29h
|
||||
bpb4_ser: equ 0x1C ; DWORD serial
|
||||
|
||||
; DOS 7.1 Extended Bios Parameter Block
|
||||
bpb7_lsf: equ 0x19 ; DWORD large sectors / fat
|
||||
bpb7_rdc: equ 0x21 ; DWORD root directory cluster
|
||||
bpb7_fsc: equ 0x25 ; WORD fsinfo sector
|
||||
bpb7_bsc: equ 0x27 ; WORD backup boot sector
|
||||
bpb7_dn: equ 0x35 ; BYTE drive number
|
||||
bpb7_sig: equ 0x37 ; BYTE 28h or 29h
|
||||
bpb7_ser: equ 0x38 ; DWORD serial
|
||||
|
||||
bpb_len: equ 0x4F
|
||||
struc bpb
|
||||
.sectorsize: resw 1 ; WORD sector size
|
||||
.clustersects: resb 1 ; BYTE sector / cluster
|
||||
.reservedsects: resw 1 ; WORD reserved sector count
|
||||
.fatnumber: resb 1 ; BYTE fat number
|
||||
.direntries: resw 1 ; WORD root dir entries
|
||||
.total: resw 1 ; WORD total sectors
|
||||
.mediadesc: resb 1 ; BYTE media descriptor
|
||||
.fatsectors: resw 1 ; WORD sectors / fat
|
||||
.tracksectors: resw 1 ; WORD sectors per track
|
||||
.heads: resw 1 ; WORD number of sides
|
||||
.sectoroffset: resd 1 ; DWORD partition offset
|
||||
.longtotal: resd 1 ; DWORD large total sectors
|
||||
.drivenum: resb 1 ; BYTE drive number
|
||||
.signature: resb 1 ; BYTE 28h
|
||||
.serial: resd 1 ; DWORD serial
|
||||
endstruc
|
||||
|
||||
Loading…
Reference in New Issue
Block a user