Greetings everyone
I was trying to convert the code of a simple VESA VBE program into the elf standard. Bin files change my settings so here I was making a simple version to try and review. I use ld when I have to use a elf .o object and I can make the elf file run for boot.asm elf object however in my makefile I realize I can only run the bin form stage1a.bin (including the org setting). When I try to make the stage1.o elf object I keep getting the error from above. Here is my code so far
boot.asm
[BITS 16]
;[ORG 0x7c00]
_prep_module:
xor ax,ax
mov ds,ax
mov es,ax
mov ss,ax
mov sp,0x7c00
DriveIdProp:
mov [DriveId],dl
mov ah,0x41
mov bx,0x55aa
int 0x13
jc CheckProp
cmp bx,0xaa55
jne CheckProp
LoadProp:
mov bx,0x0000_7E00
mov cl,2
mov ah,0x02
mov al,1
mov ch,0
mov dh,0
int 0x13
jc ReadCheck
mov dl,[DriveId]
jmp 0x7e00
ReadCheck:
CheckProp:
lea si,[Message]
Print:
lodsb
test al,al
jz .loop
mov ah,0x0E
mov bx,7
int 0x10
jmp Print
.loop:
hlt
jmp .loop
DriveId: db 0
Message: db "We have an error in boot process"
MessageLen: equ $-Message
ReadPacket: times 16 db 0
;times (0x1be-($-$$)) db 0
; db 80h
; db 0,2,0
; db 0f0h
; db 0ffh,0ffh,0ffh
; dd 1
; dd (20*16*63-1)
; times (16*3) db 0
; db 0x55
; db 0xaa
printstr.asm
[code]
bits 16
global printstr
printstr:
lodsb
test al,al
jz .done
mov ah,0x0E
mov bx,7
int 0x10
jmp printstr
.done:
ret
[/code]
stage1.asm
[BITS 16]
;[ORG 0x7E00]
modeblock: times 256 db 0
jmp LoadProp
;section .text
;modeblock: times 256 db 0
DriveIdProp:
mov [DriveId],dl
mov ah,0x41
mov bx,0x55aa
int 0x13
jc CheckProp
cmp bx,0xaa55
jne CheckProp
LoadProp:
mov bx,0x0000_7E00
;check address arithmetic base
add bx,0x0200
mov cl,3
LoadLoop:
mov ah,0x02
mov al,3
mov ch,0
mov dh,0
int 0x13
; jc ReadCheck
cmp cl,5
inc cl
jmp VideoModule
;address zone check
Gdt32:
dq 0
Code32:
dw 0xffff
dw 0
db 0
db 0x9a
db 0xcf
db 0
Data32:
dw 0xffff
dw 0
db 0
db 0x92
db 0xcf
db 0
Gdt32Len: equ $-Gdt32
Gdt32Ptr: dw Gdt32Len-1
dd Gdt32
Idt32Ptr:
dw 0
dd 0
;jmp 0x8400
stack: times 256 dd 0
stackplacer:
VideoModule:
mov ax,0x4f01
mov cx,0x4117
VideoBuff:
mov di,modeblock
int 0x10
mov esi,[modeblock+0x28]
mov ax,0x4f02
mov bx,0x4117
int 0x10
mov ax,0x2401
int 0x15
;check address base
xor edx,edx
mov dx,cs
shl edx,4
add edx,stackplacer
SetVideoMode:
; in al,0x92
; or al,2
; out 0x92,al
cli
lgdt[Gdt32Ptr]
lidt[Idt32Ptr]
mov eax,cr0
or eax,1
mov cr0,eax
jmp 0x8:protectedMode
[bits 32]
protectedMode:
mov ax,0x10
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ss,ax
mov esp,edx
; mov byte[0xb8000],'D'
; mov byte[0xb8001],0xa
l1:
xor eax,eax
mov edi,esi
mov ecx,1024*768*2/4
cld
rep stosd
mov eax,0x07FF07FF
mov ecx,32
mov edi,esi
l2:
push ecx
mov ecx,768*16
lines:
cld
rep stosd
mov ecx,0xFFFFFFFF
loop $
pop ecx
sub eax,0x00410041
loop 12
mov ecx,0xFFFFFFFF
loop $
jmp l1
.loop1:
hlt
jmp .loop1
ReadCheck:
CheckProp:
lea si,[Message]
Print:
lodsb
test al,al
jz .loop
mov ah,0x0E
mov bx,7
int 0x10
jmp Print
.loop:
hlt
jmp .loop
;section .data
DriveId: db 0
LoopProp: db 0
AddressProp: dw 0x0000_8000
Message: db "We have an error in boot process"
MessageLen: equ $-Message
ReadPacket: times 16 db 0
link.ld
* boot.ld */
/* linker script for 16 bits - mbr */
OUTPUT_FORMAT(binary)
OUTPUT_ARCH(i386)
ENTRY(_prep_module)
SECTIONS
{
. = 0x7c00;
_premier = .;
_prep_module= .;
.text : { *(.text16) *(.text) }
.rodata : { *(.rodata) }
.data : { *(.data) }
. = _premier + 512-2;
.dummy : { BYTE(0x55); BYTE(0xAA); }
_bss_begin = .;
.bss : { *(.bss) }
_bss_end = .;
_heap = .;
/DISCARD/ : { *(.comment) *(.eh_frame) *(.note.GNU-stack) }
}
Makefile
FILES=boot.o printstr.o
all:
dd if =boot.bin of=boot.img bs=512 count=1 conv=notrunc
dd if =stage1.bin of=stage1a.img bs=512 count=3 seek=1 conv=notrunc
boot.o: boot.asm
nasm -f elf32 -o boot.o boot.asm
printstr.o:printstr.asm
nasm -f elf32 -o printstr.o printstr.asm
stage1.o: stage1.asm
nasm -f elf32 -o stage1.o stage1.asm
stage1a.bin:stage1.asm
nasm -f bin -o stage1a.bin stage1.asm
boot.bin: $(FILES)
ld -T link.ld $(FILES) -o boot.bin
stage1.bin: stage1.o
ld -g -m i386 -tText 0x7E00 -o stage1.bin stage1.o
clean:
rm -rf boot.img
rm -rf boot.bin
rm -rf stage1.bin
rm -rf stage1.o
rm -rf stage1a.bin
rm -rf printstr.o
I'm really hoping this post can show where I do not understand and would be happy to continue the subject further. Also thank you to fredericopisarra's post from here
https://forum.nasm.us/index.php?topic=2850.0 that taught me about using ld.
