NASM - The Netwide Assembler
NASM Forum => Using NASM => Topic started by: Deskman243 on March 04, 2023, 04:12:24 PM
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Greetings Forum
I've got more news for the OS design subjects that I have been posting recently. I have a standard model for v86 tasking here so that we can display a very simple print function. Both methods have an output however the first one was for making a custom display function (hopefully provides a stage for a virtual VGA model). So the code should run completely however my contestion is that the method3 model label does not in fact address properly(this can be shown by comparing the method3 instruction code to the other printstr_task1 call of my code).
The standard logic for 80386 segment address = ((segment stack)(16)+(address shift)) so the protected mode address is shifted before the output method and I mainly tried making a stack (VM_VIDMEM_STACK) reference to adjust the (16) component of the segment.
I'm trying to learn how this maps to the linear address here however the object files show that mov es:[VM_VIDMEM_STACK],ax does nothing. Now I kinda have run through most thoughts I can think of so I'm really hoping that anyone else here could have a look at what had happened. I'd be happy to continue this and available for responses.
Here is the code for the Makefile
[BITS 16]
;[ORG 0x7E00]
section .text
;modeblock: times 512 db 0
jmp LoadProp
;section .text
;modeblock: times 256 db 0
SizeFunction:
mov bx,0x0000_7E00
;check address arithmetic base
add bx,0x0200
mov cl,3
SizeLoop:
mov ah,0x02
mov al,3
mov ch,0
mov dh,0
int 0x13
; jc ReadCheck
cmp cl,5
inc cl
jmp _prep_module2
;stackplacer: times 256 dd 0
;stack:
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
vm_module:
sub dword [vidmem_ptr],VIDEO_TEXT_ADDR
mov si,vm_str
mov ah,COLOR_ATTR_BSC
call printstr_task
.loopcheck: jmp $
printstr_task:
; push si
push ax
push es
mov byte [ss:0],0
mov sp,VIDEO_TEXT_ADDR >>4
mov es,sp
mov sp,[vidmem_ptr]
; mov dh,0h
; mov dl,[vidmem_ptr]
; mov dx,sp
; mov dh,0
; mov [VM_VIDMEM_STACK],dx
; mov [VM_VIDMEM_STACK],sp
mov [ss:0],es
shr sp,4
add sp,[ss:0]
mov es,sp
jmp gettext
output:
;Buffer loop cycling
; test es,sp
; cmp sp,[vidmem_ptr]
; jnz prop
prep:
prop:
mov sp,[VM_VIDMEM_STACK]
mov sp,VM_VIDMEM_STACK
; mov es:[VM_VIDMEM_STACK],ax
; mov [es:VM_VIDMEM_STACK],ax
; mov [es:0],ax
; mov es:[vidmem_ptr],ax
; mov [es:sp],ax
add byte [VM_VIDMEM_STACK],2
;method3
mov [es:0],ax
mov sp,es
add sp,2
mov es,sp
gettext:
mov al,byte [ds:si]
inc si
test al,al
jnz output
; jnz .prop
mov [vidmem_ptr],si
mov sp,VM_STACK_PREP
pop es
pop ax
ret
printstr_task1:
push di
push si
push ax
push es
mov di,VIDEO_TEXT_ADDR >>4
mov es,di
mov di,[vidmem_ptr]
jmp gettext_test
output_test: stosw
gettext_test:
lodsb
test al,al
jne output_test
mov [vidmem_ptr],di
pop es
pop ax
pop si
pop di
ret
_prep_module2:
cld
cli
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 ax,
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ss,ax
; mov esp,edx
mov esp,PM_MODE_STACK
mov ah,COLOR_ATTR_PSC
mov al,ah
mov esi, pm_str
call printstr_pm
;jmp $
prep_stage:
mov si,0
mov ds,si
push ds
push ds
push ds
push ds
push VM_STACK_SEG
push VM_STACK_OFS
push dword 1 << FLAGS_VM_CMP
push VM_CS_SEG
push vm_module
iret
printstr_pm:
push ds
; push esi
push eax
; push ebp
mov ebp,0
jmp .gettext
.output:
mov esi,[vidmem_ptr]
add esi,ebp
mov [es:esi],ax
add ebp,2
pop esi
.gettext:
mov al,[ds:si]
add si,1
push esi
test al,al
jnz .output
.stub
dec esi
shr ebp,1
add esi,ebp
mov [vidmem_ptr],esi
pop esi
pop eax
pop ds
ret
section .data
VIDEO_TEXT_ADDR EQU 0XB8000
COLOR_ATTR_PSC EQU 0X6A
COLOR_ATTR_BSC EQU 0X5F
PM_MODE_STACK EQU 0X80000
VM_STACK_SEG EQU 0X0000
VM_STACK_OFS EQU 0X0000
VM_CS_SEG EQU 0X0000
VM_STACK_PREP EQU 0xfffa
;VM_VIDMEM_STACK EQU 0X0000
FLAGS_VM_CMP EQU 17
FLAGS_CMP1 EQU 1
FLAGS_CMP_IF EQU 9
section .data
align 4
vidmem_ptr: dd VIDEO_TEXT_ADDR
VM_VIDMEM_STACK: dw 0X0000
pm_str: db 'protected mode string ',0
pm_str_length: equ $-pm_str
vm_str: db 'virtual',0
;VM_STACK_PREP: dw ?
align 4
[BITS 16]
;[ORG 0x7c00]
section .data
VIDEO_TEXT_ADDR EQU 0XB8000
COLOR_ATTR_PSC EQU 0X2F
COLOR_ATTR_BSC EQU 0X5F
PM_MODE_STACK EQU 0X80000
VM_STACK_SEG EQU 0X0000
VM_STACK_OFS EQU 0X0000
VM_CS_SEG EQU 0X0000
FLAGS_VM_CMP EQU 17
FLAGS_CMP1 EQU 1
FLAGS_IF_CMP EQU 9
section .text
_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 si,ReadPacket
; mov word[si],0x10
; mov word[si+2],5
; mov word[si+4],0x7e00
; mov word[si+6],0
; mov dword[si+8],1
; mov dword[si+0xc],0
; mov dl,[DriveId]
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:
; mov ah,0x13
; mov al,1
; mov bx,0xa
; xor dx,dx
; mov bp,Message
; mov cx,MessageLen
; int 0x10
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
; ld -tText 0x7E00 stage1.o -o stage1.bin
FILES =boot.o printstr.o
all: boot.bin stage1.bin
dd if=boot.bin of=os.img bs=512 count=1 conv=notrunc
dd if=stage1.bin of=os.img bs=512 count=3 seek=1 conv=notrunc
boot.o: boot.asm
nasm -f elf -g -o boot.o boot.asm
printstr.o: printstr.asm
nasm -f elf -g -o printstr.o printstr.asm
stage1.o: stage1.asm
nasm -f elf -g stage1.asm -o stage1.o
stage1a.bin: stage1.asm
nasm -f bin stage1.asm -o stage1a.bin
boot.bin: $(FILES)
ld -T link.ld $(FILES) -o boot.bin
stage1.bin: stage1.o
ld -g -m elf_i386 -Ttext 0x7E00 stage1.o -o stage1.bin --oformat binary
clean:
rm -rf os.img
rm -rf boot.bin
rm -rf stage1.bin
rm -rf stage1.o
rm -rf stage1a.bin