问题
I am creating my own operating system in Assembly.
I want to load .bin files from kernel. For that i copied some code from bootloader. But that did not work What is wrong in my code?
I am using WSL(Windows Subsystem for Linux) in Windows 10 I am using mtools to create disc image.
my code to load .bin files:
LOAD_IMAGE:
mov ax, WORD [cluster] ; cluster to read
pop bx ; buffer to read into
call ClusterLBA ; convert cluster to LBA
xor cx, cx
mov cl, BYTE [bpbSectorsPerCluster] ; sectors to read
call ReadSectors
push bx
; compute next cluster
mov ax, WORD [cluster] ; identify current cluster
mov cx, ax ; copy current cluster
mov dx, ax ; copy current cluster
shr dx, 0x0001 ; divide by two
add cx, dx ; sum for (3/2)
mov bx, 0x0200 ; location of FAT in memory
add bx, cx ; index into FAT
mov dx, WORD [bx] ; read two bytes from FAT
test ax, 0x0001
jnz .ODD_CLUSTER
.EVEN_CLUSTER:
and dx, 0000111111111111b ; take low twelve bits
jmp .DONE
.ODD_CLUSTER:
shr dx, 0x0004 ; take high twelve bits
.DONE:
mov WORD [cluster], dx ; store new cluster
cmp dx, 0x0FF0 ; test for end of file
jb LOAD_IMAGE
DONE:
mov si, msgCRLF
call print
push WORD 0x0050
push WORD 0x0000
retf
FAILURE:
mov si, msgFailure
call print
mov ah, 0x00
int 0x16 ; await keypress
int 0x19 ; warm boot computer
datasector dw 0x0000
cluster dw 0x0000
ImageName db "TESTOS SYS"
msgLoading db 0x0D, 0x0A, "Loading Boot Image ", 0x00
msgCRLF db 0x0D, 0x0A, 0x00
msgProgress db ".", 0x00
msgFailure db 0x0D, 0x0A, "MISSING OR CURRUPT KRNLDR. Press Any Key to Reboot", 0x0D, 0x0A, 0x00
print:
lodsb ; load next byte from string from SI to AL
or al, al ; Does AL=0?
jz PrintDone ; Yep, null terminator found-bail out
mov ah, 0eh ; Nope-Print the character
int 10h
jmp print ; Repeat until null terminator found
PrintDone:
ret
ClusterLBA:
sub ax, 0x0002 ; zero base cluster number
xor cx, cx
mov cl, BYTE [bpbSectorsPerCluster] ; convert byte to word
mul cx
add ax, WORD [datasector] ; base data sector
ret
ReadSectors:
.MAIN
mov di, 0x0005 ; five retries for error
.SECTORLOOP
push ax
push bx
push cx
call LBACHS ; convert starting sector to CHS
mov ah, 0x02 ; BIOS read sector
mov al, 0x01 ; read one sector
mov ch, BYTE [absoluteTrack] ; track
mov cl, BYTE [absoluteSector] ; sector
mov dh, BYTE [absoluteHead] ; head
mov dl, BYTE [bsDriveNumber] ; drive
int 0x13 ; invoke BIOS
jnc .SUCCESS ; test for read error
dec di ; decrement error counter
pop cx
pop bx
pop ax
jnz .SECTORLOOP ; attempt to read again
int 0x18
.SUCCESS
mov si, msgProgress
call print
pop cx
pop bx
pop ax
add bx, WORD [bpbBytesPerSector] ; queue next buffer
inc ax ; queue next sector
loop .MAIN ; read next sector
ret
LBACHS:
xor dx, dx ; prepare dx:ax for operation
div WORD [bpbSectorsPerTrack] ; calculate
inc dl ; adjust for sector 0
mov BYTE [absoluteSector], dl
xor dx, dx ; prepare dx:ax for operation
div WORD [bpbHeadsPerCylinder] ; calculate
mov BYTE [absoluteHead], dl
mov BYTE [absoluteTrack], al
ret
absoluteSector db 0x00
absoluteHead db 0x00
absoluteTrack db 0x00
My code for the test app
org 0x7E00
; Define variables in the data section
SECTION .DATA
hello: db 'Hello world!',10
helloLen: equ $-hello
; Code goes in the text section
SECTION .TEXT
GLOBAL _start
_start:
mov eax,4 ; 'write' system call = 4
mov ebx,1 ; file descriptor 1 = STDOUT
mov ecx,hello ; string to write
mov edx,helloLen ; length of string to write
int 80h ; call the kernel
; Terminate program
mov eax,1 ; 'exit' system call
mov ebx,0 ; exit with error code 0
int 80h ; call the kernel
Compiling commands:
nasm -f bin kernel.asm -o kernel.bin
nasm -f bin testos.asm -o testos.bin
Why my code is not working? What should I change to make this work?
来源：https://stackoverflow.com/questions/59478193/kernel-cannot-load-applications