Start working on rom-based kernel

This commit is contained in:
Nero 2020-05-29 00:32:30 +02:00
parent 04a7087d79
commit 65564b78af
3 changed files with 141 additions and 0 deletions

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@ -102,3 +102,6 @@ qemu-pxe: pxeboot.0 $(ROMS)
-option-rom /usr/share/qemu/pxe-rtl8139.rom \ -option-rom /usr/share/qemu/pxe-rtl8139.rom \
-device e1000,netdev=mynet0,mac=52:54:00:12:34:56 \ -device e1000,netdev=mynet0,mac=52:54:00:12:34:56 \
-netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$(CURDIR),bootfile=pxeboot.0 -netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$(CURDIR),bootfile=pxeboot.0
qemu-rom: kernel.rom
$(QEMU) $(QEMU_ARGS) --option-rom kernel.rom

70
kernel/intr.asm Normal file
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@ -0,0 +1,70 @@
; Get pointer to interrupt vector
; IN al number
; OUT 0:bx ptr to vector
intr_ptr:
xor bh, bh
mov bl, al
add bx, bx
add bx, bx
ret
; Set interrupt vector
; IN al number
; ds:dx ptr
intr_set:
push bx
call intr_ptr
ss mov [bx], dx
ss mov [bx+2], ds
pop bx
ret
; Get interrupt vector
; IN al number
; OUT es:bx ptr
intr_get:
call intr_ptr
ss mov es, [bx+2]
ss mov bx, [bx]
ret
; Save BIOS vectors
; Trashes ax, cx, bx, ds
intr_backup:
mov cx, 0x20
xor bx, bx
mov ds, bx
.loop: ; load segment
mov ax, [bx+2]
; skip transfer if not pointing to BIOS
cmp ax, 0xA000
jc .skip
; store segment
mov [bx+ivt2+2], ax
; copy offset
mov ax, [bx]
mov [bx+ivt2], ax
; iterate to next vector
.skip: add bx, 4
loop .loop
ret
; Restore BIOS vectors
intr_restore:
mov cx, 0x20
xor bx, bx
mov ds, bx
.loop: ; load segment
mov ax, [bx+ivt2+2]
; skip if not a vector to BIOS
cmp ax, 0xA000
jc .skip
; store segment
mov [bx+2], ax
; copy offset
mov ax, [bx+ivt2]
mov [bx], ax
; iterate to next vector
.skip: add bx, 4
loop .loop
ret

68
rom/kernel.asm Normal file
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@ -0,0 +1,68 @@
cpu 8086
org 0x0000
db 0x55, 0xAA
db 0x00
jmp near init
times (0x18 - ($-$$)) db 0
dw 0
dw pnp
pnp: db "$PnP"
db 1 ; version 1
db 2 ; 2 * 16 length
dw 0 ; offset of next header
db 0
db 0 ; checksum (filled by fix-rom)
dd 0 ; device identifier
dw 0 ; manufacturer string
dw name ; product name string
db 0,0,0 ; device type string
db 0x20 ; device indicator, bit for "read cacheable" set
dw 0 ; boot connection vector
dw 0 ; boot disconnect vector
dw boot ; bootstrap entry point
dw 0 ; reserved
; zero for setting sreg without using reg
zero: dw 0
name: db "rdos", 0
init: push ds
; DS := 0
mov ds, [cs:zero]
; set entry points vectors
mov word [0x19*4], boot
mov word [0x19*4+2], cs
pop ds
retf
; entry point on boot, preempting disks
; this also doubles as entry point for reboot
boot: xor ax, ax
mov ss, ax
mov sp, stack
int 3
hlt: hlt
jmp hlt
%include "kernel/intr.asm"
align 512
absolute 0x400
resb (0x501 - ($-$$))
; copy of the first 32 interrupt vectors
ivt2: resd 0x20
; 8kb stack
alignb 2
resw 0x2000
stack: