167 lines
2.4 KiB
Plaintext
167 lines
2.4 KiB
Plaintext
section .realmode
|
|
|
|
global rm_hcf
|
|
rm_hcf:
|
|
; Load BIOS IVT
|
|
lidt [.rm_idt]
|
|
|
|
; Jump to real mode
|
|
jmp 0x08:.bits16
|
|
.bits16:
|
|
bits 16
|
|
mov ax, 0x10
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
mov eax, cr0
|
|
btr ax, 0
|
|
mov cr0, eax
|
|
jmp 0x00:.cszero
|
|
.cszero:
|
|
xor ax, ax
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
|
|
sti
|
|
.hang:
|
|
hlt
|
|
jmp .hang
|
|
bits 32
|
|
|
|
.rm_idt: dw 0x3ff
|
|
dd 0
|
|
|
|
global rm_int
|
|
rm_int:
|
|
; Self-modifying code: int $int_no
|
|
mov al, byte [esp+4]
|
|
mov byte [.int_no], al
|
|
|
|
; Save out_regs
|
|
mov eax, dword [esp+8]
|
|
mov dword [.out_regs], eax
|
|
|
|
; Save in_regs
|
|
mov eax, dword [esp+12]
|
|
mov dword [.in_regs], eax
|
|
|
|
; Save GDT in case BIOS overwrites it
|
|
sgdt [.gdt]
|
|
|
|
; Save IDT
|
|
sidt [.idt]
|
|
|
|
; Load BIOS IVT
|
|
lidt [.rm_idt]
|
|
|
|
; Save non-scratch GPRs
|
|
push ebx
|
|
push esi
|
|
push edi
|
|
push ebp
|
|
|
|
; Jump to real mode
|
|
jmp 0x08:.bits16
|
|
.bits16:
|
|
bits 16
|
|
mov ax, 0x10
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
mov eax, cr0
|
|
and al, 0xfe
|
|
mov cr0, eax
|
|
jmp 0x00:.cszero
|
|
.cszero:
|
|
xor ax, ax
|
|
mov ss, ax
|
|
|
|
; Load in_regs
|
|
mov dword [ss:.esp], esp
|
|
mov esp, dword [ss:.in_regs]
|
|
pop gs
|
|
pop fs
|
|
pop es
|
|
pop ds
|
|
popfd
|
|
pop ebp
|
|
pop edi
|
|
pop esi
|
|
pop edx
|
|
pop ecx
|
|
pop ebx
|
|
pop eax
|
|
mov esp, dword [ss:.esp]
|
|
|
|
sti
|
|
|
|
; Indirect interrupt call
|
|
db 0xcd
|
|
.int_no:
|
|
db 0
|
|
|
|
cli
|
|
|
|
; Load out_regs
|
|
mov dword [ss:.esp], esp
|
|
mov esp, dword [ss:.out_regs]
|
|
lea esp, [esp + 10*4]
|
|
push eax
|
|
push ebx
|
|
push ecx
|
|
push edx
|
|
push esi
|
|
push edi
|
|
push ebp
|
|
pushfd
|
|
push ds
|
|
push es
|
|
push fs
|
|
push gs
|
|
mov esp, dword [ss:.esp]
|
|
|
|
; Restore GDT
|
|
o32 lgdt [ss:.gdt]
|
|
|
|
; Restore IDT
|
|
o32 lidt [ss:.idt]
|
|
|
|
; Jump back to pmode
|
|
mov eax, cr0
|
|
or al, 1
|
|
mov cr0, eax
|
|
jmp 0x18:.bits32
|
|
.bits32:
|
|
bits 32
|
|
mov ax, 0x20
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
|
|
; Restore non-scratch GPRs
|
|
pop ebp
|
|
pop edi
|
|
pop esi
|
|
pop ebx
|
|
|
|
; Exit
|
|
ret
|
|
|
|
align 16
|
|
.esp: dd 0
|
|
.out_regs: dd 0
|
|
.in_regs: dd 0
|
|
.gdt: dq 0
|
|
.idt: dq 0
|
|
.rm_idt: dw 0x3ff
|
|
dd 0
|