org 7c00h

use16

cli
lgdt[gdt]
mov eax,cr4
or al,1
mov cr4,eax
mov eax,cr0
or al,1
mov cr0,eax
jmp gdt_code-gdt_table:pmode

vm86:
mov ax,0e41h
mov bx,7
int 10h

;which interrupt trigger to end the virtual 8086 mode?

jmp $

use32

pmode:
mov ax,gdt_data-gdt_table
mov gs,ax
mov fs,ax
mov ds,ax
mov es,ax
mov ss,ax
mov esp,9fffch
mov ax,18h
ltr ax
mov al,11h
out 20h,al
mov al,20h
out 21h,al
mov al,4
out 21h,al
mov al,1
out 21h,al
mov al,255-1 shl 6
out 21h,al
mov edi,idt_table
mov edx,8e00h
mov eax,(gdt_code-gdt_table) shl 16
mov ecx,20h
interrupts1:
mov [edi],eax
mov [edi+4],edx
add edi,8
loop interrupts1
mov edx,8f00h
mov eax,(gdt_code-gdt_table) shl 16
add ecx,8
interrupts2:
mov [edi],eax
mov [edi+4],edx
add edi,8
loop interrupts2
mov edx,8f00h
mov eax,(gdt_code-gdt_table) shl 16
mov ecx,256-8-32
interrupts3:
mov [edi],eax
mov [edi+4],edx
add edi,8
loop interrupts3
mov word[idt_table+20h*8+6*8],second_sector
mov word[idt_table+49*8],function_floppy
lidt[idt]
sti
push 0
push 0
push 0
push 0
push 0
push 0fffeh
push 23000h
push 0
push vm86
iretd
int 49
jmp $

function_floppy:
mov dx,3f2h
mov al,1ch
out dx,al
mov al,6
out 0ah,al
mov al,0ffh
out 0ch,al
mov al,0
out 4,al
mov ax,second_sector
out 81h,al
mov al,ah
out 4,al
mov al,0ffh
out 5,al
mov al,1
out 5,al
mov al,2
out 0ah,al
call readmsr
mov dx,3f5h
mov al,66h
out dx,al
mov al,0
out dx,al
mov al,0
out dx,al
mov al,0
out dx,al
mov al,2
out dx,al
mov al,2
out dx,al
mov al,18
out dx,al
mov al,27
out dx,al
mov al,0ffh
out dx,al
iret

readmsr:
mov dx,3f4h
in al,dx
and al,0c0h
cmp al,80h
jne readmsr
ret

gdt:
dw gdt_end-gdt_table-1
dd gdt_table

gdt_table:
dq 0

gdt_code:
dw 0ffffh
dw 0
db 0
db 9ah
db 0cfh
db 0

gdt_data:
dw 0ffffh
dw 0
db 0
db 92h
db 0cfh
db 0

gdt_tss:
dw 0ffffh
dw 0
db 0
db 89h
db 8fh
db 0

gdt_end:

idt:
dw idt_end-256*8-1
dd idt_table

idt_table=256*4

idt_end:

times 510-($-$$) db 0
dw 0aa55h

second_sector:
mov byte[0b8000h],43h
mov byte[0b8000h+1],0ch
mov byte[0b8000h+2],69h
mov byte[0b8000h+3],0ch
mov byte[0b8000h+4],61h
mov byte[0b8000h+5],0ch
mov byte[0b8000h+6],6fh
mov byte[0b8000h+7],0ch
mov byte[0b8000h+8],21h
mov byte[0b8000h+9],0ch
mov byte[0b8000h+10],20h
mov byte[0b8000h+11],0ch
mov byte[0b8000h+12],3ah
mov byte[0b8000h+13],0ch
mov byte[0b8000h+14],29h
mov byte[0b8000h+15],0ch
jmp $

times 512-($-second_sector) db 0