- org 0xA8000
-[bits 16]
-entry:
- mov ax, 0xA800
- mov ds, ax ; Take us out of flat unreal mode, and
- mov es, ax ; put us in true real mode.
- mov fs, ax
- mov gs, ax
- mov ss, ax
- jmp 0xA800:(entry2-0xA8000) ; Long jump to a correct cs.
-entry2:
- lgdt [(gdtr-0xA8000)] ; Set up a new GDT.
- mov eax, 0x1
- mov cr0, eax ; ... and enter pmode!
- jmp long 0x10:continue ; Now longjmp into the new code.
-[bits 32]
-continue:
- mov ax, 0x08 ; Set up segment selectors.
- mov ds, ax
- mov es, ax
- mov fs, ax
- mov gs, ax
- mov ss, ax
- mov esp, [dataptr]
-
- mov al, [needclear]
- cmp al, 0
- jz noclear
- mov al, 0 ; clear BSS
- mov edi, [dataptr+4]
- mov ecx, [dataptr+8]
- rep stosb
- mov [needclear], al
-
-noclear:
- mov eax, [dataptr+12] ; jump into C
- call eax
-
- mov al, 0x40 ; ack the periodic IRQ
- mov dx, 0x834
- out dx, al
-
- mov dx, 0x830 ; now ack the SMI itself
- in al, dx
- or al, 0x02
- and al, 0xBF
- out dx, al
- or al, 0x40
- out dx, al
-
- rsm ; and leave SMM
-
- align 0x4
-gdtr:
- db 0x27, 0x00
- dd gdt
- align 0x4
-gdt:
- db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
- db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x93, 0xCF, 0x00 ; data segment
- db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9B, 0xCF, 0x00 ; code segment
- db 0xFF, 0xFF, 0x00, 0x80, 0x0A, 0x9B, 0xCF, 0x00 ; code segment for trampoline
-
-needclear:
- db 0x01
-
-dataptr:
- ; 4 bytes of stack top
- ; 4 bytes of BSS start
- ; 4 bytes of BSS length
- ; 4 bytes of C entry point
- ; These show up