[netwatch.git] / netwatch / entry.asm

; entry.asm
; SMI entry point
; NetWatch system management mode administration console
;
; Copyright (c) 2008 Jacob Potter and Joshua Wise.  All rights reserved.
; This program is free software; you can redistribute and/or modify it under
; the terms found in the file LICENSE in the root of this source tree.

        org 0xA8000
[bits 16]
entry:
        mov ax, 0xA800                  ; Take us out of flat unreal mode,
        mov ds, ax                      ; and put us in true real mode.
        mov es, ax
        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]              ; Load stack pointer.

        ; Before we do anything, turn off alignment checking.
        pushf
        pop eax
        and eax, ~(1 << 18)
        push eax
        popf
        
        mov eax, [dataptr+4]            ; Load target jump address
        call eax                        ; then jump into C.

        rsm                             ; and leave SMM

        align 0x4
gdtr:
        db 0x17, 0x00
        dd gdt
        align 0x4
gdt:
        db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00       ; initial null entry
        db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x93, 0xCF, 0x00       ; data segment
        db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9B, 0xCF, 0x00       ; code segment


dataptr:
        ; 4 bytes of stack top
        ; 4 bytes of C entry point
        ; These show up