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! At entry, the processor is in 16 bit real mode and the code is being
! executed from an address it was not linked to. Code must be pic and
! 32 bit sensitive until things are fixed up.
#include "loader.inc"
.text
_main:
.word 0xAA55 ! BIOS extension signature
size: .byte 0 ! number of 512 byte blocks
! = number of 256 word blocks
! filled in by makerom program
jmp over ! skip over checksum
.byte 0 ! checksum
jmp blockmove ! alternate entry point +6
! used by floppyload
over:
#ifndef NOINT19H
push ax
push ds
xor ax,ax
mov ds,ax ! access first 64kB segment
mov ax,SCRATCHVEC+4 ! check if already installed
cmp ax,#MAGIC ! check magic word
jz installed
mov ax,INT19VEC ! hook into INT19h
mov SCRATCHVEC,ax
mov ax,INT19VEC+2
mov SCRATCHVEC+2,ax
mov ax,#start19h
mov INT19VEC,ax
mov ax,cs
mov INT19VEC+2,ax
mov ax,#MAGIC ! set magic word
mov SCRATCHVEC+4,ax
installed:
pop ds
pop ax
retf
start19h: ! clobber magic id, so that we will
xor ax,ax ! not inadvertendly end up in an
mov ds,ax ! endless loop
mov SCRATCHVEC+4,ax
mov ax,SCRATCHVEC+2 ! restore original INT19h handler
mov INT19VEC+2,ax
mov ax,SCRATCHVEC
mov INT19VEC,ax
#endif /* NOINT19H */
blockmove:
mov si,#_body-_main ! offset of _body
/* fall thru */
! Relocate body of boot code to RELOC:0
cld
xor di,di ! di = 0
mov ax,#RELOC>>4
mov es,ax
xor cx,cx
mov ax,cs
mov ds,ax ! for the ref to size below
mov ch,size-_main
push cx ! save cx before decrementing
seg cs
rep
movsw
! Save ROMs CS and length in floppy boot block before jumping to relocated
! code
pop cx
push ds
mov ax,#FLOPPY_SEGMENT
mov ds,ax
mov ax,cs
mov ROM_SEGMENT,ax
mov ROM_LENGTH,cx
pop ds
! Change stack
mov bx,#RELOC>>4 ! new ss
mov ds,bx ! new ds
int #0x12 ! get conventional memory size in KB
shl ax, #6
sub ax, bx
shl ax, #4 ! new sp
cli
mov ss,bx
mov sp,ax
callf #0,RELOC>>4 ! call Etherboot body
int #0x19
! The body of etherboot is attached here at build time
! Force 4 byte alignment
if ((*-_main)&3) != 0
.blkb 3-((*-_main)&3)
.byte 0
endif
_body:
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