[following up to myself]
Christer Weinigel <christer@weinigel.se> writes:
> Well, it should be possible to use a trick similar to the BIG REAL or
> UNREAL mode. Just load CS with a segment that has a base of
> 0xffff0000 in protected mode and then jump back to real mode.
> Something like this, completely untested of course, should do it:
>
> .align 4
> reset_gdt:
> .word reset_gdt_end - reset_gdt -1
> .long reset_gdt
> .word 0
>
> /* 16 bit code segment starting at 0xffff0000 */
> .word 0xffff, 0x0000
> .byte 0xff, 0x9b, 0x00, 0xff
better add the following too:
move.l %cr0, %eax
and.l $~1, %eax
move.l %eax, %cr0
> reset_gdt_end:
>
> lgdt %cs:reset_gdt
> ljmp $ROM_CODE_SEG, 0xfff0
BTW, what does Windows do here? Whatever Windows is using should work
with Linux too.
/Christer
-- "Just how much can I get away with and still go to heaven?"Freelance consultant specializing in device driver programming for Linux Christer Weinigel <christer@weinigel.se> http://www.weinigel.se - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu May 15 2003 - 22:00:37 EST