pxeboot PC Engines WRAP
john at baldwin.cx
Mon Jul 31 18:03:14 UTC 2006
On Saturday 29 July 2006 13:31, Adrian Steinmann wrote:
> On Fri, Jul 28, 2006 at 12:36:54PM -0400, John Baldwin wrote:
> > This is because the BIOS you are talking to here is trying to enter
> > protected mode on its own, which simply does not play well with VM86 at
> > It's not something you are going to "fix" in VM86 unless you change BTX
> > drastically to pop back into real mode to call the BIOS and handle IRQs
> > rather than using vm86 mode.
> PC-Engines says that only the int 15, function 87 goes back into
> protected mode, and that seems to be trapped in boot/i386/btx/btx/btx.S
> line 609 so the FreeBSD BTX should cover that case. Or am I
> misunderstanding something here?
That's correct in that BTX does handle int15/87 directly.
> The disassembled code you mention:
> > 00000000 660F01975200 o32 lgdt [bx+0x52]
> > 00000006 0F20C0 mov eax,cr0
> > 00000009 0C01 or al,0x1
> > 0000000B 0F22C0 mov cr0,eax
> > 0000000E 66FFAF6A00 jmp dword far [bx+0x6a]
> > 00000013 66B810008ED0 mov eax,0xd08e0010
> > 00000019 89EC mov sp,bp
> > 0000001B 8ED8 mov ds,ax
> > 0000001D 8EC0 mov es,ax
> > 0000001F 8E db 0x8E
> seems to indeed stem from http://www.pcengines.ch/tb13.zip INT1X.8
> where the "Int 15, AH=87: block move" is handled in "unreal mode", as
> described in http://www.pcengines.ch/tb13.pdf. So would that mean that
> BTX didn't trap that or something else was amiss before?
Are you sure that's the only place it enters protected mode?
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