[coreboot] SimNOW VGA int 1a

Myles Watson mylesgw at gmail.com
Wed Oct 15 22:51:04 CEST 2008

> -----Original Message-----
> From: Marc Jones [mailto:Marc.Jones at amd.com]
> Sent: Wednesday, October 15, 2008 2:45 PM
> To: Myles Watson
> Cc: Tom Sylla; ron minnich; Coreboot
> Subject: Re: [coreboot] SimNOW VGA int 1a
> Myles Watson wrote:
> > Here's the next part of the log now that I've enabled setup_realmode_idt
> > (I'm running it right before real_mode_switch_call_vga.
> >
> > Copying VGA ROM image from 0xfe040000 to 0xc0000, 0x8000 bytes
> > BREAK HERE run_bios = 0x0000944a
> > biosint: INT# 0x18
> > biosint: eax 0x2e ebx 0x10000 ecx 0xfe4 edx 0xcf11c
> > biosint: ebp 0xc0000000 esp 0xd0000 edi 0x1a esi 0x0
> > biosint:  ip 0x1022   cs 0xf  flags 0x2067
> > BIOSINT: Unsupport int #0x18
> >
> That isn't the same emulator that most of v2 uses. setup_realmode_idt is
> certainly required. 0x18 is a strange INT to see.
> http://www.ctyme.com/intr/int.htm
> Can you get back to the calling code and see what it was doing?

The VGA BIOS calls 1a, but it looks like too many things get pushed onto the
stack, and it thinks it's 18 instead.  I'm not an assembly programmer, but
it looks like the problem is in callbiosint or handler.  It looks like the
registers are being pushed onto the stack too many times?


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