Re: [Xen-devel] Xen & Transmeta (from xen-users)

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 24 May 2005, at 16:31, Carl Holtje ;021;vcsg6; wrote:

> > Connect a null modem serial cable and outb printable characters to
> > 0x3f8 at various points in the assembly code (immediately followed by
> > an infinite loop, or characters may not be emitted on the serial line
> > before the system crashes). As you say it crashes pretty early, so you
> > won't have to move the debug output around very much to work out which
> > instruction is causing the crash.
> This is an OQO, so I don't have the facilities to plug a serial cable
> into... can I do anything over USB at this level?
Worst case: does it fail by crashing and rebooting? If so, then you 
could move an infinite loop around in the boot assembly code and 
observe whether the system reboots or hangs. When the behaviour changes 
you have found the offending instruction.
If it fails by hanging you can instead add an instruction that causes a 
reboot crash (e.g., invalid opcode like ud2) and move that around in 
the assembly code.
 -- Keir


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