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

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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