Re: [Qemu-devel] Re: gdbstub: packet reply is too long

[Jan Kiszka <jan.kiszka@web.de>]

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Jamie Lokier wrote:
> Jan Kiszka wrote:
>> You need CR0.PE to detect if you are in real or protected mode. And then
>> you need GDTR/LDTR to find the descriptor CS is pointing at, parsing it
>> to detect if you are running 16, 32 or 64 bit code (by default). Those
>> extensions would also be useful in order to decode memory addresses in
>> case descriptor.base != 0 (or if it's CS >> 4, ie. you are in real
>> mode).
> 
> If you're going to decode segment descriptors (great idea, btw, and
> helpful for threaded code), it might be better to supply the CPU's
> internal segment state, if that's possible, instead of looking at the
> LDT/GDT in memory, since the CPU's state can differ from the memory
> version when the latter is written to.

Good point. I included this in an initial suggestion of an extended
register set, see [1]. Providing this information will likely remain
VM-business, but that doesn't mean we shouldn't use it when available.

Jan

[1] http://sourceware.org/ml/gdb/2009-01/msg00008.html


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