[Qemu-devel] Re: [PATCH] gdbstub: x86-64: reintroduce dynamic register sets

[Jan Kiszka <jan.kiszka@siemens.com>]

Jamie Lokier wrote:
> Jan Kiszka wrote:
>> Paul Brook wrote:
>>> On Tuesday 04 November 2008, Jan Kiszka wrote:
>>>> Commit 5459 broke the dynamic register set switching of qemu's gdbstub
>>>> for x86-64. This prevents setting the correct architecture in gdb when
>>>> debugging 32 or 16-bit code in a 64-bit emulator. Fix this.
>>> Is this really a feature? Surely any attached gdb is going to break horribly 
>>> when we transition from a 64-bit to a 32-bit code segment.
>> Well, it would be real feature if gdb was smart enough to track those
>> switches automatically...
>>
>> However, you can (and obviously have to) call "set arch ..." after that
>> switch in order to get the proper disassembly. Or you happen to use
>> qemu-system-x86_64 with a 32-bit guest and fire up gdb with the
>> appropriate 32-bit binary directly. Both used to work fine.
> 
> How does it handle mixed 32-bit and 16-bit code?  (Since you mentioned
> it supports 16-bit code).
> 
> Does that require manual intervention too?

Same here: 'set arch i8086' will make gdb switch to 16-bit disassembly
mode. But the remote protocol's register set format does not change
then, compared to arch i386.

BTW, more glue (including gdb patches) is required for full support of
x86 segmentation. I'm currently trying to get out changes in shape again
that were once based on older versions of qemu and gdb.

Jan

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