Re: [Qemu-devel] [PATCH] gdb: Fix gdb error

["Andreas Färber" <afaerber@suse.de>]

Am 12.08.2013 11:17, schrieb Aneesh Kumar K.V:
> Andreas Färber <afaerber@suse.de> writes:
>> Am 11.08.2013 20:14, schrieb Aneesh Kumar K.V:
>>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>>>
>>> Don't update the global register count if not requested.
>>> Without this patch a remote gdb session gives
>>>
>>> (gdb) target remote localhost:1234
>>> Remote debugging using localhost:1234
>>> Remote 'g' packet reply is too long:
>>> 0000000028000084c000000000ccba50c000000000c ...
>>> ....
>>> ...
>>> (gdb)
>>>
>>> This is a regression introduce by a0e372f0c49ac01faeaeb73a6e8f50e8ac615f34
>>>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>>
>> Thanks for tracking this down. I'm willing to include a variation in
>> today's pull to fix 1.6.0-rc3. However, did you find an explanation
>> *why* it needs to be like this?
> 
> IIUC our reply packet for 'g' contain more data becaue we ended up with
> larger cpu->gdb_num_regs. This only happens for archs that do a
> gdb_register_coprocessor with gpos == 0. The older code didn't update
> num_g_regs in that case. Not sure why we do like that
> 
>> I understand it is a revert to using the
>> static variable, updated to using the CPUClass field rather than the
>> previous preprocessor constant.
>>
> 
> I don't really like the patch. But I also don't know enough to fix this
> without using the static variable.  If you want me to try another
> version please send it across. I can easily reproduce this on PowerPC.

While it's always unfortunate to have a known breakage, we decided it's
too late/risky to address this for -rc3 today.

I put together a different patch that hopefully fixes the breakage while
avoiding to revert to static variables:
http://patchwork.ozlabs.org/patch/266594/

If this fixes things for you and doesn't break other things, we can get
it into qemu.git after Thursday [1] and backport it into 1.6.1.

Regards,
Andreas

[1] http://wiki.qemu.org/Planning/1.6

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