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

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

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Paul Brook wrote:
>>>> From a higher perspective, it is surely not the cleanest approach. But
>>>> it still appears to be the only one which helps us working around this
>>>> gdb shortcoming.
>>> Actually it isn't. You could add an explicit switch.
>> And what would this buy us? I would have to go from your gdb terminal to
>> qemu, probably the monitor, just to switch manually what now happens
>> automatically. I don't see the case where you wouldn't want to switch
>> when you try to debug 16 or 32 bit code, so what would be the gain? Or
>> do you want some switch to disable this automatic register format
>> switching?
> 
> Because, as I've said several times before, the "automatic switching" is 
> wrong. It may happen to work in your very limited circumstances, but there 
> are many fairly common circumstances (e.g. stepping between a 64-bit kernel 
> and a 32-bit userspace) where it's just plain broken. I object strongly to 
> a "fix" that prevents a proper gdb from working.

Well, I'm using gdb over qemu and kvm in precisely that hybrid
scenarios, but also in normal ones. Heavily. And I'm only able to do
this because of the workaround. But I'm willing to learn about scenarios
where it causes /regressions/.

> 
>> There are internal issues in gdb (hard coupling of current and target
>> arch) that will not allow this to be fixed in the near future
> 
> Really? I'm pretty sure other architectures already manage it.

What other archs are comparably weird like x86?

Please have a look at the gdb code that I pointed out and explain to me
how it can be fixed so that the next gdb version will be fine again with
current qemu. I will happily do the patching then. Though, it would
still leave us with broken setups until that release is spread sufficiently.

Jan


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