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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: gdbstub: packet reply is too long
Date: Sat, 20 Dec 2008 22:08:33 +0000
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Andreas Schultz <aschultz@warp10.net>, qemu-devel@nongnu.org, kvm@vger.kernel.org

> 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/.

I find that hard to believe. Doesn't it break horribly as soon as the CPU 
switches modes?

It's not just regressions that are important. It's the fact that once qemu has 
your automatic switching hack it's impossible to make it work properly.

> >> 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?

ARM has multiple instruction sets/cpu modes (and can mix the two within the 
same process). PPC and MIPS also have something similar, though I'm not sure 
how well they're supported by gdb.

I suspect you may be approaching this the wrong way. Instead of trying to 
switch architectures, you probably need to teach the 64-bit debugger how to 
debug 32-bit code.

Paul