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Date: Wed, 06 Nov 2013 22:11:01 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] BUG: QEMU aborts when setting breakpoint in gdb
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: marcel.a@redhat.com, qemu-devel <qemu-devel@nongnu.org>, mst@redhat.com

Il 06/11/2013 19:36, Luiz Capitulino ha scritto:
> On Wed, 06 Nov 2013 18:39:42 +0100
> Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>> Il 06/11/2013 17:22, Luiz Capitulino ha scritto:
>>> 1. Run qemu with gdb server support
>>>
>>>    # qemu [...] -s -S
>>>
>>> 2. Connect gdb and try to set a breakpoint
>>>
>>>    $ gdb /path/to/vmlinux
>>>    (gdb) target remote:1234
>>>    (gdb) b secondary_startup_64
>>
>> (Note that this doesn't make much sense until the kernel has been loaded
>> into memory.  You probably want hbreak instead).
> 
> hbreak didn't work either, gdb doesn't stop at the breakpoint. I tried to
> test this with another random function and got a "Remote 'g' packet
> reply is too long" (which seems to be yet another different problem).

Yeah, that's very messy and it would nice to have a fix for it, but I
don't know enough about gdb to say whether it's fixable.

It happens when the processor switches from 32 to 64-bit under gdb's
feet.  The solution is typically to do "set arch  i386:x86-64" before
running the guest with "c" if you know the breakpoint will happen in
64-bit mode.

Paolo