Re: [Qemu-devel] single-stepping issue in aarch64 full-system emulation

[Akos Kiss]

Hi,

Peter Maydell írta:
> On 18 August 2014 09:41, Akos Kiss <address@hidden> wrote:
>> I've "stock" Ubuntu 14.04.1 running under an aarch64-qemu (built from
>> mainline git) in full-system emulation [1]. Everything worked fine until
>> I tried to find a bug in an application built for aarch64 (that bug most
>> likely being not the fault of qemu but the app itself). When I started
>> debugging, strange things happened: breakpoints in gdb did not behave as
>> they should. First, together with gdb developers, we speculated that
>> it's a bug in gdb (which still may hold, at least partially) [2], but
>> then I traced back the problem to a point where it has led out of gdb.
>> It seems that PTRACE_SINGLESTEP is not working as it should, it does not
>> stop the execution of the child after a step but lets it run
>> indefinitely.
> Yes, this feature wasn't implemented yet in QEMU 2.1.
> I posted a set of patches to the list last week for this:
>
> https://lists.nongnu.org/archive/html/qemu-devel/2014-08/msg01291.html
>
> You might like to try testing them.
>
> There's also a bug where we don't report the correct PC
> value to the kernel when we hit a BRK instruction. I've
> just sent the one-liner fix to the list (cc'ing you). That ought
> to make gdb work without having to hack it to call
> set_gdbarch_decr_pc_after_break.

I've tried these patches and they work for me flawlessly with the stock gdb.

Thanks!
-Akos

>
> thanks
> -- PMM

-- 
Ákos Kiss, PhD
assistant professor

Department of Software Engineering, University of Szeged
Dugonics tér 13., 6720 Szeged, Hungary
Phone: +36-62-544143
Fax: +36-62-546723
address@hidden