Re: [Xen-devel] Xen on ARM: Force register dump from guest.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-06-05 at 20:18 +0200, Sander Bogaert wrote:
> On 5 June 2013 17:11, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > On Wed, 2013-06-05 at 16:36 +0200, Sander Bogaert wrote:
> >> Hi,
> >>
> >> I'm working on some kind of microOS for Xen on ARM a bit like miniOS
> >> but with less features. I'm having totally random crashes after make
> >> use of variadic arguments ( using newlib ).
> >>
> >> To debug this I'd really need a way to force a register dump from the
> >> guest, is there a good way to do this? I don't think any of the
> >> available hypercalls has that ability?
> >
> > Sounds like you want "xenctx" which is in tools/xentrace/
> 
> I doesn't show any output when invoked. Is it supposed to work for Xen
> on ARM?

Yes, although you will need a new enough tree, where new enough means
at least 66425df7ce61, from mid-April

>  It's also not really what I need, some hypercall or other
> break that crashes the domain and does a show_execution_state() is
> more like it.

Well, such a thing would be trivial to write, but checkout do_debug_trap
in xen/arch/arm/traps.c, you probably want "hvc #0xffff" in your code.

> My application crashes whenever I use variadic arguments,

crashes how, segfault or something else?

Where did your stdargs.h come from? I'd have thought the compiler
provided stuff ought to be reasonably robust assuming your application
isn't buggy.

Ian.


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