Re: [Xen-devel] refcount errors then crash on XenoLinux with the latest source

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> > 'objdump -d xen >xen.s'. Then you can search in xen.s with a text
> > editor to find the call-trace addresses.
> 
> I did this and got what you see below. It looks like to backtraces
> interleaved. All of the values in brackets are legitimate return
> addresses (they immediately follow a call instruction). "function addr"
> is the address of the function itself and "ret addr" is the address
> taken from the oops.

Yeah, we cannot precisly print the call trace because we build Xen
with '-fomit-frame-pointer', even when doing a debug build. If we
included a frame pointer then we could "chase" register %ebp to find
the true call trace.

As it is, we just look at the entire stack contents and enclose in
square brackets any value that could correspond to an address between
labels '_start' and '_end' in Xen.

The effect of this is that if you have stale return addresses on your
stack then they get included on the approximate call trace. These
stale addresses may occur because the stack frame was popped, then
another functyion invocation has pushed itself a large stack frame
that encompasses teh stale one, but hasn't blown away all of the stale
contents. 

 -- Keir


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