Re: aarch64 systemtap testsuite results

[Martin Cermak <mcermak at redhat dot com>]

Hi Jakub,

At the moment, I believe, the most important issue is correct kprobes support, tracked as bug 1074123 in Red Hat bugzilla. Important points:

> There are two issues:
> (1) kprobes needs a 'blacklist' of kernel functions that can't be probed, b/c kprobe uses them -- infinite loop.  upstream has a V10 of a 7-patch series for this, so hopefully its close for us to use in near term.
> (2) Linaro kprobe developer agrees there is a bug in the multi-kprobe implementation.  I have hooked him up w/Will Cohen to get systemtap sources to use for their duplication, then debug & test efforts.

It'd be great to move on with this.

Kind Regards, 
Martin

----- Original Message -----
> Hello William,
> 
> many thanks for the update!
> 
> Is any of the reported issues something that Linaro should work on fixing?
> Here at Linaro we want to get Systemtap running in our automated testing
> loop for ARMv8 and we hope to fare better in pass-rates as we have ARM64
> kprobes implementation included in Linaro kernel already.
> 
> 
> On 7 May 2014 16:15, William Cohen <wcohen@redhat.com> wrote:
> 
> > Some actual aarch64 hardware is now available and the testsuite can be run
> > in a ressonable amount of time. The test results show signs of life, but
> > there is definitely room for improvement:
> >
> >
> > https://web.elastic.org/~dejazilla/viewsummary.php?variant=%3D%27aarch64-unknown-linux-gnu%27
> >
> > There are going to be a lot of failures in these tests because the kernel
> > did not have kprobe patches in it. There is also no uprobes support in the
> > kernel.
> >
> > Some other things observed when reviewing the results:
> >
> > -a number of tests failed to build because of missing kernel header
> > hypervisor.h. The kernel-devel rpm appeared to omit some needed header
> > files
> >
> > -tracepoints probe locations did not work.  The probe points are visible
> > in "perf list" but "stap -L 'kernel.trace("*")'" returns nothing.
> >
> > -aarch64 stack backtraces are not yet supported.
> >
> > -Can't find  @cast(sock, "inet_sock", "kernel<net/ip.h>") for
> >  stap -v ./systemtap.base/ipaddr1.stp
> >
> > -The preprocessor sets arch to "arm64" rather than "aarch64" "preprocessor
> > basic ops" fails
> >
> > -The nd_syscall probes points are not available
> >
> > -SystemTap could not find locations of $prev or $next arguments for
> > kernel.function("context_switch")
> >
> >
> >
> >
> > -Will
> >
> 
> 
> 
> --
> With best regards,
> 
> Jakub Pavelek
> 
> Kernel working group and Android engineering project manager
> Linaro.orgâ Open source software for ARM SoCs
>