Re: guru mode: invalid module format

[Aubrey Li <aubreylee at gmail dot com>]

On Tue, Jun 18, 2019 at 4:13 AM Serhei Makarov <me@serhei.io> wrote:
>
> On Fri, Jun 14, 2019, at 10:55 AM, Serhei Makarov wrote:
> > On Thu, Jun 13, 2019, at 7:48 PM, Frank Ch. Eigler wrote:
> > > Thanks for your patience.  I have not been able to reproduce this here
> > > on Fedora, so didn't look deeper until today.  I believe the problem
> > > may be buildrun.cxx:124, which for guru mode adds a
> > > CONFIG_MODEVERSIONS= override into the module kbuild makefile.
> > > Non-fedora kernels may interpret this differently.
> > I haven't been able to reproduce on Ubuntu either. Trying to think if
> > there's any other distribution/kernel where this option is likely to
> > work differently.
> >
> > The reproduction steps point to another potential problem -- the
> > regular and guru mode scripts are being compiled differently, but they
> > appear to be treated equivalently by stap's compilation cache.
> > Therefore deleting the cache changes the outcome of $ stap
> > helloworld.stp -g
>
> I pushed a commit to include guru-mode status in the hashing data to avoid this problem.
>
> For overriding SystemTap's current behaviour wrt modversions it may be worth trying
> $ stap -B CONFIG_MODVERSIONS=y -g hello.stp

This works for me. Thanks a lot!

>
> Later I'll test on a kernel config where CONFIG_MODVERSIONS= disabled modules are rejected.
> If the problem is too complex, I can revert the change to PR10280, at the cost of more risk when transferring guru-mode modules to a different kernel version.
>
> All the best,
>       Serhei