Re: [PATCH v2 05/28] objtool: Add a pass for generating __mcount_loc

Sami Tolvanen
2020-09-03T22:04:00Z

On Thu, Sep 3, 2020 at 2:51 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Sep 03, 2020 at 01:30:30PM -0700, Sami Tolvanen wrote:
> > From: Peter Zijlstra <peterz@infradead.org>
> >
> > Add the --mcount option for generating __mcount_loc sections
> > needed for dynamic ftrace. Using this pass requires the kernel to
> > be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
> > in Makefile.
> >
> > Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/
> > Signed-off-by: Peter Zijlstra <peterz@infradead.org>
>
> Hmm, I'm not sure why this hasn't gotten picked up yet. Is this expected
> to go through -tip or something else?

Note that I picked up this patch from Peter's original email, to which
I included a link in the commit message, but it wasn't officially
submitted as a patch. However, the previous discussion seems to have
died, so I included the patch in this series, as it cleanly solves the
problem of whitelisting non-call references to __fentry__. I was
hoping for Peter and Steven to comment on how they prefer to proceed
here.

Sami