Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS)

Mark Rutland
2019-10-22T16:50:25Z

On Tue, Oct 22, 2019 at 09:30:53AM -0700, Kees Cook wrote:
> On Tue, Oct 22, 2019 at 05:28:27PM +0100, Mark Rutland wrote:
> > On Fri, Oct 18, 2019 at 09:10:21AM -0700, Sami Tolvanen wrote:
> > > +ifdef CONFIG_SHADOW_CALL_STACK
> > > +KBUILD_CFLAGS += -fsanitize=shadow-call-stack
> > > +DISABLE_SCS := -fno-sanitize=shadow-call-stack
> > > +export DISABLE_SCS
> > > +endif
> >
> > I think it would be preferable to follow the example of CC_FLAGS_FTRACE
> > so that this can be filtered out, e.g.
> >
> > ifdef CONFIG_SHADOW_CALL_STACK
> > CFLAGS_SCS := -fsanitize=shadow-call-stack
> ^^^ was this meant to be CC_FLAGS_SCS here
>
> > KBUILD_CFLAGS += $(CFLAGS_SCS)
> ^^^ and here?

Whoops; yes in both cases...

> > export CC_FLAGS_SCS
> > endif
> >
> > ... with removal being:
> >
> > CFLAGS_REMOVE := $(CC_FLAGS_SCS)
> >
> > ... or:
> >
> > CFLAGS_REMOVE_obj.o := $(CC_FLAGS_SCS)
> >
> > That way you only need to define the flags once, so the enable and
> > disable falgs remain in sync by construction.
^^^^^ "flags" here, too.

Mark.