Re: [PATCH v2 4/8] objtool: Retpoline validation tweaks

[Peter Zijlstra]

On Mon, Feb 12, 2018 at 12:57:40PM +0000, David Woodhouse wrote:
> 
> 
> On Mon, 2018-02-12 at 13:48 +0100, Peter Zijlstra wrote:
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -486,6 +486,11 @@ KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG
> >  KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
> >  endif
> >  
> > +ifneq ($(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register),)
> > +  CC_HAS_RETPOLINE := 1
> > +endif
> > +export CC_HAS_RETPOLINE
> 
> Can't you do that with the existing check in arch/x86/Makefile? 

I couldn't make it work there, but it could be my makefile foo isn't
strong enough. The ordering of arch/*/Makefile vs scripts/Makefile.build
is forever confusing me.