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Date: Mon, 12 Feb 2018 15:59:24 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>, linux-kernel@vger.kernel.org,
	Dave Hansen <dave.hansen@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andi Kleen <ak@linux.intel.com>,
	Arjan Van De Ven <arjan.van.de.ven@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>
Subject: Re: [PATCH v2 4/8] objtool: Retpoline validation tweaks
Message-ID: <20180212145924.GN25181@hirez.programming.kicks-ass.net>
References: <20180212124855.882405399@infradead.org>
 <20180212125033.448828374@infradead.org>
 <1518440260.6606.58.camel@infradead.org>
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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.