Messages in this thread |  | | Date | Mon, 8 Jan 2018 14:46:32 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH v6 01/10] x86/retpoline: Add initial retpoline support |
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On Mon, 8 Jan 2018, Josh Poimboeuf wrote: > On Sun, Jan 07, 2018 at 10:11:16PM +0000, David Woodhouse wrote: > > diff --git a/arch/x86/Makefile b/arch/x86/Makefile > > index a20eacd..918e550 100644 > > --- a/arch/x86/Makefile > > +++ b/arch/x86/Makefile > > @@ -235,6 +235,16 @@ KBUILD_CFLAGS += -Wno-sign-compare > > # > > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > > > > +# Avoid indirect branches in kernel to deal with Spectre > > +ifdef CONFIG_RETPOLINE > > + RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) > > + ifneq ($(RETPOLINE_CFLAGS),) > > + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE > > + else > > + $(warning Retpoline not supported in compiler. System may be insecure.) > > + endif > > +endif > > I wonder if an error might be more appropriate than a warning. I > learned from experience that a lot of people don't see these Makefile > warnings, and this would be a dangerous one to miss. > > Also if this were an error, you could get rid of the RETPOLINE define, > and that would be one less define cluttering up the already way-too-long > GCC arg list.
It still allows to get the ASM part covered. If that's worth it I can't tell.
Thanks,
tglx
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