Re: [PATCH 6/6] s390: introduce execute-trampolines for branches

[David Woodhouse]

On Wed, 2018-02-07 at 11:07 +0100, Pavel Machek wrote:
> This is really unfortunate naming of kernel option.
> 
> spectre_v2=off sounds like we are turning the "bug" off, but i somehow
> suspect you are turning the bug _workaround_ off.

That's consistent with what we have on x86.

> > +ifdef CONFIG_EXPOLINE
> > +ÂÂifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),y)
> > +ÂÂÂÂCC_FLAGS_EXPOLINE := -mindirect-branch=thunk
> > +ÂÂÂÂCC_FLAGS_EXPOLINE += -mfunction-return=thunk
> > +ÂÂÂÂCC_FLAGS_EXPOLINE += -mindirect-branch-table
> > +ÂÂÂÂexport CC_FLAGS_EXPOLINE
> > +ÂÂÂÂcflags-y += $(CC_FLAGS_EXPOLINE)
> > +ÂÂelse
> > +ÂÂÂÂ$(warning "Your gcc lacks the -mindirect-branch= option")
> > +ÂÂendif
> > +endif

That isn't, though. Linus asked us to drop the $(warning) part.

... and then spent a week building with a non-retpoline compiler and
not noticing, so he might have changed his mind ;)

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