Messages in this thread | | | Date | Tue, 30 Oct 2018 11:09:54 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it |
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On Tue, Oct 30, 2018 at 06:39:24PM +0900, Masahiro Yamada wrote: > Hi, > > > > On Tue, Oct 30, 2018 at 3:57 PM Zhenzhong Duan > <zhenzhong.duan@oracle.com> wrote: > > > > Since retpoline capable compilers are widely available, make > > CONFIG_RETPOLINE hard depend on it. > > > > Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with > > CONFIG_RETPOLINE which is used by kernel. > > > > With all that stuff, the check of RETPOLINE is changed to > > CONFIG_RETPOLINE. > > > > This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016 > > > > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Borislav Petkov <bp@suse.de> > > Cc: Daniel Borkmann <daniel@iogearbox.net> > > Cc: David Woodhouse <dwmw@amazon.co.uk> > > Cc: H. Peter Anvin <hpa@zytor.com> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > > Cc: Andy Lutomirski <luto@kernel.org> > > Cc: Masahiro Yamada <yamada.masahiro@socionext.com> > > Cc: Michal Marek <michal.lkml@markovi.net> > > --- > > > Instead of adding another CONFIG option, > does it make sense to add compiler support checks > to 'depends on' syntax ? > > > config RETPOLINE > bool "Avoid speculative indirect branches in kernel" > depends on $(cc-option,-mindirect-branch=thunk-extern > -mindirect-branch-register) || \ > $(cc-option,-mretpoline-external-thunk) > default y > select STACK_VALIDATION if HAVE_STACK_VALIDATION
That seems to be what we did for stackprotector, which is similar in that it used to fail the build. So yes, this seems sane.
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