Messages in this thread | | | Date | Thu, 1 Nov 2018 09:56:34 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/3] kprobes/x86: Simplify indirect-jump check in retpoline |
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On Thu, Nov 01, 2018 at 10:02:14AM +0800, Zhenzhong Duan wrote: > > Hmm, what about the case where we have RETPOLINE runtime disabled? Then > > the CALL_NOSPEC alternative patches in an indirect call again, and the > > retpolines are gone. > > Is RETPOLINE runtime toggle supported in upstream? I don't see such code.
arch/x86/kernel/cpu/bugs.c look for the "nospectre_v2" and related options. That will avoid X86_FEATURE_RETPOLINE from being set, and thus the JMP_NOSPEC and CALL_NOSPEC alternatives will not patch out the indirect jump / call.
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