Messages in this thread | | | Date | Fri, 19 Nov 2021 16:11:25 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86: Use -mindirect-branch-cs-prefix for RETPOLINE builds |
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On Thu, Nov 18, 2021 at 02:08:04PM -0800, Nick Desaulniers wrote: > On Thu, Nov 18, 2021 at 10:54 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > In order to further enable commit: > > > > bbe2df3f6b6d ("x86/alternative: Try inline spectre_v2=retpoline,amd") > > > > add the new GCC flag -mindirect-branch-cs-prefix: > > > > https://gcc.gnu.org/g:2196a681d7810ad8b227bf983f38ba716620545e > > > > to RETPOLINE=y builds. This should allow fully inlining retpoline,amd > > for GCC builds. > > Do you mind adding the following link tags: > > Link: https://gcc.gnu.org/g:2196a681d7810ad8b227bf983f38ba716620545e > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952 > Link: https://bugs.llvm.org/show_bug.cgi?id=52323
My scripts will strip that, they only like to have a Link to to the actual email as posted. I can put in the URLs, the first is already in the Changelog.
> If the feature would be helpful to implement in Clang, would you mind > keeping the cc-option, but moving the check outside of the `ifdef > CONFIG_CC_IS_GCC` block? That way, we don't need to revisit the > Makefile?
I was thinking that clang would want to name it differently to be consistent with their own retpoline flags, something like:
-mretpoline-cs-prefix
> (Tangential: I wonder why RETPOLINE_CFLAGS aren't defined in > arch/x86/Makefile; they seem to be x86 specific at the moment).
Yeah, I think there was hoping that other archs would find it useful, but so far x86 is the only one having grown them things. I can move them I suppose. If ever another arch grows them we can reconsider.
> With the above link tags, and with or without moving this outside the > gcc-specific guard: > Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Thanks, let me repost as two patches.
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