Re: [PATCH v2 10/18] arm64: add a workaround for GNU gold with ARM64_MODULE_PLTS

Will Deacon
2017-11-16T18:47:07Z

On Thu, Nov 16, 2017 at 08:41:01AM -0800, Sami Tolvanen wrote:
> On Thu, Nov 16, 2017 at 11:50:12AM +0000, Will Deacon wrote:
> > Why don't we just not do LTO if the toolchain is busted?
>
> Because LTO can not only potentially improve performance, especially
> when combined with PGO (Profile Guided Optimization), but it also
> makes it possible to enable features like Control Flow Integrity that
> can make kernel vulnerabilities more difficult to exploit:
>
> https://clang.llvm.org/docs/ControlFlowIntegrity.html
>
> > This feels like it will end up being a game of whack-a-mole as code
> > could be introduced that tickles known bugs on older toolchains.
>
> I'm not sure this is much different from dealing with older versions
> of the existing toolchain. Otherwise, we wouldn't need cc-version or
> other similar macros, for example.

I think the big difference is that we have no compelling need to support
older versions of clang or gold.

Will