Re: [PATCH v7 00/17] Add support for Clang LTO

Will Deacon
2020-11-30T12:02:35Z

Hi Sami,

On Wed, Nov 18, 2020 at 02:07:14PM -0800, Sami Tolvanen wrote:
> This patch series adds support for building the kernel with Clang's
> Link Time Optimization (LTO). In addition to performance, the primary
> motivation for LTO is to allow Clang's Control-Flow Integrity (CFI) to
> be used in the kernel. Google has shipped millions of Pixel devices
> running three major kernel versions with LTO+CFI since 2018.
>
> Most of the patches are build system changes for handling LLVM bitcode,
> which Clang produces with LTO instead of ELF object files, postponing
> ELF processing until a later stage, and ensuring initcall ordering.
>
> Note that v7 brings back arm64 support as Will has now staged the
> prerequisite memory ordering patches [1], and drops x86_64 while we work
> on fixing the remaining objtool warnings [2].

Sounds like you're going to post a v8, but that's the plan for merging
that? The arm64 parts look pretty good to me now.

Will