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Wed, 24 Jun 2020 14:30:21 -0700 (PDT) Date: Wed, 24 Jun 2020 14:30:14 -0700 From: Sami Tolvanen To: Peter Zijlstra Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200624213014.GB26253@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> <20200624211540.GS4817@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200624211540.GS4817@hirez.programming.kicks-ass.net> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, x86@kernel.org, Kees Cook , "Paul E. McKenney" , kernel-hardening@lists.openwall.com, Greg Kroah-Hartman , Masahiro Yamada , linux-kbuild@vger.kernel.org, Nick Desaulniers , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, linux-pci@vger.kernel.org, Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 24, 2020 at 11:15:40PM +0200, Peter Zijlstra wrote: > On Wed, Jun 24, 2020 at 01:31:38PM -0700, Sami Tolvanen wrote: > > This patch series adds support for building x86_64 and arm64 kernels > > 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's > > Pixel devices have shipped with LTO+CFI kernels 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 first objtool patch in the series is already in linux-next, > > but as it's needed with LTO, I'm including it also here to make testing > > easier. > > I'm very sad that yet again, memory ordering isn't addressed. LTO vastly > increases the range of the optimizer to wreck things. I believe Will has some thoughts about this, and patches, but I'll let him talk about it. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel