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Fri, 09 Oct 2020 14:05:54 -0700 (PDT) Date: Fri, 9 Oct 2020 14:05:48 -0700 From: Sami Tolvanen To: Steven Rostedt Subject: Re: [PATCH v5 00/29] Add support for Clang LTO Message-ID: <20201009210548.GB1448445@google.com> References: <20201009161338.657380-1-samitolvanen@google.com> <20201009153512.1546446a@gandalf.local.home> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201009153512.1546446a@gandalf.local.home> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201009_170558_630889_69B66283 X-CRM114-Status: GOOD ( 25.40 ) 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, Peter Zijlstra , 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 Fri, Oct 09, 2020 at 03:35:12PM -0400, Steven Rostedt wrote: > On Fri, 9 Oct 2020 09:13:09 -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 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 this version is based on tip/master to reduce the number > > of prerequisite patches, and to make it easier to manage changes to > > objtool. Patch 1 is from Masahiro's kbuild tree, and while it's not > > directly related to LTO, it makes the module linker script changes > > cleaner. > > > > I went to test this, but it appears that the latest tip/master fails to > build for me. This error is on tip/master, before I even applied a single > patch. > > (config attached) Ah yes, X86_DECODER_SELFTEST seems to be broken in tip/master. If you prefer, I have these patches on top of mainline here: https://github.com/samitolvanen/linux/tree/clang-lto Testing your config with LTO on this tree, it does build and boot for me, although I saw a couple of new objtool warnings, and with LLVM=1, one warning from llvm-objdump. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel