Date: Fri, 20 Nov 2020 12:25:09 -0800 From: Sami Tolvanen <samitolvanen@...gle.com> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: Masahiro Yamada <masahiroy@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Paul E. McKenney" <paulmck@...nel.org>, Kees Cook <keescook@...omium.org>, Nick Desaulniers <ndesaulniers@...gle.com>, clang-built-linux <clang-built-linux@...glegroups.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-arch <linux-arch@...r.kernel.org>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, linux-kbuild <linux-kbuild@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org Subject: Re: [PATCH v7 00/17] Add support for Clang LTO On Thu, Nov 19, 2020 at 8:04 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote: > > 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 , and drops x86_64 while we work > > on fixing the remaining objtool warnings . > > Sami, > > Here are some patches to fix the objtool issues (other than crypto which > I'll work on next). > > https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git objtool-vmlinux Thanks, Josh! I can confirm that these fix all the non-crypto objtool warnings with LTO as well. Sami
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