From patchwork Tue Dec 1 21:36:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11943925 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04740C71155 for ; Tue, 1 Dec 2020 21:37:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93BE420870 for ; Tue, 1 Dec 2020 21:37:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="uP8b9Pac" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728947AbgLAVhv (ORCPT ); Tue, 1 Dec 2020 16:37:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728051AbgLAVhu (ORCPT ); Tue, 1 Dec 2020 16:37:50 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 828D4C0613CF for ; Tue, 1 Dec 2020 13:37:10 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id v13so3968502ybe.18 for ; Tue, 01 Dec 2020 13:37:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=/Ydp+qeiWXHO6I7zK5gxOYIhZihlQbGAyMr7COYjNo8=; b=uP8b9PacbViNuju3jU4Y7pQopc/D13IK9+EgFguKjQ71Rj4a4pDH62wMzEVMzTGdgL A3A67LktcpWWVek2Xxu10AIYqibTKqLwW/RJnT0sIk9Sp7B6dRZsUkovRq6s2dpn3cga 2wHcebF3x2YFGZP6VqaT8vo5ANbAkpHZH/rp2ALxYckkRwVNaaEgWhFOB0m3mB96lVrQ KhneUkQCpG+O4jwnVJbzSzP7J/KIEDqqIwxIExNayWW0lDsj1em6+v9ZazfgE8/gduNa 8aXAzKqIaIL1cj2a5t+vFZlekXsZNzqTLBCQguZ23yyj4s9L2GONhXh+25Fm257CMHTt kOYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=/Ydp+qeiWXHO6I7zK5gxOYIhZihlQbGAyMr7COYjNo8=; b=tgBfKEVibENizfvwoloQ+jSfnMSX/WKB/vhTtDftMKoI8itrQrhnq11Ysw9eP9RaTg jcVnmuhq/Tal/wmUqJwaCsna2OkWWPhbKMa4DFBud+sSrS1icauWTfVuG+H8rYJjvsC9 cTot8iqt2/pddDsL953GbQHGA1fB16TQ80KV9rH/OjA+hp4FrJxjkrUuXnM6I1ucU3ui e5PVfEel/z75C603ZbCVx6uOQRlx9gHbiX3lfSdzTe60H2LVaG53qYm4NE5Aglvde9w7 MkSNh4cpAqaOi4HdUMQssKQNk5wJyA5I7eMFXfgq5wU0XZgGSYam8fdd3oTlblZ2Q3Lb arrg== X-Gm-Message-State: AOAM5334hFxbFIRfJ96q+4PXy1EEiEhWJZQOFeSezRPc/nvucZ+fA8Em TPAqR/COj64oY/JdZ/VM6DS0zGdipavXFOK+bJQ= X-Google-Smtp-Source: ABdhPJynKo/QcQ3ER0aMzDLxbXuS+BG4gD3OR3K6Nh+qfPOFy0xY1fApLMu+UZgd7x2StzuuvUUGP/FHZZDZBVMpQcA= Sender: "samitolvanen via sendgmr" X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:f693:9fff:fef4:1b6d]) (user=samitolvanen job=sendgmr) by 2002:a25:abae:: with SMTP id v43mr6680681ybi.397.1606858629755; Tue, 01 Dec 2020 13:37:09 -0800 (PST) Date: Tue, 1 Dec 2020 13:36:51 -0800 Message-Id: <20201201213707.541432-1-samitolvanen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH v8 00/16] Add support for Clang LTO From: Sami Tolvanen To: Masahiro Yamada , Steven Rostedt , Will Deacon Cc: Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org 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 arm64 support depends on Will's memory ordering patches [1]. I will post x86_64 patches separately after we have fixed the remaining objtool warnings [2][3]. [1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/lto [2] https://lore.kernel.org/lkml/20201120040424.a3wctajzft4ufoiw@treble/ [3] https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/log/?h=objtool-vmlinux You can also pull this series from https://github.com/samitolvanen/linux.git lto-v8 Tested-by: Nick Desaulniers --- Changes in v8: - Cleaned up the LTO Kconfig options based on suggestions from Nick and Kees. - Dropped the patch to disable LTO for the arm64 nVHE KVM code as David pointed out it's not needed anymore. Changes in v7: - Rebased to master again. - Added back arm64 patches as the prerequisites are now staged, and dropped x86_64 support until the remaining objtool issues are resolved. - Dropped ifdefs from module.lds.S. Changes in v6: - Added the missing --mcount flag to patch 5. - Dropped the arm64 patches from this series and will repost them later. Changes in v5: - Rebased on top of tip/master. - Changed the command line for objtool to use --vmlinux --duplicate to disable warnings about retpoline thunks and to fix .orc_unwind generation for vmlinux.o. - Added --noinstr flag to objtool, so we can use --vmlinux without also enabling noinstr validation. - Disabled objtool's unreachable instruction warnings with LTO to disable false positives for the int3 padding in vmlinux.o. - Added ANNOTATE_RETPOLINE_SAFE annotations to the indirect jumps in x86 assembly code to fix objtool warnings with retpoline. - Fixed modpost warnings about missing version information with CONFIG_MODVERSIONS. - Included Makefile.lib into Makefile.modpost for ld_flags. Thanks to Sedat for pointing this out. - Updated the help text for ThinLTO to better explain the trade-offs. - Updated commit messages with better explanations. Changes in v4: - Fixed a typo in Makefile.lib to correctly pass --no-fp to objtool. - Moved ftrace configs related to generating __mcount_loc to Kconfig, so they are available also in Makefile.modfinal. - Dropped two prerequisite patches that were merged to Linus' tree. Changes in v3: - Added a separate patch to remove the unused DISABLE_LTO treewide, as filtering out CC_FLAGS_LTO instead is preferred. - Updated the Kconfig help to explain why LTO is behind a choice and disabled by default. - Dropped CC_FLAGS_LTO_CLANG, compiler-specific LTO flags are now appended directly to CC_FLAGS_LTO. - Updated $(AR) flags as KBUILD_ARFLAGS was removed earlier. - Fixed ThinLTO cache handling for external module builds. - Rebased on top of Masahiro's patch for preprocessing modules.lds, and moved the contents of module-lto.lds to modules.lds.S. - Moved objtool_args to Makefile.lib to avoid duplication of the command line parameters in Makefile.modfinal. - Clarified in the commit message for the initcall ordering patch that the initcall order remains the same as without LTO. - Changed link-vmlinux.sh to use jobserver-exec to control the number of jobs started by generate_initcall_ordering.pl. - Dropped the x86/relocs patch to whitelist L4_PAGE_OFFSET as it's no longer needed with ToT kernel. - Disabled LTO for arch/x86/power/cpu.c to work around a Clang bug with stack protector attributes. Changes in v2: - Fixed -Wmissing-prototypes warnings with W=1. - Dropped cc-option from -fsplit-lto-unit and added .thinlto-cache scrubbing to make distclean. - Added a comment about Clang >=11 being required. - Added a patch to disable LTO for the arm64 KVM nVHE code. - Disabled objtool's noinstr validation with LTO unless enabled. - Included Peter's proposed objtool mcount patch in the series and replaced recordmcount with the objtool pass to avoid whitelisting relocations that are not calls. - Updated several commit messages with better explanations. Sami Tolvanen (17): tracing: move function tracer options to Kconfig kbuild: add support for Clang LTO kbuild: lto: fix module versioning kbuild: lto: limit inlining kbuild: lto: merge module sections kbuild: lto: remove duplicate dependencies from .mod files init: lto: ensure initcall ordering init: lto: fix PREL32 relocations PCI: Fix PREL32 relocations for LTO modpost: lto: strip .lto from module names scripts/mod: disable LTO for empty.c efi/libstub: disable LTO drivers/misc/lkdtm: disable LTO for rodata.o arm64: vdso: disable LTO KVM: arm64: disable LTO for the nVHE directory arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS arm64: allow LTO_CLANG and THINLTO to be selected .gitignore | 1 + Makefile | 45 +++-- arch/Kconfig | 74 +++++++ arch/arm64/Kconfig | 4 + arch/arm64/kernel/vdso/Makefile | 3 +- arch/arm64/kvm/hyp/nvhe/Makefile | 4 +- drivers/firmware/efi/libstub/Makefile | 2 + drivers/misc/lkdtm/Makefile | 1 + include/asm-generic/vmlinux.lds.h | 11 +- include/linux/init.h | 79 +++++++- include/linux/pci.h | 19 +- kernel/trace/Kconfig | 16 ++ scripts/Makefile.build | 50 ++++- scripts/Makefile.lib | 6 +- scripts/Makefile.modfinal | 9 +- scripts/Makefile.modpost | 25 ++- scripts/generate_initcall_order.pl | 270 ++++++++++++++++++++++++++ scripts/link-vmlinux.sh | 70 ++++++- scripts/mod/Makefile | 1 + scripts/mod/modpost.c | 16 +- scripts/mod/modpost.h | 9 + scripts/mod/sumversion.c | 6 +- scripts/module.lds.S | 24 +++ 23 files changed, 677 insertions(+), 68 deletions(-) create mode 100755 scripts/generate_initcall_order.pl base-commit: 0fa8ee0d9ab95c9350b8b84574824d9a384a9f7d