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[23.128.96.18]) by mx.google.com with ESMTP id gy5si1185208ejb.207.2020.11.18.14.09.03; Wed, 18 Nov 2020 14:09:32 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=FEACl+hP; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726625AbgKRWHe (ORCPT + 99 others); Wed, 18 Nov 2020 17:07:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726374AbgKRWHe (ORCPT ); Wed, 18 Nov 2020 17:07:34 -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 153AFC061A4D for ; Wed, 18 Nov 2020 14:07:34 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id o5so4510155ybe.12 for ; Wed, 18 Nov 2020 14:07:34 -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=RLGcqGrpsLlRbzosDVd0xMcJRplKck51D58hnCA0m40=; b=FEACl+hPLvLCehd5Y1IKJBTJMbR0QNknmx7JyEdblpLzyJtFGWeraZl9sfry0j3+TK kM1Ew0qwvXu8KiNhkl6/Lts6lfNP0QOtRmYpgESW0VKFUjrDc5GbVOF5mwwP/eHkKFsy FofVx9oGp4zsyD83lrr4uaPQAiM/oxp3HRLr27hBWDGyYPHGds3tdIhKnE0AUSYvkx+1 TwEFXYs+aBQvHKOt2LEYwCaN+5eXT83BFAe3QJVAC6b+iFUY+dDobgfDt2BlWuLx2V4z 3XbU9NTi2LeOeIv8rGJ6XXsrxQN/svzHG1smnTQhehYdm8prrKq5jKeMSosG+9Wvmj5x VHGw== 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=RLGcqGrpsLlRbzosDVd0xMcJRplKck51D58hnCA0m40=; b=pRSKaGbm89q05+qiaIs7Cb1faYYHcqpZoAFNjJiB5PdVMVJP5MV8M+0KA4cvWLAxrK RPrjIr8HSdSksagRrjeV2BKESf4IxfFB5ETGilU4IQ0EypwztEgNQsJ+nJCRWry4r6eM l++SpYWkb9c6PB1wxckj423VBinT6lM7i/KI2kb4Ug5O+Xqrtyz/DzWGmt4JeiinSV5v YeWLnjfrkQbKlscwGkPCF/TeqPzeq7+kK9nk5wkpeNSSmkGSEbqphEDx9Gqz3GVbLHzU daINcM2/gCdCFuDuUrw9NqqBRIxGdNYoFR2lRswu1d9Bg1XSxDp/dGfAsDmGg4IHfbNp PaNA== X-Gm-Message-State: AOAM530jSdB5bYQ5g1Cy2TF0FeEr0o1bDpkmBTifgXEHg465egd2o4ck 4GYYVZaV134YCyhC6FaNxfKMHoM9GFouSmVeGRg= 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:cb11:: with SMTP id b17mr8848931ybg.236.1605737253032; Wed, 18 Nov 2020 14:07:33 -0800 (PST) Date: Wed, 18 Nov 2020 14:07:14 -0800 Message-Id: <20201118220731.925424-1-samitolvanen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog Subject: [PATCH v7 00/17] 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 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]. [1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/lto [2] https://lore.kernel.org/lkml/20201114004911.aip52eimk6c2uxd4@treble/ You can also pull this series from https://github.com/samitolvanen/linux.git lto-v7 --- 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 -- 2.29.2.299.gdc1121823c-goog