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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to:cc; bh=doA4ol07JEk8RvmCDvE+88F3JtPRfseL2+6tdCDWQqw=; b=hPerZ0IGFfWp/sLvwDFN7egzOKgTvGnT9+ZWryMqtfYpn2Y4EOwgRHRXduTEHBQXyn OBz0qpAHPtH5XE6lXDcRZKvYJi2ALHmtTmGtFxlvy4J0Z+Uu9iRCGFf24QTe2GgT0Uro p2fdjMwfajzyZgPKXhA+vAU6sqIjY5s4P5xS6YGbEq8huPyyB3ooBIqN4lPTJS+U6FPF snpwYAmylpAx9s5NUhRXOYGa8K2NjLMh9wpQJgwOTaE+3nr6E1tX/NTMAqcr6o/EiC7N wfz8Hh2RB6CGx14i8zBJDEx3Z16wbmLE4RB64AJyc38any5tHyGFjTX5EdmL0Ls5n3Ir 6sPQ== X-Gm-Message-State: AOAM532R5Zy+8iLzPUv4RSZjY7onJanzL6s6SVlcRGx32ChAgAQke/+H 1KQxFbLaQJNwiuK4GUC6KO64hqP+D3WuxlwaqXI= X-Google-Smtp-Source: ABdhPJwphP9ojdahsOdNIORs8jQM7iAKWDDRb89RyKBzU9JdoeiJZQyTzCMhdFKMEp06LRl3gHYmyPqZfVD8YGyWrm4= X-Received: by 2002:aca:4754:: with SMTP id u81mr10252669oia.72.1600460577384; Fri, 18 Sep 2020 13:22:57 -0700 (PDT) MIME-Version: 1.0 References: <20200918201436.2932360-1-samitolvanen@google.com> In-Reply-To: <20200918201436.2932360-1-samitolvanen@google.com> From: Sedat Dilek Date: Fri, 18 Sep 2020 22:22:46 +0200 Message-ID: Subject: Re: [PATCH v3 00/30] Add support for Clang LTO To: Sami Tolvanen X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200918_162300_744087_CDC376BB X-CRM114-Status: GOOD ( 41.29 ) 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: , Reply-To: sedat.dilek@gmail.com 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, Steven Rostedt , Clang-Built-Linux ML , 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, Sep 18, 2020 at 10:14 PM 'Sami Tolvanen' via Clang Built Linux 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 patches 1-5 are not directly related to LTO, but are > needed to compile LTO kernels with ToT Clang, so I'm including them > in the series for your convenience: > > - Patches 1-3 fix build issues with LLVM and they are already in > linux-next. > > - Patch 4 fixes x86 builds with LLVM IAS, but it hasn't yet been > picked up by maintainers. > > - Patch 5 is from Masahiro's kbuild tree and makes the LTO linker > script changes much cleaner. > Hi Sami, might be good to point to your GitHub tree and corresponding release-tag for easy fetching. Thanks. Regards, - Sedat - > --- > 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. > > > Arvind Sankar (2): > x86/boot/compressed: Disable relocation relaxation > x86/asm: Replace __force_order with memory clobber > > Luca Stefani (1): > RAS/CEC: Fix cec_init() prototype > > Masahiro Yamada (1): > kbuild: preprocess module linker script > > Nick Desaulniers (1): > lib/string.c: implement stpcpy > > Peter Zijlstra (1): > objtool: Add a pass for generating __mcount_loc > > Sami Tolvanen (24): > objtool: Don't autodetect vmlinux.o > kbuild: add support for objtool mcount > x86, build: use objtool mcount > treewide: remove DISABLE_LTO > kbuild: add support for Clang LTO > kbuild: lto: fix module versioning > kbuild: lto: postpone objtool > 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: export CC_USING_PATCHABLE_FUNCTION_ENTRY > arm64: vdso: disable LTO > KVM: arm64: disable LTO for the nVHE directory > arm64: allow LTO_CLANG and THINLTO to be selected > x86, vdso: disable LTO only for vDSO > x86, cpu: disable LTO for cpu.c > x86, build: allow LTO_CLANG and THINLTO to be selected > > .gitignore | 1 + > Makefile | 74 ++++- > arch/Kconfig | 68 +++++ > arch/arm/Makefile | 4 - > .../module.lds => include/asm/module.lds.h} | 2 + > arch/arm64/Kconfig | 2 + > arch/arm64/Makefile | 5 +- > .../module.lds => include/asm/module.lds.h} | 2 + > arch/arm64/kernel/vdso/Makefile | 4 +- > arch/arm64/kvm/hyp/nvhe/Makefile | 4 +- > arch/ia64/Makefile | 1 - > .../{module.lds => include/asm/module.lds.h} | 0 > arch/m68k/Makefile | 1 - > .../module.lds => include/asm/module.lds.h} | 0 > arch/powerpc/Makefile | 1 - > .../module.lds => include/asm/module.lds.h} | 0 > arch/riscv/Makefile | 3 - > .../module.lds => include/asm/module.lds.h} | 3 +- > arch/sparc/vdso/Makefile | 2 - > arch/um/include/asm/Kbuild | 1 + > arch/x86/Kconfig | 3 + > arch/x86/Makefile | 5 + > arch/x86/boot/compressed/Makefile | 2 + > arch/x86/boot/compressed/pgtable_64.c | 9 - > arch/x86/entry/vdso/Makefile | 5 +- > arch/x86/include/asm/special_insns.h | 28 +- > arch/x86/kernel/cpu/common.c | 4 +- > arch/x86/power/Makefile | 4 + > drivers/firmware/efi/libstub/Makefile | 2 + > drivers/misc/lkdtm/Makefile | 1 + > drivers/ras/cec.c | 9 +- > include/asm-generic/Kbuild | 1 + > include/asm-generic/module.lds.h | 10 + > include/asm-generic/vmlinux.lds.h | 11 +- > include/linux/init.h | 79 ++++- > include/linux/pci.h | 19 +- > kernel/Makefile | 3 - > kernel/trace/Kconfig | 5 + > lib/string.c | 24 ++ > scripts/.gitignore | 1 + > scripts/Makefile | 3 + > scripts/Makefile.build | 69 +++-- > scripts/Makefile.lib | 17 +- > scripts/Makefile.modfinal | 29 +- > scripts/Makefile.modpost | 22 +- > scripts/generate_initcall_order.pl | 270 ++++++++++++++++++ > scripts/link-vmlinux.sh | 95 +++++- > scripts/mod/Makefile | 1 + > scripts/mod/modpost.c | 16 +- > scripts/mod/modpost.h | 9 + > scripts/mod/sumversion.c | 6 +- > scripts/{module-common.lds => module.lds.S} | 31 ++ > scripts/package/builddeb | 2 +- > tools/objtool/builtin-check.c | 13 +- > tools/objtool/builtin.h | 2 +- > tools/objtool/check.c | 83 ++++++ > tools/objtool/check.h | 1 + > tools/objtool/objtool.h | 1 + > 58 files changed, 919 insertions(+), 154 deletions(-) > rename arch/arm/{kernel/module.lds => include/asm/module.lds.h} (72%) > rename arch/arm64/{kernel/module.lds => include/asm/module.lds.h} (76%) > rename arch/ia64/{module.lds => include/asm/module.lds.h} (100%) > rename arch/m68k/{kernel/module.lds => include/asm/module.lds.h} (100%) > rename arch/powerpc/{kernel/module.lds => include/asm/module.lds.h} (100%) > rename arch/riscv/{kernel/module.lds => include/asm/module.lds.h} (84%) > create mode 100644 include/asm-generic/module.lds.h > create mode 100755 scripts/generate_initcall_order.pl > rename scripts/{module-common.lds => module.lds.S} (59%) > > > base-commit: 92ab97adeefccf375de7ebaad9d5b75d4125fe8b > -- > 2.28.0.681.g6f77f65b4e-goog > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200918201436.2932360-1-samitolvanen%40google.com. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel