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McKenney" , kernel-hardening@lists.openwall.com, Peter Zijlstra , Greg Kroah-Hartman , linux-kbuild@vger.kernel.org, Nick Desaulniers , linux-kernel@vger.kernel.org, Steven Rostedt , clang-built-linux@googlegroups.com, Sami Tolvanen , linux-pci@vger.kernel.org, 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 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. --- 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel