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's Pixel devices have shipped with LTO+CFI kernels 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 first objtool patch in the series is already in linux-next, but as it's needed with LTO, I'm including it also here to make testing easier. Sami Tolvanen (22): objtool: use sh_info to find the base for .rela sections kbuild: add support for Clang LTO kbuild: lto: fix module versioning kbuild: lto: fix recordmcount 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: lto: fix PREL32 relocations 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 arm64: allow LTO_CLANG and THINLTO to be selected x86, vdso: disable LTO only for vDSO x86, ftrace: disable recordmcount for ftrace_make_nop x86, relocs: Ignore L4_PAGE_OFFSET relocations x86, build: allow LTO_CLANG and THINLTO to be selected .gitignore | 1 + Makefile | 27 ++- arch/Kconfig | 65 +++++++ arch/arm64/Kconfig | 2 + arch/arm64/Makefile | 1 + arch/arm64/kernel/vdso/Makefile | 4 +- arch/x86/Kconfig | 2 + arch/x86/Makefile | 5 + arch/x86/entry/vdso/Makefile | 5 +- arch/x86/kernel/ftrace.c | 1 + arch/x86/tools/relocs.c | 1 + drivers/firmware/efi/libstub/Makefile | 2 + drivers/misc/lkdtm/Makefile | 1 + include/asm-generic/vmlinux.lds.h | 12 +- include/linux/compiler-clang.h | 4 + include/linux/compiler.h | 2 +- include/linux/compiler_types.h | 4 + include/linux/init.h | 78 +++++++- include/linux/pci.h | 15 +- kernel/trace/ftrace.c | 1 + lib/Kconfig.debug | 2 +- scripts/Makefile.build | 55 +++++- scripts/Makefile.lib | 6 +- scripts/Makefile.modfinal | 40 +++- scripts/Makefile.modpost | 26 ++- scripts/generate_initcall_order.pl | 270 ++++++++++++++++++++++++++ scripts/link-vmlinux.sh | 100 +++++++++- scripts/mod/Makefile | 1 + scripts/mod/modpost.c | 16 +- scripts/mod/modpost.h | 9 + scripts/mod/sumversion.c | 6 +- scripts/module-lto.lds | 26 +++ scripts/recordmcount.c | 3 +- tools/objtool/elf.c | 2 +- 34 files changed, 737 insertions(+), 58 deletions(-) create mode 100755 scripts/generate_initcall_order.pl create mode 100644 scripts/module-lto.lds base-commit: 26e122e97a3d0390ebec389347f64f3730fdf48f -- 2.27.0.212.ge8ba1cc988-goog
