On Thu, Jun 25, 2020 at 5:32 AM 'Sami Tolvanen' via Clang Built Linux <clang-built-linux@xxxxxxxxxxxxxxxx> 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'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. I put this series on a testing branch, and 0-day bot started reporting some issues. (but 0-day bot is quieter than I expected. Perhaps, 0-day bot does not turn on LLVM=1 ?) I also got an error for ARCH=arm64 allyesconfig + CONFIG_LTO_CLANG=y $ make ARCH=arm64 LLVM=1 LLVM_IAS=1 CROSS_COMPILE=~/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu- -j24 ... GEN .version CHK include/generated/compile.h UPD include/generated/compile.h CC init/version.o AR init/built-in.a GEN .tmp_initcalls.lds GEN .tmp_symversions.lds LTO vmlinux.o MODPOST vmlinux.symvers MODINFO modules.builtin.modinfo GEN modules.builtin LD .tmp_vmlinux.kallsyms1 ld.lld: error: undefined symbol: __compiletime_assert_905 >>> referenced by irqbypass.c >>> vmlinux.o:(jeq_imm) make: *** [Makefile:1161: vmlinux] Error 1 > 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 > > -- > 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@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200624203200.78870-1-samitolvanen%40google.com. -- Best Regards Masahiro Yamada
