From 6107467ed9704d08847f113e62c84bc6535cbb25 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 23 Sep 2020 02:06:57 +0400 Subject: [PATCH] Makefile: Add '-fno-builtin-bcmp' to CLANG_FLAGS After LLVM revision r355672 [1], all known working kernel configurations fail to link [2]: ld: init/do_mounts.o: in function `prepare_namespace': do_mounts.c:(.init.text+0x5ca): undefined reference to `bcmp' ld: do_mounts.c:(.init.text+0x5e6): undefined reference to `bcmp' ld: init/initramfs.o: in function `do_header': initramfs.c:(.init.text+0x6e0): undefined reference to `bcmp' ld: initramfs.c:(.init.text+0x6f8): undefined reference to `bcmp' ld: arch/x86/kernel/setup.o: in function `setup_arch': setup.c:(.init.text+0x21d): undefined reference to `bcmp' Commit 6edfba1b33c7 ("[PATCH] x86_64: Don't define string functions to builtin") removed '-ffreestanding' globally and the kernel doesn't provide a bcmp definition so the linker cannot find a reference to it. Fix this by explicitly telling LLVM through Clang not to emit bcmp references. This flag does not need to be behind 'cc-option' because all working versions of Clang support this flag. [1]: https://github.com/llvm/llvm-project/commit/8e16d73346f8091461319a7dfc4ddd18eedcff13 [2]: https://travis-ci.com/ClangBuiltLinux/continuous-integration/builds/104027249 Link: https://github.com/ClangBuiltLinux/linux/issues/416 Link: https://bugs.llvm.org/show_bug.cgi?id=41035 Cc: stable@vger.kernel.org Signed-off-by: Nathan Chancellor Change-Id: Ide8b905b0406ef698916f07d728c7d5fd72978e2 --- Makefile | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Makefile b/Makefile index 7bece7a1f052..57f89c474165 100755 --- a/Makefile +++ b/Makefile @@ -760,6 +760,9 @@ KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior) KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) +CLANG_FLAGS += -fno-builtin-bcmp +KBUILD_CFLAGS += $(CLANG_FLAGS) +KBUILD_AFLAGS += $(CLANG_FLAGS) else # These warnings generated too much noise in a regular build. -- 2.20.1