On Thu, Jun 25, 2020 at 02:36:27AM +0800, kernel test robot wrote: > I love your patch! Perhaps something to improve: > [...] > config: x86_64-randconfig-a012-20200624 (attached as .config)
CONFIG_KCSAN=y > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project > 1d4c87335d5236ea1f35937e1014980ba961ae34) > [...] > All warnings (new ones prefixed by >>): > > ld.lld: warning: drivers/built-in.a(mfd/mt6397-irq.o):(.init_array.0) is > being placed in '.init_array.0' As far as I can tell, this is a Clang bug. But I don't know the internals here, so I've opened: https://bugs.llvm.org/show_bug.cgi?id=46478 and created a work-around patch for the kernel: commit 915f2c343e59a14f00c68f4d7afcfdc621de0674 Author: Kees Cook <keesc...@chromium.org> Date: Sat Jun 27 08:07:54 2020 -0700 vmlinux.lds.h: Avoid KCSAN's unwanted sections KCSAN (-fsanitize=thread) produces unwanted[1] .eh_frame and .init_array.* sections. Add them to DISCARDS, except with CONFIG_CONSTRUCTORS, which wants to keep .init_array.* sections. [1] https://bugs.llvm.org/show_bug.cgi?id=46478 Signed-off-by: Kees Cook <keesc...@chromium.org> diff --git a/arch/x86/Makefile b/arch/x86/Makefile index f8a5b2333729..41c8c73de6c4 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -195,7 +195,9 @@ endif # Workaround for a gcc prelease that unfortunately was shipped in a suse release KBUILD_CFLAGS += -Wno-sign-compare # -KBUILD_CFLAGS += -fno-asynchronous-unwind-tables +KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_LDFLAGS += $(call ld-option,--no-ld-generated-unwind-info) # Avoid indirect branches in kernel to deal with Spectre ifdef CONFIG_RETPOLINE diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index b1dca0762fc5..a44ee16abc78 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -934,10 +934,28 @@ EXIT_DATA #endif +/* + * Clang's -fsanitize=thread produces unwanted sections (.eh_frame + * and .init_array.*), but CONFIG_CONSTRUCTORS wants to keep any + * .init_array.* sections. + * https://bugs.llvm.org/show_bug.cgi?id=46478 + */ +#if defined(CONFIG_KCSAN) && !defined(CONFIG_CONSTRUCTORS) +#define KCSAN_DISCARDS \ + *(.init_array) *(.init_array.*) \ + *(.eh_frame) +#elif defined(CONFIG_KCSAN) && defined(CONFIG_CONSTRUCTORS) +#define KCSAN_DISCARDS \ + *(.eh_frame) +#else +#define KCSAN_DISCARDS +#endif + #define DISCARDS \ /DISCARD/ : { \ EXIT_DISCARDS \ EXIT_CALL \ + KCSAN_DISCARDS \ *(.discard) \ *(.discard.*) \ *(.modinfo) \ -- Kees Cook
