From: Gustavo A. R. Silva Date: Sun, 14 Nov 2021 00:57:25 +0000 (-0600) Subject: kconfig: Add support for -Wimplicit-fallthrough X-Git-Tag: baikal/aarch64/sdk6.1~5270 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=f2416bb37622a9b9ec189d673b1248ce452f13b3;p=kernel.git kconfig: Add support for -Wimplicit-fallthrough Add Kconfig support for -Wimplicit-fallthrough for both GCC and Clang. The compiler option is under configuration CC_IMPLICIT_FALLTHROUGH, which is enabled by default. Special thanks to Nathan Chancellor who fixed the Clang bug[1][2]. This bugfix only appears in Clang 14.0.0, so older versions still contain the bug and -Wimplicit-fallthrough won't be enabled for them, for now. This concludes a long journey and now we are finally getting rid of the unintentional fallthrough bug-class in the kernel, entirely. :) Link: https://github.com/llvm/llvm-project/commit/9ed4a94d6451046a51ef393cd62f00710820a7e8 [1] Link: https://bugs.llvm.org/show_bug.cgi?id=51094 [2] Link: https://github.com/KSPP/linux/issues/115 Link: https://github.com/ClangBuiltLinux/linux/issues/236 Co-developed-by: Kees Cook Signed-off-by: Kees Cook Co-developed-by: Linus Torvalds Signed-off-by: Linus Torvalds Signed-off-by: Gustavo A. R. Silva Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Linus Torvalds --- diff --git a/Makefile b/Makefile index d83d72c26aaa9..9cf9d5c1ed8ff 100644 --- a/Makefile +++ b/Makefile @@ -789,7 +789,7 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong KBUILD_CFLAGS += $(stackp-flags-y) KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror -KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) +KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) ifdef CONFIG_CC_IS_CLANG KBUILD_CPPFLAGS += -Qunused-arguments @@ -801,10 +801,6 @@ KBUILD_CFLAGS += -Wno-gnu KBUILD_CFLAGS += -mno-global-merge else -# Warn about unmarked fall-throughs in switch statement. -# Disabled for clang while comment to attribute conversion happens and -# https://github.com/ClangBuiltLinux/linux/issues/636 is discussed. -KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=5,) # gcc inanely warns about local variables called 'main' KBUILD_CFLAGS += -Wno-main endif diff --git a/init/Kconfig b/init/Kconfig index 45bcaa8e7481d..036b750e8d8a8 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -885,6 +885,11 @@ config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH config CC_HAS_INT128 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT +config CC_IMPLICIT_FALLTHROUGH + string + default "-Wimplicit-fallthrough=5" if CC_IS_GCC + default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) + # # For architectures that know their GCC __int128 support is sound #