Re: [PATCH kernel v3] powerpc/makefile: Do not redefine $(CPP) for preprocessor
From: Nathan Chancellor <nathan@kernel.org>
Date: 2021-05-13 18:59:19
Also in:
linux-kbuild, lkml
On 5/13/2021 4:59 AM, Alexey Kardashevskiy wrote:
quoted hunk ↗ jump to hunk
The $(CPP) (do only preprocessing) macro is already defined in Makefile. However POWERPC redefines it and adds $(KBUILD_CFLAGS) which results in flags duplication. Which is not a big deal by itself except for the flags which depend on other flags and the compiler checks them as it parses the command line. Specifically, scripts/Makefile.build:304 generates ksyms for .S files. If clang+llvm+sanitizer are enabled, this results in -emit-llvm-bc -fno-lto -flto -fvisibility=hidden \ -fsanitize=cfi-mfcall -fno-lto ... in the clang command line and triggers error: clang-13: error: invalid argument '-fsanitize=cfi-mfcall' only allowed with '-flto' This removes unnecessary CPP redefinition. Which works fine as in most place KBUILD_CFLAGS is passed to $CPP except arch/powerpc/kernel/vdso64/vdso(32|64).lds. To fix vdso, this does: 1. add -m(big|little)-endian to $CPP 2. add target to $KBUILD_CPPFLAGS as otherwise clang ignores -m(big|little)-endian if the building platform does not support big endian (such as x86). Signed-off-by: Alexey Kardashevskiy <redacted> --- Changes: v3: * moved vdso cleanup in a separate patch * only add target to KBUILD_CPPFLAGS for CLANG v2: * fix KBUILD_CPPFLAGS * add CLANG_FLAGS to CPPFLAGS --- Makefile | 1 + arch/powerpc/Makefile | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-)diff --git a/Makefile b/Makefile index 15b6476d0f89..5b545bef7653 100644 --- a/Makefile +++ b/Makefile@@ -576,6 +576,7 @@ CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head - ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) ifneq ($(CROSS_COMPILE),) CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) +KBUILD_CPPFLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
You can avoid the duplication here by just doing: KBUILD_CPPFLAGS += $(CLANG_FLAGS) I am still not super happy about the flag duplication but I am not sure I can think of a better solution. If KBUILD_CPPFLAGS are always included when building .o files, maybe we should just add $(CLANG_FLAGS) to KBUILD_CPPFLAGS instead of KBUILD_CFLAGS?
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endif ifeq ($(LLVM_IAS),1) CLANG_FLAGS += -integrated-asdiff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index 3212d076ac6a..306bfd2797ad 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile@@ -76,6 +76,7 @@ endif ifdef CONFIG_CPU_LITTLE_ENDIAN KBUILD_CFLAGS += -mlittle-endian +KBUILD_CPPFLAGS += -mlittle-endian KBUILD_LDFLAGS += -EL LDEMULATION := lppc GNUTARGET := powerpcle@@ -83,6 +84,7 @@ MULTIPLEWORD := -mno-multiple KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-save-toc-indirect) else KBUILD_CFLAGS += $(call cc-option,-mbig-endian) +KBUILD_CPPFLAGS += $(call cc-option,-mbig-endian) KBUILD_LDFLAGS += -EB LDEMULATION := ppc GNUTARGET := powerpc@@ -208,7 +210,6 @@ KBUILD_CPPFLAGS += -I $(srctree)/arch/$(ARCH) $(asinstr) KBUILD_AFLAGS += $(AFLAGS-y) KBUILD_CFLAGS += $(call cc-option,-msoft-float) KBUILD_CFLAGS += -pipe $(CFLAGS-y) -CPP = $(CC) -E $(KBUILD_CFLAGS) CHECKFLAGS += -m$(BITS) -D__powerpc__ -D__powerpc$(BITS)__ ifdef CONFIG_CPU_BIG_ENDIAN