On 5/10/2021 9:48 PM, Alexey Kardashevskiy wrote:
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 (and probably some others,
not yet detected). To fix vdso, we do:
1. explicitly add -m(big|little)-endian to $CPP
2. (for clang) add $CLANG_FLAGS to $KBUILD_CPPFLAGS as otherwise clang
silently ignores -m(big|little)-endian if the building platform does not
support big endian (such as x86) so --prefix= is required.
While at this, remove some duplication from CPPFLAGS_vdso(32|64)
as cmd_cpp_lds_S has them anyway. It still puzzles me why we need -C
(preserve comments in the preprocessor output) flag here.
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
---
Changes:
v2:
* fix KBUILD_CPPFLAGS
* add CLANG_FLAGS to CPPFLAGS
---
Makefile | 1 +
arch/powerpc/Makefile | 3 ++-
arch/powerpc/kernel/vdso32/Makefile | 2 +-
arch/powerpc/kernel/vdso64/Makefile | 2 +-
4 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/Makefile b/Makefile
index 72af8e423f11..13acd2183d55 100644
--- a/Makefile
+++ b/Makefile
@@ -591,6 +591,7 @@ CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
endif
CLANG_FLAGS += -Werror=unknown-warning-option
KBUILD_CFLAGS += $(CLANG_FLAGS)
+KBUILD_CPPFLAGS += $(CLANG_FLAGS)
This is going to cause flag duplication, which would be nice to avoid. I
do not know if we can get away with just adding $(CLANG_FLAGS) to
KBUILD_CPPFLAGS instead of KBUILD_CFLAGS though. It seems like this
assignment might be better in arch/powerpc/Makefile with the
KBUILD_CPPFLAGS additions there.
Cheers,
Nathan
KBUILD_AFLAGS += $(CLANG_FLAGS)
export CLANG_FLAGS
endif
diff --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
diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 7d9a6fee0e3d..ea001c6df1fa 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -44,7 +44,7 @@ asflags-y := -D__VDSO32__ -s
obj-y += vdso32_wrapper.o
targets += vdso32.lds
-CPPFLAGS_vdso32.lds += -P -C -Upowerpc
+CPPFLAGS_vdso32.lds += -C
# link rule for the .so file, .lds has to be first
$(obj)/vdso32.so.dbg: $(src)/vdso32.lds $(obj-vdso32) $(obj)/vgettimeofday.o FORCE
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 2813e3f98db6..07eadba48c7a 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -30,7 +30,7 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
asflags-y := -D__VDSO64__ -s
targets += vdso64.lds
-CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)
+CPPFLAGS_vdso64.lds += -C
# link rule for the .so file, .lds has to be first
$(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE
