Hi Nick 2017-11-08 4:46 GMT+09:00 Nick Desaulniers <ndesaulniers@xxxxxxxxxx>: > From: Chris Fries <cfries@xxxxxxxxxx> > > Set the clang KBUILD_CFLAGS up before including arch/ Makefiles, > so that ld-options (etc.) can work correctly. > > This fixes errors with clang such as ld-options trying to CC > against your host architecture, but LD trying to link against > your target architecture. OK. Your previous patch was applied (and we have not received 0-day report so far), so this makes sense now. > We didn't notice this problem on Android, because we took the original > LLVMLinux patch into our 4.4 kernels, which did not have this issue. We > ran into this taking the proper upstream patch on newer kernel versions. > The original LLVMLinux patch can be seen at: > > http://git.linuxfoundation.org/?p=llvmlinux/kernel.git;a=blobdiff;f=Makefile;h=389006c4ef494cda3a1ee52bf355618673ab4f31;hp=e41a3356abee83f08288362950bfceebd25ec3c2;hb=ef9126da11b18ff34eb1f01561f53c378860336c;hpb=f800c25b7a762d445ba1439a2428c8362157eba6 > > It seems that when the patch was re-upstreamed, a V2 was requested that > moved the definition of Clang's target triple to be later in the top > level Makefile than the inclusion of the arch specific Makefile, > breaking macros like ld-option when cross compiling. V2 was requested > at: > > https://lkml.org/lkml/2017/4/21/116 IMO, this description is not helpful in any way in upstream. Moreover, 785f11aa595bc3d4e74096cbd598ada54ecc0d81 did not break anything. It sound unfair to me. > diff --git a/Makefile b/Makefile > index a7476e6934f1..d349734c7ef7 100644 > --- a/Makefile > +++ b/Makefile > @@ -472,6 +472,38 @@ ifneq ($(KBUILD_SRC),) > $(srctree) $(objtree) $(VERSION) $(PATCHLEVEL) > endif > > +ifeq ($(cc-name),clang) > +ifneq ($(CROSS_COMPILE),) > +CLANG_TARGET := -target $(notdir $(CROSS_COMPILE:%-=%)) > +GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..) > +endif > +ifneq ($(GCC_TOOLCHAIN),) > +CLANG_GCC_TC := -gcc-toolchain $(GCC_TOOLCHAIN) > +endif > +KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) > +KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) > +KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable) > +KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) > +KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > +KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) > +# Quiet clang warning: comparison of unsigned expression < 0 is always false > +KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) > +# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the > +# source of a reference will be _MergedGlobals and not on of the whitelisted names. > +# See modpost pattern 2 > +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) > +else > + > +# These warnings generated too much noise in a regular build. > +# Use make W=1 to enable them (see scripts/Makefile.extrawarn) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > +endif > + Could you move this a bit later, please? # These warnings generated too much noise in a regular build. # Use make W=1 to enable them (see scripts/Makefile.extrawarn) KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) endif << INSERT HERE >> # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default # values of the respective KBUILD_* variables ARCH_CPPFLAGS := ARCH_AFLAGS := ARCH_CFLAGS := include arch/$(SRCARCH)/Makefile arch/$(SRCARCH)/Makefile is included for config targets for KBUILD_DEFCONFIG, but no reason to compute compiler flags. I want to cut unnecessary cc-option parsing. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
