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Date: Wed, 21 Feb 2024 16:11:36 +0100
From: Nicolas Schier <nicolas@fjasle.eu>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Thomas Gleixner <tglx@linutronix.de>, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 1/2] kbuild: change tool coverage variables to take the
 path relative to $(obj)
Message-ID: <ZdYSqKnJqiiBnQHu@bergen.fjasle.eu>
References: <20240217055504.2059803-1-masahiroy@kernel.org>
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On Sat 17 Feb 2024 14:55:03 GMT, Masahiro Yamada wrote:
> Commit 54b8ae66ae1a ("kbuild: change *FLAGS_<basetarget>.o to take the
> path relative to $(obj)") changed the syntax of per-file compiler flags.
>=20
> The situation is the same for the following variables:
>=20
>   OBJECT_FILES_NON_STANDARD_<basetarget>.o
>   GCOV_PROFILE_<basetarget>.o
>   KASAN_SANITIZE_<basetarget>.o
>   KMSAN_SANITIZE_<basetarget>.o
>   KMSAN_ENABLE_CHECKS_<basetarget>.o
>   UBSAN_SANITIZE_<basetarget>.o
>   KCOV_INSTRUMENT_<basetarget>.o
>   KCSAN_SANITIZE_<basetarget>.o
>   KCSAN_INSTRUMENT_BARRIERS_<basetarget>.o
>=20
> The <basetarget> is the filename of the target with its directory and
> suffix stripped.
>=20
> This syntax comes into a trouble when two files with the same basename
> appear in one Makefile, for example:
>=20
>   obj-y +=3D dir1/foo.o
>   obj-y +=3D dir2/foo.o
>   OBJECT_FILES_NON_STANDARD_foo.o :=3D y
>=20
> OBJECT_FILES_NON_STANDARD_foo.o is applied to both dir1/foo.o and
> dir2/foo.o. This syntax is not flexbile enough to handle cases where
> one of them is a standard object, but the other is not.
>=20
> It is more sensible to use the relative path to the Makefile, like this:
>=20
>   obj-y +=3D dir1/foo.o
>   OBJECT_FILES_NON_STANDARD_dir1/foo.o :=3D y
>   obj-y +=3D dir2/foo.o
>   OBJECT_FILES_NON_STANDARD_dir2/foo.o :=3D y
>=20
> To maintain the current behavior, I made adjustments to two Makefiles:
>=20
>  - arch/x86/entry/vdso/Makefile, which compiles vclock_gettime.o and
>    vdso32/vclock_gettime.o
>=20
>  - arch/x86/kvm/Makefile, which compiles vmx/vmenter.o and svm/vmenter.o
>=20
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>=20
>  arch/x86/entry/vdso/Makefile |  2 ++
>  arch/x86/kvm/Makefile        |  3 ++-
>  scripts/Makefile.build       |  2 +-
>  scripts/Makefile.lib         | 16 ++++++++--------
>  4 files changed, 13 insertions(+), 10 deletions(-)
>=20
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index 7a97b17f28b7..148adfdb2325 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -9,7 +9,9 @@ include $(srctree)/lib/vdso/Makefile
>  # Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE			:=3D n
>  KMSAN_SANITIZE_vclock_gettime.o :=3D n
> +KMSAN_SANITIZE_vdso32/vclock_gettime.o	:=3D n
>  KMSAN_SANITIZE_vgetcpu.o	:=3D n
> +KMSAN_SANITIZE_vdso32/vgetcpu.o	:=3D n
> =20
>  UBSAN_SANITIZE			:=3D n
>  KCSAN_SANITIZE			:=3D n
> diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
> index 475b5fa917a6..a88bb14266b6 100644
> --- a/arch/x86/kvm/Makefile
> +++ b/arch/x86/kvm/Makefile
> @@ -4,7 +4,8 @@ ccflags-y +=3D -I $(srctree)/arch/x86/kvm
>  ccflags-$(CONFIG_KVM_WERROR) +=3D -Werror
> =20
>  ifeq ($(CONFIG_FRAME_POINTER),y)
> -OBJECT_FILES_NON_STANDARD_vmenter.o :=3D y
> +OBJECT_FILES_NON_STANDARD_vmx/vmenter.o :=3D y
> +OBJECT_FILES_NON_STANDARD_svm/vmenter.o :=3D y
>  endif
> =20
>  include $(srctree)/virt/kvm/Makefile.kvm
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 4971f54c855e..256db2a0e984 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -214,7 +214,7 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
>  # 'OBJECT_FILES_NON_STANDARD_foo.o :=3D 'y': skip objtool checking for a=
 file
>  # 'OBJECT_FILES_NON_STANDARD_foo.o :=3D 'n': override directory skip for=
 a file
> =20
> -is-standard-object =3D $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD=
_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
> +is-standard-object =3D $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD=
_$(target-stem).o)$(OBJECT_FILES_NON_STANDARD)n),y)
> =20
>  $(obj)/%.o: objtool-enabled =3D $(if $(is-standard-object),$(if $(delay-=
objtool),$(is-single-obj-m),y))
> =20
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index b35d39022a30..328c0d77ed48 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -154,7 +154,7 @@ _cpp_flags     =3D $(KBUILD_CPPFLAGS) $(cppflags-y) $=
(CPPFLAGS_$(target-stem).lds)
>  #
>  ifeq ($(CONFIG_GCOV_KERNEL),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -		$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_AL=
L)), \
> +		$(GCOV_PROFILE_$(target-stem).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_A=
LL)), \
>  		$(CFLAGS_GCOV))
>  endif
> =20
> @@ -165,29 +165,29 @@ endif
>  ifeq ($(CONFIG_KASAN),y)
>  ifneq ($(CONFIG_KASAN_HW_TAGS),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -		$(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \
> +		$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)y), \
>  		$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
>  endif
>  endif
> =20
>  ifeq ($(CONFIG_KMSAN),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -		$(KMSAN_SANITIZE_$(basetarget).o)$(KMSAN_SANITIZE)y), \
> +		$(KMSAN_SANITIZE_$(target-stem).o)$(KMSAN_SANITIZE)y), \
>  		$(CFLAGS_KMSAN))
>  _c_flags +=3D $(if $(patsubst n%,, \
> -		$(KMSAN_ENABLE_CHECKS_$(basetarget).o)$(KMSAN_ENABLE_CHECKS)y), \
> +		$(KMSAN_ENABLE_CHECKS_$(target-stem).o)$(KMSAN_ENABLE_CHECKS)y), \
>  		, -mllvm -msan-disable-checks=3D1)
>  endif
> =20
>  ifeq ($(CONFIG_UBSAN),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -		$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANIT=
IZE_ALL)), \
> +		$(UBSAN_SANITIZE_$(target-stem).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANI=
TIZE_ALL)), \
>  		$(CFLAGS_UBSAN))
>  endif
> =20
>  ifeq ($(CONFIG_KCOV),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -	$(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INSTR=
UMENT_ALL)), \
> +	$(KCOV_INSTRUMENT_$(target-stem).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INST=
RUMENT_ALL)), \
>  	$(CFLAGS_KCOV))
>  endif
> =20
> @@ -197,12 +197,12 @@ endif
>  #
>  ifeq ($(CONFIG_KCSAN),y)
>  _c_flags +=3D $(if $(patsubst n%,, \
> -	$(KCSAN_SANITIZE_$(basetarget).o)$(KCSAN_SANITIZE)y), \
> +	$(KCSAN_SANITIZE_$(target-stem).o)$(KCSAN_SANITIZE)y), \
>  	$(CFLAGS_KCSAN))
>  # Some uninstrumented files provide implied barriers required to avoid f=
alse
>  # positives: set KCSAN_INSTRUMENT_BARRIERS for barrier instrumentation o=
nly.
>  _c_flags +=3D $(if $(patsubst n%,, \
> -	$(KCSAN_INSTRUMENT_BARRIERS_$(basetarget).o)$(KCSAN_INSTRUMENT_BARRIERS=
)n), \
> +	$(KCSAN_INSTRUMENT_BARRIERS_$(target-stem).o)$(KCSAN_INSTRUMENT_BARRIER=
S)n), \
>  	-D__KCSAN_INSTRUMENT_BARRIERS__)
>  endif
> =20
> --=20
> 2.40.1
>=20

Looks good to me!

Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

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