[PATCH bpf-next] selftest/bpf: Use -m{little,big}-endian for clang

[PATCH bpf-next] selftest/bpf: Use -m{little,big}-endian for clang

[Ilya Leoshkevich]

When cross-compiling tests from x86 to s390, the resulting BPF objects
fail to load due to endianness mismatch.

Fix by using BPF-GCC endianness check for clang as well.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/testing/selftests/bpf/Makefile | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 11ff34e7311b..59b93a5667c8 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -131,10 +131,16 @@ $(shell $(1) -v -E - </dev/null 2>&1 \
 	| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
 endef
 
+# Determine target endianness.
+IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
+			grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
+MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
+
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
 BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) 				\
 	     -I. -I./include/uapi -I$(APIDIR)				\
-	     -I$(BPFDIR) -I$(abspath $(OUTPUT)/../usr/include)
+	     -I$(BPFDIR) -I$(abspath $(OUTPUT)/../usr/include)		\
+	     $(MENDIAN)
 
 CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
 	       -Wno-compare-distinct-pointer-types
@@ -271,12 +277,8 @@ $(eval $(call DEFINE_TEST_RUNNER,test_progs,no_alu32))
 
 # Define test_progs BPF-GCC-flavored test runner.
 ifneq ($(BPF_GCC),)
-IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
-			grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
-MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
-
 TRUNNER_BPF_BUILD_RULE := GCC_BPF_BUILD_RULE
-TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc) $(MENDIAN)
+TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc)
 TRUNNER_BPF_LDFLAGS :=
 $(eval $(call DEFINE_TEST_RUNNER,test_progs,bpf_gcc))
 endif
-- 
2.23.0

Re: [PATCH bpf-next] selftest/bpf: Use -m{little,big}-endian for clang

[Andrii Nakryiko]

On Fri, Oct 25, 2019 at 11:51 AM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> When cross-compiling tests from x86 to s390, the resulting BPF objects
> fail to load due to endianness mismatch.
>
> Fix by using BPF-GCC endianness check for clang as well.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  tools/testing/selftests/bpf/Makefile | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 11ff34e7311b..59b93a5667c8 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -131,10 +131,16 @@ $(shell $(1) -v -E - </dev/null 2>&1 \
>         | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
>  endef
>
> +# Determine target endianness.
> +IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
> +                       grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
> +MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
> +
>  CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
>  BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH)                             \
>              -I. -I./include/uapi -I$(APIDIR)                           \
> -            -I$(BPFDIR) -I$(abspath $(OUTPUT)/../usr/include)
> +            -I$(BPFDIR) -I$(abspath $(OUTPUT)/../usr/include)          \
> +            $(MENDIAN)

minor nit: I'd put $(MENDIAN) next to -g and -D__TARGET_ARCH stuff and
keep a list of -Is at the end.

But besides that:

Acked-by: Andrii Nakryiko <andriin@fb.com>

>
>  CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
>                -Wno-compare-distinct-pointer-types
> @@ -271,12 +277,8 @@ $(eval $(call DEFINE_TEST_RUNNER,test_progs,no_alu32))
>
>  # Define test_progs BPF-GCC-flavored test runner.
>  ifneq ($(BPF_GCC),)
> -IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
> -                       grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
> -MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
> -
>  TRUNNER_BPF_BUILD_RULE := GCC_BPF_BUILD_RULE
> -TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc) $(MENDIAN)
> +TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc)
>  TRUNNER_BPF_LDFLAGS :=
>  $(eval $(call DEFINE_TEST_RUNNER,test_progs,bpf_gcc))
>  endif
> --
> 2.23.0
>