[bpf,2/2] selftests/bpf: Pass target triple to get_sys_includes macro

From: Björn Töpel <bjorn@rivosinc.com>

When cross-compiling [1], the get_sys_includes make macro should use
the target system include path, and not the build hosts system include
path.

Make clang honor the CROSS_COMPILE triple.

[1] e.g. "ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make"

Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
---
 tools/testing/selftests/bpf/Makefile | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

On Tue, 15 Nov 2022 at 19:21, Björn Töpel <bjorn@kernel.org> wrote:
>
> From: Björn Töpel <bjorn@rivosinc.com>
>
> When cross-compiling [1], the get_sys_includes make macro should use
> the target system include path, and not the build hosts system include
> path.
>
> Make clang honor the CROSS_COMPILE triple.
>
> [1] e.g. "ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make"
>
> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

For both patches.
Tested-by: Anders Roxell <anders.roxell@linaro.org>

> ---
>  tools/testing/selftests/bpf/Makefile | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 8f8ede30e94e..a2a1eae75820 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -309,9 +309,9 @@ $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids        \
>  # Use '-idirafter': Don't interfere with include mechanics except where the
>  # build would have failed anyways.
>  define get_sys_includes
> -$(shell $(1) -v -E - </dev/null 2>&1 \
> +$(shell $(1) $(2) -v -E - </dev/null 2>&1 \
>         | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
> -$(shell $(1) -dM -E - </dev/null | grep '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
> +$(shell $(1) $(2) -dM -E - </dev/null | grep '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
>  endef
>
>  # Determine target endianness.
> @@ -319,7 +319,11 @@ 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))
> +ifneq ($(CROSS_COMPILE),)
> +CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
> +endif
> +
> +CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))

Maybe it would make sense to move this trick into selftests/lib.mk
since there are more Makefiles that
would benefit from this, like tc-testing or net/bpf to name a few.

Cheers,
Anders

>  BPF_CFLAGS = -g -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)          \
>              -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)                   \
>              -I$(abspath $(OUTPUT)/../usr/include)
> @@ -539,7 +543,7 @@ $(eval $(call DEFINE_TEST_RUNNER,test_progs,no_alu32))
>  # Define test_progs BPF-GCC-flavored test runner.
>  ifneq ($(BPF_GCC),)
>  TRUNNER_BPF_BUILD_RULE := GCC_BPF_BUILD_RULE
> -TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc)
> +TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(call get_sys_includes,gcc,)
>  $(eval $(call DEFINE_TEST_RUNNER,test_progs,bpf_gcc))
>  endif
>
> --
> 2.37.2
>