[Devel] [PATCH vz10 5/5] fixup! samples/bpf: fix -Wduplicate-decl-specifier and -Wmissing-declarations

[Konstantin Khorenko]

i have asked to send this patch to mainstream first.

Please, add a link to the mainstream version of the patch to https://virtuozzo.atlassian.net/browse/VSTOR-127585

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 6/25/26 20:16, Eva Kurchatova wrote:
> BPF programs include arch-specific headers, which use address space
> qualifiers for percpu variables via __seg_gs / __seg_fs, however those
> are meaningless for BPF compiler and will raise a warning
> 
> Fix this by redefining __seg_gs and __seg_fs to a no-op attribute
> 
> Additionally, enable ms-extensions, as generated vmlinux.h uses these
> for structure layout inheritance, an acceptable practice in upstream
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-127585
> Feature: fix selftests
> 
> Signed-off-by: Eva Kurchatova <eva.kurchatova at virtuozzo.com>
> ---
>  samples/bpf/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 2b93779b9cbf..39b20bb69bcd 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -339,9 +339,11 @@ CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
>  
>  $(obj)/xdp_router_ipv4.bpf.o: $(obj)/xdp_sample.bpf.o
>  
> +# Generated vmlinux.h uses ms-extensions to inherit struct layout
>  $(obj)/%.bpf.o: $(src)/%.bpf.c $(obj)/vmlinux.h $(src)/xdp_sample.bpf.h $(src)/xdp_sample_shared.h
>  	@echo "  CLANG-BPF " $@
>  	$(Q)$(CLANG) -g -O2 --target=bpf -D__TARGET_ARCH_$(SRCARCH) \
> +		-fms-extensions -Wno-microsoft-anon-tag \
>  		-Wno-compare-distinct-pointer-types -I$(srctree)/include \
>  		-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
>  		-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
> @@ -372,11 +374,13 @@ $(BPF_SKELS_LINKED): $(BPF_OBJS_LINKED) $(BPFTOOL)
>  # with native target, e.g., x64, arm64, etc. 'opt' does bpf CORE IR builtin
>  # processing (llvm12) and IR optimizations. 'llvm-dis' converts
>  # 'opt' output to IR, and finally 'llc' generates bpf byte code.
> +# Additionally, __seg_gs and __seg_fs are ignored in BPF code
>  $(obj)/%.o: $(src)/%.c
>  	@echo "  CLANG-bpf " $@
>  	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(BPF_EXTRA_CFLAGS) \
>  		-I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \
>  		-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
> +		-U__seg_gs -D__seg_gs= -U__seg_fs -D__seg_fs= \
>  		-D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \
>  		-D__TARGET_ARCH_$(SRCARCH) -Wno-compare-distinct-pointer-types \
>  		-Wno-gnu-variable-sized-type-not-at-end \