On 5/7/26 17:58, 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
Dot is missing.
Fix this by redefining __seg_gs and __seg_fs to a no-op attribute
Dot is missing.
Additionally, enable ms-extensions, as generated vmlinux.h uses these
for structure layout inheritance, an acceptable practice in upstream
Dot i missing.
https://virtuozzo.atlassian.net/browse/VSTOR-127585
feature: fix kselftests
Signed-off-by: Eva Kurchatova <[email protected]>
---
samples/bpf/Makefile | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 7afe040cf43b..fa92d2494b96 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -363,9 +363,11 @@ 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_$(SRCARCH) \
+ -fms-extensions -Wno-microsoft-anon-tag \
1. ms does not have "-fms-extensions". Why it's not needed there? May be they went another way to fix
that?
2. Why do we need "-Wno-microsoft-anon-tag" here?
Does "-fms-extensions" enabled those warnings? If yes, please describe that.
If no - why to disabled those warnings?
-Wno-compare-distinct-pointer-types -I$(srctree)/include \
-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
@@ -396,11 +398,13 @@ $(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) \
+ -U__seg_gs -D__seg_gs= -U__seg_fs -D__seg_fs= \
Why ms is missing this patch?
-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 \
AFAIS here we have 2 completely unrelated changes, so please, split the patch
into 2 parts.
Or explain why those changes should go together.
In general i would say - let's push such patches to mainstream first and backport them to our kernel
after they are accepted in mainstream.
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