This patch modifies selftests/bpf/Makefile to pass -Wno-attributes to GCC. This is because of the following attributes which are ignored: - btf_decl_tag - btf_type_tag There are many of these. At the moment none of these are recognized/handled by gcc-bpf. We are aware that btf_decl_tag is necessary for some of the selftest harness to communicate test failure/success. Support for it is in progress in GCC upstream: https://gcc.gnu.org/pipermail/gcc-patches/2024-May/650482.html However, the GCC master branch is not yet open, so the series above (currently under review upstream) wont be able to make it there until 14.1 gets released, probably mid next week. As for btf_type_tag, more extensive work will be needed in GCC upstream to support it in both BTF and DWARF. We have a WIP big patch for that, but that is not needed to compile/build the selftests. - used There are SEC macros defined in the selftests as: #define SEC(N) __attribute__((section(N),used)) The SEC macro is used for both functions and global variables. According to the GCC documentation `used' attribute is really only meaningful for functions, and it warns when the attribute is used for other global objects, like for example ctl_array in test_xdp_noinline.c. Ignoring this is bening. - visibility In progs/cpumask_common.h:13 there is: #define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8))) private(MASK) static struct bpf_cpumask __kptr * global_mask; The __hidden macro defines to: tools/lib/bpf/bpf_helpers.h:#define __hidden __attribute__((visibility("hidden"))) GCC emits an "attribute ignored" warning because static implies hidden visibility. Ignoring this warning is benign. An alternative would be to make global_mask as non-static. - align_value In progs/test_cls_redirect.c:127 there is: typedef uint8_t *net_ptr __attribute__((align_value(8))); GCC warns that it is ignoring this attribute, because it is not implemented by GCC. I think ignoring this attribute in GCC is bening, because according to the clang documentation [1] its purpose seems to be merely declarative and doesn't seem to translate into extra checks at run-time, only to pehaps better optimized code ("runtime behavior is undefined if the pointed memory object is not aligned to the specified alignment"). [1] https://clang.llvm.org/docs/AttributeReference.html#align-value Tested in bpf-next master. Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> Cc: david.faust@xxxxxxxxxx Cc: cupertino.miranda@xxxxxxxxxx Cc: Yonghong Song <yonghong.song@xxxxxxxxx> Cc: Eduard Zingerman <eddyz87@xxxxxxxxx> --- tools/testing/selftests/bpf/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index ba28d42b74db..5d9c906bc3cb 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -431,7 +431,7 @@ endef # Build BPF object using GCC define GCC_BPF_BUILD_RULE $(call msg,GCC-BPF,$(TRUNNER_BINARY),$2) - $(Q)$(BPF_GCC) $3 -O2 -c $1 -o $2 + $(Q)$(BPF_GCC) $3 -Wno-attributes -O2 -c $1 -o $2 endef SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c -- 2.30.2
