GCC implements the -Wno-address-of-packed-member warning, which is
enabled by -Wall, that warns about taking the address of a packed
struct field when it can lead to an "unaligned" address. Clang
doesn't support this warning.
This triggers the following errors (-Werror) when building three
particular BPF selftests with GCC:
progs/test_cls_redirect.c
986 | if (ipv4_is_fragment((void *)&encap->ip)) {
progs/test_cls_redirect_dynptr.c
410 | pkt_ipv4_checksum((void *)&encap_gre->ip);
progs/test_cls_redirect.c
521 | pkt_ipv4_checksum((void *)&encap_gre->ip);
progs/test_tc_tunnel.c
232 | set_ipv4_csum((void *)&h_outer.ip);
These warnings do not signal any real problem in the tests as far as I
can see.
This patch modifies selftests/bpf/Makefile to build these particular
selftests with -Wno-address-of-packed-member when bpf-gcc is used.
Note that we cannot use diagnostics pragmas (which are generally
preferred if I understood properly in a recent BPF office hours)
because Clang doesn't support these warnings.
Tested in bpf-next master.
No regressions.
Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxxxx>
Cc: Eduard Zingerman <eddyz87@xxxxxxxxx>
Cc: David Faust <david.faust@xxxxxxxxxx>
Cc: Cupertino Miranda <cupertino.miranda@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 1a3654bcb5dd..036473060bae 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -73,6 +73,12 @@ progs/btf_dump_test_case_namespacing.c-CFLAGS := -Wno-error
progs/btf_dump_test_case_packing.c-CFLAGS := -Wno-error
progs/btf_dump_test_case_padding.c-CFLAGS := -Wno-error
progs/btf_dump_test_case_syntax.c-CFLAGS := -Wno-error
+
+# The following selftests take the address of packed struct fields in
+# a way that can lead to unaligned addresses. GCC warns about this.
+progs/test_cls_redirect.c-CFLAGS := -Wno-address-of-packed-member
+progs/test_cls_redirect_dynpr.c-CFLAGS := -Wno-address-of-packed-member
+progs/test_tc_tunnel.c-CFLAGS := -Wno-address-of-packed-member
endif
ifneq ($(CLANG_CPUV4),)
--
2.30.2
