From 90978b2ff422b07724468ad2ff686dd50288b309 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Wed, 2 Aug 2023 08:39:06 +0100 Subject: [PATCH] selftests/bpf: fix static assert compilation issue for test_cls_*.c [ Upstream commit 416c6d01244ecbf0abfdb898fd091b50ef951b48 ] commit bdeeed3498c7 ("libbpf: fix offsetof() and container_of() to work with CO-RE") ...was backported to stable trees such as 5.15. The problem is that with older LLVM/clang (14/15) - which is often used for older kernels - we see compilation failures in BPF selftests now: In file included from progs/test_cls_redirect_subprogs.c:2: progs/test_cls_redirect.c:90:2: error: static assertion expression is not an integral constant expression sizeof(flow_ports_t) != ^~~~~~~~~~~~~~~~~~~~~~~ progs/test_cls_redirect.c:91:3: note: cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression offsetofend(struct bpf_sock_tuple, ipv4.dport) - ^ progs/test_cls_redirect.c:32:3: note: expanded from macro 'offsetofend' (offsetof(TYPE, MEMBER) + sizeof((((TYPE *)0)->MEMBER))) ^ tools/testing/selftests/bpf/tools/include/bpf/bpf_helpers.h:86:33: note: expanded from macro 'offsetof' ^ In file included from progs/test_cls_redirect_subprogs.c:2: progs/test_cls_redirect.c:95:2: error: static assertion expression is not an integral constant expression sizeof(flow_ports_t) != ^~~~~~~~~~~~~~~~~~~~~~~ progs/test_cls_redirect.c:96:3: note: cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression offsetofend(struct bpf_sock_tuple, ipv6.dport) - ^ progs/test_cls_redirect.c:32:3: note: expanded from macro 'offsetofend' (offsetof(TYPE, MEMBER) + sizeof((((TYPE *)0)->MEMBER))) ^ tools/testing/selftests/bpf/tools/include/bpf/bpf_helpers.h:86:33: note: expanded from macro 'offsetof' ^ 2 errors generated. make: *** [Makefile:594: tools/testing/selftests/bpf/test_cls_redirect_subprogs.bpf.o] Error 1 The problem is the new offsetof() does not play nice with static asserts. Given that the context is a static assert (and CO-RE relocation is not needed at compile time), offsetof() usage can be replaced by restoring the original offsetof() definition as __builtin_offsetof(). Fixes: bdeeed3498c7 ("libbpf: fix offsetof() and container_of() to work with CO-RE") Reported-by: Colm Harrington Signed-off-by: Alan Maguire Tested-by: Yipeng Zou Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20230802073906.3197480-1-alan.maguire@oracle.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- tools/testing/selftests/bpf/progs/test_cls_redirect.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/test_cls_redirect.h b/tools/testing/selftests/bpf/progs/test_cls_redirect.h index 76eab0a..233b089 100644 --- a/tools/testing/selftests/bpf/progs/test_cls_redirect.h +++ b/tools/testing/selftests/bpf/progs/test_cls_redirect.h @@ -12,6 +12,15 @@ #include #include +/* offsetof() is used in static asserts, and the libbpf-redefined CO-RE + * friendly version breaks compilation for older clang versions <= 15 + * when invoked in a static assert. Restore original here. + */ +#ifdef offsetof +#undef offsetof +#define offsetof(type, member) __builtin_offsetof(type, member) +#endif + struct gre_base_hdr { uint16_t flags; uint16_t protocol; -- 2.7.4