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 <email address hidden>
Signed-off-by: Alan Maguire <email address hidden>
Tested-by: Yipeng Zou <email address hidden>
Acked-by: Yonghong Song <email address hidden>
Link: https://<email address hidden>
Signed-off-by: Alexei Starovoitov <email address hidden>
(cherry picked from commit 416c6d01244ecbf0abfdb898fd091b50ef951b48)
Signed-off-by: Po-Hsu Lin <email address hidden>
Acked-by: Stefan Bader <email address hidden>
Acked-by: Roxana Nicolescu <email address hidden>
Signed-off-by: Stefan Bader <email address hidden>
