6.4-stable review patch. If anyone has any objections, please let me know.
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From: Alan Maguire alan.maguire@oracle.com
[ 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 colm.harrington@oracle.com Signed-off-by: Alan Maguire alan.maguire@oracle.com Tested-by: Yipeng Zou zouyipeng@huawei.com Acked-by: Yonghong Song yonghong.song@linux.dev Link: https://lore.kernel.org/r/20230802073906.3197480-1-alan.maguire@oracle.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 76eab0aacba0c..233b089d1fbac 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 <linux/ipv6.h> #include <linux/udp.h>
+/* 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;