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selftests/bpf: fix static assert compilation issue for test_cls_*.c

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[ Upstream commit 416c6d0124 ]

commit bdeeed3498 ("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: bdeeed3498 ("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>
This commit is contained in:
Alan Maguire 2023-08-02 08:39:06 +01:00 committed by Greg Kroah-Hartman
parent f12a425a7c
commit 713f9c0308
1 changed files with 9 additions and 0 deletions
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9
tools/testing/selftests/bpf/progs/test_cls_redirect.h
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@ -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;