selftests/bpf: Fix field existence CO-RE reloc tests
[ Upstream commit 5a30eb23 ] Negative field existence cases for have a broken assumption that FIELD_EXISTS CO-RE relo will fail for fields that match the name but have incompatible type signature. That's not how CO-RE relocations generally behave. Types and fields that match by name but not by expected type are treated as non-matching candidates and are skipped. Error later is reported if no matching candidate was found. That's what happens for most relocations, but existence relocations (FIELD_EXISTS and TYPE_EXISTS) are more permissive and they are designed to return 0 or 1, depending if a match is found. This allows to handle name-conflicting but incompatible types in BPF code easily. Combined with ___flavor suffixes, it's possible to handle pretty much any structural type changes in kernel within the compiled once BPF source code. So, long story short, negative field existence test cases are invalid in their assumptions, so this patch reworks them into a single consolidated positive case that doesn't match any of the fields. Fixes: c7566a69 ("selftests/bpf: Add field existence CO-RE relocs tests") Reported-by: Lorenz Bauer <lmb@cloudflare.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Lorenz Bauer <lmb@cloudflare.com> Link: https://lore.kernel.org/bpf/20210426192949.416837-5-andrii@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org>
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