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libbpf: Fix a couple of missed btf_type_tag handling in btf.c

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Commit 2dc1e488e5 ("libbpf: Support BTF_KIND_TYPE_TAG") added the
BTF_KIND_TYPE_TAG support. But to test vmlinux build with ...

  #define __user __attribute__((btf_type_tag("user")))

... I needed to sync libbpf repo and manually copy libbpf sources to
pahole. To simplify process, I used BTF_KIND_RESTRICT to simulate the
BTF_KIND_TYPE_TAG with vmlinux build as "restrict" modifier is barely
used in kernel.

But this approach missed one case in dedup with structures where
BTF_KIND_RESTRICT is handled and BTF_KIND_TYPE_TAG is not handled in
btf_dedup_is_equiv(), and this will result in a pahole dedup failure.
This patch fixed this issue and a selftest is added in the subsequent
patch to test this scenario.

The other missed handling is in btf__resolve_size(). Currently the compiler
always emit like PTR->TYPE_TAG->... so in practice we don't hit the missing
BTF_KIND_TYPE_TAG handling issue with compiler generated code. But lets
add case BTF_KIND_TYPE_TAG in the switch statement to be future proof.

Fixes: 2dc1e488e5 ("libbpf: Support BTF_KIND_TYPE_TAG")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211115163937.3922235-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2021-11-15 08:39:37 -08:00 committed by Daniel Borkmann
parent e47d0bf800
commit 69a055d546
1 changed files with 2 additions and 0 deletions
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2
tools/lib/bpf/btf.c
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@ -610,6 +610,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
case BTF_KIND_RESTRICT:
case BTF_KIND_VAR:
case BTF_KIND_DECL_TAG:
case BTF_KIND_TYPE_TAG:
type_id = t->type;
break;
case BTF_KIND_ARRAY:
@ -4023,6 +4024,7 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_TYPE_TAG:
if (cand_type->info != canon_type->info)
return 0;
return btf_dedup_is_equiv(d, cand_type->type, canon_type->type);