From: Yonghong Song <yhs@fb.com>
Date: Mon, 15 Nov 2021 08:39:37 -0800
Subject: libbpf: Fix a couple of missed btf_type_tag handling in btf.c
Patch-mainline: v5.17-rc1
Git-commit: 69a055d546156adc6f7727ec981f721d5ba9231a
References: jsc#PED-1368
Commit 2dc1e488e5cd ("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: 2dc1e488e5cd ("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
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/btf.c | 2 ++
1 file changed, 2 insertions(+)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -610,6 +610,7 @@ __s64 btf__resolve_size(const struct btf
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
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);