In some cases compiler seems to generate distinct DWARF types for identical
arrays within the same CU. That seems like a bug, but it's already out there
and breaks type graph equivalence checks, so accommodate it anyway by checking
for identical arrays, regardless of their type ID.
Acked-by: Song Liu <songliubrav...@fb.com>
Signed-off-by: Andrii Nakryiko <and...@kernel.org>
---
tools/lib/bpf/btf.c | 27 +++++++++++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 8d04d9becb67..2d0d064c6d31 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -3785,6 +3785,19 @@ static inline __u16 btf_fwd_kind(struct btf_type *t)
return btf_kflag(t) ? BTF_KIND_UNION : BTF_KIND_STRUCT;
}
+/* Check if given two types are identical ARRAY definitions */
+static int btf_dedup_identical_arrays(struct btf_dedup *d, __u32 id1, __u32
id2)
+{
+ struct btf_type *t1, *t2;
+
+ t1 = btf_type_by_id(d->btf, id1);
+ t2 = btf_type_by_id(d->btf, id2);
+ if (!btf_is_array(t1) || !btf_is_array(t2))
+ return 0;
+
+ return btf_equal_array(t1, t2);
+}
+
/*
* Check equivalence of BTF type graph formed by candidate struct/union (we'll
* call it "candidate graph" in this description for brevity) to a type graph
@@ -3895,8 +3908,18 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32
cand_id,
canon_id = resolve_fwd_id(d, canon_id);
hypot_type_id = d->hypot_map[canon_id];
- if (hypot_type_id <= BTF_MAX_NR_TYPES)
- return hypot_type_id == cand_id;
+ if (hypot_type_id <= BTF_MAX_NR_TYPES) {
+ /* In some cases compiler will generate different DWARF types
+ * for *identical* array type definitions and use them for
+ * different fields within the *same* struct. This breaks type
+ * equivalence check, which makes an assumption that candidate
+ * types sub-graph has a consistent and deduped-by-compiler
+ * types within a single CU. So work around that by explicitly
+ * allowing identical array types here.
+ */
+ return hypot_type_id == cand_id ||
+ btf_dedup_identical_arrays(d, hypot_type_id, cand_id);
+ }
if (btf_dedup_hypot_map_add(d, canon_id, cand_id))
return -ENOMEM;
--
2.24.1
