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resolve_btfids: Deduplicate BTF after btf2btf transformations

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btf2btf() adds new types to the BTF: the KF_IMPLICIT_ARGS transform
synthesizes an _impl FUNC together with its FUNC_PROTO and copies of the
kfunc's decl tags. Nothing deduplicates them afterwards. pahole runs
btf__dedup() on its own output, but that happens before resolve_btfids
sees the BTF, so any type the tool itself creates is emitted as-is, even
when a structurally identical type is already present.

Call btf__dedup() at the start of finalize_btf(), so that base
distillation and the by-name sort both operate on the canonical set of
types.

On an x86_64 build with the BPF selftests config this removes 17
duplicate FUNC_PROTOs from vmlinux BTF.

The dedup call increases runtime of resolve_btfids on vmlinux by 30-40%.
The performance hit is an acceptable cost to keep kernel BTF deduped [1].

[1] https://lore.kernel.org/bpf/986e6f4e-4b51-4440-a37c-9624906d7370@linux.dev/

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://patch.msgid.link/20260807032029.78092-2-ihor.solodrai@linux.dev
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
This commit is contained in:
Ihor Solodrai
2026-08-06 20:20:24 -07:00
committed by Eduard Zingerman
parent 8c7f55d60a
commit 3d72aca40b
1 changed files with 6 additions and 0 deletions
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6
tools/bpf/resolve_btfids/main.c
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@@ -1379,6 +1379,12 @@ static int finalize_btf(struct object *obj)
struct btf *base_btf = obj->base_btf, *btf = obj->btf;
int err;
err = btf__dedup(obj->btf, NULL);
if (err) {
pr_err("FAILED to dedup BTF: %s\n", strerror(errno));
goto out_err;
}
if (obj->base_btf && obj->distill_base) {
err = btf__distill_base(obj->btf, &base_btf, &btf);
if (err) {