forked from pool/libbpf
4fc55ab17f
issue since the introduction of TYPEOF_UNQUAL * add 0001-libbpf-Add-identical-pointer-detection-to-btf_dedup_.patch OBS-URL: https://build.opensuse.org/package/show/devel:libraries:c_c++/libbpf?expand=0&rev=55
68 lines
2.3 KiB
Diff
68 lines
2.3 KiB
Diff
From 1f7c2f78d74e239ee4fce03f9a858062ae3d5512 Mon Sep 17 00:00:00 2001
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From: Alan Maguire <alan.maguire@oracle.com>
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Date: Tue, 29 Apr 2025 17:10:42 +0100
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Subject: [PATCH 1/1] libbpf: Add identical pointer detection to
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btf_dedup_is_equiv()
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Recently as a side-effect of
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commit ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro")
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issues were observed in deduplication between modules and kernel BTF
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such that a large number of kernel types were not deduplicated so
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were found in module BTF (task_struct, bpf_prog etc). The root cause
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appeared to be a failure to dedup struct types, specifically those
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with members that were pointers with __percpu annotations.
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The issue in dedup is at the point that we are deduplicating structures,
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we have not yet deduplicated reference types like pointers. If multiple
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copies of a pointer point at the same (deduplicated) integer as in this
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case, we do not see them as identical. Special handling already exists
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to deal with structures and arrays, so add pointer handling here too.
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Reported-by: Alexei Starovoitov <ast@kernel.org>
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Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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Link: https://lore.kernel.org/bpf/20250429161042.2069678-1-alan.maguire@oracle.com
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---
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src/btf.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/src/btf.c b/src/btf.c
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index e9673c0..c7df63d 100644
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--- a/src/btf.c
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+++ b/src/btf.c
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@@ -4337,6 +4337,19 @@ static bool btf_dedup_identical_structs(struct btf_dedup *d, __u32 id1, __u32 id
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return true;
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}
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+static bool btf_dedup_identical_ptrs(struct btf_dedup *d, __u32 id1, __u32 id2)
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+{
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+ struct btf_type *t1, *t2;
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+
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+ t1 = btf_type_by_id(d->btf, id1);
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+ t2 = btf_type_by_id(d->btf, id2);
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+
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+ if (!btf_is_ptr(t1) || !btf_is_ptr(t2))
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+ return false;
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+
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+ return t1->type == t2->type;
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+}
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+
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/*
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* Check equivalence of BTF type graph formed by candidate struct/union (we'll
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* call it "candidate graph" in this description for brevity) to a type graph
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@@ -4469,6 +4482,9 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
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*/
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if (btf_dedup_identical_structs(d, hypot_type_id, cand_id))
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return 1;
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+ /* A similar case is again observed for PTRs. */
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+ if (btf_dedup_identical_ptrs(d, hypot_type_id, cand_id))
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+ return 1;
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return 0;
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}
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--
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2.49.0
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