linux-kernel - [RFC PATCH v3 3/3] btf: Reuse libbpf code for BTF type sorting verification and binary search

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Message-Id: <20251027135423.3098490-4-dolinux.peng@gmail.com>
Date: Mon, 27 Oct 2025 21:54:23 +0800
From: Donglin Peng <dolinux.peng@...il.com>
To: ast@...nel.org
Cc: linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	Donglin Peng <dolinux.peng@...il.com>,
	Eduard Zingerman <eddyz87@...il.com>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Alan Maguire <alan.maguire@...cle.com>,
	Song Liu <song@...nel.org>,
	pengdonglin <pengdonglin@...omi.com>
Subject: [RFC PATCH v3 3/3] btf: Reuse libbpf code for BTF type sorting verification and binary search

The previous commit implemented BTF sorting verification and binary
search algorithm in libbpf. This patch enables this functionality in
the kernel.

Cc: Eduard Zingerman <eddyz87@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alan Maguire <alan.maguire@...cle.com>
Cc: Song Liu <song@...nel.org>
Signed-off-by: pengdonglin <pengdonglin@...omi.com>
Signed-off-by: Donglin Peng <dolinux.peng@...il.com>
---
v2->v3:
- Include btf_sort.c directly in btf.c to reduce function call overhead
---
 kernel/bpf/btf.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0de8fc8a0e0b..df258815a6ca 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -33,6 +33,7 @@
 #include <net/sock.h>
 #include <net/xdp.h>
 #include "../tools/lib/bpf/relo_core.h"
+#include "../tools/lib/bpf/btf_sort.h"
 
 /* BTF (BPF Type Format) is the meta data format which describes
  * the data types of BPF program/map.  Hence, it basically focus
@@ -259,6 +260,7 @@ struct btf {
 	void *nohdr_data;
 	struct btf_header hdr;
 	u32 nr_types; /* includes VOID for base BTF */
+	u32 nr_sorted_types; /* All named types in the sorted BTF instance */
 	u32 types_size;
 	u32 data_size;
 	refcount_t refcnt;
@@ -527,6 +529,11 @@ static bool btf_type_is_decl_tag_target(const struct btf_type *t)
 	       btf_type_is_var(t) || btf_type_is_typedef(t);
 }
 
+static u32 btf_start_id(const struct btf *btf)
+{
+	return btf->start_id + (btf->base_btf ? 0 : 1);
+}
+
 bool btf_is_vmlinux(const struct btf *btf)
 {
 	return btf->kernel_btf && !btf->base_btf;
@@ -546,22 +553,7 @@ u32 btf_nr_types(const struct btf *btf)
 
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
 {
-	const struct btf_type *t;
-	const char *tname;
-	u32 i, total;
-
-	total = btf_nr_types(btf);
-	for (i = 1; i < total; i++) {
-		t = btf_type_by_id(btf, i);
-		if (BTF_INFO_KIND(t->info) != kind)
-			continue;
-
-		tname = btf_name_by_offset(btf, t->name_off);
-		if (!strcmp(tname, name))
-			return i;
-	}
-
-	return -ENOENT;
+	return _btf_find_by_name_kind(btf, 1, name, kind);
 }
 
 s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)
@@ -6230,6 +6222,7 @@ static struct btf *btf_parse_base(struct btf_verifier_env *env, const char *name
 	if (err)
 		goto errout;
 
+	btf_check_sorted(btf, 1);
 	refcount_set(&btf->refcnt, 1);
 
 	return btf;
@@ -6362,6 +6355,7 @@ static struct btf *btf_parse_module(const char *module_name, const void *data,
 		base_btf = vmlinux_btf;
 	}
 
+	btf_check_sorted(btf, btf_nr_types(base_btf));
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
 	return btf;
@@ -9577,3 +9571,11 @@ bool btf_param_match_suffix(const struct btf *btf,
 	param_name += len - suffix_len;
 	return !strncmp(param_name, suffix, suffix_len);
 }
+
+/*
+ * btf_sort.c is included directly to avoid function call overhead
+ * when accessing BTF private data, as this file is shared between
+ * libbpf and kernel and may be called frequently (especially when
+ * funcgraph-args or func-args tracing options are enabled).
+ */
+#include "../../tools/lib/bpf/btf_sort.c"
-- 
2.34.1