From: pengdonglin <pengdonglin@xiaomi.com>

This introduces a new BTF sorting phase that specifically sorts
BTF types by name in ascending order, so that the binary search
can be used to look up types.

Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
---
 tools/bpf/resolve_btfids/main.c | 68 +++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index e0e792017e77..b4ec3b556518 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -846,6 +846,71 @@ static int dump_raw_btf(struct btf *btf, const char *out_path)
 	return 0;
 }
 
+/*
+ * Sort types by name in ascending order resulting in all
+ * anonymous types being placed before named types.
+ */
+static int cmp_type_names(const void *a, const void *b, void *priv)
+{
+	struct btf *btf = (struct btf *)priv;
+	const struct btf_type *ta = btf__type_by_id(btf, *(__u32 *)a);
+	const struct btf_type *tb = btf__type_by_id(btf, *(__u32 *)b);
+	const char *na, *nb;
+
+	na = btf__str_by_offset(btf, ta->name_off);
+	nb = btf__str_by_offset(btf, tb->name_off);
+	return strcmp(na, nb);
+}
+
+static int sort_btf_by_name(struct btf *btf)
+{
+	__u32 *permute_ids = NULL, *id_map = NULL;
+	int nr_types, i, err = 0;
+	__u32 start_id = 1, id;
+
+	if (btf__base_btf(btf))
+		start_id = btf__type_cnt(btf__base_btf(btf));
+	nr_types = btf__type_cnt(btf) - start_id;
+	if (nr_types < 2)
+		goto out;
+
+	permute_ids = calloc(nr_types, sizeof(*permute_ids));
+	if (!permute_ids) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	id_map = calloc(nr_types, sizeof(*id_map));
+	if (!id_map) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0, id = start_id; i < nr_types; i++, id++)
+		permute_ids[i] = id;
+
+	qsort_r(permute_ids, nr_types, sizeof(*permute_ids), cmp_type_names, btf);
+
+	for (i = 0; i < nr_types; i++) {
+		id = permute_ids[i] - start_id;
+		id_map[id] = i + start_id;
+	}
+
+	err = btf__permute(btf, id_map, nr_types, NULL);
+	if (err)
+		pr_err("FAILED: btf permute: %s\n", strerror(-err));
+
+out:
+	free(permute_ids);
+	free(id_map);
+	return err;
+}
+
+static int btf2btf(struct object *obj)
+{
+	return sort_btf_by_name(obj->btf);
+}
+
 static inline int make_out_path(char *buf, const char *in_path, const char *suffix)
 {
 	int len = snprintf(buf, PATH_MAX, "%s%s", in_path, suffix);
@@ -904,6 +969,9 @@ int main(int argc, const char **argv)
 	if (load_btf(&obj))
 		goto out;
 
+	if (btf2btf(&obj))
+		goto out;
+
 	if (elf_collect(&obj))
 		goto out;
 
-- 
2.34.1