tools/resolve_btfids: Support BTF sorting feature

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.

Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260109130003.3313716-4-dolinux.peng@gmail.com

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index df39982f51dfb7d0e01fcd7d1bfa32e5da6617a1..343d080501169adceee5e2d32987a7b8212a8ac1 100644 (file)
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -850,6 +850,67 @@ 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 = 0, start_offs = 1, id;
+
+       if (btf__base_btf(btf)) {
+               start_id = btf__type_cnt(btf__base_btf(btf));
+               start_offs = 0;
+       }
+       nr_types = btf__type_cnt(btf) - start_id;
+
+       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 + start_offs, nr_types - start_offs,
+               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 inline int make_out_path(char *buf, u32 buf_sz, const char *in_path, const char *suffix)
 {
        int len = snprintf(buf, buf_sz, "%s%s", in_path, suffix);
@@ -1025,6 +1086,9 @@ int main(int argc, const char **argv)
        if (load_btf(&obj))
                goto out;
 
+       if (sort_btf_by_name(obj.btf))
+               goto out;
+
        if (elf_collect(&obj))
                goto out;