libbpf: Verify BTF sorting

This patch checks whether the BTF is sorted by name in ascending
order. If sorted, binary search will be used when looking 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/20260109130003.3313716-6-dolinux.peng@gmail.com

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 5a6ac40439e42f1b5d1ab0be6344f8e9284390b6..808e53961ed6351256ca0beb63fe4b7d91174a46 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -899,6 +899,30 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
        return type_id;
 }
 
+static void btf_check_sorted(struct btf *btf)
+{
+       __u32 i, n, named_start_id = 0;
+
+       n = btf__type_cnt(btf);
+       for (i = btf->start_id + 1; i < n; i++) {
+               struct btf_type *ta = btf_type_by_id(btf, i - 1);
+               struct btf_type *tb = btf_type_by_id(btf, i);
+               const char *na = btf__str_by_offset(btf, ta->name_off);
+               const char *nb = btf__str_by_offset(btf, tb->name_off);
+
+               if (strcmp(na, nb) > 0)
+                       return;
+
+               if (named_start_id == 0 && na[0] != '\0')
+                       named_start_id = i - 1;
+               if (named_start_id == 0 && nb[0] != '\0')
+                       named_start_id = i;
+       }
+
+       if (named_start_id)
+               btf->named_start_id = named_start_id;
+}
+
 static __s32 btf_find_type_by_name_bsearch(const struct btf *btf, const char *name,
                                           __s32 start_id)
 {
@@ -1130,6 +1154,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf, b
        err = err ?: btf_sanity_check(btf);
        if (err)
                goto done;
+       btf_check_sorted(btf);
 
 done:
        if (err) {