bpf: add find_containing_subprog() utility function

Add a utility function, looking for a subprogram containing a given
instruction index, rewrite find_subprog() to use this function.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241210041100.1898468-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 01fbef9576e0003bd0d978b14d176cf2d17887e0..277c1892bb9a8777a127bfd7d77cdfd790ab0a70 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2597,16 +2597,36 @@ static int cmp_subprogs(const void *a, const void *b)
               ((struct bpf_subprog_info *)b)->start;
 }
 
+/* Find subprogram that contains instruction at 'off' */
+static struct bpf_subprog_info *find_containing_subprog(struct bpf_verifier_env *env, int off)
+{
+       struct bpf_subprog_info *vals = env->subprog_info;
+       int l, r, m;
+
+       if (off >= env->prog->len || off < 0 || env->subprog_cnt == 0)
+               return NULL;
+
+       l = 0;
+       r = env->subprog_cnt - 1;
+       while (l < r) {
+               m = l + (r - l + 1) / 2;
+               if (vals[m].start <= off)
+                       l = m;
+               else
+                       r = m - 1;
+       }
+       return &vals[l];
+}
+
+/* Find subprogram that starts exactly at 'off' */
 static int find_subprog(struct bpf_verifier_env *env, int off)
 {
        struct bpf_subprog_info *p;
 
-       p = bsearch(&off, env->subprog_info, env->subprog_cnt,
-                   sizeof(env->subprog_info[0]), cmp_subprogs);
-       if (!p)
+       p = find_containing_subprog(env, off);
+       if (!p || p->start != off)
                return -ENOENT;
        return p - env->subprog_info;
-
 }
 
 static int add_subprog(struct bpf_verifier_env *env, int off)