bpf: add upper complexity limit to verifier log

Given the limit could potentially get further adjustments in the
future, add it to the log so it becomes obvious what the current
limit is w/o having to check the source first. This may also be
helpful for debugging complexity related issues on kernels that
backport from upstream.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

kernel/bpf/verifier.c

@@ -4810,7 +4810,8 @@ static int do_check(struct bpf_verifier_env *env)
 		insn_idx++;
 	}
 
-	verbose(env, "processed %d insns, stack depth ", insn_processed);
+	verbose(env, "processed %d insns (limit %d), stack depth ",
+		insn_processed, BPF_COMPLEXITY_LIMIT_INSNS);
 	for (i = 0; i < env->subprog_cnt + 1; i++) {
 		u32 depth = env->subprog_stack_depth[i];