add a test for tail calls from static functions

Author: tecki

tools/testing/selftests/bpf/progs/verifier_sock.c

@@ -1117,10 +1117,17 @@ int tail_call(struct __sk_buff *sk)
 	return 0;
 }
 
+static __noinline
+int static_tail_call(struct __sk_buff *sk)
+{
+	bpf_tail_call_static(sk, &jmp_table, 0);
+	return 0;
+}
+
 /* Tail calls in sub-programs invalidate packet pointers. */
 SEC("tc")
 __failure __msg("invalid mem access")
-int invalidate_pkt_pointers_by_indirect_tail_call(struct __sk_buff *sk)
+int invalidate_pkt_pointers_by_global_tail_call(struct __sk_buff *sk)
 {
 	int *p = (void *)(long)sk->data;
 
@@ -1131,6 +1138,20 @@ int invalidate_pkt_pointers_by_indirect_tail_call(struct __sk_buff *sk)
 	return TCX_PASS;
 }
 
+/* Tail calls in static sub-programs invalidate packet pointers. */
+SEC("tc")
+__failure __msg("invalid mem access")
+int invalidate_pkt_pointers_by_static_tail_call(struct __sk_buff *sk)
+{
+	int *p = (void *)(long)sk->data;
+
+	if ((void *)(p + 1) > (void *)(long)sk->data_end)
+		return TCX_DROP;
+	static_tail_call(sk);
+	*p = 42; /* this is unsafe */
+	return TCX_PASS;
+}
+
 /* Direct tail calls do not invalidate packet pointers. */
 SEC("tc")
 __success