Add a test that returns a 'random' number between [0, 2^20)
If state pruning is not working correctly for loop body the number of
processed insns will be 2^20 * num_of_insns_in_loop_body and the program
will be rejected.

Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
 .../bpf/prog_tests/bpf_verif_scale.c          |  1 +
 tools/testing/selftests/bpf/progs/loop4.c     | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/loop4.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c 
b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
index b4be96162ff4..757e39540eda 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
@@ -71,6 +71,7 @@ void test_bpf_verif_scale(void)
 
                { "loop1.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
                { "loop2.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
+               { "loop4.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
 
                /* partial unroll. 19k insn in a loop.
                 * Total program size 20.8k insn.
diff --git a/tools/testing/selftests/bpf/progs/loop4.c 
b/tools/testing/selftests/bpf/progs/loop4.c
new file mode 100644
index 000000000000..3e7ee14fddbd
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop4.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("socket")
+int combinations(volatile struct __sk_buff* skb)
+{
+       int ret = 0, i;
+
+#pragma nounroll
+       for (i = 0; i < 20; i++)
+               if (skb->len)
+                       ret |= 1 << i;
+       return ret;
+}
-- 
2.20.0

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