Subject: [PATCH v2 bpf-next 2/2] selftests/bpf: add loop test 5

From: Alexei Starovoitov <[email-masked]>
Date: Mon, 5 Aug 2019 19:17:44 -0700

Add a test with multiple exit conditions.
It's not an infinite loop only when the verifier can properly track
all math on variable 'i' through all possible ways of executing this loop.

barrier()s are needed to disable llvm optimization that combines multiple
branches into fewer branches.

Signed-off-by: Alexei Starovoitov <[email-masked]>
---
 .../bpf/prog_tests/bpf_verif_scale.c          |  1 +
 tools/testing/selftests/bpf/progs/loop5.c     | 32 +++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/loop5.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 e9e72d8d7aae..0caf8eafa9eb 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
@@ -72,6 +72,7 @@ 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_SCHED_CLS },
+		{ "loop5.o", BPF_PROG_TYPE_SCHED_CLS },
 
 		/* partial unroll. 19k insn in a loop.
 		 * Total program size 20.8k insn.
diff --git a/tools/testing/selftests/bpf/progs/loop5.c b/tools/testing/selftests/bpf/progs/loop5.c
new file mode 100644
index 000000000000..28d1d668f07c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop5.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#define barrier() __asm__ __volatile__("": : :"memory")
+
+char _license[] SEC("license") = "GPL";
+
+SEC("socket")
+int while_true(volatile struct __sk_buff* skb)
+{
+	int i = 0;
+
+	while (1) {
+		if (skb->len)
+			i += 3;
+		else
+			i += 7;
+		if (i == 9)
+			break;
+		barrier();
+		if (i == 10)
+			break;
+		barrier();
+		if (i == 13)
+			break;
+		barrier();
+		if (i == 14)
+			break;
+	}
+	return i;
+}
-- 
2.20.0