1 files changed, 82 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c
new file mode 100644
index 000000000000..525d47d7b589
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#include "bpf_trace_helpers.h"
+
+struct sk_buff {
+	unsigned int len;
+};
+
+static volatile __u64 test_result;
+BPF_TRACE_2("fexit/test_pkt_access", test_main,
+	    struct sk_buff *, skb, int, ret)
+{
+	int len;
+
+	__builtin_preserve_access_index(({
+		len = skb->len;
+	}));
+	if (len != 74 || ret != 0)
+		return 0;
+	test_result = 1;
+	return 0;
+}
+
+static volatile __u64 test_result_subprog1;
+BPF_TRACE_2("fexit/test_pkt_access_subprog1", test_subprog1,
+	    struct sk_buff *, skb, int, ret)
+{
+	int len;
+
+	__builtin_preserve_access_index(({
+		len = skb->len;
+	}));
+	if (len != 74 || ret != 148)
+		return 0;
+	test_result_subprog1 = 1;
+	return 0;
+}
+
+/* Though test_pkt_access_subprog2() is defined in C as:
+ * static __attribute__ ((noinline))
+ * int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
+ * {
+ *     return skb->len * val;
+ * }
+ * llvm optimizations remove 'int val' argument and generate BPF assembly:
+ *   r0 = *(u32 *)(r1 + 0)
+ *   w0 <<= 1
+ *   exit
+ * In such case the verifier falls back to conservative and
+ * tracing program can access arguments and return value as u64
+ * instead of accurate types.
+ */
+struct args_subprog2 {
+	__u64 args[5];
+	__u64 ret;
+};
+static volatile __u64 test_result_subprog2;
+SEC("fexit/test_pkt_access_subprog2")
+int test_subprog2(struct args_subprog2 *ctx)
+{
+	struct sk_buff *skb = (void *)ctx->args[0];
+	__u64 ret;
+	int len;
+
+	bpf_probe_read_kernel(&len, sizeof(len),
+			      __builtin_preserve_access_index(&skb->len));
+
+	ret = ctx->ret;
+	/* bpf_prog_load() loads "test_pkt_access.o" with BPF_F_TEST_RND_HI32
+	 * which randomizes upper 32 bits after BPF_ALU32 insns.
+	 * Hence after 'w0 <<= 1' upper bits of $rax are random.
+	 * That is expected and correct. Trim them.
+	 */
+	ret = (__u32) ret;
+	if (len != 74 || ret != 148)
+		return 0;
+	test_result_subprog2 = 1;
+	return 0;
+}
+char _license[] SEC("license") = "GPL";