bpf: add mod default A and X test cases

When running "mod X" operation, if X is 0 the filter has to be halt.
Add new test cases to cover A = A mod X if X is 0, and A = A mod 1.

CC: Xi Wang <xi.wang@gmail.com>
CC: Zi Shen Lim <zlim.lnx@gmail.com>
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/test_bpf.c

@@ -5055,6 +5055,36 @@ static struct bpf_test tests[] = {
 		{},
 		{ {0x1, 0x0 } },
 	},
+	{
+		"MOD default X",
+		.u.insns = {
+			/*
+			 * A = 0x42
+			 * A = A mod X ; this halt the filter execution if X is 0
+			 * ret 0x42
+			 */
+			BPF_STMT(BPF_LD | BPF_IMM, 0x42),
+			BPF_STMT(BPF_ALU | BPF_MOD | BPF_X, 0),
+			BPF_STMT(BPF_RET | BPF_K, 0x42),
+		},
+		CLASSIC | FLAG_NO_DATA,
+		{},
+		{ {0x1, 0x0 } },
+	},
+	{
+		"MOD default A",
+		.u.insns = {
+			/*
+			 * A = A mod 1
+			 * ret A
+			 */
+			BPF_STMT(BPF_ALU | BPF_MOD | BPF_K, 0x1),
+			BPF_STMT(BPF_RET | BPF_A, 0x0),
+		},
+		CLASSIC | FLAG_NO_DATA,
+		{},
+		{ {0x1, 0x0 } },
+	},
 	{
 		"JMP EQ default A",
 		.u.insns = {