[PATCH v2 2/6] test/bpf: add JSET test with small immediate

[Stephen Hemminger <stephen@networkplumber.org>]

The existing jump test only used a 32-bit JSET mask,
so the broken imm8 encoding of TEST in the x86 JIT was never exercised.
Add a case with a byte-sized mask;
run_test() runs it through the interpreter and the JIT.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 app/test/test_bpf.c | 82 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/app/test/test_bpf.c b/app/test/test_bpf.c
index dd24722450..e70dea736f 100644
--- a/app/test/test_bpf.c
+++ b/app/test/test_bpf.c
@@ -3158,7 +3158,89 @@ static const struct ebpf_insn test_ld_mbuf3_prog[] = {
 };
 
 /* all bpf test cases */
+/*
+ * JSET with a byte-sized mask: exercises the imm8 path of the TEST
+ * encoding in the x86 JIT (a 32-bit mask takes a different path).
+ */
+static const struct ebpf_insn test_jset1_prog[] = {
+	{
+		.code = (BPF_ALU | EBPF_MOV | BPF_K),
+		.dst_reg = EBPF_REG_0,
+		.imm = 0,
+	},
+	{
+		.code = (BPF_LDX | BPF_MEM | BPF_B),
+		.dst_reg = EBPF_REG_2,
+		.src_reg = EBPF_REG_1,
+		.off = offsetof(struct dummy_offset, u8),
+	},
+	/* bit 0 is set in the input: branch is taken */
+	{
+		.code = (BPF_JMP | BPF_JSET | BPF_K),
+		.dst_reg = EBPF_REG_2,
+		.imm = 0x1,
+		.off = 1,
+	},
+	{
+		.code = (BPF_JMP | BPF_JA),
+		.off = 1,
+	},
+	{
+		.code = (EBPF_ALU64 | BPF_OR | BPF_K),
+		.dst_reg = EBPF_REG_0,
+		.imm = 0x1,
+	},
+	/* bit 1 is clear in the input: branch is not taken */
+	{
+		.code = (BPF_JMP | BPF_JSET | BPF_K),
+		.dst_reg = EBPF_REG_2,
+		.imm = 0x2,
+		.off = 1,
+	},
+	{
+		.code = (BPF_JMP | BPF_JA),
+		.off = 1,
+	},
+	{
+		.code = (EBPF_ALU64 | BPF_OR | BPF_K),
+		.dst_reg = EBPF_REG_0,
+		.imm = 0x2,
+	},
+	{
+		.code = (BPF_JMP | EBPF_EXIT),
+	},
+};
+
+static void
+test_jset1_prepare(void *arg)
+{
+	struct dummy_offset *df = arg;
+
+	memset(df, 0, sizeof(*df));
+	df->u8 = 0x1;	/* bit 0 set, bit 1 clear */
+}
+
+static int
+test_jset1_check(uint64_t rc, const void *arg)
+{
+	return cmp_res(__func__, 0x1, rc, arg, arg, 0);
+}
+
 static const struct bpf_test tests[] = {
+	{
+		.name = "test_jset1",
+		.arg_sz = sizeof(struct dummy_offset),
+		.prm = {
+			.ins = test_jset1_prog,
+			.nb_ins = RTE_DIM(test_jset1_prog),
+			.prog_arg = {
+				.type = RTE_BPF_ARG_PTR,
+				.size = sizeof(struct dummy_offset),
+			},
+		},
+		.prepare = test_jset1_prepare,
+		.check_result = test_jset1_check,
+	},
 	{
 		.name = "test_store1",
 		.arg_sz = sizeof(struct dummy_offset),
-- 
2.53.0