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

[Stephen Hemminger]

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 <step...@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