[PATCH bpf-next 2/2] bpf: selftest: verifier test on refill from a smaller spill

[Martin KaFai Lau <kafai@fb.com>]

This patch adds a verifier test to ensure the verifier
can read 8 bytes from the stack after two 32bit write at
fp-4 and fp-8.  The test is similar to the reported case from bcc [0].

[0]: https://github.com/iovisor/bcc/pull/3683

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 .../testing/selftests/bpf/verifier/spill_fill.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c
index c9991c3f3bd2..7ab3de108761 100644
--- a/tools/testing/selftests/bpf/verifier/spill_fill.c
+++ b/tools/testing/selftests/bpf/verifier/spill_fill.c
@@ -265,3 +265,20 @@
 	.result = ACCEPT,
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 },
+{
+	"Spill a u32 scalar at fp-4 and then at fp-8",
+	.insns = {
+	/* r4 = 4321 */
+	BPF_MOV32_IMM(BPF_REG_4, 4321),
+	/* *(u32 *)(r10 -4) = r4 */
+	BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4),
+	/* *(u32 *)(r10 -8) = r4 */
+	BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8),
+	/* r4 = *(u64 *)(r10 -8) */
+	BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+},
-- 
2.30.2