From: Martin KaFai Lau <kafai@fb.com>
Date: Mon, 1 Nov 2021 23:45:41 -0700
Subject: selftests/bpf: Verifier test on refill from a smaller spill
Patch-mainline: v5.16-rc1
Git-commit: c08455dec5acf4668f5d1eb099f7fedb29f2de5f
References: jsc#PED-1377

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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211102064541.316414-1-kafai@fb.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/testing/selftests/bpf/verifier/spill_fill.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- 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,
+},