[PATCH bpf-next 2/2] selftests/bpf: Add test for immediate spilled to stack

Hao Sun
2023-10-26T15:13:59Z

Add a test to check if the verifier correctly reason about the sign
of an immediate spilled to stack by BPF_ST instruction.

Signed-off-by: Hao Sun <sunhao.th@gmail.com>
---
tools/testing/selftests/bpf/verifier/bpf_st_mem.c | 32 +++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/bpf_st_mem.c b/tools/testing/selftests/bpf/verifier/bpf_st_mem.c
index 3af2501082b2..0ba23807c46c 100644
--- a/tools/testing/selftests/bpf/verifier/bpf_st_mem.c
+++ b/tools/testing/selftests/bpf/verifier/bpf_st_mem.c
@@ -65,3 +65,35 @@
.expected_attach_type = BPF_SK_LOOKUP,
.runs = -1,
},
+{
+ "BPF_ST_MEM stack imm sign",
+ /* Check if verifier correctly reasons about sign of an
+ * immediate spilled to stack by BPF_ST instruction.
+ *
+ * fp[-8] = -44;
+ * r0 = fp[-8];
+ * if r0 s< 0 goto ret0;
+ * r0 = -1;
+ * exit;
+ * ret0:
+ * r0 = 0;
+ * exit;
+ */
+ .insns = {
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, -44),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
+ BPF_JMP_IMM(BPF_JSLT, BPF_REG_0, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, -1),
+ BPF_EXIT_INSN(),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ /* Use prog type that requires return value in range [0, 1] */
+ .prog_type = BPF_PROG_TYPE_SK_LOOKUP,
+ .expected_attach_type = BPF_SK_LOOKUP,
+ .result = VERBOSE_ACCEPT,
+ .runs = -1,
+ .errstr = "0: (7a) *(u64 *)(r10 -8) = -44 ; R10=fp0 fp-8_w=-44\
+ 2: (c5) if r0 s< 0x0 goto pc+2\
+ 2: R0_w=-44",
+},

--
2.34.1