selftests/bpf: Add pruning test case for bpf_spin_lock

Test that when reg->id is not same for the same register of type
PTR_TO_MAP_VALUE between current and old explored state, we currently
return false from regsafe and continue exploring.

Without the fix in prior commit, the test case fails.

Signed-off-by: Kumar Kartikeya Dwivedi <[e-mail]>
Signed-off-by: Eduard Zingerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/verifier/spin_lock.c

···
 	.errstr = "inside bpf_spin_lock",
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 },
+{
+	"spin_lock: regsafe compare reg->id for map value",
+	.insns = {
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+	BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_6, offsetof(struct __sk_buff, mark)),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),
+	BPF_ST_MEM(BPF_W, BPF_REG_10, -4, 0),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 4),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_spin_lock),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 1),
+	BPF_JMP_IMM(BPF_JA, 0, 0, 1),
+	BPF_MOV64_REG(BPF_REG_7, BPF_REG_8),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 4),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_spin_unlock),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.fixup_map_spin_lock = { 2 },
+	.result = REJECT,
+	.errstr = "bpf_spin_unlock of different lock",
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.flags = BPF_F_TEST_STATE_FREQ,
+},