selftests/bpf: test case for relaxed prunning of active_lock.id
authorEduard Zingerman <eddyz87@gmail.com>
Fri, 9 Dec 2022 13:57:33 +0000 (15:57 +0200)
committerAlexei Starovoitov <ast@kernel.org>
Sat, 10 Dec 2022 21:36:22 +0000 (13:36 -0800)
Check that verifier.c:states_equal() uses check_ids() to match
consistent active_lock/map_value configurations. This allows to prune
states with active spin locks even if numerical values of
active_lock ids do not match across compared states.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221209135733.28851-8-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
tools/testing/selftests/bpf/verifier/spin_lock.c

index 0a8dcfc..eaf114f 100644 (file)
        .prog_type = BPF_PROG_TYPE_SCHED_CLS,
        .flags = BPF_F_TEST_STATE_FREQ,
 },
+/* Make sure that regsafe() compares ids for spin lock records using
+ * check_ids():
+ *  1: r9 = map_lookup_elem(...)  ; r9.id == 1
+ *  2: r8 = map_lookup_elem(...)  ; r8.id == 2
+ *  3: r7 = ktime_get_ns()
+ *  4: r6 = ktime_get_ns()
+ *  5: if r6 > r7 goto <9>
+ *  6: spin_lock(r8)
+ *  7: r9 = r8
+ *  8: goto <10>
+ *  9: spin_lock(r9)
+ * 10: spin_unlock(r9)             ; r9.id == 1 || r9.id == 2 and lock is active,
+ *                                 ; second visit to (10) should be considered safe
+ *                                 ; if check_ids() is used.
+ * 11: exit(0)
+ */
+{
+       "spin_lock: regsafe() check_ids() similar id mappings",
+       .insns = {
+       BPF_ST_MEM(BPF_W, BPF_REG_10, -4, 0),
+       /* r9 = map_lookup_elem(...) */
+       BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
+       BPF_LD_MAP_FD(BPF_REG_1,
+                     0),
+       BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+       BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 24),
+       BPF_MOV64_REG(BPF_REG_9, BPF_REG_0),
+       /* r8 = map_lookup_elem(...) */
+       BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
+       BPF_LD_MAP_FD(BPF_REG_1,
+                     0),
+       BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+       BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 18),
+       BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),
+       /* r7 = ktime_get_ns() */
+       BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),
+       BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+       /* r6 = ktime_get_ns() */
+       BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),
+       BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+       /* if r6 > r7 goto +5      ; no new information about the state is derived from
+        *                         ; this check, thus produced verifier states differ
+        *                         ; only in 'insn_idx'
+        * spin_lock(r8)
+        * r9 = r8
+        * goto unlock
+        */
+       BPF_JMP_REG(BPF_JGT, BPF_REG_6, BPF_REG_7, 5),
+       BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 4),
+       BPF_EMIT_CALL(BPF_FUNC_spin_lock),
+       BPF_MOV64_REG(BPF_REG_9, BPF_REG_8),
+       BPF_JMP_A(3),
+       /* spin_lock(r9) */
+       BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 4),
+       BPF_EMIT_CALL(BPF_FUNC_spin_lock),
+       /* spin_unlock(r9) */
+       BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 4),
+       BPF_EMIT_CALL(BPF_FUNC_spin_unlock),
+       /* exit(0) */
+       BPF_MOV64_IMM(BPF_REG_0, 0),
+       BPF_EXIT_INSN(),
+       },
+       .fixup_map_spin_lock = { 3, 10 },
+       .result = VERBOSE_ACCEPT,
+       .errstr = "28: safe",
+       .result_unpriv = REJECT,
+       .errstr_unpriv = "",
+       .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+       .flags = BPF_F_TEST_STATE_FREQ,
+},