selftests/bpf: Test kptr arrays and kptrs in nested struct fields.

Make sure that BPF programs can declare global kptr arrays and kptr fields
in struct types that is the type of a global variable or the type of a
nested descendant field in a global variable.

An array with only one element is special case, that it treats the element
like a non-array kptr field. Nested arrays are also tested to ensure they
are handled properly.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240523174202.461236-8-thinker.li@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c
index ecf89df781098e27fabcfb75341410271b497d54..2570bd4b0cb228d3cdb9aae05a22cb4cb5534758 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/cpumask.c
+++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c
@@ -18,6 +18,11 @@ static const char * const cpumask_success_testcases[] = {
        "test_insert_leave",
        "test_insert_remove_release",
        "test_global_mask_rcu",
+       "test_global_mask_array_one_rcu",
+       "test_global_mask_array_rcu",
+       "test_global_mask_array_l2_rcu",
+       "test_global_mask_nested_rcu",
+       "test_global_mask_nested_deep_rcu",
        "test_cpumask_weight",
 };
 

diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c
index 7a1e64c6c065ce48df3059332378dc91165402a2..fd8106831c32c356a5a494b09f374a55221e1133 100644 (file)
--- a/tools/testing/selftests/bpf/progs/cpumask_success.c
+++ b/tools/testing/selftests/bpf/progs/cpumask_success.c
@@ -12,6 +12,31 @@ char _license[] SEC("license") = "GPL";
 
 int pid, nr_cpus;
 
+struct kptr_nested {
+       struct bpf_cpumask __kptr * mask;
+};
+
+struct kptr_nested_pair {
+       struct bpf_cpumask __kptr * mask_1;
+       struct bpf_cpumask __kptr * mask_2;
+};
+
+struct kptr_nested_mid {
+       int dummy;
+       struct kptr_nested m;
+};
+
+struct kptr_nested_deep {
+       struct kptr_nested_mid ptrs[2];
+       struct kptr_nested_pair ptr_pairs[3];
+};
+
+private(MASK) static struct bpf_cpumask __kptr * global_mask_array[2];
+private(MASK) static struct bpf_cpumask __kptr * global_mask_array_l2[2][1];
+private(MASK) static struct bpf_cpumask __kptr * global_mask_array_one[1];
+private(MASK) static struct kptr_nested global_mask_nested[2];
+private(MASK_DEEP) static struct kptr_nested_deep global_mask_nested_deep;
+
 static bool is_test_task(void)
 {
        int cur_pid = bpf_get_current_pid_tgid() >> 32;
@@ -460,6 +485,152 @@ int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags)
        return 0;
 }
 
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_array_one_rcu, struct task_struct *task, u64 clone_flags)
+{
+       struct bpf_cpumask *local, *prev;
+
+       if (!is_test_task())
+               return 0;
+
+       /* Kptr arrays with one element are special cased, being treated
+        * just like a single pointer.
+        */
+
+       local = create_cpumask();
+       if (!local)
+               return 0;
+
+       prev = bpf_kptr_xchg(&global_mask_array_one[0], local);
+       if (prev) {
+               bpf_cpumask_release(prev);
+               err = 3;
+               return 0;
+       }
+
+       bpf_rcu_read_lock();
+       local = global_mask_array_one[0];
+       if (!local) {
+               err = 4;
+               bpf_rcu_read_unlock();
+               return 0;
+       }
+
+       bpf_rcu_read_unlock();
+
+       return 0;
+}
+
+static int _global_mask_array_rcu(struct bpf_cpumask **mask0,
+                                 struct bpf_cpumask **mask1)
+{
+       struct bpf_cpumask *local;
+
+       if (!is_test_task())
+               return 0;
+
+       /* Check if two kptrs in the array work and independently */
+
+       local = create_cpumask();
+       if (!local)
+               return 0;
+
+       bpf_rcu_read_lock();
+
+       local = bpf_kptr_xchg(mask0, local);
+       if (local) {
+               err = 1;
+               goto err_exit;
+       }
+
+       /* [<mask 0>, NULL] */
+       if (!*mask0 || *mask1) {
+               err = 2;
+               goto err_exit;
+       }
+
+       local = create_cpumask();
+       if (!local) {
+               err = 9;
+               goto err_exit;
+       }
+
+       local = bpf_kptr_xchg(mask1, local);
+       if (local) {
+               err = 10;
+               goto err_exit;
+       }
+
+       /* [<mask 0>, <mask 1>] */
+       if (!*mask0 || !*mask1 || *mask0 == *mask1) {
+               err = 11;
+               goto err_exit;
+       }
+
+err_exit:
+       if (local)
+               bpf_cpumask_release(local);
+       bpf_rcu_read_unlock();
+       return 0;
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_array_rcu, struct task_struct *task, u64 clone_flags)
+{
+       return _global_mask_array_rcu(&global_mask_array[0], &global_mask_array[1]);
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_array_l2_rcu, struct task_struct *task, u64 clone_flags)
+{
+       return _global_mask_array_rcu(&global_mask_array_l2[0][0], &global_mask_array_l2[1][0]);
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_nested_rcu, struct task_struct *task, u64 clone_flags)
+{
+       return _global_mask_array_rcu(&global_mask_nested[0].mask, &global_mask_nested[1].mask);
+}
+
+/* Ensure that the field->offset has been correctly advanced from one
+ * nested struct or array sub-tree to another. In the case of
+ * kptr_nested_deep, it comprises two sub-trees: ktpr_1 and kptr_2.  By
+ * calling bpf_kptr_xchg() on every single kptr in both nested sub-trees,
+ * the verifier should reject the program if the field->offset of any kptr
+ * is incorrect.
+ *
+ * For instance, if we have 10 kptrs in a nested struct and a program that
+ * accesses each kptr individually with bpf_kptr_xchg(), the compiler
+ * should emit instructions to access 10 different offsets if it works
+ * correctly. If the field->offset values of any pair of them are
+ * incorrectly the same, the number of unique offsets in btf_record for
+ * this nested struct should be less than 10. The verifier should fail to
+ * discover some of the offsets emitted by the compiler.
+ *
+ * Even if the field->offset values of kptrs are not duplicated, the
+ * verifier should fail to find a btf_field for the instruction accessing a
+ * kptr if the corresponding field->offset is pointing to a random
+ * incorrect offset.
+ */
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_nested_deep_rcu, struct task_struct *task, u64 clone_flags)
+{
+       int r, i;
+
+       r = _global_mask_array_rcu(&global_mask_nested_deep.ptrs[0].m.mask,
+                                  &global_mask_nested_deep.ptrs[1].m.mask);
+       if (r)
+               return r;
+
+       for (i = 0; i < 3; i++) {
+               r = _global_mask_array_rcu(&global_mask_nested_deep.ptr_pairs[i].mask_1,
+                                          &global_mask_nested_deep.ptr_pairs[i].mask_2);
+               if (r)
+                       return r;
+       }
+       return 0;
+}
+
 SEC("tp_btf/task_newtask")
 int BPF_PROG(test_cpumask_weight, struct task_struct *task, u64 clone_flags)
 {