The BTF_TYPE_SAFE_NESTED macro was replaced by the BTF_TYPE_SAFE_TRUSTED,
BTF_TYPE_SAFE_RCU, and BTF_TYPE_SAFE_RCU_OR_NULL macros. Fix the docs
correspondingly.
Fixes: 6fcd486b3a0a ("bpf: Refactor RCU enforcement in the verifier.")
Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
---
Documentation/bpf/kfuncs.rst | 38 ++++++++++++++++++++++++++++++------
1 file changed, 32 insertions(+), 6 deletions(-)
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 7a3d9de5f315..0d2647fb358d 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -227,23 +227,49 @@ absolutely no ABI stability guarantees.
As mentioned above, a nested pointer obtained from walking a trusted pointer is
no longer trusted, with one exception. If a struct type has a field that is
-guaranteed to be valid as long as its parent pointer is trusted, the
-``BTF_TYPE_SAFE_NESTED`` macro can be used to express that to the verifier as
-follows:
+guaranteed to be valid (trusted or rcu, as in KF_RCU description below) as long
+as its parent pointer is valid, the following macros can be used to express
+that to the verifier:
+
+* ``BTF_TYPE_SAFE_TRUSTED``
+* ``BTF_TYPE_SAFE_RCU``
+* ``BTF_TYPE_SAFE_RCU_OR_NULL``
+
+For example,
+
+.. code-block:: c
+
+ BTF_TYPE_SAFE_TRUSTED(struct socket) {
+ struct sock *sk;
+ };
+
+or
.. code-block:: c
- BTF_TYPE_SAFE_NESTED(struct task_struct) {
+ BTF_TYPE_SAFE_RCU(struct task_struct) {
const cpumask_t *cpus_ptr;
+ struct css_set __rcu *cgroups;
+ struct task_struct __rcu *real_parent;
+ struct task_struct *group_leader;
};
In other words, you must:
-1. Wrap the trusted pointer type in the ``BTF_TYPE_SAFE_NESTED`` macro.
+1. Wrap the valid pointer type in a ``BTF_TYPE_SAFE_*`` macro.
-2. Specify the type and name of the trusted nested field. This field must match
+2. Specify the type and name of the valid nested field. This field must match
the field in the original type definition exactly.
+A new type declared by a ``BTF_TYPE_SAFE_*`` macro also needs to be emitted so
+that it appears in BTF. For example, ``BTF_TYPE_SAFE_TRUSTED(struct socket)``
+is emitted in the ``type_is_trusted()`` function as follows:
+
+.. code-block:: c
+
+ BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED(struct socket));
+
+
2.4.5 KF_SLEEPABLE flag
-----------------------
--
2.34.1
