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-rw-r--r--Documentation/bpf/kfuncs.rst24
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diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 723408e399..7985c6615f 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -135,6 +135,30 @@ Either way, the returned buffer is either NULL, or of size buffer_szk. Without t
annotation, the verifier will reject the program if a null pointer is passed in with
a nonzero size.
+2.2.5 __str Annotation
+----------------------------
+This annotation is used to indicate that the argument is a constant string.
+
+An example is given below::
+
+ __bpf_kfunc bpf_get_file_xattr(..., const char *name__str, ...)
+ {
+ ...
+ }
+
+In this case, ``bpf_get_file_xattr()`` can be called as::
+
+ bpf_get_file_xattr(..., "xattr_name", ...);
+
+Or::
+
+ const char name[] = "xattr_name"; /* This need to be global */
+ int BPF_PROG(...)
+ {
+ ...
+ bpf_get_file_xattr(..., name, ...);
+ ...
+ }
.. _BPF_kfunc_nodef: