Merge tag 'block-5.14-2021-08-07' of git://git.kernel.dk/linux-block

[linux-2.6-microblaze.git] / Documentation / arm64 / tagged-address-abi.rst

diff --git a/Documentation/arm64/tagged-address-abi.rst b/Documentation/arm64/tagged-address-abi.rst
index 459e6b6..0c9120e 100644 (file)
--- a/Documentation/arm64/tagged-address-abi.rst
+++ b/Documentation/arm64/tagged-address-abi.rst
@@ -45,14 +45,24 @@ how the user addresses are used by the kernel:
 
 1. User addresses not accessed by the kernel but used for address space
    management (e.g. ``mprotect()``, ``madvise()``). The use of valid
-   tagged pointers in this context is allowed with the exception of
-   ``brk()``, ``mmap()`` and the ``new_address`` argument to
-   ``mremap()`` as these have the potential to alias with existing
-   user addresses.
-
-   NOTE: This behaviour changed in v5.6 and so some earlier kernels may
-   incorrectly accept valid tagged pointers for the ``brk()``,
-   ``mmap()`` and ``mremap()`` system calls.
+   tagged pointers in this context is allowed with these exceptions:
+
+   - ``brk()``, ``mmap()`` and the ``new_address`` argument to
+     ``mremap()`` as these have the potential to alias with existing
+      user addresses.
+
+     NOTE: This behaviour changed in v5.6 and so some earlier kernels may
+     incorrectly accept valid tagged pointers for the ``brk()``,
+     ``mmap()`` and ``mremap()`` system calls.
+
+   - The ``range.start``, ``start`` and ``dst`` arguments to the
+     ``UFFDIO_*`` ``ioctl()``s used on a file descriptor obtained from
+     ``userfaultfd()``, as fault addresses subsequently obtained by reading
+     the file descriptor will be untagged, which may otherwise confuse
+     tag-unaware programs.
+
+     NOTE: This behaviour changed in v5.14 and so some earlier kernels may
+     incorrectly accept valid tagged pointers for this system call.
 
 2. User addresses accessed by the kernel (e.g. ``write()``). This ABI
    relaxation is disabled by default and the application thread needs to