Re: [PATCH v3 2/8] xen/hypfs: switch write function handles to const

[Jürgen Groß]

On 16.12.20 17:08, Jan Beulich wrote:

On 09.12.2020 17:09, Juergen Gross wrote:

--- a/xen/include/xen/guest_access.h
+++ b/xen/include/xen/guest_access.h
@@ -26,6 +26,11 @@
      type *_x = (hnd).p;                         \
      (XEN_GUEST_HANDLE_PARAM(type)) { _x };      \
  })
+/* Same for casting to a const type. */
+#define guest_handle_const_cast(hnd, type) ({       \
+    const type *_x = (const type *)((hnd).p);       \
+    (XEN_GUEST_HANDLE_PARAM(const_##type)) { _x };  \
+})

Afaict this allow casting from e.g. uint to const_ulong. We
don't want to permit this (i.e. if really needed one is to
go through two steps). I think all it takes is dropping the
cast:

#define guest_handle_const_cast(hnd, type) ({      \
     const type *_x = (hnd).p;                      \
     (XEN_GUEST_HANDLE_PARAM(const_##type)) { _x }; \
})

With this
Reviewed-by: Jan Beulich <jbeul...@suse.com>
and I'd be okay making the adjustment while committing
(provided it works and I didn't overlook anything).

At least it is still compiling, and I guess that was the main
concern.


Juergen

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