On 02.12.20 16:36, Jan Beulich wrote:
> On 01.12.2020 09:21, Juergen Gross wrote:
>>   static int hypfs_write(struct hypfs_entry *entry,
>>                          XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
> 
> As a tangent, is there a reason these write functions don't take
> handles of "const void"? (I realize this likely is nothing that
> wants addressing right here.)

Uh, this is harder than I thought.

guest_handle_cast() doesn't handle const guest handle types currently:

hypfs.c:447:58: error: unknown type name ‘const_void’; did you mean ‘const’?
          ret = hypfs_write(entry, guest_handle_cast(arg3, const_void), 
arg4);
                                                           ^
/home/gross/xen/unstable/xen/include/xen/guest_access.h:26:5: note: in 
definition of macro ‘guest_handle_cast’
      type *_x = (hnd).p;                         \
      ^~~~

Currently my ideas would be to either:

- add a new macro for constifying a guest handle (type -> const_type)
- add a new macro for casting a guest handle to a const_type
- add typedefs for the const_* types (typedef const x const_x)
- open code the cast

Or am I missing an existing variant?


Juergen