(cc in Eitan as he may be interested in the extra restrict cases)


On 02/03/2018 11:47, Konstantin Belousov wrote:
Author: kib
Date: Fri Mar  2 16:47:02 2018
New Revision: 330285
URL: https://svnweb.freebsd.org/changeset/base/330285

Log:
   Remove _Nonnull attributes from user addresses arguments for
   copyout(9) family.
The addresses are user-controllable, and if the process ABI allows
   mapping at zero, then the zero address is meaningful, contradicting
   the definition of _Nonnull.  In any case, it does not require any
   special code to handle NULL udaddr.

FWIW, the _Nonnull attributes didn't do much at all beyond producing a warning.
They replaced the GNU __nonnull() attributes which were much more dangerous.
I am OK with seeing both gone here though.

   It is not clear if __restrict makes sense as well, since kaddr and
   udaddr point to different address spaces, so equal numeric values of
   the pointers do not imply aliasing and a legitimate.  But leave it for
   later.
copyinstr(9) does not have its user address argument annotated.

I think use of _Nonnull attributes in the threading functions may also be a waste (I introduced them mostly to be compatible with Android).
FWIW, Dragonfly sprinkled some restrict there recently:

http://gitweb.dragonflybsd.org/dragonfly.git/commit/d33005aaee6af52c80428b59b52aee522c002492

Just in case someone is considering more cleanups.

Cheers,

Pedro.

   Sponsored by:        The FreeBSD Foundation
   MFC after:   1 week

Modified:
   head/sys/sys/systm.h

Modified: head/sys/sys/systm.h
==============================================================================
--- head/sys/sys/systm.h        Fri Mar  2 16:31:23 2018        (r330284)
+++ head/sys/sys/systm.h        Fri Mar  2 16:47:02 2018        (r330285)
@@ -277,14 +277,14 @@ int       copystr(const void * _Nonnull __restrict kfaddr,
  int   copyinstr(const void * __restrict udaddr,
            void * _Nonnull __restrict kaddr, size_t len,
            size_t * __restrict lencopied);
-int    copyin(const void * _Nonnull __restrict udaddr,
+int    copyin(const void * __restrict udaddr,
            void * _Nonnull __restrict kaddr, size_t len);
-int    copyin_nofault(const void * _Nonnull __restrict udaddr,
+int    copyin_nofault(const void * __restrict udaddr,
            void * _Nonnull __restrict kaddr, size_t len);
  int   copyout(const void * _Nonnull __restrict kaddr,
-           void * _Nonnull __restrict udaddr, size_t len);
+           void * __restrict udaddr, size_t len);
  int   copyout_nofault(const void * _Nonnull __restrict kaddr,
-           void * _Nonnull __restrict udaddr, size_t len);
+           void * __restrict udaddr, size_t len);
int fubyte(volatile const void *base);
  long  fuword(volatile const void *base);


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