sparc64: do not clobber personality flags in sys_sparc64_personality()

There are multiple errors in how sys_sparc64_personality() handles
personality flags stored in top three bytes.

- directly comparing current->personality against PER_LINUX32 doesn't work
  in cases when any of the personality flags stored in the top three bytes
  are used.
- directly forcefully setting personality to PER_LINUX32 or PER_LINUX
  discards any flags stored in the top three bytes

Fix the first one by properly using personality() macro to compare only
PER_MASK bytes.
Fix the second one by setting only the bits that should be set, instead of
overwriting the whole value.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/sys_sparc_64.c

@@ -502,12 +502,12 @@ SYSCALL_DEFINE1(sparc64_personality, unsigned long, personality)
 {
 	int ret;
 
-	if (current->personality == PER_LINUX32 &&
-	    personality == PER_LINUX)
-		personality = PER_LINUX32;
+	if (personality(current->personality) == PER_LINUX32 &&
+	    personality(personality) == PER_LINUX)
+		personality |= PER_LINUX32;
 	ret = sys_personality(personality);
-	if (ret == PER_LINUX32)
-		ret = PER_LINUX;
+	if (personality(ret) == PER_LINUX32)
+		ret &= ~PER_LINUX32;
 
 	return ret;
 }