powerpc: Fix personality handling in ppc64_personality()

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

Use personality() macro to compare only PER_MASK bytes and make sure that
we are 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: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/syscalls.c

@@ -107,11 +107,11 @@ long ppc64_personality(unsigned long personality)
 	long ret;
 
 	if (personality(current->personality) == PER_LINUX32
-	    && personality == PER_LINUX)
+	    && personality(personality) == PER_LINUX)
-		personality = PER_LINUX32;
+		personality = (personality & ~PER_MASK) | PER_LINUX32;
 	ret = sys_personality(personality);
-	if (ret == PER_LINUX32)
+	if (personality(ret) == PER_LINUX32)
-		ret = PER_LINUX;
+		ret = (ret & ~PER_MASK) | PER_LINUX;
 	return ret;
 }
 #endif