From 4003a436fc74f03b4f4efd76a35ea9408fb560bb Mon Sep 17 00:00:00 2001
From: Peter Rugg <pdr32@cam.ac.uk>
Date: Sat, 25 May 2019 14:30:31 +0100
Subject: [PATCH] Add XOR with null cap when casting to/from memory cap

---
 CHERICC_Fat.bsv | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CHERICC_Fat.bsv b/CHERICC_Fat.bsv
index 78d6842..dfb9fd8 100644
--- a/CHERICC_Fat.bsv
+++ b/CHERICC_Fat.bsv
@@ -1052,13 +1052,13 @@ endinstance
 
 instance Cast#(CapMem, CapReg);
   function CapReg cast (CapMem thin);
-    return unpackCap(thin);
+    return unpackCap(thin ^ packCap(null_cap));
   endfunction
 endinstance
 
 instance Cast#(CapReg, CapMem);
   function CapMem cast (CapReg fat);
-    return packCap(fat);
+    return packCap(fat) ^ packCap(null_cap);
   endfunction
 endinstance