diff -r 2ab81a7ae20b -r 4cd0dfe5b9ab util/m5/m5.c
--- a/util/m5/m5.c	Mon Aug 09 10:18:59 2010 -0700
+++ b/util/m5/m5.c	Mon Aug 09 10:19:05 2010 -0700
@@ -65,6 +65,11 @@
     int offset = 0;
     int len;
 
+    // Touch all buffer pages to ensure they are mapped in the
+    // page table. This is required in the case of X86_FS, where
+    // Linux does demand paging.
+    memset(buf, 0, sizeof(buf));
+
     while ((len = m5_readfile(buf, sizeof(buf), offset)) > 0) {
         write(dest_fid, buf, len);
         offset += len;