[src/trunk]: src/sys/arch/x86/x86 On amd64, mark the whole tree as NX. No rea...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/bbc3fea78b9b
branches:  trunk
changeset: 745845:bbc3fea78b9b
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Mar 14 05:19:50 2020 +0000

description:
On amd64, mark the whole tree as NX. No real functional change, just to
prevent possible future surprises, and to make it a little harder to map
executable pages in ROP chains.

diffstat:

 sys/arch/x86/x86/pmap.c |  9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diffs (37 lines):

diff -r 7c5e7e68976d -r bbc3fea78b9b sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Sat Mar 14 04:55:14 2020 +0000
+++ b/sys/arch/x86/x86/pmap.c   Sat Mar 14 05:19:50 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.363 2020/03/10 22:38:41 ad Exp $    */
+/*     $NetBSD: pmap.c,v 1.364 2020/03/14 05:19:50 maxv Exp $  */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017, 2019, 2020 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.363 2020/03/10 22:38:41 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.364 2020/03/14 05:19:50 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -4601,7 +4601,7 @@
 /*
  * Expand the page tree with the specified amount of PTPs, mapping virtual
  * addresses starting at kva. We populate all the levels but the last one
- * (L1). The nodes of the tree are created as RWX, but the pages covered
+ * (L1). The nodes of the tree are created as RW, but the pages covered
  * will be kentered in L1, with proper permissions.
  *
  * Used only by pmap_growkernel.
@@ -4632,6 +4632,9 @@
                        KASSERT(!pmap_valid_entry(pdep[i]));
                        pa = pmap_get_physpage();
                        pte = pmap_pa2pte(pa) | PTE_P | PTE_W;
+#ifdef __x86_64__
+                       pte |= pmap_pg_nx;
+#endif
                        pmap_pte_set(&pdep[i], pte);
 
 #ifdef XENPV