[src/trunk]: src/sys/arch/i386/i386 Enable the NX bit feature early in i386 M...

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

details:   https://anonhg.NetBSD.org/src/rev/10839047a40f
branches:  trunk
changeset: 756684:10839047a40f
user:      jym <jym%NetBSD.org@localhost>
date:      Wed Jul 28 17:05:51 2010 +0000

description:
Enable the NX bit feature early in i386 MP trampoline code (do not rely on
cpu_init_msrs() to do it). Having NX bit set on a page will raise a #GP
on fetch if NXE is not enabled, which can happen early when structures
(like idlelwp) are allocated with just rw- rights.

NX is enabled with PAE (if host supports it).

Exact same issue as for amd64, some weeks ago. Same player, shoot again...

diffstat:

 sys/arch/i386/i386/mptramp.S |  17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diffs (45 lines):

diff -r 85ad001906bd -r 10839047a40f sys/arch/i386/i386/mptramp.S
--- a/sys/arch/i386/i386/mptramp.S      Wed Jul 28 16:29:11 2010 +0000
+++ b/sys/arch/i386/i386/mptramp.S      Wed Jul 28 17:05:51 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mptramp.S,v 1.21 2010/07/24 00:45:55 jym Exp $ */
+/*     $NetBSD: mptramp.S,v 1.22 2010/07/28 17:05:51 jym Exp $ */
 
 /*-
  * Copyright (c) 2000 The NetBSD Foundation, Inc.
@@ -76,7 +76,7 @@
  */
 
 #include <machine/asm.h>
-__KERNEL_RCSID(0, "$NetBSD: mptramp.S,v 1.21 2010/07/24 00:45:55 jym Exp $");
+__KERNEL_RCSID(0, "$NetBSD: mptramp.S,v 1.22 2010/07/28 17:05:51 jym Exp $");
        
 #include "opt_mpbios.h"                /* for MPDEBUG */
                
@@ -158,6 +158,7 @@
        movl    %cr4,%eax
        orl     $CR4_PSE,%eax
        movl    %eax,%cr4
+
 1:
 
 #ifdef PAE /* Enable PAE */
@@ -181,6 +182,18 @@
 #endif
        HALT(0x6)
 
+       /*
+        * If EFER_NXE is not enabled, fetching a page with a NX bit set
+        * will raise a #GP. Avoid that by setting the NXE feature now.
+        */
+       movl    _C_LABEL(cpu_feature)+2*4,%eax  /* cpu_feature[2] */
+       andl    $CPUID_NOX,%eax
+       jz      1f
+       movl    $MSR_EFER,%ecx
+       rdmsr
+       orl     $EFER_NXE,%eax  /* enable No-Execute feature */
+       wrmsr
+
 /*
  * ok, we are now running with paging enabled and sharing page tables
  * with cpu0.  figure out which processor we really are, what stack we