[src/trunk]: src/sys/arch/i386/i386 Put an unmapped page below the kernel sta...

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

details:   https://anonhg.NetBSD.org/src/rev/248310161e34
branches:  trunk
changeset: 537835:248310161e34
user:      fvdl <fvdl%NetBSD.org@localhost>
date:      Sun Oct 06 12:35:16 2002 +0000

description:
Put an unmapped page below the kernel stack (and above struct user) to
catch kernel stack overflows. This bumps UPAGES from 2 to 4 (one unmapped),
because struct user take 1 page then there's the unmapped page, and
then the 2 pages for the kernel stack. If the NOREDZONE option is
set, UPAGES is 2 as before, and no unmapped page is used.

diffstat:

 sys/arch/i386/i386/vm_machdep.c |  39 +++++++++++++++++++++++----------------
 1 files changed, 23 insertions(+), 16 deletions(-)

diffs (89 lines):

diff -r 97ef4bf9f378 -r 248310161e34 sys/arch/i386/i386/vm_machdep.c
--- a/sys/arch/i386/i386/vm_machdep.c   Sun Oct 06 12:35:01 2002 +0000
+++ b/sys/arch/i386/i386/vm_machdep.c   Sun Oct 06 12:35:16 2002 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vm_machdep.c,v 1.103 2002/10/01 12:57:02 fvdl Exp $    */
+/*     $NetBSD: vm_machdep.c,v 1.104 2002/10/06 12:35:16 fvdl Exp $    */
 
 /*-
  * Copyright (c) 1995 Charles M. Hannum.  All rights reserved.
@@ -46,11 +46,12 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.103 2002/10/01 12:57:02 fvdl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.104 2002/10/06 12:35:16 fvdl Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_largepages.h"
 #include "opt_mtrr.h"
+#include "opt_noredzone.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -73,7 +74,9 @@
 
 #include "npx.h"
 
-void   setredzone __P((u_short *, caddr_t));
+#ifndef NOREDZONE
+static void setredzone __P((struct proc *p));
+#endif
 
 /*
  * Finish a fork operation, with process p2 nearly set up.
@@ -147,6 +150,9 @@
        p2->p_md.md_regs = tf = (struct trapframe *)pcb->pcb_tss.tss_esp0 - 1;
        *tf = *p1->p_md.md_regs;
 
+#ifndef NOREDZONE
+       setredzone(p2);
+#endif
        /*
         * If specified, give the child a different stack.
         */
@@ -162,6 +168,15 @@
 }
 
 void
+cpu_swapin(p)
+       struct proc *p;
+{
+#ifndef NOREDZONE
+       setredzone(p);
+#endif
+}
+
+void
 cpu_swapout(p)
        struct proc *p;
 {
@@ -281,23 +296,15 @@
        return 0;
 }
 
-#if 0
+#ifndef NOREDZONE
 /*
  * Set a red zone in the kernel stack after the u. area.
  */
-void
-setredzone(pte, vaddr)
-       u_short *pte;
-       caddr_t vaddr;
+static void
+setredzone(struct proc *p)
 {
-/* eventually do this by setting up an expand-down stack segment
-   for ss0: selector, allowing stack access down to top of u.
-   this means though that protection violations need to be handled
-   thru a double fault exception that must do an integral task
-   switch to a known good context, within which a dump can be
-   taken. a sensible scheme might be to save the initial context
-   used by sched (that has physical memory mapped 1:1 at bottom)
-   and take the dump while still in mapped mode */
+       pmap_remove(pmap_kernel(), (vaddr_t)p->p_addr + PAGE_SIZE,
+           (vaddr_t)p->p_addr + 2 * PAGE_SIZE);
 }
 #endif