[src/trunk]: src/sys/arch/x86/x86 Limit the size of the direct map with a 2MB...

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

details:   https://anonhg.NetBSD.org/src/rev/7fb57c90d247
branches:  trunk
changeset: 824700:7fb57c90d247
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Jun 15 07:05:32 2017 +0000

description:
Limit the size of the direct map with a 2MB granularity (instead of 1GB).
This way if there's a computation error somewhere we will fault earlier
instead of letting the cpu access non-present physmem - which may cause
some bizarre behavior.

diffstat:

 sys/arch/x86/x86/pmap.c |  13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diffs (48 lines):

diff -r 355335627ae5 -r 7fb57c90d247 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Thu Jun 15 06:51:18 2017 +0000
+++ b/sys/arch/x86/x86/pmap.c   Thu Jun 15 07:05:32 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.247 2017/06/15 06:32:52 maxv Exp $  */
+/*     $NetBSD: pmap.c,v 1.248 2017/06/15 07:05:32 maxv Exp $  */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.247 2017/06/15 06:32:52 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.248 2017/06/15 07:05:32 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -1443,7 +1443,8 @@
        pt_entry_t *pte;
        pd_entry_t *pde;
        phys_ram_seg_t *mc;
-       size_t nL4e, nL3e, pn, npd;
+       size_t nL4e, nL3e, nL2e;
+       size_t pn, npd;
        int i, n;
 
        const pd_entry_t pteflags = PG_V | PG_KW | pmap_pg_nx;
@@ -1503,6 +1504,9 @@
                /* Allocate L2. */
                L2page_pa = pmap_bootstrap_palloc(nL3e);
 
+               /* Number of L2 entries. */
+               nL2e = (lastpa + NBPD_L2 - 1) >> L2_SHIFT;
+
                KASSERT(pmap_largepages != 0);
 
                /* Large pages are supported. Just create L2. */
@@ -1514,7 +1518,8 @@
                        memset((void *)tmpva, 0, PAGE_SIZE);
 
                        pde = (pd_entry_t *)tmpva;
-                       for (n = 0; n < NPDPG; n++) {
+                       npd = (i == nL3e - 1) ? (nL2e % NPDPG) : NPDPG;
+                       for (n = 0; n < npd; n++) {
                                pn = (i * NPDPG) + n;
                                pde[n] = ((paddr_t)pn << L2_SHIFT) | pteflags |
                                        PG_U | PG_PS | PG_G;