[src/trunk]: src/sys/arch/x86 The L1 entry of the first page of the data segm...

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

details:   https://anonhg.NetBSD.org/src/rev/dae1abeec88d
branches:  trunk
changeset: 346647:dae1abeec88d
user:      maxv <maxv%NetBSD.org@localhost>
date:      Mon Jul 25 12:11:40 2016 +0000

description:
The L1 entry of the first page of the data segment is overwritten for the
LAPIC page, and set as RWX+PG_N. The LAPIC pa is fixed, and its va resides
in the data segment. Because of this error-prone design, the kernel image
map is not linear, and I first thought it was a bug (as I vaguely said in
PR/51148). Using large pages for the data segment is therefore wrong, since
the first page does not actually belong to the data segment (even if its va
is in the range). This bug is not triggered currently, since local_apic is
not large-page-aligned.

We will certainly have to allocate a va dynamically instead of using the
first page of data; but for now, disable large pages on the data segment,
and map the LAPIC as RW.

This is the last x86-specific RWX page.

diffstat:

 sys/arch/x86/include/pmap.h |  3 ++-
 sys/arch/x86/x86/lapic.c    |  6 +++---
 sys/arch/x86/x86/pmap.c     |  8 ++++++--
 3 files changed, 11 insertions(+), 6 deletions(-)

diffs (88 lines):

diff -r adff67debe2a -r dae1abeec88d sys/arch/x86/include/pmap.h
--- a/sys/arch/x86/include/pmap.h       Mon Jul 25 08:30:19 2016 +0000
+++ b/sys/arch/x86/include/pmap.h       Mon Jul 25 12:11:40 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.h,v 1.58 2016/07/01 11:10:48 maxv Exp $   */
+/*     $NetBSD: pmap.h,v 1.59 2016/07/25 12:11:40 maxv Exp $   */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -209,6 +209,7 @@
 extern u_long PDPpaddr;
 
 extern pd_entry_t pmap_pg_g;                   /* do we support PG_G? */
+extern pd_entry_t pmap_pg_nx;                  /* do we support PG_NX? */
 extern long nkptp[PTP_LEVELS];
 
 /*
diff -r adff67debe2a -r dae1abeec88d sys/arch/x86/x86/lapic.c
--- a/sys/arch/x86/x86/lapic.c  Mon Jul 25 08:30:19 2016 +0000
+++ b/sys/arch/x86/x86/lapic.c  Mon Jul 25 12:11:40 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lapic.c,v 1.51 2015/07/27 15:45:20 msaitoh Exp $       */
+/*     $NetBSD: lapic.c,v 1.52 2016/07/25 12:11:40 maxv Exp $  */
 
 /*-
  * Copyright (c) 2000, 2008 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: lapic.c,v 1.51 2015/07/27 15:45:20 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: lapic.c,v 1.52 2016/07/25 12:11:40 maxv Exp $");
 
 #include "opt_ddb.h"
 #include "opt_mpbios.h"                /* for MPDEBUG */
@@ -125,7 +125,7 @@
         */
 
        pte = kvtopte(va);
-       *pte = lapic_base | PG_RW | PG_V | PG_N | pmap_pg_g;
+       *pte = lapic_base | PG_RW | PG_V | PG_N | pmap_pg_g | pmap_pg_nx;
        invlpg(va);
 
 #ifdef MULTIPROCESSOR
diff -r adff67debe2a -r dae1abeec88d sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Mon Jul 25 08:30:19 2016 +0000
+++ b/sys/arch/x86/x86/pmap.c   Mon Jul 25 12:11:40 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.216 2016/07/22 14:08:33 maxv Exp $  */
+/*     $NetBSD: pmap.c,v 1.217 2016/07/25 12:11:40 maxv Exp $  */
 
 /*-
  * Copyright (c) 2008, 2010, 2016 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.216 2016/07/22 14:08:33 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.217 2016/07/25 12:11:40 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -1573,7 +1573,9 @@
 {
        extern char __rodata_start;
        extern char __data_start;
+#if 0
        extern char __kernel_end;
+#endif
        pd_entry_t *pde;
        vaddr_t kva, kva_end;
        paddr_t pa;
@@ -1604,6 +1606,7 @@
                tlbflushg();
        }
 
+#if 0
        /* Remap the kernel data+bss using large pages. */
        kva = roundup((vaddr_t)&__data_start, NBPD_L2);
        kva_end = rounddown((vaddr_t)&__kernel_end, NBPD_L1);
@@ -1613,6 +1616,7 @@
                *pde = pa | pmap_pg_g | PG_PS | pmap_pg_nx | PG_KW | PG_V;
                tlbflushg();
        }
+#endif
 }
 #endif /* !XEN */