[src/trunk]: src/sys/arch/i386/i386 Use pmap_pte_*bits macros to set/clear bi...

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

details:   https://anonhg.NetBSD.org/src/rev/4f57247fd864
branches:  trunk
changeset: 779159:4f57247fd864
user:      jym <jym%NetBSD.org@localhost>
date:      Mon May 07 02:32:09 2012 +0000

description:
Use pmap_pte_*bits macros to set/clear bits in a PTE. Remove pmap_pte_flush
calls as these operations are synchronously flushed under Xen; they should
not be cached.

XXX the code can be shared between i386 and amd64, but I will merge
them once I figure out why db_write_text() can cause page faults for
certain CPUs in long mode (code looks correct, but single stepping or
adding debug printf's makes the bug magically disappear... sigh)

Bug reported by David Laight on port-amd64@ when attempting to set
breakpoints through ddb(4).

diffstat:

 sys/arch/i386/i386/db_memrw.c |  30 ++++++++++++++++--------------
 1 files changed, 16 insertions(+), 14 deletions(-)

diffs (88 lines):

diff -r 3036d632d204 -r 4f57247fd864 sys/arch/i386/i386/db_memrw.c
--- a/sys/arch/i386/i386/db_memrw.c     Mon May 07 02:15:34 2012 +0000
+++ b/sys/arch/i386/i386/db_memrw.c     Mon May 07 02:32:09 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: db_memrw.c,v 1.27 2012/05/07 02:15:34 jym Exp $        */
+/*     $NetBSD: db_memrw.c,v 1.28 2012/05/07 02:32:09 jym Exp $        */
 
 /*-
  * Copyright (c) 1996, 2000 The NetBSD Foundation, Inc.
@@ -49,7 +49,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: db_memrw.c,v 1.27 2012/05/07 02:15:34 jym Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_memrw.c,v 1.28 2012/05/07 02:32:09 jym Exp $");
 
 #include "opt_xen.h"
 
@@ -97,7 +97,7 @@
 static void
 db_write_text(vaddr_t addr, size_t size, const char *data)
 {
-       pt_entry_t *pte, oldpte, tmppte;
+       pt_entry_t *ppte, pte;
        vaddr_t pgva;
        size_t limit;
        char *dst;
@@ -111,10 +111,10 @@
                /*
                 * Get the PTE for the page.
                 */
-               pte = kvtopte(addr);
-               oldpte = *pte;
+               ppte = kvtopte(addr);
+               pte = *ppte;
 
-               if ((oldpte & PG_V) == 0) {
+               if ((pte & PG_V) == 0) {
                        printf(" address %p not a valid page\n", dst);
                        return;
                }
@@ -122,7 +122,7 @@
                /*
                 * Get the VA for the page.
                 */
-               if (oldpte & PG_PS)
+               if (pte & PG_PS)
                        pgva = (vaddr_t)dst & PG_LGFRAME;
                else
                        pgva = x86_trunc_page((vaddr_t)dst);
@@ -132,7 +132,7 @@
                 * with this mapping and subtract it from the
                 * total size.
                 */
-               if (oldpte & PG_PS)
+               if (pte & PG_PS)
                        limit = NBPD_L2 - ((vaddr_t)dst & (NBPD_L2 - 1));
                else
                        limit = PAGE_SIZE - ((vaddr_t)dst & PGOFSET);
@@ -140,9 +140,11 @@
                        limit = size;
                size -= limit;
 
-               tmppte = (oldpte & ~PG_KR) | PG_KW;
-               pmap_pte_set(pte, tmppte);
-               pmap_pte_flush();
+               /*
+                * Make the kernel text page writable.
+                */
+               pmap_pte_clearbits(ppte, PG_KR);
+               pmap_pte_setbits(ppte, PG_KW);
                pmap_update_pg(pgva);
                /*
                 * MULTIPROCESSOR: no shootdown required as the PTE continues to
@@ -157,10 +159,10 @@
                        *dst++ = *data++;
 
                /*
-                * Restore the old PTE.
+                * Turn the page back to read-only.
                 */
-               pmap_pte_set(pte, oldpte);
-               pmap_pte_flush();
+               pmap_pte_clearbits(ppte, PG_KW);
+               pmap_pte_setbits(ppte, PG_KR);
                pmap_update_pg(pgva);
                /*
                 * MULTIPROCESSOR: no shootdown required as all other CPUs