[src/trunk]: src/sys/arch/usermode/usermode To avoid possible collisions betw...

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

details:   https://anonhg.NetBSD.org/src/rev/6486a777aee9
branches:  trunk
changeset: 834279:6486a777aee9
user:      reinoud <reinoud%NetBSD.org@localhost>
date:      Sun Aug 05 16:51:59 2018 +0000

description:
To avoid possible collisions between the NetBSD/userland kernel and possible
host kernel memory allocation schemes, allocate two dedicated pages for page
copying and page zeroing.

diffstat:

 sys/arch/usermode/usermode/pmap.c |  39 ++++++++++++++++++++-------------------
 1 files changed, 20 insertions(+), 19 deletions(-)

diffs (91 lines):

diff -r c9b6e7f00098 -r 6486a777aee9 sys/arch/usermode/usermode/pmap.c
--- a/sys/arch/usermode/usermode/pmap.c Sun Aug 05 15:37:10 2018 +0000
+++ b/sys/arch/usermode/usermode/pmap.c Sun Aug 05 16:51:59 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.112 2018/08/03 11:18:22 reinoud Exp $ */
+/* $NetBSD: pmap.c,v 1.113 2018/08/05 16:51:59 reinoud Exp $ */
 
 /*-
  * Copyright (c) 2011 Reinoud Zandijk <reinoud%NetBSD.org@localhost>
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.112 2018/08/03 11:18:22 reinoud Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.113 2018/08/05 16:51:59 reinoud Exp $");
 
 #include "opt_memsize.h"
 #include "opt_kmempages.h"
@@ -101,6 +101,8 @@
 static int pm_nl1 = 0;
 static int pm_l1_size = 0;
 static uint64_t pm_entries_size = 0;
+static void *pm_tmp_p0;
+static void *pm_tmp_p1;
 
 static struct pool pmap_pool;
 static struct pool pmap_pventry_pool;
@@ -183,6 +185,11 @@
        kmem_kvm_end    = kmem_k_start - barrier_len;
        kmem_kvm_start  = kmem_kvm_end - KVMSIZE;
 
+       /* allow some pmap scratch space */
+       pm_tmp_p0 = (void *) (kmem_kvm_start);
+       pm_tmp_p1 = (void *) (kmem_kvm_start + PAGE_SIZE);
+       kmem_kvm_start += 2*PAGE_SIZE;
+
        /* claim an area for userland (---/R--/RW-/RWX) */
        kmem_user_start = vm_min_addr;
        kmem_user_end   = kmem_kvm_start - barrier_len;
@@ -1227,14 +1234,12 @@
        if (pa & (PAGE_SIZE-1))
                panic("%s: unaligned address passed : %p\n", __func__, (void *) pa);
 
-       blob = thunk_mmap(NULL, PAGE_SIZE,
+       blob = thunk_mmap(pm_tmp_p0, PAGE_SIZE,
                THUNK_PROT_READ | THUNK_PROT_WRITE,
-               THUNK_MAP_FILE | THUNK_MAP_SHARED,
+               THUNK_MAP_FILE | THUNK_MAP_FIXED | THUNK_MAP_SHARED,
                mem_fh, pa);
-       if (!blob)
+       if (blob != pm_tmp_p0)
                panic("%s: couldn't get mapping", __func__);
-       if (blob < (char *) kmem_k_end)
-               panic("%s: mmap in illegal memory range", __func__);
 
        memset(blob, 0, PAGE_SIZE);
 
@@ -1254,25 +1259,21 @@
        thunk_printf_debug("pmap_copy_page: pa src %p, pa dst %p\n",
                (void *) src_pa, (void *) dst_pa);
 
-       /* XXX bug alart: can we allow the kernel to make a decision on this? */
-       sblob = thunk_mmap(NULL, PAGE_SIZE,
+       /* source */
+       sblob = thunk_mmap(pm_tmp_p0, PAGE_SIZE,
                THUNK_PROT_READ,
-               THUNK_MAP_FILE | THUNK_MAP_SHARED,
+               THUNK_MAP_FILE | THUNK_MAP_FIXED | THUNK_MAP_SHARED,
                mem_fh, src_pa);
-       if (!sblob)
+       if (sblob != pm_tmp_p0)
                panic("%s: couldn't get src mapping", __func__);
-       if (sblob < (char *) kmem_k_end)
-               panic("%s: mmap in illegal memory range", __func__);
 
-       /* XXX bug alart: can we allow the kernel to make a decision on this? */
-       dblob = thunk_mmap(NULL, PAGE_SIZE,
+       /* destination */
+       dblob = thunk_mmap(pm_tmp_p1, PAGE_SIZE,
                THUNK_PROT_READ | THUNK_PROT_WRITE,
-               THUNK_MAP_FILE | THUNK_MAP_SHARED,
+               THUNK_MAP_FILE | THUNK_MAP_FIXED | THUNK_MAP_SHARED,
                mem_fh, dst_pa);
-       if (!dblob)
+       if (dblob != pm_tmp_p1)
                panic("%s: couldn't get dst mapping", __func__);
-       if (dblob < (char *) kmem_k_end)
-               panic("%s: mmap in illegal memory range", __func__);
 
        memcpy(dblob, sblob, PAGE_SIZE);