[src/trunk]: src/sys/uvm Use UVM_PROT_ALL only if UVM_KMF_EXEC is given as ar...

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

details:   https://anonhg.NetBSD.org/src/rev/9f25819fcccb
branches:  trunk
changeset: 346683:9f25819fcccb
user:      maxv <maxv%NetBSD.org@localhost>
date:      Wed Jul 27 16:45:00 2016 +0000

description:
Use UVM_PROT_ALL only if UVM_KMF_EXEC is given as argument. Otherwise, if
UVM_KMF_PAGEABLE is also given as argument, only the VA is allocated and
UVM waits for the page to fault before kentering it. When kentering it, it
will use the UVM_PROT_ flag that was passed to uvm_map; which means that it
will kenter it as RWX.

With this change, the number of RWX pages in the amd64 kernel reaches
strictly zero.

diffstat:

 sys/uvm/uvm_km.c |  9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diffs (38 lines):

diff -r 502fcc259dba -r 9f25819fcccb sys/uvm/uvm_km.c
--- a/sys/uvm/uvm_km.c  Wed Jul 27 13:04:28 2016 +0000
+++ b/sys/uvm/uvm_km.c  Wed Jul 27 16:45:00 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_km.c,v 1.140 2016/07/20 12:38:43 maxv Exp $        */
+/*     $NetBSD: uvm_km.c,v 1.141 2016/07/27 16:45:00 maxv Exp $        */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -152,7 +152,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_km.c,v 1.140 2016/07/20 12:38:43 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_km.c,v 1.141 2016/07/27 16:45:00 maxv Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -593,7 +593,7 @@
        struct vm_page *pg;
        struct uvm_object *obj;
        int pgaflags;
-       vm_prot_t prot;
+       vm_prot_t prot, vaprot;
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
 
        KASSERT(vm_map_pmap(map) == pmap_kernel());
@@ -617,8 +617,9 @@
         * allocate some virtual space
         */
 
+       vaprot = (flags & UVM_KMF_EXEC) ? UVM_PROT_ALL : UVM_PROT_RW;
        if (__predict_false(uvm_map(map, &kva, size, obj, UVM_UNKNOWN_OFFSET,
-           align, UVM_MAPFLAG(UVM_PROT_ALL, UVM_PROT_ALL, UVM_INH_NONE,
+           align, UVM_MAPFLAG(vaprot, UVM_PROT_ALL, UVM_INH_NONE,
            UVM_ADV_RANDOM,
            (flags & (UVM_KMF_TRYLOCK | UVM_KMF_NOWAIT | UVM_KMF_WAITVA
             | UVM_KMF_COLORMATCH)))) != 0)) {