[src/trunk]: src/sys/arch/amd64/amd64 Attempt to clarify panic messages for n...

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

details:   https://anonhg.NetBSD.org/src/rev/8e6fb9f2adcd
branches:  trunk
changeset: 828293:8e6fb9f2adcd
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Thu Dec 07 03:25:51 2017 +0000

description:
Attempt to clarify panic messages for null pointer access/execute.

diffstat:

 sys/arch/amd64/amd64/trap.c |  24 +++++++++++++++++-------
 1 files changed, 17 insertions(+), 7 deletions(-)

diffs (50 lines):

diff -r 23699d77d092 -r 8e6fb9f2adcd sys/arch/amd64/amd64/trap.c
--- a/sys/arch/amd64/amd64/trap.c       Thu Dec 07 03:16:24 2017 +0000
+++ b/sys/arch/amd64/amd64/trap.c       Thu Dec 07 03:25:51 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: trap.c,v 1.105 2017/12/02 12:40:03 maxv Exp $  */
+/*     $NetBSD: trap.c,v 1.106 2017/12/07 03:25:51 riastradh Exp $     */
 
 /*
  * Copyright (c) 1998, 2000, 2017 The NetBSD Foundation, Inc.
@@ -64,7 +64,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.105 2017/12/02 12:40:03 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.106 2017/12/07 03:25:51 riastradh Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -518,16 +518,26 @@
 
                if (frame->tf_err & PGEX_X) {
                        /* SMEP might have brought us here */
-                       if (cr2 < VM_MAXUSER_ADDRESS)
-                               panic("prevented execution of %p (SMEP)",
-                                   (void *)cr2);
+                       if (cr2 < VM_MAXUSER_ADDRESS) {
+                               if (cr2 == 0)
+                                       panic("prevented jump to null"
+                                           " instruction pointer (SMEP)");
+                               else
+                                       panic("prevented execution of"
+                                           " user address %p (SMEP)",
+                                           (void *)cr2);
+                       }
                }
 
                if (cr2 < VM_MAXUSER_ADDRESS) {
                        /* SMAP might have brought us here */
-                       if (onfault_handler(pcb, frame) == NULL)
-                               panic("prevented access to %p (SMAP)",
+                       if (onfault_handler(pcb, frame) == NULL) {
+                               panic("prevented %s %p (SMAP)",
+                                   (cr2 < PAGE_SIZE
+                                       ? "null pointer dereference at"
+                                       : "access to"),
                                    (void *)cr2);
+                       }
                }
 
                goto faultcommon;