[src/trunk]: src/sys/arch/amd64/amd64 If the kernel jumps to NULL, print wher...

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

details:   https://anonhg.NetBSD.org/src/rev/d96f944e2b06
branches:  trunk
changeset: 341907:d96f944e2b06
user:      dholland <dholland%NetBSD.org@localhost>
date:      Sat Nov 28 15:06:55 2015 +0000

description:
If the kernel jumps to NULL, print where it came from instead of trying
to dereference and faulting again.

diffstat:

 sys/arch/amd64/amd64/trap.c |  14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diffs (35 lines):

diff -r 0f14005335db -r d96f944e2b06 sys/arch/amd64/amd64/trap.c
--- a/sys/arch/amd64/amd64/trap.c       Sat Nov 28 14:45:24 2015 +0000
+++ b/sys/arch/amd64/amd64/trap.c       Sat Nov 28 15:06:55 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: trap.c,v 1.81 2015/11/22 13:41:24 maxv Exp $   */
+/*     $NetBSD: trap.c,v 1.82 2015/11/28 15:06:55 dholland Exp $       */
 
 /*-
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.81 2015/11/22 13:41:24 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.82 2015/11/28 15:06:55 dholland Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -342,6 +342,16 @@
                /* Get %rsp value before fault - there may be a pad word
                 * below the trap frame. */
                vframe = (void *)frame->tf_rsp;
+               if (frame->tf_rip == 0) {
+                       /*
+                        * Assume that if we jumped to null we
+                        * probably did it via a null function
+                        * pointer, so print the return address.
+                        */
+                       printf("kernel jumped to null; return addr was %p\n",
+                              *(void **)frame->tf_rsp);
+                       goto we_re_toast;
+               }
                switch (*(uint16_t *)frame->tf_rip) {
                case 0xcf48:    /* iretq */
                        /*