[src/trunk]: src/sys/arch/alpha/alpha - Add exception_return() to the list of...

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

details:   https://anonhg.NetBSD.org/src/rev/9c53bf1db565
branches:  trunk
changeset: 955083:9c53bf1db565
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Fri Sep 18 00:09:29 2020 +0000

description:
- Add exception_return() to the list of trap vector symbols, which will
  enable us to trace back through an exception if the fault happens
  during the exception return.
- Identify and report the kernel thread backstop when back tracing
  kernel threads.

diffstat:

 sys/arch/alpha/alpha/db_trace.c |  20 ++++++++++++++++++--
 1 files changed, 18 insertions(+), 2 deletions(-)

diffs (48 lines):

diff -r 6c180f5092ba -r 9c53bf1db565 sys/arch/alpha/alpha/db_trace.c
--- a/sys/arch/alpha/alpha/db_trace.c   Fri Sep 18 00:06:35 2020 +0000
+++ b/sys/arch/alpha/alpha/db_trace.c   Fri Sep 18 00:09:29 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: db_trace.c,v 1.28 2012/02/06 02:14:10 matt Exp $ */
+/* $NetBSD: db_trace.c,v 1.29 2020/09/18 00:09:29 thorpej Exp $ */
 
 /*-
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -35,7 +35,7 @@
 
 #include <sys/cdefs.h>                 /* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: db_trace.c,v 1.28 2012/02/06 02:14:10 matt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_trace.c,v 1.29 2020/09/18 00:09:29 thorpej Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -85,6 +85,12 @@
        { (vaddr_t)&XentSys,            "syscall" },
        { (vaddr_t)&XentUna,            "unaligned access fault" },
        { (vaddr_t)&XentRestart,        "console restart" },
+
+       /*
+        * We'll not know what trap we took, but we'll find the
+        * trap frame, at least...
+        */
+       { (vaddr_t)&exception_return,   "(exception return)" },
        { 0 }
 };
 
@@ -256,6 +262,16 @@
                }
 
                /*
+                * If the previous RA pointed at the kernel thread
+                * backstop, then we are at the root of the call
+                * graph.
+                */
+               if (symval == (vaddr_t)&alpha_kthread_backstop) {
+                       (*pr)("--- kernel thread backstop ---\n");
+                       break;
+               }
+
+               /*
                 * XXX Printing out arguments is Hard.  We'd have to
                 * keep lots of state as we traverse the frame, figuring
                 * out where the arguments to the function are stored