From b5329c1d857cab764251d763e91373ce7c3e922b Mon Sep 17 00:00:00 2001
From: atatat <atatat@NetBSD.org>
Date: Thu, 15 May 2003 13:18:18 +0000
Subject: [PATCH] (1) Don't print the message buffer (via ddb's dmesg command)
 if the message buffer has not yet been set up, mimicking code from the top of
 the sysctl routine for retrieving the message buffer.

(2) Add a /l modifier to the trace command.  This makes it print the
backtrace using printf() instead of db_printf(), which has the nice
side-effect of also putting it into the message buffer.  A kernel with
ddb in it but disabled (ie, ddb.onpanic set to zero) will print a
backtrace (which ends up in the message buffer) before dumping (or
not, depending on the value of kern.dump_on_panic) and rebooting, but
if ddb is not disabled, the backtrace is not printed, and there's no
way to get it to display a backtrace such that you can retrieve it
after the dump.  The backtrace printed by gdb is sometimes a little
different.

(3) Documentation for the above.
---
 share/man/man4/ddb.4 | 21 +++++++++++++++++----
 sys/ddb/db_command.c | 14 +++++++++++---
 sys/ddb/db_xxx.c     |  9 +++++++--
 3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/share/man/man4/ddb.4 b/share/man/man4/ddb.4
index 70c2287e449b..dd0118ab0d31 100644
--- a/share/man/man4/ddb.4
+++ b/share/man/man4/ddb.4
@@ -1,4 +1,4 @@
-.\"	$NetBSD: ddb.4,v 1.64 2003/05/08 05:38:10 wiz Exp $
+.\"	$NetBSD: ddb.4,v 1.65 2003/05/15 13:18:19 atatat Exp $
 .\"
 .\" Copyright (c) 1997 - 2003 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -357,6 +357,10 @@ or by the breakpoint number returned by
 if it's prefixed with
 .Sq Cm \&# .
 .It Xo
+.Ic dmesg
+.Xc
+Prints the contents of the kernel message buffer.
+.It Xo
 .Ic dwatch
 .Ar address
 .Xc
@@ -730,7 +734,8 @@ do the wrong thing.
 .It Ic sync
 Force a crash dump, and then reboot.
 .It Xo
-.Ic trace Ns Op Cm /u
+.Ic trace
+.Ic Ns Op Cm /u Ns Op Cm l
 .Sm off
 .Op Ar frame-address
 .Op Cm , Ar count
@@ -746,11 +751,15 @@ is the number of frames to be traced.
 If
 .Ar count
 is omitted, all frames are printed.
+If
+.Cm /l
+is specified, the trace is printed and also stored in the kernel
+message buffer.
 .Pp
 Warning: user-space stack trace is valid only if the machine dependent
 code supports it.
 .It Xo
-.Ic trace/t
+.Ic trace/t Ns Op Cm l
 .Sm off
 .Op Ar pid
 .Op Cm , Ar count
@@ -771,7 +780,11 @@ with
 .Sq 0t
 to force it to be interpreted as decimal (see
 .Sx VARIABLES
-section for radix)
+section for radix).
+If
+.Cm /l
+is specified, the trace is printed and also stored in the kernel
+message buffer.
 .Pp
 Warning: trace by pid is valid only if the machine dependent code
 supports it.
diff --git a/sys/ddb/db_command.c b/sys/ddb/db_command.c
index 2da441b20a18..2dc47e36fd36 100644
--- a/sys/ddb/db_command.c
+++ b/sys/ddb/db_command.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: db_command.c,v 1.69 2003/04/28 02:49:54 briggs Exp $	*/
+/*	$NetBSD: db_command.c,v 1.70 2003/05/15 13:18:18 atatat Exp $	*/
 
 /*
  * Mach Operating System
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: db_command.c,v 1.69 2003/04/28 02:49:54 briggs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_command.c,v 1.70 2003/05/15 13:18:18 atatat Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -707,11 +707,19 @@ db_sifting_cmd(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
 static void
 db_stack_trace_cmd(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
 {
+	register char *cp = modif;
+	register char c;
+	void (*pr)(const char *, ...);
+
+	pr = db_printf;
+	while ((c = *cp++) != 0)
+		if (c == 'l')
+			pr = printf;
 
 	if (count == -1)
 		count = 65535;
 
-	db_stack_trace_print(addr, have_addr, count, modif, db_printf);
+	db_stack_trace_print(addr, have_addr, count, modif, pr);
 }
 
 static void
diff --git a/sys/ddb/db_xxx.c b/sys/ddb/db_xxx.c
index dbacde33ff07..9203f76d479c 100644
--- a/sys/ddb/db_xxx.c
+++ b/sys/ddb/db_xxx.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: db_xxx.c,v 1.21 2003/04/28 02:49:55 briggs Exp $	*/
+/*	$NetBSD: db_xxx.c,v 1.22 2003/05/15 13:18:18 atatat Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1991, 1993
@@ -43,7 +43,7 @@
 #include "opt_kgdb.h"
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: db_xxx.c,v 1.21 2003/04/28 02:49:55 briggs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_xxx.c,v 1.22 2003/05/15 13:18:18 atatat Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -237,6 +237,11 @@ db_dmesg(db_expr_t addr, int haddr, db_expr_t count, char *modif)
 	int ch, newl, skip, i;
 	char *p, *bufdata;
 
+        if (!msgbufenabled || msgbufp->msg_magic != MSG_MAGIC) {
+		db_printf("message buffer not available\n");
+		return;
+	}
+
 	mbp = msgbufp;
 	bufdata = &mbp->msg_bufc[0];