From owner-freebsd-current@FreeBSD.ORG  Sun May 18 23:25:12 2003
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 6A84E37B405; Sun, 18 May 2003 23:25:12 -0700 (PDT)
Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 366C743FBD; Sun, 18 May 2003 23:25:08 -0700 (PDT)
	(envelope-from bde@zeta.org.au)
Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246])
	by mailman.zeta.org.au (8.9.3p2/8.8.7) with ESMTP id QAA20402;
	Mon, 19 May 2003 16:24:53 +1000
Date: Mon, 19 May 2003 16:24:52 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
X-X-Sender: bde@gamplex.bde.org
To: Ian Dowse <iedowse@maths.tcd.ie>
In-Reply-To: <200305182227.aa40061@salmon.maths.tcd.ie>
Message-ID: <20030519161526.T22357@gamplex.bde.org>
References: <200305182227.aa40061@salmon.maths.tcd.ie>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: current@freebsd.org
Subject: Re: kgdb missing stack frames
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 19 May 2003 06:25:12 -0000

On Sun, 18 May 2003, Ian Dowse wrote:

> Support for decoding i386 trap frames in kgdb appears to have been
> lost by revision 1.3 of contrib/gdb/gdb/config/i386/tm-fbsd.h, since
> FRAME_SAVED_PC() is defined there in terms of i386bsd_frame_saved_pc(),
> so fbsd_kern_frame_saved_pc() in gnu/usr.bin/binutils/gdb/kvm-fbsd.c
> never gets called. A simple way to see this is to run
>
> 	gdb -k kernel.debug /dev/mem
>
> and get a backtrace from the idle process:
>
> 	(kgdb) proc 11
> 	(kgdb) bt
> 	#0  mi_switch () at ../../../kern/kern_synch.c:530
> 	#1  0xc01edb92 in ithread_schedule (ithread=0xc1898280, do_switch=1)
> 	    at ../../../kern/kern_intr.c:402
> 	#2  0xc034ad43 in sched_ithd (cookie=0xc1894d80)
> 	    at ../../../i386/isa/ithread.c:77
> 	#3  0xc03380cc in Xintr14 () at {standard input}:382
> 	#4  0xc01ed16c in idle_proc (dummy=0x0) at ../../../kern/kern_idle.c:114
> 	#5  0xc01ecea0 in fork_exit (callout=0xc01ed130 <idle_proc>, arg=0x0,
> 	    frame=0x0) at ../../../kern/kern_fork.c:792
>
> This is what it should look like:
>
> 	(kgdb) proc 11
> 	(kgdb) bt
> 	#0  mi_switch () at ../../../kern/kern_synch.c:530
> 	#1  0xc01edb92 in ithread_schedule (ithread=0xc1898280, do_switch=1)
> 	    at ../../../kern/kern_intr.c:402
> 	#2  0xc034ad43 in sched_ithd (cookie=0xc1898280)
> 	    at ../../../i386/isa/ithread.c:77
> 	#3  0xc033e242 in cpu_idle () at ../../../i386/i386/machdep.c:1074
> 	#4  0xc01ed16c in idle_proc (dummy=0x0) at ../../../kern/kern_idle.c:114
> 	#5  0xc01ecea0 in fork_exit (callout=0xc01ed130 <idle_proc>, arg=0x0,
> 	    frame=0x0) at ../../../kern/kern_fork.c:792
>
> i.e, the cpu_idle() frame now appears instead of Xintr14().

This is no better, since it loses Xintr14()'s frame instead of cpu_idle()'s
frame.

OTOH, it wouldnt hurt in most cases to lose all the frames below
cpu_idle() and above idle_proc(), since they are not really associated
with the process.

Bruce