From owner-freebsd-current@FreeBSD.ORG Mon Feb 23 18:04:19 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CCFF610656CA; Mon, 23 Feb 2009 18:04:19 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.freebsd.org (Postfix) with ESMTP id 379E38FC21; Mon, 23 Feb 2009 18:04:19 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from phobos.local ([192.168.254.200]) (authenticated bits=0) by pooker.samsco.org (8.14.2/8.14.2) with ESMTP id n1NHxQ0E033163; Mon, 23 Feb 2009 10:59:26 -0700 (MST) (envelope-from scottl@samsco.org) Message-ID: <49A2E3FE.2070106@samsco.org> Date: Mon, 23 Feb 2009 10:59:26 -0700 From: Scott Long User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.13) Gecko/20080313 SeaMonkey/1.1.9 MIME-Version: 1.0 To: John Baldwin References: <5D267A3F22FD854F8F48B3D2B5238193394588D54D@IRVEXCHCCR01.corp.ad.broadcom.com> <200902231119.54925.jhb@freebsd.org> <49A2D86F.1000509@samsco.org> <200902231257.28060.jhb@freebsd.org> In-Reply-To: <200902231257.28060.jhb@freebsd.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.4 required=3.8 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on pooker.samsco.org Cc: David Christensen , freebsd-current@freebsd.org Subject: Re: Hopefully Simple Question on Debugging Kernel Modules X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 Feb 2009 18:04:20 -0000 John Baldwin wrote: > On Monday 23 February 2009 12:10:07 pm Scott Long wrote: >> John Baldwin wrote: >>> On Friday 20 February 2009 6:40:56 pm David Christensen wrote: >>>> I'm sure this is a simple question but the answer is alluding my Google >>>> search capabilities. My driver is being loaded as a kernel module and >>>> is failing with the following error: >>>> >>>> Fatal trap 12: page fault while in kernel mode >>>> cpuid = 0; apic id = 00 >>>> fault virtual address = 0xfffffffe40abe9dc >>>> fault code = supervisor write data, page not present >>>> instruction pointer = 0x8:0xffffffff920b638f >>>> stack pointer = 0x10:0xffffffff9212bb10 >>>> frame pointer = 0x10:0xffffffff9212bbb0 >>>> code segment = base 0x0, limit 0xfffff, type 0x1b >>>> = DPL 0, pres 1, long 1, def32 0, gran 1 >>>> processor eflags = interrupt enabled, resume, IOPL = 0 >>>> current process = 12 (irq268: bce0) >>>> [thread pid 12 tid 100166 ] >>>> Stopped at bce_intr+0x8df: addl $0x1,0x2c854(%r12,%rax,4) >>>> db> >>>> >>>> I simply need to find the offending source line in my driver. Not sure >>>> how I've managed to get the driver running at all without this but it's >>>> time to do things the right way. I have KDB/DDB/GDB built into my >>>> -CURRENT kernel already. It'd be great to find the source line while in >>>> the kernel debugger but I'm also fine with rebooting the system to >>>> identify the line number. >>> Just use gdb on bce.ko (built with debug symbols): >>> >>> gdb /path/to/if_bce.ko >>> (gdb) l *bce_intr+0x8df >>> >>> If you get a crashdump you can run kgdb on it and just walk up to the > relevant >>> stack frame and use 'l' there to get a listing. >>> >> One thing that I've never figured out is how debugging symbols are >> handled in module builds these days. If I go to /sys/modules/bce and >> do 'make', it generates a .ko and explicitly strips it. I wind up >> having to re-run the link command by hand so I get symbols. What is >> the correct way to do this? Note that I'm not interested in answers >> that involve "go to /usr/src and run make buildkernel" =-) > > make DEBUG_FLAGS=-g is what I use. The same thing works for userland tools > and the kernel (usually we put 'makeoptions DEBUG_FLAGS=-g' in a kernel > config so it is "automatic" for kernels though). > Ah, I was still using 'CFLAGS+= -g". Thanks to you and Mr. Campbell for the tip. Scott