From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25066 invoked by alias); 8 Jun 2005 15:11:46 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 25000 invoked by uid 22791); 8 Jun 2005 15:11:40 -0000 Received: from smtp002.mail.ukl.yahoo.com (HELO smtp002.mail.ukl.yahoo.com) (217.12.11.33) by sourceware.org (qpsmtpd/0.30-dev) with SMTP; Wed, 08 Jun 2005 15:11:40 +0000 Received: (qmail 35302 invoked from network); 8 Jun 2005 15:11:38 -0000 Received: from unknown (HELO ?151.97.230.33?) (blaisorblade@151.97.230.33 with login) by smtp002.mail.ukl.yahoo.com with SMTP; 8 Jun 2005 15:11:38 -0000 From: Blaisorblade To: user-mode-linux-user@lists.sourceforge.net Subject: Re: [uml-user] problems debugging an uml skas kernel with gdb Date: Wed, 08 Jun 2005 15:11:00 -0000 User-Agent: KMail/1.8.1 Cc: marco ghidinelli , gdb ml References: <20050608123442.GB8481@localhost.localdomain> In-Reply-To: <20050608123442.GB8481@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200506081715.07405.blaisorblade@yahoo.it> X-SW-Source: 2005-06/txt/msg00068.txt.bz2 On Wednesday 08 June 2005 14:34, marco ghidinelli wrote: > hello, > > i've problems debugging a UML SKAS kernel. > the host is an x86 kernel 2.6.12-rc4-skas3-v9-pre4 > the guest is a kernel 2.6.12-rc4. > > GNU gdb 6.3.50.20050606-cvs, > gcc version 3.3.5 (Debian 1:3.3.5-8ubuntu2) > > the problems are: > > 1) a pointer to a struct was not seen by the debugger: > > example session: > > Breakpoint 4, yoghi_init (sch=0x9d1b830, opt=0x9d1b400) > at net/sched/sch_yoghi.c:235 > 235 printk(KERN_DEBUG "Yoghi 0.0.3 Initiaziled\n"); > (gdb) n > Yoghi 0.0.3 Initiaziled > 236 if(q != NULL) > (gdb) n > 237 printk(KERN_DEBUG "yoghi_init: q = > 0x%x\n",(u32)q); > (gdb) n > yoghi_init: q = 0x9d1b480 > 238 return 0; > (gdb) p q > No symbol "q" in current context. > > this is quite annoying but i can get my info in another way: > (gdb) p (struct yoghi_sched_data)*0x9d1b480 Probably the variable was optimized out by the compiler... > 2) sometimes the debugger get lost: > > Breakpoint 3, yoghi_bind (sch=0xa8bcf20, parent=0, classid=176934688) > at net/sched/sch_yoghi.c:271 > 271 return yoghi_get(sch, classid); > (gdb) s > yoghi_get (sch=0x10003, classid=65539) at net/sched/sch_yoghi.c:257 > > note that sch was changed!! > > and sometimes it get completly lost: > > Breakpoint 1, yoghi_get (sch=0x10013, classid=65555) > at net/sched/sch_yoghi.c:259 > 259 u32 band = TC_H_MIN(classid); > (gdb) n > 261 printk(KERN_DEBUG "yoghi_get: classid = %d ; band = %d ; > band2 = %d\n",classid,band,band2); > (gdb) p band > $8 = 19 > (gdb) n > yoghi_get: classid = 65555 ; band = 19 ; band2 = 19 > 262 if (band -1 > q->bands) > (gdb) n > 263 return 0; /* means not found */ > (gdb) n > 265 } > (gdb) n > 0x0a8846d2 in ?? () > (gdb) bt > #0 0x0a8846d2 in ?? () > #1 0x09d1b000 in ?? () > #2 0x00010013 in ?? () > #3 0x00010013 in ?? () > #4 0x00000000 in ?? () > > bye! Sadly gdb is not very reliable, and I can confirm all this is normal... you could try compiling the kernel (or at least the modules of your interest, but you'd better patch the Makefiles) with -O1 instead of -O2... -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it