From owner-freebsd-sparc64@freebsd.org Tue Apr 12 12:51:54 2016 Return-Path: Delivered-To: freebsd-sparc64@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5AD8BB0D6F4 for ; Tue, 12 Apr 2016 12:51:54 +0000 (UTC) (envelope-from mark.cave-ayland@ilande.co.uk) Received: from s16892447.onlinehome-server.info (chuckie.co.uk [82.165.15.123]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1F49B1886 for ; Tue, 12 Apr 2016 12:51:53 +0000 (UTC) (envelope-from mark.cave-ayland@ilande.co.uk) Received: from host81-154-31-210.range81-154.btcentralplus.com ([81.154.31.210] helo=[192.168.1.65]) by s16892447.onlinehome-server.info with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1apxnJ-0004OY-G8 for freebsd-sparc64@freebsd.org; Tue, 12 Apr 2016 13:51:50 +0100 To: "freebsd-sparc64@freebsd.org" References: <570CAFD6.2010004@ilande.co.uk> <570CBA7E.2080509@ilande.co.uk> From: Mark Cave-Ayland Message-ID: <570CEF42.9050400@ilande.co.uk> Date: Tue, 12 Apr 2016 13:51:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.7.0 MIME-Version: 1.0 In-Reply-To: <570CBA7E.2080509@ilande.co.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 81.154.31.210 X-SA-Exim-Mail-From: mark.cave-ayland@ilande.co.uk X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on s16892447.onlinehome-server.info X-Spam-Level: X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00, URIBL_BLOCKED autolearn=ham version=3.3.2 Subject: Re: qemu-system-sparc64: entering the debugger X-SA-Exim-Version: 4.2.1 (built Sun, 08 Jan 2012 02:45:44 +0000) X-SA-Exim-Scanned: Yes (on s16892447.onlinehome-server.info) X-BeenThere: freebsd-sparc64@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Porting FreeBSD to the Sparc List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Apr 2016 12:51:54 -0000 On 12/04/16 10:06, Mark Cave-Ayland wrote: >> So it looks like something has already gone wrong simply trying to dump >> the process map. Fortunately the number of QEMU translation blocks >> between the output of the "ps/m" header and the "KDB reentering" is >> quite small so I've uploaded it to >> https://www.ilande.co.uk/tmp/qemu/freebsd-tb.txt. >> >> Can anyone have a quick look at the link above and give me an idea as to >> roughly what the code is doing here? It seems that if you boot directly into ddb and use ps/m then you end up with a NULL pointer dereference: FreeBSD/sparc64 bootstrap loader, Revision 1.0 (mca@freebsd, Thu Sep 24 00:27:19 BST 2015) bootpath="/pci@1fe,0/pci-ata@5/ide1@8200/cdrom@0:a" Loading /boot/defaults/loader.conf /boot/kernel/kernel data=0xd893c0+0x20ffd8 syms=[0x8+0xdc578+0x8+0xcb349] \ Hit [Enter] to boot immediately, or any other key for command prompt. Booting [/boot/kernel/kernel] in 9 seconds... Type '?' for a list of commands, 'help' for more detailed help. OK boot -d Booting... jumping to kernel entry at 0xc00b0000. GDB: no debug ports present KDB: debugger backends: ddb KDB: current backend: ddb KDB: enter: Boot flags requested debugger [ thread pid 0 tid 0 ] Stopped at 0xc0630b00 db> ps/m pid ppid pgrp uid state wmesg wchan cmd 0 0 0 0KDB: reentering KDB: stack backtrace: (null)() at 0xc063105c (null)() at 0xc09e193c (null)() at 0xc00b1078 (null)() at 0xc011bb1c The NULL pointer reference occurs here: 0x00000000c0122008: ldx [ %l2 + 0x3d8 ], %g1 ! %g1 = 0 0x00000000c012200c: ldx [ %g1 + 0x18 ], %g1 ! 0x00000000c0122010: brz,pn %g1, 0xc0122050 0x00000000c0122014: nop AFAICT the corresponding part of db_ps.c is this: if (p->p_session != NULL && SESS_LEADER(p)) strlcat(state, "s", sizeof(state)); Here p->p_session expands to p->p_pgrp->pg_session which gives us the exception because p->p_pgrp is set to NULL. So I guess this is a bug, but not the bug I'm looking for... (Note: I know this is an oldish checkout, so maybe someone else has already found and fixed this) ATB, Mark.