From owner-freebsd-stable@FreeBSD.ORG Wed Dec 3 15:45:34 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 568D51065670 for ; Wed, 3 Dec 2008 15:45:34 +0000 (UTC) (envelope-from dudu@dudu.ro) Received: from yx-out-2324.google.com (yx-out-2324.google.com [74.125.44.28]) by mx1.freebsd.org (Postfix) with ESMTP id 164A38FC17 for ; Wed, 3 Dec 2008 15:45:33 +0000 (UTC) (envelope-from dudu@dudu.ro) Received: by yx-out-2324.google.com with SMTP id 8so1487435yxb.13 for ; Wed, 03 Dec 2008 07:45:33 -0800 (PST) Received: by 10.151.150.20 with SMTP id c20mr26254995ybo.139.1228319133334; Wed, 03 Dec 2008 07:45:33 -0800 (PST) Received: by 10.151.137.13 with HTTP; Wed, 3 Dec 2008 07:45:33 -0800 (PST) Message-ID: Date: Wed, 3 Dec 2008 17:45:33 +0200 From: "Vlad GALU" To: "Dan Nelson" In-Reply-To: <20081203152330.GD22076@dan.emsphone.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20081203152330.GD22076@dan.emsphone.com> Cc: freebsd-stable@freebsd.org Subject: Re: Weird truss output X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Dec 2008 15:45:34 -0000 On Wed, Dec 3, 2008 at 5:23 PM, Dan Nelson wrote: > In the last episode (Dec 03), Vlad GALU said: >> I'm running a statically linked binary, which I've built inside a >> jail. The jail's libc & co are in sync with the host's. Truss then >> shows this: >> >> -- cut here -- >> -- UNKNOWN SYSCALL 1048532 -- >> -- UNKNOWN SYSCALL 1048532 -- > > Is this a threaded app that you attached truss to after it was started? > The method that truss uses to catch syscall enter/exit events doesn't > indicate whether the event is an enter or an exit, so if you attach > while a syscall is active, truss handles the exit event as if it were a > syscall entry event, and never gets back in synch. It gets worse with > threaded apps because each thread is another chance to get out of > synch. Try this patch: > > Index: i386-fbsd.c > =================================================================== > RCS file: /home/ncvs/src/usr.bin/truss/i386-fbsd.c,v > retrieving revision 1.29 > diff -u -p -r1.29 i386-fbsd.c > --- i386-fbsd.c 28 Jul 2007 23:15:04 -0000 1.29 > +++ i386-fbsd.c 3 Dec 2008 15:20:09 -0000 > @@ -149,7 +149,14 @@ i386_syscall_entry(struct trussinfo *tru > fsc.name = > (syscall_num < 0 || syscall_num > nsyscalls) ? NULL : syscallnames[syscall_num]; > if (!fsc.name) { > - fprintf(trussinfo->outfile, "-- UNKNOWN SYSCALL %d --\n", syscall_num); > + fprintf(trussinfo->outfile, "-- UNKNOWN SYSCALL %u (0x%08x) --\n", syscall_num, syscall_num); > + if ((unsigned int)syscall_num > 0x1000) { > + /* When attaching to a running process, we have a 50-50 chance > + of attaching to a process waiting in a syscall, which means > + our first trap is an exit instead of an entry and we're out > + of synch. Reset our flag */ > + trussinfo->curthread->in_syscall = 0; > + } > } > > if (fsc.name && (trussinfo->flags & FOLLOWFORKS) > > > -- > Dan Nelson > dnelson@allantgroup.com > Hi Dan, You were right, this application was indeed threaded. The messages still occur, although at a slightly lower rate. One other thing that's not particularly helpful is this: -- cut here-- read(1074283119,"\M-Ry\^A\0",7356800) = 4 (0x4) -- and here -- I obviously don't have that many descriptors in my process. I can live with the malformed message, but it's a PITA not to know which fd the read was actually made from :( -- ~/.signature: no such file or directory