From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750879AbZHZHsD (ORCPT ); Wed, 26 Aug 2009 03:48:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750716AbZHZHsC (ORCPT ); Wed, 26 Aug 2009 03:48:02 -0400 Received: from mtagate7.uk.ibm.com ([195.212.29.140]:56726 "EHLO mtagate7.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1749667AbZHZHsB (ORCPT ); Wed, 26 Aug 2009 03:48:01 -0400 Date: Wed, 26 Aug 2009 09:47:36 +0200 From: Heiko Carstens To: Frederic Weisbecker Cc: Martin Schwidefsky , Hendrik Brueckner , Jason Baron , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, rostedt@goodmis.org, peterz@infradead.org, mathieu.desnoyers@polymtl.ca, jiayingz@google.com, mbligh@google.com, lizf@cn.fujitsu.com Subject: Re: [PATCH 08/12] add trace events for each syscall entry/exit Message-ID: <20090826074735.GB4749@osiris.boeblingen.de.ibm.com> References: <20090825125027.GE4639@cetus.boeblingen.de.ibm.com> <20090825214020.GF8215@nowhere> <20090825220900.GA9953@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090825220900.GA9953@nowhere> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 26, 2009 at 12:09:01AM +0200, Frederic Weisbecker wrote: > On Tue, Aug 25, 2009 at 11:40:21PM +0200, Frederic Weisbecker wrote: > > On Tue, Aug 25, 2009 at 02:50:27PM +0200, Hendrik Brueckner wrote: > > > Most arch syscall_get_nr() implementations returns -1 if the syscall > > > number is not valid. Accessing the bit field without a check might > > > result in a kernel oops (at least I saw it on s390 for ftrace selftest). > > > > > > Before this change, this problem did not occur, because the invalid > > > syscall number (-1) caused syscall_nr_to_meta() to return NULL. > > > > > > There are at least two scenarios where syscall_get_nr() can return -1: > > > > > > 1. For example, ptrace stores an invalid syscall number, and thus, > > > tracing code resets it. > > > (see do_syscall_trace_enter in arch/s390/kernel/ptrace.c) > > > > > > 2. The syscall_regfunc() (kernel/tracepoint.c) sets the TIF_SYSCALL_FTRACE > > > (now: TIF_SYSCALL_TRACEPOINT) flag for all threads which includes > > > kernel threads. > > > However, the ftrace selftest triggers a kernel oops when testing syscall > > > trace points: > > > - The kernel thread is started as ususal (do_fork()), > > > - tracing code sets TIF_SYSCALL_FTRACE, > > > - the ret_from_fork() function is triggered and starts > > > ftrace_syscall_exit() with an invalid syscall number. > > > > > > To avoid these scenarios, I suggest to check the syscall_nr. > > > > > > [...] > > > > > > Signed-off-by: Hendrik Brueckner > > > > > > > > I'm queueing this one for .32 > > > > Thanks. > > Btw it would be nice to have an ack from s390 maintainers. > Martin, Heiko, no problem with this patch? Acked-by: Heiko Carstens