From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756305AbaDKMCf (ORCPT ); Fri, 11 Apr 2014 08:02:35 -0400 Received: from mail-qg0-f54.google.com ([209.85.192.54]:61558 "EHLO mail-qg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755522AbaDKMCd (ORCPT ); Fri, 11 Apr 2014 08:02:33 -0400 X-Greylist: delayed 614 seconds by postgrey-1.27 at vger.kernel.org; Fri, 11 Apr 2014 08:02:33 EDT MIME-Version: 1.0 X-Originating-IP: [46.139.80.5] In-Reply-To: <20140411115421.GL16119@n2100.arm.linux.org.uk> References: <1397211951-20549-1-git-send-email-miklos@szeredi.hu> <1397211951-20549-3-git-send-email-miklos@szeredi.hu> <20140411103351.GJ16119@n2100.arm.linux.org.uk> <20140411115421.GL16119@n2100.arm.linux.org.uk> Date: Fri, 11 Apr 2014 14:02:32 +0200 Message-ID: Subject: Re: [PATCH 02/15] arm: __NR_syscalls fix From: Miklos Szeredi To: Russell King - ARM Linux Cc: linux-arch , Kernel Mailing List , Miklos Szeredi Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 11, 2014 at 1:54 PM, Russell King - ARM Linux wrote: > On Fri, Apr 11, 2014 at 01:50:50PM +0200, Miklos Szeredi wrote: >> On Fri, Apr 11, 2014 at 12:33 PM, Russell King - ARM Linux >> wrote: >> > On Fri, Apr 11, 2014 at 12:25:38PM +0200, Miklos Szeredi wrote: >> >> From: Miklos Szeredi >> >> >> >> Signed-off-by: Miklos Szeredi >> >> Cc: Russell King >> >> --- >> > >> > This has me wondering... >> > >> > (a) what you think it fixes >> > (b) whether you tried to build-test this >> > >> > The ARM instruction set supports 8-bit immediate constants with an even >> > power of two shift. 384 fits that (0x180), 382 does not (0x17e), and >> > in your following patch, 383 definitely doesn't (0x17f). >> > >> > Having this constant larger than necessary does not cause any problem >> > for the syscall table: we explicitly pad it with calls to sys_ni_syscall >> > to make up the difference. >> >> Yes, and the padding will be of wrong length if NR_syscalls is >> incorrect (which may be Oopsable?). At least that is my impression >> from a casual glance. > > Please explain. Look at ending lines of arch/arm/kernel/calls.S: if NR_syscalls is a multiple of 4, then syscalls_padding will be zero. I.e. no padding despite the fact that there is in fact only 382 system calls in table and there should be 2 sys_ni_syscall pads. So there's some crap in there, for sure. If it causes actual problems, I don't know. Thanks, Miklos