From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752459AbeDONMe (ORCPT ); Sun, 15 Apr 2018 09:12:34 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:50012 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbeDONMc (ORCPT ); Sun, 15 Apr 2018 09:12:32 -0400 Date: Sun, 15 Apr 2018 14:12:06 +0100 From: Russell King - ARM Linux To: Linus Torvalds Cc: Dave Martin , Linux Kernel Mailing List , "Dmitry V. Levin" , "Eric W. Biederman" , sparclinux , ppc-dev , linux-arm-kernel Subject: Re: sparc/ppc/arm compat siginfo ABI regressions: sending SIGFPE via kill() returns wrong values in si_pid and si_uid Message-ID: <20180415131206.GR16141@n2100.armlinux.org.uk> References: <20180412172051.GK16141@n2100.armlinux.org.uk> <20180413094211.GN16141@n2100.armlinux.org.uk> <20180413170827.GB16308@e103592.cambridge.arm.com> <20180413175407.GO16141@n2100.armlinux.org.uk> <20180413184522.GD16308@e103592.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 13, 2018 at 12:53:49PM -0700, Linus Torvalds wrote: > On Fri, Apr 13, 2018 at 11:45 AM, Dave Martin wrote: > > > > Most uses I've seen do nothing more than use the FPE_xyz value to > > format diagnostic messages while dying. I struggled to find code that > > made a meaningful functional decision based on the value, though that's > > not proof... > > Yeah. I've seen code that cares about SIGFPE deeply, but it's almost > invariably about some emulated environment (eg Java VM, or CPU > emulation). > > And the siginfo data is basically never good enough for those > environments anyway on its own, so they will go and look at the actual > instruction that caused the fault and the register state instead, > because they need *all* the information. > > The cases that use si_code are the ones that just trapped signals in > order to give a more helpful abort message. > > So I could certainly imagine that si_code is actually used by somebody > who then decides to actuall act differently on it, but aside from > perhaps printing out a different message, it sounds far-fetched. Okay, in that case let's just use FPE_FLTINV. That makes the patch easily back-portable for stable kernels. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up