From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA1ACC00449 for ; Fri, 5 Oct 2018 10:24:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 897302084D for ; Fri, 5 Oct 2018 10:24:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="gi+DDpld" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 897302084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727878AbeJERWn (ORCPT ); Fri, 5 Oct 2018 13:22:43 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:52202 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727601AbeJERWm (ORCPT ); Fri, 5 Oct 2018 13:22:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZYX+zoljw6FLZWp7ebzRfQsxvvNeDL1RIUspnNkZTiE=; b=gi+DDpldXv8v6IJcxUdjqlDe/ 3yP7alK0ecgSMeZfbBNgf15PYa7qx0IzqrGyOGgrud0PyOHaE1zRikp4tzFsd5Igrhrb6QyRsXZRT B6BEOmgpEseoZoZM+Yi+HSPlvQ49oap1LKmcHQPD15miN0+/v+vujbq2MfPVECaO8RWdg=; Received: from n2100.armlinux.org.uk ([2002:4e20:1eda:1:214:fdff:fe10:4f86]:50927) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.90_1) (envelope-from ) id 1g8NHS-0003Td-ND; Fri, 05 Oct 2018 11:24:22 +0100 Received: from linux by n2100.armlinux.org.uk with local (Exim 4.90_1) (envelope-from ) id 1g8NHM-00089u-Vk; Fri, 05 Oct 2018 11:24:17 +0100 Date: Fri, 5 Oct 2018 11:24:13 +0100 From: Russell King - ARM Linux To: Manjeet Pawar Cc: ebiederm@xmission.com, arnd@arndb.de, akpm@linux-foundation.org, mhiramat@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, pankaj.m@samsung.com, a.sahrawat@samsung.com, Rohit Thapliyal Subject: Re: [PATCH] traps:Recover undefined user instruction on ARM Message-ID: <20181005102412.GI30658@n2100.armlinux.org.uk> References: <20181005045237epcas5p3bc0ab07cfb8c25ef81188b4614b978ba~anUhv_CDP0965009650epcas5p34@epcas5p3.samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181005045237epcas5p3bc0ab07cfb8c25ef81188b4614b978ba~anUhv_CDP0965009650epcas5p34@epcas5p3.samsung.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 05, 2018 at 10:15:57AM +0530, Manjeet Pawar wrote: > From: Rohit Thapliyal > > During user undefined instruction exception, the arm exception > handler currently results in application crash through SIGILL. > The bad instruction can be due to ddr/hardware issue. > For such cases, exception trap handler could try to recover the corrupted > text by clearing pagetable entry of undefined instruction pc and trying to fetch > the instruction opcode by generating major page fault. > Resulting in loading the page with correct instruction from mapped file. > If there is no error in root filesystem i.e. the opcode is intact > in file, then filemap fault shall be able to recover > the instruction and continue execution normally instead of crashing. For the reasons others have pointed out in previous replies, I will not merge this patch or anything similar to this for mainline. The only sane solution to the above problem is to fix the hardware or the hardware timings so that DDR access is reliable. Sorry. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up