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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=unavailable 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 136A8C43441 for ; Wed, 28 Nov 2018 16:16:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8AA02081C for ; Wed, 28 Nov 2018 16:16:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8AA02081C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-pci-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728928AbeK2DSp (ORCPT ); Wed, 28 Nov 2018 22:18:45 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:44772 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727979AbeK2DSp (ORCPT ); Wed, 28 Nov 2018 22:18:45 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 442ED3644; Wed, 28 Nov 2018 08:16:34 -0800 (PST) Received: from [10.1.196.75] (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 51EEB3F5AF; Wed, 28 Nov 2018 08:16:32 -0800 (PST) Subject: Re: [PATCH] pci: imx6: support kernels built in Thumb-2 mode To: Stefan Agner , hongxing.zhu@nxp.com, l.stach@pengutronix.de Cc: lorenzo.pieralisi@arm.com, andrew.smirnov@gmail.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, bhelgaas@google.com, leonard.crestez@nxp.com, festevam@gmail.com, linux-arm-kernel@lists.infradead.org, tpiepho@impinj.com References: <20181128132554.28139-1-stefan@agner.ch> From: Robin Murphy Message-ID: Date: Wed, 28 Nov 2018 16:16:30 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181128132554.28139-1-stefan@agner.ch> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hi Stefan, On 28/11/2018 13:25, Stefan Agner wrote: > Add a fault handler which handles reads in Thumb-2 mode. Install > the appropriate handler depending on which mode the kernel has > been built. This avoids an "Unhandled fault: external abort on > non-linefetch (0x1008) at 0xf0a80000" during boot on a device > with a PCIe switch connected. > > Link: https://lore.kernel.org/linux-pci/20181126161645.8177-1-stefan@agner.ch/ > Signed-off-by: Stefan Agner > --- > FWIW, I found this manual helpful to write the code below: > http://hermes.wings.cs.wisc.edu/files/Thumb-2SupplementReferenceManual.pdf#page=43&zoom=100,0,66 This one's rather less ancient and even more authoritative ;) https://static.docs.arm.com/ddi0406/cd/DDI0406C_d_armv7ar_arm.pdf (ARMv7 had a few new encodings over and above ARMv6T2, although in fairness I don't think any should be relevant to this specific case) > -- > Stefan > > drivers/pci/controller/dwc/pci-imx6.c | 37 ++++++++++++++++++++++++++- > 1 file changed, 36 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c > index 69f86234f7c0..683deb74d69f 100644 > --- a/drivers/pci/controller/dwc/pci-imx6.c > +++ b/drivers/pci/controller/dwc/pci-imx6.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > > #include "pcie-designware.h" > > @@ -299,6 +300,37 @@ static int imx6q_pcie_abort_handler(unsigned long addr, > return 1; > } > > +static int imx6q_pcie_abort_handler_thumb2(unsigned long addr, > + unsigned int fsr, struct pt_regs *regs) > +{ > + unsigned long pc = instruction_pointer(regs); > + unsigned long instr = *(unsigned long *)pc; > + unsigned long thumb2_instr = __mem_to_opcode_thumb16(instr); > + int reg = thumb2_instr & 7; > + > + if (!__opcode_is_thumb16(instr & 0x0000ffffUL)) > + return 1; There are plenty of 32-bit Thumb encodings of various LDR/STR variants, and I doubt we can guarantee that the offset, target register, and/or addressing mode for a config space access will *always* suit the (relatively limited) 16-bit ones. > + > + /* Load word/byte and halfword immediate offset */ > + if (((thumb2_instr & 0xe800) == 0x6800) || > + ((thumb2_instr & 0xf800) == 0x8800)) { > + unsigned long val; > + > + if (thumb2_instr & 0x1000) > + val = 0xff; > + else if (thumb2_instr & 0x8000) > + val = 0xffff; > + else > + val = 0xffffffffUL; > + > + regs->uregs[reg] = val; > + regs->ARM_pc += 2; > + return 0; > + } What about stores? The existing implementation handles them, so either that's dead code which could perhaps be cleaned up, or they need to be handled here too. > + > + return 1; > +} > + > static int imx6_pcie_attach_pd(struct device *dev) > { > struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev); > @@ -1069,6 +1101,8 @@ static struct platform_driver imx6_pcie_driver = { > > static int __init imx6_pcie_init(void) > { > + bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL); Can these aborts definitely *only* be triggered by kernel accesses, and never, say, via an mmap() of anything exposed to userspace? Robin. > + > /* > * Since probe() can be deferred we need to make sure that > * hook_fault_code is not called after __init memory is freed > @@ -1076,7 +1110,8 @@ static int __init imx6_pcie_init(void) > * we can install the handler here without risking it > * accessing some uninitialized driver state. > */ > - hook_fault_code(8, imx6q_pcie_abort_handler, SIGBUS, 0, > + hook_fault_code(8, thumb2 ? imx6q_pcie_abort_handler_thumb2 : > + imx6q_pcie_abort_handler, SIGBUS, 0, > "external abort on non-linefetch"); > > return platform_driver_register(&imx6_pcie_driver); >