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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1744AC19759 for ; Fri, 2 Aug 2019 01:05:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E7FEB2080C for ; Fri, 2 Aug 2019 01:05:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390611AbfHBBFq (ORCPT ); Thu, 1 Aug 2019 21:05:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51406 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388659AbfHBBFq (ORCPT ); Thu, 1 Aug 2019 21:05:46 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D9D1430C1953; Fri, 2 Aug 2019 01:05:45 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-80.pek2.redhat.com [10.72.12.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6A06E19C4F; Fri, 2 Aug 2019 01:05:42 +0000 (UTC) Date: Fri, 2 Aug 2019 09:05:38 +0800 From: Dave Young To: lijiang Cc: "Lendacky, Thomas" , "linux-kernel@vger.kernel.org" , Dave Anderson , kexec@lists.infradead.org, vgoyal@redhat.com, bhe@redhat.com, ebiederm@xmission.com Subject: Re: crash: `kmem -s` reported "kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e" on a dumped vmcore Message-ID: <20190802010538.GA2202@dhcp-128-65.nay.redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Fri, 02 Aug 2019 01:05:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add kexec cc list. On 08/01/19 at 11:02pm, lijiang wrote: > Hi, Tom > > Recently, i ran into a problem about SME and used crash tool to check the vmcore as follow: > > crash> kmem -s | grep -i invalid > kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e > kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e > > And the crash tool reported the above error, probably, the main reason is that kernel does not > correctly handle the first 640k region when SME is enabled. > > When SME is enabled, the kernel and initramfs images are loaded into the decrypted memory, and > the backup area(first 640k) is also mapped as decrypted, but the first 640k data is copied to > the backup area in purgatory(). Please refer to this file: arch/x86/purgatory/purgatory.c > ...... > static int copy_backup_region(void) > { > if (purgatory_backup_dest) { > memcpy((void *)purgatory_backup_dest, > (void *)purgatory_backup_src, purgatory_backup_sz); > } > return 0; > } > ...... > > arch/x86/kernel/machine_kexec_64.c > ...... > machine_kexec_prepare()-> > arch_update_purgatory()-> > ..... > > Actually, the firs 640k area is encrypted in the first kernel when SME is enabled, here kernel > copies the first 640k data to the backup area in purgatory(), because the backup area is mapped > as decrypted, this copying operation makes that the first 640k data is decrypted(decoded) and > saved to the backup area, but probably kernel can not aware of SME in purgatory(), which causes > kernel mistakenly read out the first 640k. > > In addition, i hacked kernel code as follow: > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > index 7bcc92add72c..a51631d36a7a 100644 > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -377,6 +378,16 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos, > m->offset + m->size - *fpos, > buflen); > start = m->paddr + *fpos - m->offset; > + if (m->paddr == 0x73f60000) {//the backup area's start address:0x73f60000 > + tmp = read_from_oldmem(buffer, tsz, &start, > + userbuf, false); > + } else > tmp = read_from_oldmem(buffer, tsz, &start, > userbuf, mem_encrypt_active()); > if (tmp < 0) > > Here, i used the crash tool to check the vmcore, i can see that the backup area is decrypted, > except for the dma-kmalloc-512. So i suspect that kernel did not correctly read out the first > 640k data to backup area. Do you happen to know how to deal with the first 640k area in purgatory() > when SME is enabled? Any idea? > > BTW: I' curious the reason why the address of dma-kmalloc-512k always falls into the first 640k > region, and i did not see the same issue on another machine. > > Machine: > Serial Number diesel-sys9079-0001 > Model AMD Diesel (A0C) > CPU AMD EPYC 7601 32-Core Processor > > > Background: > On x86_64, the first 640k region is special because of some historical reasons. And kdump kernel will > reuse the first 640k region, so kernel will back up(copy) the first 640k region to a backup area in > purgatory(), in order not to rewrite the old region(640k) in kdump kernel, which makes sure that kdump > can read out the old memory from vmcore. > > > Thanks. > Lianbo