From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752229Ab3BDGYt (ORCPT ); Mon, 4 Feb 2013 01:24:49 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:45502 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750901Ab3BDGYs (ORCPT ); Mon, 4 Feb 2013 01:24:48 -0500 From: HATAYAMA Daisuke Subject: [PATCH 0/4] kdump: make saved_max_pfn exlusive To: ralf@linux-mips.org, michael@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, holzheu@linux.vnet.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, vgoyal@in.ibm.com Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org Date: Mon, 04 Feb 2013 15:24:45 +0900 Message-ID: <20130204062349.13161.29478.stgit@localhost6.localdomain6> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org First, there are two kinds of notation to represent a map: inclusive and exclusive. Here are the examples: 1) [mem 0x0000000100000000-0x000000013fffffff] 2) [mem 0x0000000100000000-0x0000000140000000] 1) is inclusive and 2) is exclusive. In case of 1), the pfn calculated from the end address belongs to the map, while in case of 2), it doesn't. Currently, saved_max_pfn is used in read_oldmem() as inclusive for a check to see if a given request is to within kernel's memory mapping regions. while (count) { pfn = *ppos / PAGE_SIZE; if (pfn > saved_max_pfn) return read; Unfortunately, on x86 and ia64, there are bugs below: - On the 1st kernel, saved_max_pfn is not initialized so 0. Then, read to pfn 0 is not guarded by the condition and the execution goes into ioremap path. - On the 2nd kernel, x86 and ia64 wrongly initializes saved_max_pfn by exclusive value, on x86 as: saved_max_pfn = e820_end_of_ram_pfn(); by which via /dev/oldmem we can read max_pfn that is not kernel's memory. To fix this, fixing x86 and ia64 part needs smaller change, but max_pfn is originally treated as exclusive so saved_max_pfn should normally be exclusive. Also, the memory map information passed from kexec is all exclusive on every architectures; it's possible to make saved_max_pfn exclusive now. However, ppc and ppc64 on kexec doesn't increment end address now and this should be done as an insurance when map passed from firmware is inclusive, for which I'll post a patch later. --- HATAYAMA Daisuke (4): kdump, oldmem: compare with saved_max_pfn exclusively kdump, s390: make saved_max_pfn exclusive kdump, ppc: make saved_max_pfn exclusive kdump, mips: make saved_max_pfn exclusive arch/mips/kernel/crash_dump.c | 2 +- arch/powerpc/kernel/crash_dump.c | 2 +- arch/s390/kernel/setup.c | 4 ++-- drivers/char/mem.c | 2 +- 4 files changed, 5 insertions(+), 5 deletions(-) -- Thanks. HATAYAMA, Daisuke