From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933377AbcHaWar (ORCPT ); Wed, 31 Aug 2016 18:30:47 -0400 Received: from mail-pa0-f65.google.com ([209.85.220.65]:33367 "EHLO mail-pa0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752513AbcHaWaq (ORCPT ); Wed, 31 Aug 2016 18:30:46 -0400 Date: Wed, 31 Aug 2016 22:30:41 +0000 From: Wei Yang To: Wei Yang Cc: tglx@linutronix.de, yinghai@kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/e820: set end to (start + size - 1) in __append_e820_map() Message-ID: <20160831223041.GA27174@vultr.guest> Reply-To: Wei Yang References: <1471657213-31817-1-git-send-email-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1471657213-31817-1-git-send-email-richard.weiyang@gmail.com> 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 Hi, All, Is my understanding correct? On Sat, Aug 20, 2016 at 01:40:13AM +0000, Wei Yang wrote: >The (start, size) tuple represents a range [start, start + size - 1], >which means "start" and "start + size - 1" should be compared to see >whether the range overflows. > >For example, a range with (start, size) > > (0xffffffff fffffff0, 0x00000000 00000010) > >represents > > [0xffffffff fffffff0, 0xffffffff ffffffff] > >would be judged overflow in the original code, while actually it is not. > >This patch fixes this and makes sure it still works when size is zero. > >Signed-off-by: Wei Yang >--- > arch/x86/kernel/e820.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > >diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c >index 621b501..871f186 100644 >--- a/arch/x86/kernel/e820.c >+++ b/arch/x86/kernel/e820.c >@@ -388,11 +388,11 @@ static int __init __append_e820_map(struct e820entry *biosmap, int nr_map) > while (nr_map) { > u64 start = biosmap->addr; > u64 size = biosmap->size; >- u64 end = start + size; >+ u64 end = start + size - 1; > u32 type = biosmap->type; > > /* Overflow in 64 bits? Ignore the memory map. */ >- if (start > end) >+ if (start > end && likely(size)) > return -1; > > e820_add_region(start, size, type); >-- >1.7.9.5 -- Wei Yang Help you, Help me