From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx114.postini.com [74.125.245.114]) by kanga.kvack.org (Postfix) with SMTP id DE1416B0073 for ; Wed, 3 Oct 2012 00:32:01 -0400 (EDT) Date: Wed, 3 Oct 2012 05:31:17 +0100 From: Matthew Garrett Subject: Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine Message-ID: <20121003043116.GA26241@srcf.ucam.org> References: <1349213536-3436-1-git-send-email-tmac@hp.com> <506B6191.6080605@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <506B6191.6080605@zytor.com> Sender: owner-linux-mm@kvack.org List-ID: To: "H. Peter Anvin" Cc: T Makphaibulchoke , tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, akpm@linux-foundation.org, yinghai@kernel.org, tiwai@suse.de, viro@zeniv.linux.org.uk, aarcange@redhat.com, tony.luck@intel.com, mgorman@suse.de, weiyang@linux.vnet.ibm.com, octavian.purdila@intel.com, paul.gortmaker@windriver.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, Oct 02, 2012 at 02:50:09PM -0700, H. Peter Anvin wrote: > That sounds like exactly the opposite of normal /dev/mem behavior... we > allow access to non-memory resources (which really could do anything if > misused), but not memory. >>From arch/x86/mm/init.c: * On x86, access has to be given to the first megabyte of ram because that area * contains bios code and data regions used by X and dosemu and similar apps. Limiting this to just RAM would be safer than it currently is. I'm not convinced that there's any good reason to allow *any* access down there for EFI systems, though. -- Matthew Garrett | mjg59@srcf.ucam.org -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org