From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx160.postini.com [74.125.245.160]) by kanga.kvack.org (Postfix) with SMTP id DF0996B006E for ; Wed, 3 Oct 2012 01:15:51 -0400 (EDT) Date: Wed, 3 Oct 2012 06:15:22 +0100 From: Matthew Garrett Subject: Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine Message-ID: <20121003051522.GA27113@srcf.ucam.org> References: <1349213536-3436-1-git-send-email-tmac@hp.com> <506B6191.6080605@zytor.com> <20121003043116.GA26241@srcf.ucam.org> <506BC2A0.8060500@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <506BC2A0.8060500@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 09:44:16PM -0700, H. Peter Anvin wrote: > We *always* expose the I/O regions to /dev/mem. That is what /dev/mem > *does*. The above is an exception (which is really obsolete, too: we > should simply disallow access to anything which is treated as system > RAM, which doesn't include the BIOS regions in question; the only reason > we don't is that some versions of X take a checksum of the RAM in the > first megabyte as some kind of idiotic random seed.) Oh, right, got you. In that case I think we potentially need a finer-grained check on EFI platforms - the EFI memory map is kind enough to tell us the difference between unusable regions and io regions, and we could avoid access to the unusable ones. -- 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