From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Date: Wed, 14 Dec 2005 15:48:56 +0000 Subject: Re: [patch 2/2] /dev/mem validate mmap requests Message-Id: <200512140848.56570.bjorn.helgaas@hp.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Luck, Tony" Cc: linux-kernel@vger.kernel.org, Andrew Morton , linux-ia64@vger.kernel.org On Tuesday 13 December 2005 5:25 pm, Luck, Tony wrote: > > Tony, can you ack/nak this please? It touches both ia64 and generic > > code. > > So if someone tries to mmap a range that spans across more than > one EFI memory descriptor, the size will get trimmed back to an > EFI memory boundary. Isn't that a problem since 1< is less than the default ia64 Linux page size? The EFI page size is smaller than the Linux page size, but firmware typically coalesces adjacent ranges with the same attributes. > I think you may need a more complex checker that does aggregation > of adjacent efi memory descriptors with the same attributes. We could, but I don't think it's worth it at this point. We've been using the same simple-minded scheme for validating /dev/mem read & write requests for quite a while with no problems, and I don't want to over-engineer this. If hot-plug memory is ever finished, the checker may have to be extended to comprehend regions described by ACPI as well as those described in the boot-time EFI memory map. I think that would be the right time to make it smarter about spanning descriptors.