Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752022Ab3FVRac (ORCPT ); Sat, 22 Jun 2013 13:30:32 -0400 Received: from mail-ve0-f179.google.com ([209.85.128.179]:53187 "EHLO mail-ve0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751862Ab3FVRab (ORCPT ); Sat, 22 Jun 2013 13:30:31 -0400 MIME-Version: 1.0 In-Reply-To: <20130622103158.GA16304@infradead.org> References: <20130622103158.GA16304@infradead.org> Date: Sat, 22 Jun 2013 10:30:30 -0700 Message-ID: Subject: Re: RFC: named anonymous vmas From: Colin Cross To: Christoph Hellwig Cc: lkml , Linux-MM , Android Kernel Team , John Stultz Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1054 Lines: 20 On Sat, Jun 22, 2013 at 3:31 AM, Christoph Hellwig wrote: > On Fri, Jun 21, 2013 at 04:42:41PM -0700, Colin Cross wrote: >> ranges, which John Stultz has been implementing. The second is >> anonymous shareable memory without having a world-writable tmpfs that >> untrusted apps could fill with files. > > I still haven't seen any explanation of what ashmem buys over a shared > mmap of /dev/zero in that respect, btw. I believe the difference is that ashmem ties the memory to an fd, so it can be passed to another process and mmaped to get to the same memory, but /dev/zero does not. Passing a /dev/zero fd and mmaping it would result in a brand new region of zeroed memory. Opening a tmpfs file would allow sharing memory by passing the fd, but we don't want a world-writable tmpfs. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/