From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx171.postini.com [74.125.245.171]) by kanga.kvack.org (Postfix) with SMTP id 57FB16B0034 for ; Sat, 22 Jun 2013 13:30:31 -0400 (EDT) Received: by mail-ve0-f176.google.com with SMTP id c13so7379831vea.21 for ; Sat, 22 Jun 2013 10:30:30 -0700 (PDT) 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 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: lkml , Linux-MM , Android Kernel Team , John Stultz 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, 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