From mboxrd@z Thu Jan 1 00:00:00 1970 From: robherring2@gmail.com (Rob Herring) Date: Mon, 14 Nov 2011 12:05:54 -0600 Subject: [PATCH 2/2] ARM: topdown mmap support In-Reply-To: References: <1320709421-14469-1-git-send-email-robherring2@gmail.com> <1320709421-14469-2-git-send-email-robherring2@gmail.com> Message-ID: <4EC15882.7070909@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/14/2011 11:41 AM, Nicolas Pitre wrote: > On Mon, 7 Nov 2011, Rob Herring wrote: > >> From: Rob Herring >> >> Similar to other architectures, this adds topdown mmap support in user >> process address space allocation policy. This allows mmap sizes greater >> than 2GB. This support is largely copied from MIPS and the generic >> implementations. >> >> The address space randomization is moved into arch_pick_mmap_layout. > > This is a problem by effectively weakening the randomization greatly. > Now you get a random starting point but all mmaps are otherwise fixed > relative to each other, whereas you had random distances between each > mmaps before. > You mean within a single process the mmap's are not randomized? Couldn't that end up wasting a lot of virtual space if you have a lot of mmaps? It is aligned with other arch's and the generic implementation. The generic implementation doesn't even do randomization for legacy layouts. Rob