From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 939106B0033 for ; Wed, 13 Dec 2017 07:51:00 -0500 (EST) Received: by mail-pg0-f72.google.com with SMTP id f8so1507759pgs.9 for ; Wed, 13 Dec 2017 04:51:00 -0800 (PST) Received: from bombadil.infradead.org (bombadil.infradead.org. [65.50.211.133]) by mx.google.com with ESMTPS id y2si1327963pli.150.2017.12.13.04.50.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Dec 2017 04:50:59 -0800 (PST) Date: Wed, 13 Dec 2017 04:50:53 -0800 From: Matthew Wilcox Subject: Re: [PATCH 1/2] mm: introduce MAP_FIXED_SAFE Message-ID: <20171213125053.GB2384@bombadil.infradead.org> References: <20171213092550.2774-1-mhocko@kernel.org> <20171213092550.2774-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171213092550.2774-2-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-api@vger.kernel.org, Khalid Aziz , Michael Ellerman , Andrew Morton , Russell King - ARM Linux , Andrea Arcangeli , linux-mm@kvack.org, LKML , linux-arch@vger.kernel.org, Florian Weimer , John Hubbard , Michal Hocko On Wed, Dec 13, 2017 at 10:25:49AM +0100, Michal Hocko wrote: > +++ b/mm/mmap.c > @@ -1342,6 +1342,10 @@ unsigned long do_mmap(struct file *file, unsigned long addr, > if (!(file && path_noexec(&file->f_path))) > prot |= PROT_EXEC; > > + /* force arch specific MAP_FIXED handling in get_unmapped_area */ > + if (flags & MAP_FIXED_SAFE) > + flags |= MAP_FIXED; > + > if (!(flags & MAP_FIXED)) > addr = round_hint_to_min(addr); > We're up to 22 MAP_ flags now. We'll run out soon. Let's preserve half of a flag by giving userspace the definition: #define MAP_FIXED_SAFE (MAP_FIXED | _MAP_NOT_HINT) then in here: if ((flags & _MAP_NOT_HINT) && !(flags & MAP_FIXED)) return -EINVAL; Now we can use _MAP_NOT_HINT all by itself in the future to mean something else. -- 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