From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 1/2] mm: introduce MAP_FIXED_SAFE Date: Wed, 13 Dec 2017 14:01:35 +0100 Message-ID: <20171213130135.GG25185@dhcp22.suse.cz> References: <20171213092550.2774-1-mhocko@kernel.org> <20171213092550.2774-2-mhocko@kernel.org> <20171213125053.GB2384@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20171213125053.GB2384@bombadil.infradead.org> Sender: owner-linux-mm@kvack.org To: Matthew Wilcox 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 List-Id: linux-api@vger.kernel.org On Wed 13-12-17 04:50:53, Matthew Wilcox wrote: > 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) I've already tried to explain why this cannot be a modifier for MAP_FIXED. Read about the backward compatibility note... Or do I misunderstand what you are saying here? > 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. -- Michal Hocko SUSE Labs -- 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