From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 587BB6B025E for ; Tue, 10 May 2016 12:30:49 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id j8so14888355lfd.0 for ; Tue, 10 May 2016 09:30:49 -0700 (PDT) Received: from mail-lf0-x22b.google.com (mail-lf0-x22b.google.com. [2a00:1450:4010:c07::22b]) by mx.google.com with ESMTPS id xt9si2046291lbb.94.2016.05.10.09.30.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 May 2016 09:30:48 -0700 (PDT) Received: by mail-lf0-x22b.google.com with SMTP id y84so21259468lfc.0 for ; Tue, 10 May 2016 09:30:47 -0700 (PDT) Date: Tue, 10 May 2016 19:30:45 +0300 From: Cyrill Gorcunov Subject: Re: Getting rid of dynamic TASK_SIZE (on x86, at least) Message-ID: <20160510163045.GH14377@uranus.lan> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Ruslan Kabatsayev , X86 ML , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Borislav Petkov , Pavel Emelyanov , Oleg Nesterov On Tue, May 10, 2016 at 09:07:49AM -0700, Andy Lutomirski wrote: > Hi all- > > I'm trying to get rid of x86's dynamic TASK_SIZE and just redefine it > to TASK_SIZE_MAX. So far, these are the TASK_SIZE users that actually > seem to care about the task in question: > > get_unmapped_area. This is used by mmap, mremap, exec, uprobe XOL, > and maybe some other things. > > - mmap, mremap, etc: IMO this should check in_compat_syscall, not > TIF_ADDR32. If a 64-bit task does an explicit 32-bit mmap (using int > $0x80, for example), it should get a 32-bit address back. > > - xol_add_vma: This one is weird: uprobes really is doing something > behind the task's back, and the addresses need to be consistent with > the address width. I'm not quite sure what to do here. > > - exec. This wants to set up mappings that are appropriate for the new task. > > My inclination would be add a new 'limit' parameter to all the > get_unmapped_area variants and possible to vm_brk and friends and to > thus push the decision into the callers. For the syscalls, we could > add: > > static inline unsigned long this_syscall_addr_limit(void) { return TASK_SIZE; } > > and override it on x86. > > I'm not super excited to write that patch, though... Andy, could you please highlight what's wrong with TASK_SIZE helper in first place? The idea behind is to clean up the code or there some real problem? -- 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