From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755050AbcGFOEc (ORCPT ); Wed, 6 Jul 2016 10:04:32 -0400 Received: from mail-vk0-f54.google.com ([209.85.213.54]:35288 "EHLO mail-vk0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754173AbcGFOEa (ORCPT ); Wed, 6 Jul 2016 10:04:30 -0400 MIME-Version: 1.0 In-Reply-To: <20160628113539.13606-2-dsafonov@virtuozzo.com> References: <20160628113539.13606-1-dsafonov@virtuozzo.com> <20160628113539.13606-2-dsafonov@virtuozzo.com> From: Andy Lutomirski Date: Wed, 6 Jul 2016 07:03:48 -0700 Message-ID: Subject: Re: [PATCHv10 1/2] x86/vdso: add mremap hook to vm_special_mapping To: Dmitry Safonov Cc: "linux-kernel@vger.kernel.org" , Dmitry Safonov <0x7f454c46@gmail.com>, Ingo Molnar , Andrew Lutomirski , "linux-mm@kvack.org" , Thomas Gleixner , "H. Peter Anvin" , X86 ML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 28, 2016 at 4:35 AM, Dmitry Safonov wrote: > Add possibility for userspace 32-bit applications to move > vdso mapping. Previously, when userspace app called > mremap for vdso, in return path it would land on previous > address of vdso page, resulting in segmentation violation. > Now it lands fine and returns to userspace with remapped vdso. > This will also fix context.vdso pointer for 64-bit, which does not > affect the user of vdso after mremap by now, but this may change. > > As suggested by Andy, return EINVAL for mremap that splits vdso image. > > Renamed and moved text_mapping structure declaration inside > map_vdso, as it used only there and now it complement > vvar_mapping variable. > > There is still problem for remapping vdso in glibc applications: > linker relocates addresses for syscalls on vdso page, so > you need to relink with the new addresses. Or the next syscall > through glibc may fail: > Program received signal SIGSEGV, Segmentation fault. > #0 0xf7fd9b80 in __kernel_vsyscall () > #1 0xf7ec8238 in _exit () from /usr/lib32/libc.so.6 Acked-by: Andy Lutomirski