From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753388AbcEPKyf (ORCPT ); Mon, 16 May 2016 06:54:35 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35568 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750787AbcEPKye (ORCPT ); Mon, 16 May 2016 06:54:34 -0400 Date: Mon, 16 May 2016 12:54:29 +0200 From: Ingo Molnar To: Dmitry Safonov Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, 0x7f454c46@gmail.com Subject: Re: [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping Message-ID: <20160516105429.GA20440@gmail.com> References: <1462886951-23376-1-git-send-email-dsafonov@virtuozzo.com> <79f9fe67-a343-43b8-0933-a79461900c1b@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <79f9fe67-a343-43b8-0933-a79461900c1b@virtuozzo.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Dmitry Safonov wrote: > On 05/10/2016 04:29 PM, 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 > > > >Signed-off-by: Dmitry Safonov > >Acked-by: Andy Lutomirski > >--- > >v8: add WARN_ON_ONCE on current->mm != new_vma->vm_mm > >v7: build fix > >v6: moved vdso_image_32 check and fixup code into vdso_fix_landing function > > with ifdefs around > >v5: as Andy suggested, add a check that new_vma->vm_mm and current->mm are > > the same, also check not only in_ia32_syscall() but image == &vdso_image_32 > >v4: drop __maybe_unused & use image from mm->context instead vdso_image_32 > >v3: as Andy suggested, return EINVAL in case of splitting vdso blob on mremap; > > used is_ia32_task instead of ifdefs > >v2: added __maybe_unused for pt_regs in vdso_mremap > > Ping? There's no 0/2 boilerplate explaining the background of the changes - why do you want to mremap() the vDSO? Thanks, Ingo