Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751214AbeACWMF (ORCPT + 1 other); Wed, 3 Jan 2018 17:12:05 -0500 Received: from mail-ot0-f196.google.com ([74.125.82.196]:35983 "EHLO mail-ot0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750928AbeACWMD (ORCPT ); Wed, 3 Jan 2018 17:12:03 -0500 X-Google-Smtp-Source: ACJfBotR2qbGMPFz3ozZI07cY0+kuSzaAnlcVfnfQFv0aN00c3ltM9AXp2S7d0vlrk3kJOAByo42ng== Subject: Re: CONFIG_PAGE_TABLE_ISOLATION=y on x86_64 causes gcc to segfault when building x86_32 binaries To: Thomas Gleixner , Lars Wendler Cc: LKML , x86@kernel.org, Borislav Betkov , Andy Lutomirski , Dave Hansen , Peter Zijlstra , Greg KH , Boris Ostrovsky , Juergen Gross References: <20180103123723.1dd26828@abudhabi.paradoxon.rec> <20180103143036.60e592eb@abudhabi.paradoxon.rec> From: Laura Abbott Message-ID: Date: Wed, 3 Jan 2018 14:12:00 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 01/03/2018 10:52 AM, Thomas Gleixner wrote: > On Wed, 3 Jan 2018, Thomas Gleixner wrote: > >> On Wed, 3 Jan 2018, Lars Wendler wrote: >>> Am Wed, 3 Jan 2018 13:05:38 +0100 (CET) >>> schrieb Thomas Gleixner : >>>> Also can you please try Linus v4.15-rc6 with PTI enabled so we can see >>>> whether that's a backport issue or a general one? >>> >>> Same problem with 4.15-rc6. So I suppose that means it's a general >>> issue. >> >> Just a shot in the dark as I just decoded another issue on a AMD CPU. Can >> you please try the patch below? > > Ok. Found the real issue. This is a problem on AMD boxen. > Fedora reporter says it fixes it. > Fix below. > > Can Xen folks please have a look at that as well? > > Thanks, > > tglx > > 8<------------------- > > arch/x86/entry/entry_64_compat.S | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > --- a/arch/x86/entry/entry_64_compat.S > +++ b/arch/x86/entry/entry_64_compat.S > @@ -190,8 +190,13 @@ ENTRY(entry_SYSCALL_compat) > /* Interrupts are off on entry. */ > swapgs > > - /* Stash user ESP and switch to the kernel stack. */ > + /* Stash user ESP */ > movl %esp, %r8d > + > + /* Use %rsp as scratch reg. User ESP is stashed in r8 */ > + SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp > + > + /* Switch to the kernel stack */ > movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp > > /* Construct struct pt_regs on stack */ > @@ -220,12 +225,6 @@ GLOBAL(entry_SYSCALL_compat_after_hwfram > pushq $0 /* pt_regs->r15 = 0 */ > > /* > - * We just saved %rdi so it is safe to clobber. It is not > - * preserved during the C calls inside TRACE_IRQS_OFF anyway. > - */ > - SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi > - > - /* > * User mode is traced as though IRQs are on, and SYSENTER > * turned them off. > */ >