Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751284AbeACT2G (ORCPT + 1 other); Wed, 3 Jan 2018 14:28:06 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:40375 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751141AbeACT2D (ORCPT ); Wed, 3 Jan 2018 14:28:03 -0500 Date: Wed, 3 Jan 2018 19:52:04 +0100 (CET) From: Thomas Gleixner To: Lars Wendler cc: LKML , x86@kernel.org, Borislav Betkov , Andy Lutomirski , Dave Hansen , Peter Zijlstra , Greg KH , Laura Abbott , Boris Ostrovsky , Juergen Gross Subject: Re: CONFIG_PAGE_TABLE_ISOLATION=y on x86_64 causes gcc to segfault when building x86_32 binaries In-Reply-To: Message-ID: References: <20180103123723.1dd26828@abudhabi.paradoxon.rec> <20180103143036.60e592eb@abudhabi.paradoxon.rec> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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. 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. */