From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752846AbdKWNQ5 (ORCPT ); Thu, 23 Nov 2017 08:16:57 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:40822 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752794AbdKWNQz (ORCPT ); Thu, 23 Nov 2017 08:16:55 -0500 X-Google-Smtp-Source: AGs4zMbfnmEXMTTZQv8Pdk3qsDh/OuDPVD6fbh7PfBOCNt1DtALNy8N/tMthqW+lS8WIFx+tEoGqxXzoFXdI5eR2RWo= MIME-Version: 1.0 In-Reply-To: <4195a4db127cbf769666e283f5dba551d29d5ef0.1511325444.git.luto@kernel.org> References: <4195a4db127cbf769666e283f5dba551d29d5ef0.1511325444.git.luto@kernel.org> From: Denys Vlasenko Date: Thu, 23 Nov 2017 14:16:33 +0100 Message-ID: Subject: Re: [PATCH v2 09/18] x86/asm: Move SYSENTER_stack to the beginning of struct tss_struct To: Andy Lutomirski Cc: X86 ML , Borislav Petkov , "linux-kernel@vger.kernel.org" , Brian Gerst , Dave Hansen , Linus Torvalds , Josh Poimboeuf 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 Wed, Nov 22, 2017 at 5:44 AM, Andy Lutomirski wrote: > I want SYSENTER_stack to have reliable overflow detection, which > means that it needs to be at the bottom of a page, not the top. > Move it to the beginning of struct tss_struct and page-align it. > > Also add an assertion to make sure that the fixed hardware TSS > doesn't cross a page boundary. > > Signed-off-by: Andy Lutomirski > --- > arch/x86/include/asm/processor.h | 21 ++++++++++++--------- > arch/x86/kernel/cpu/common.c | 22 ++++++++++++++++++++++ > 2 files changed, 34 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > index d32a3c88a968..8f5dac9dfbdc 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -327,7 +327,16 @@ struct x86_hw_tss { > > struct tss_struct { > /* > - * The hardware state: > + * Space for the temporary SYSENTER stack, used for SYSENTER > + * and the entry trampoline as well. > + */ > + unsigned long SYSENTER_stack_canary; > + unsigned long SYSENTER_stack[64]; > + > + /* > + * The fixed hardware portion. This must not cross a page boundary > + * at risk of violating the SDM's advice and potentially triggering > + * errata. > */ > struct x86_hw_tss x86_tss; > > @@ -338,15 +347,9 @@ struct tss_struct { > * be within the limit. > */ > unsigned long io_bitmap[IO_BITMAP_LONGS + 1]; > +} __attribute__((__aligned__(PAGE_SIZE))); > > - /* > - * Space for the temporary SYSENTER stack. > - */ > - unsigned long SYSENTER_stack_canary; > - unsigned long SYSENTER_stack[64]; > -} ____cacheline_aligned; You may also move this initializer in process.c: .SYSENTER_stack_canary = STACK_END_MAGIC,