From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF038C433E0 for ; Thu, 4 Feb 2021 10:52:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C7A164DDD for ; Thu, 4 Feb 2021 10:52:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235512AbhBDKwq (ORCPT ); Thu, 4 Feb 2021 05:52:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234873AbhBDKwp (ORCPT ); Thu, 4 Feb 2021 05:52:45 -0500 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33233C061573; Thu, 4 Feb 2021 02:52:05 -0800 (PST) Received: from zn.tnic (p200300ec2f0c7e00dc348a22cc2c06fb.dip0.t-ipconnect.de [IPv6:2003:ec:2f0c:7e00:dc34:8a22:cc2c:6fb]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A80071EC00F8; Thu, 4 Feb 2021 11:52:01 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1612435921; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=x+q7M5BysVCq0z73BCA5GL6K1zhxLeh9Ep6YuQ1rvpw=; b=NkbeH0s9FBLOV+Wse/Y6c3Vc6CDqAD5AEy6ZGsLflQepqjqCjWV3lxVgMi6lbhBpftYVew 9QtP+ljkKRefd9fZoY1dFln9/Q9e2nFNnzMC/0s/gZU154j1HyoOWlWHrCTQqsJfebf8Q9 FrVVybE3qHTptJdYnKQsjd6ae3frQgg= Date: Thu, 4 Feb 2021 11:51:55 +0100 From: Borislav Petkov To: Ard Biesheuvel Cc: Nathan Chancellor , Arvind Sankar , Arnd Bergmann , Thomas Gleixner , Ingo Molnar , X86 ML , Nathan Chancellor , Nick Desaulniers , Arnd Bergmann , Darren Hart , Andy Shevchenko , "H. Peter Anvin" , linux-efi , platform-driver-x86@vger.kernel.org, Linux Kernel Mailing List , clang-built-linux , "Kirill A. Shutemov" Subject: Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index Message-ID: <20210204105155.GA32255@zn.tnic> References: <20210107223424.4135538-1-arnd@kernel.org> <20210118202409.GG30090@zn.tnic> <20210203185148.GA1711888@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 03, 2021 at 09:29:18PM +0100, Ard Biesheuvel wrote: > I think we have agreement on the approach but it is unclear who is > going to write the patch. How's that below? And frankly, I'd even vote for removing those assertions altogether. If somehow the EFI pgd lands somewhere else, the kernel will crash'n'burn spectacularly and quickly so it's not like we won't catch it... --- diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 91ac10654570..b6be19c09841 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -156,8 +156,8 @@ extern unsigned int ptrs_per_p4d; #define CPU_ENTRY_AREA_PGD _AC(-4, UL) #define CPU_ENTRY_AREA_BASE (CPU_ENTRY_AREA_PGD << P4D_SHIFT) -#define EFI_VA_START ( -4 * (_AC(1, UL) << 30)) -#define EFI_VA_END (-68 * (_AC(1, UL) << 30)) +#define EFI_VA_START ( -4UL * (_AC(1, UL) << 30)) +#define EFI_VA_END (-68UL * (_AC(1, UL) << 30)) #define EARLY_DYNAMIC_PAGE_TABLES 64 diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index e1e8d4e3a213..56fdc0bbb554 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -123,9 +123,7 @@ void efi_sync_low_kernel_mappings(void) * only span a single PGD entry and that the entry also maps * other important kernel regions. */ - MAYBE_BUILD_BUG_ON(pgd_index(EFI_VA_END) != pgd_index(MODULES_END)); - MAYBE_BUILD_BUG_ON((EFI_VA_START & PGDIR_MASK) != - (EFI_VA_END & PGDIR_MASK)); + MAYBE_BUILD_BUG_ON((EFI_VA_START & PGDIR_MASK) != PGDIR_MASK); pgd_efi = efi_pgd + pgd_index(PAGE_OFFSET); pgd_k = pgd_offset_k(PAGE_OFFSET); @@ -137,8 +135,7 @@ void efi_sync_low_kernel_mappings(void) * As with PGDs, we share all P4D entries apart from the one entry * that covers the EFI runtime mapping space. */ - BUILD_BUG_ON(p4d_index(EFI_VA_END) != p4d_index(MODULES_END)); - BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != (EFI_VA_END & P4D_MASK)); + BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != P4D_MASK); pgd_efi = efi_pgd + pgd_index(EFI_VA_END); pgd_k = pgd_offset_k(EFI_VA_END); -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette