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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=ham 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 153A6C433DB for ; Thu, 4 Feb 2021 21:45:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA92A64F8C for ; Thu, 4 Feb 2021 21:45:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229976AbhBDVo5 (ORCPT ); Thu, 4 Feb 2021 16:44:57 -0500 Received: from mail-qv1-f54.google.com ([209.85.219.54]:41058 "EHLO mail-qv1-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229586AbhBDVom (ORCPT ); Thu, 4 Feb 2021 16:44:42 -0500 Received: by mail-qv1-f54.google.com with SMTP id h21so2497571qvb.8; Thu, 04 Feb 2021 13:44:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=pKT1129goorIBDoVw07+oNDIAL0ruSPyAoYmTeYA4JM=; b=Bn4a9GTTajo10p4tP/SXrggABMPkJiStl+9Rl154EHydZPM0sccgLHJBGlGUeXzuWR n9ylZkthg6+C7NMtJrc5HylZAK3vlgmlZQMxAeyBATSzWDAGhdD3fzk7CZL8Sb7Oj8jM njs8NZ2udBguOEgzT8/psSTweXcv+UbFQXmxWCK1/KP5APvKiuSt9EM0ZKIWuV59nJex psAGevQyiZ1KpYlZYVOtSP4U8dW/8yU2D9ffU7GwQAWsyrfLfSfTvZCf/Ee1BB8Gqj9z nfvwW7yx2SaUHds+sfC+l9+Q4dEjWvfOBTRJOLXNbzX3n4VHJiL3JuIqgOWVwBsMMK+5 ZjGg== X-Gm-Message-State: AOAM533a0v1fk95TsoUMhENJjzfLrGtuR+Jx5ur+4B/UQrOOsem+FaRk 2VoB0yhR2b18N0xauOHu+Kg= X-Google-Smtp-Source: ABdhPJz2GAyRB5K1dve72PPvUvmzJgXl6kFeOkPJ4uljCE4HZUquh+9dhzFcCpdxEuS+c3JQWtBHqg== X-Received: by 2002:a05:6214:a4f:: with SMTP id ee15mr1429073qvb.10.1612475041219; Thu, 04 Feb 2021 13:44:01 -0800 (PST) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id p22sm6267413qkk.128.2021.02.04.13.43.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Feb 2021 13:44:00 -0800 (PST) Date: Thu, 4 Feb 2021 16:43:58 -0500 From: Arvind Sankar To: Borislav Petkov Cc: Ard Biesheuvel , Nathan Chancellor , 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: References: <20210107223424.4135538-1-arnd@kernel.org> <20210118202409.GG30090@zn.tnic> <20210203185148.GA1711888@localhost> <20210204105155.GA32255@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210204105155.GA32255@zn.tnic> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 04, 2021 at 11:51:55AM +0100, Borislav Petkov wrote: > 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... Removing altogether should be fine, but see below if we don't. > > --- > 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)) This doesn't have any effect right? And the reason for the _AC() stuff in there is to allow the #define to be used in assembler -- this particular one isn't, but it makes no sense to use the UL suffix as well as _AC() in the same macro. > > #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); This check is superfluous. Just do the P4D one. > > 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); This should check EFI_VA_END instead of EFI_VA_START, and maybe throw in a BUG_ON if EFI_VA_END >= EFI_VA_START. > > 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