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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 0BC9CC433FF for ; Tue, 13 Aug 2019 13:17:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D563E20840 for ; Tue, 13 Aug 2019 13:17:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="V2RLDQsy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728977AbfHMNRF (ORCPT ); Tue, 13 Aug 2019 09:17:05 -0400 Received: from mail-ed1-f66.google.com ([209.85.208.66]:41374 "EHLO mail-ed1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728796AbfHMNRF (ORCPT ); Tue, 13 Aug 2019 09:17:05 -0400 Received: by mail-ed1-f66.google.com with SMTP id w5so4048834edl.8 for ; Tue, 13 Aug 2019 06:17:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=76Zl8K6WH7/FZX4d76q6nmLAaHErNOtgWon5idKRpYM=; b=V2RLDQsyKUoeN1d2FMlrbWcDjccHyEk4ucb2XXg8BSSsx6oezbVRhf5M1szQTLEB9e o7o98QPzUl1v35IdBgfwxT8NGOyxNnfFBdtQ6895+3AwYKCUnNPRwRi9Nzo4/6nYOMj/ +GY5bB2iym4sUO4qbgWjB43P/Uu/ZNxxVVach8cqc6bYdBUUw9j14Jva5RVjld3lR1ro HpYSzZR8jeSOUcTqFFA+e89Bca3EmBytnrRx0nETEr9hXYEwp3SWIR5otnfQWrCIVfpt 4LdiipyUsLd8s1QwzcAv1ShwMzQDDaQljZB2ol7Xa5Q67PzGs0plHhuqmdYpeO+4igjJ 1npQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=76Zl8K6WH7/FZX4d76q6nmLAaHErNOtgWon5idKRpYM=; b=lIIPA3rQNJ+7XfA6o29G6Nz4XM1REOK0i5TnhCsUs6CBKD+6XTH/2+Q8RIh3S/6ltP l8eLz5zbIHATV6NiEtunNqjSCN553CaRVxVkR2jHN8Y/9qGYl/cpy8svdsxWDFXQGvuh vf34JzX6BXy0wVOuWnlZ/r6PLnc8A8efaq6pnVPoiNST5fUa2ZnMbxcTIjCaAyCXEL+E xdqKbq0Fhp7qS1z0eTZjlvAjV1CppbQKROrJh0hmZ78SVeG27W6OnWL2HJuygkhS3I/p gs09Iij3N8fBWDaNJT9dhMxIZTsjV0tJ5pLSMg2ouIx8392Rl1nA8l54nz5336WnBdJz 1IFw== X-Gm-Message-State: APjAAAWbtlz349qFHVcKzaOaj0NzqoJ/UBTc298turwMB+OqO4/f/rCj tW/XfbYiJLq5siJ9c6WNqWZnTQ== X-Google-Smtp-Source: APXvYqyHZMRQC9jevvwyI5H9cw12yvfnbE9hVa/qLokzq6j4Lk0stEKtqG7ZfiLGqY0AApwnw+f7og== X-Received: by 2002:a05:6402:129a:: with SMTP id w26mr20369818edv.167.1565702223689; Tue, 13 Aug 2019 06:17:03 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id z9sm3564790edd.18.2019.08.13.06.17.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Aug 2019 06:17:03 -0700 (PDT) From: "Kirill A. Shutemov" X-Google-Original-From: "Kirill A. Shutemov" Received: by box.localdomain (Postfix, from userid 1000) id B2599100854; Tue, 13 Aug 2019 16:17:02 +0300 (+03) To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCH] x86/boot/compressed/64: Fix boot on machines with broken E820 table Date: Tue, 13 Aug 2019 16:16:54 +0300 Message-Id: <20190813131654.24378-1-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org BIOS on Samsung 500C Chromebook reports very rudimentary E820 table that consists of 2 entries: BIOS-e820: [mem 0x0000000000000000-0x0000000000000fff] usable BIOS-e820: [mem 0x00000000fffff000-0x00000000ffffffff] reserved It breaks logic in find_trampoline_placement(): bios_start lands on the end of the first 4k page and trampoline start gets placed below 0. Detect underflow and don't touch bios_start for such cases. It makes kernel ignore E820 table on machines that doesn't have two usable pages below BIOS_START_MAX. Signed-off-by: Kirill A. Shutemov Fixes: 1b3a62643660 ("x86/boot/compressed/64: Validate trampoline placement against E820") Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203463 --- arch/x86/boot/compressed/pgtable_64.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index 5f2d03067ae5..2faddeb0398a 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -72,6 +72,8 @@ static unsigned long find_trampoline_placement(void) /* Find the first usable memory region under bios_start. */ for (i = boot_params->e820_entries - 1; i >= 0; i--) { + unsigned long new; + entry = &boot_params->e820_table[i]; /* Skip all entries above bios_start. */ @@ -84,15 +86,20 @@ static unsigned long find_trampoline_placement(void) /* Adjust bios_start to the end of the entry if needed. */ if (bios_start > entry->addr + entry->size) - bios_start = entry->addr + entry->size; + new = entry->addr + entry->size; /* Keep bios_start page-aligned. */ - bios_start = round_down(bios_start, PAGE_SIZE); + new = round_down(new, PAGE_SIZE); /* Skip the entry if it's too small. */ - if (bios_start - TRAMPOLINE_32BIT_SIZE < entry->addr) + if (new - TRAMPOLINE_32BIT_SIZE < entry->addr) continue; + /* Protect against underflow. */ + if (new - TRAMPOLINE_32BIT_SIZE > bios_start) + break; + + bios_start = new; break; } -- 2.21.0