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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 CBEBAC3524B for ; Thu, 30 Jan 2020 20:04:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A29872467B for ; Thu, 30 Jan 2020 20:04:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727613AbgA3UEt (ORCPT ); Thu, 30 Jan 2020 15:04:49 -0500 Received: from mail-qk1-f194.google.com ([209.85.222.194]:34011 "EHLO mail-qk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727161AbgA3UEt (ORCPT ); Thu, 30 Jan 2020 15:04:49 -0500 Received: by mail-qk1-f194.google.com with SMTP id d10so4263032qke.1; Thu, 30 Jan 2020 12:04:48 -0800 (PST) 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=Z5UX2NdM3cfVWh/gVO4PCQr35u5EguDY40Iisa5P8eI=; b=ZfvnyZbHLv48gCXAfbWjjO8R8r2FSqRAsLnb1Gfd2+P2/Qg/4rV7uEVmVvz7IQpcDM rph1nuINtVP0fWzUEP7ejSSSyMO0zg4bd1NV2c27KrwHVDE1fHMe6scJrLprvoUl0ozY 4FuoZDmryBRURLEGuMq3RFDtyDpw5L1nKbUky0G0aZyqQqTl18VOGAZq7eaq1RXcHOJ8 Rwxly47BMwX6y9PfUI3Q08ZVPCk74b4ZGq+TZwfkPW+oFVSleAYselVV79GyYfxjk4LR okA26dtl1PMGDuxCd+a9u0aMAFAme8z/qD/6yNlXn1UB5YzOT5o4kWaDuSD2+FNGDHkU GYbQ== X-Gm-Message-State: APjAAAVY+HDfl4PXtCRQNth/GocxsKMh9GwoGRcLXqT6cvx03tkBayMJ 8j32qR4XVdS+oUjHcY9PWHA= X-Google-Smtp-Source: APXvYqzaPn9nWlNV0dKpLcZCIuA+cUjkceuKmWkJdS51ETLoGuZ+X4u4MtRlYICxJLClDx7ctXk6Qg== X-Received: by 2002:ae9:ec0a:: with SMTP id h10mr6596149qkg.303.1580414688403; Thu, 30 Jan 2020 12:04:48 -0800 (PST) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id k15sm3262865qkk.103.2020.01.30.12.04.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jan 2020 12:04:48 -0800 (PST) From: Arvind Sankar To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Jonathan Corbet , Ard Biesheuvel Cc: linux-efi@vger.kernel.org, x86@kernel.org, linux-doc@vger.kernel.org Subject: [PATCH 7/8] Documentation/x86/boot: Clarify segment requirements for EFI handover Date: Thu, 30 Jan 2020 15:04:39 -0500 Message-Id: <20200130200440.1796058-8-nivedita@alum.mit.edu> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200130200440.1796058-1-nivedita@alum.mit.edu> References: <20200130200440.1796058-1-nivedita@alum.mit.edu> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org The 32-bit EFI handover entry point requires segments to be setup in the same way as for the regular 32-bit boot. Signed-off-by: Arvind Sankar --- Documentation/x86/boot.rst | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst index c9c201596c3e..3e13b7d57271 100644 --- a/Documentation/x86/boot.rst +++ b/Documentation/x86/boot.rst @@ -1412,6 +1412,12 @@ from the boot media and jump to the EFI handover protocol entry point which is hdr->handover_offset bytes from the beginning of startup_{32,64}. +For the 32-bit handover entry point, the GDT and segments must be setup as for +the 32-bit boot protocol, i.e. a GDT must be loaded with the descriptors for +selectors __BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat +segment; __BOOT_CS must have execute/read permission, and __BOOT_DS must have +read/write permission; CS must be __BOOT_CS and DS, ES, SS must be __BOOT_DS. + The function prototype for the handover entry point looks like this:: efi_main(void *handle, efi_system_table_t *table, struct boot_params *bp) -- 2.24.1