From patchwork Tue Jun 24 15:51:36 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 32434 Return-Path: X-Original-To: linaro@patches.linaro.org Delivered-To: linaro@patches.linaro.org Received: from mail-pa0-f72.google.com (mail-pa0-f72.google.com [209.85.220.72]) by ip-10-151-82-157.ec2.internal (Postfix) with ESMTPS id 34CFD201EF for ; Tue, 24 Jun 2014 15:54:30 +0000 (UTC) Received: by mail-pa0-f72.google.com with SMTP id rd3sf1779466pab.7 for ; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:delivered-to:from:to:subject:date:message-id :in-reply-to:references:cc:precedence:list-id:list-unsubscribe :list-archive:list-post:list-help:list-subscribe:mime-version:sender :errors-to:x-original-sender:x-original-authentication-results :mailing-list:content-type:content-transfer-encoding; bh=sZan+GMBng/VmfiQNW1WW5MmqcmeM4B4Iq+7CCzUC0U=; b=Rv4MGOSh2tlccoPVG8W9IfTN8pfUyYuhUrahBYR7PPTwikrR4py9fcmVZzip2DnuT4 xNyn1wEaSKP5pCtVI8+hvs8gWW4fKf55qOFtKqBOkDUfY4pFHRy64kkFEugHdwZ8DeVc y6IRGvBMhgYxk6fAtb8yuQAg7TT9eWibZX9CwnsJQ/SzPcAosJFDWXg7LI4hcge0AdSv +qgPkrN/Z/FjogunVjLuVE32dG+coy5ZH4czypEbY8U6AElhymHcEUD8Rkyfxj4bwN6/ 6aBX1t8NA4wOqzODdzlMlspstoyKsaCJn5rnERI0FPKf/PcP2GGTd4u2FJdZ68/JU62+ ud/g== X-Gm-Message-State: ALoCoQlRL7jWASnpxWpIp0vj8vCAcwcPTfgZqCAGU/wZ4Pwh+Sgrj9zmDL5qJ2T5RszrU69nJmDx X-Received: by 10.66.217.170 with SMTP id oz10mr916059pac.9.1403625269531; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) X-BeenThere: patchwork-forward@linaro.org Received: by 10.140.106.99 with SMTP id d90ls2370829qgf.57.gmail; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) X-Received: by 10.52.27.209 with SMTP id v17mr1224683vdg.23.1403625269399; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) Received: from mail-ve0-f169.google.com (mail-ve0-f169.google.com [209.85.128.169]) by mx.google.com with ESMTPS id kt17si441227veb.84.2014.06.24.08.54.29 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 24 Jun 2014 08:54:29 -0700 (PDT) Received-SPF: pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.128.169 as permitted sender) client-ip=209.85.128.169; Received: by mail-ve0-f169.google.com with SMTP id pa12so557421veb.14 for ; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) X-Received: by 10.58.119.75 with SMTP id ks11mr1557529veb.20.1403625269291; Tue, 24 Jun 2014 08:54:29 -0700 (PDT) X-Forwarded-To: patchwork-forward@linaro.org X-Forwarded-For: patch@linaro.org patchwork-forward@linaro.org Delivered-To: patch@linaro.org Received: by 10.221.37.5 with SMTP id tc5csp221732vcb; Tue, 24 Jun 2014 08:54:28 -0700 (PDT) X-Received: by 10.140.89.18 with SMTP id u18mr2898789qgd.90.1403625268524; Tue, 24 Jun 2014 08:54:28 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id m3si880356qaz.59.2014.06.24.08.54.28 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Jun 2014 08:54:28 -0700 (PDT) Received-SPF: none (google.com: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org does not designate permitted sender hosts) client-ip=2001:1868:205::9; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1WzT1P-0007lf-KT; Tue, 24 Jun 2014 15:52:35 +0000 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1WzT1K-0007f9-QG for linux-arm-kernel@lists.infradead.org; Tue, 24 Jun 2014 15:52:33 +0000 Received: from leverpostej.cambridge.arm.com (leverpostej.cambridge.arm.com [10.1.205.151]) by cam-admin0.cambridge.arm.com (8.12.6/8.12.6) with ESMTP id s5OFpgwr020511; Tue, 24 Jun 2014 16:52:09 +0100 (BST) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Subject: [PATCHv4 3/4] arm64: Update the Image header Date: Tue, 24 Jun 2014 16:51:36 +0100 Message-Id: <1403625097-18235-4-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1403625097-18235-1-git-send-email-mark.rutland@arm.com> References: <1403625097-18235-1-git-send-email-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140624_085231_286268_CAD055B2 X-CRM114-Status: GOOD ( 27.19 ) X-Spam-Score: -5.0 (-----) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-5.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.96.50 listed in list.dnswl.org] -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record Cc: Mark Rutland , rob.herring@linaro.org, lauraa@codeaurora.org, peter.maydell@linaro.org, geoff@infradead.org, Catalin.Marinas@arm.com, Will.Deacon@arm.com, leif.lindholm@linaro.org, Marc.Zyngier@arm.com, kevin.hilman@linaro.org, ijc@hellion.org.uk, trini@ti.com, Dave.Martin@arm.com X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: , List-Help: , List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: mark.rutland@arm.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.128.169 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 Currently the kernel Image is stripped of everything past the initial stack, and at runtime the memory is initialised and used by the kernel. This makes the effective minimum memory footprint of the kernel larger than the size of the loaded binary, though bootloaders have no mechanism to identify how large this minimum memory footprint is. This makes it difficult to choose safe locations to place both the kernel and other binaries required at boot (DTB, initrd, etc), such that the kernel won't clobber said binaries or other reserved memory during initialisation. Additionally when big endian support was added the image load offset was overlooked, and is currently of an arbitrary endianness, which makes it difficult for bootloaders to make use of it. It seems that bootloaders aren't respecting the image load offset at present anyway, and are assuming that offset 0x80000 will always be correct. This patch adds an effective image size to the kernel header which describes the amount of memory from the start of the kernel Image binary which the kernel expects to use before detecting memory and handling any memory reservations. This can be used by bootloaders to choose suitable locations to load the kernel and/or other binaries such that the kernel will not clobber any memory unexpectedly. As before, memory reservations are required to prevent the kernel from clobbering these locations later. Both the image load offset and the effective image size are forced to be little-endian regardless of the native endianness of the kernel to enable bootloaders to load a kernel of arbitrary endianness. Bootloaders which wish to make use of the load offset can inspect the effective image size field for a non-zero value to determine if the offset is of a known endianness. To enable software to determine the endinanness of the kernel as may be required for certain use-cases, a new flags field (also little-endian) is added to the kernel header to export this information. The documentation is updated to clarify these details. To discourage future assumptions regarding the value of text_offset, the value at this point in time is removed from the main flow of the documentation (though kept as a compatibility note). Some minor formatting issues in the documentation are also corrected. Signed-off-by: Mark Rutland Acked-by: Tom Rini Cc: Geoff Levand Cc: Kevin Hilman Acked-by: Will Deacon --- Documentation/arm64/booting.txt | 43 ++++++++++++++++++++++------ arch/arm64/kernel/head.S | 6 ++-- arch/arm64/kernel/image.h | 62 +++++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 4 +++ 4 files changed, 104 insertions(+), 11 deletions(-) create mode 100644 arch/arm64/kernel/image.h diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt index 37fc4f6..85af34d 100644 --- a/Documentation/arm64/booting.txt +++ b/Documentation/arm64/booting.txt @@ -72,27 +72,54 @@ The decompressed kernel image contains a 64-byte header as follows: u32 code0; /* Executable code */ u32 code1; /* Executable code */ - u64 text_offset; /* Image load offset */ - u64 res0 = 0; /* reserved */ - u64 res1 = 0; /* reserved */ + u64 text_offset; /* Image load offset, little endian */ + u64 image_size; /* Effective Image size, little endian */ + u64 flags; /* kernel flags, little endian */ u64 res2 = 0; /* reserved */ u64 res3 = 0; /* reserved */ u64 res4 = 0; /* reserved */ u32 magic = 0x644d5241; /* Magic number, little endian, "ARM\x64" */ - u32 res5 = 0; /* reserved */ + u32 res5; /* reserved (used for PE COFF offset) */ Header notes: +- As of v3.17, all fields are little endian unless stated otherwise. + - code0/code1 are responsible for branching to stext. + - when booting through EFI, code0/code1 are initially skipped. res5 is an offset to the PE header and the PE header has the EFI - entry point (efi_stub_entry). When the stub has done its work, it + entry point (efi_stub_entry). When the stub has done its work, it jumps to code0 to resume the normal boot process. -The image must be placed at the specified offset (currently 0x80000) -from the start of the system RAM and called there. The start of the -system RAM must be aligned to 2MB. +- Prior to v3.17, the endianness of text_offset was not specified. In + these cases image_size is zero and text_offset is 0x80000 in the + endianness of the kernel. Where image_size is non-zero image_size is + little-endian and must be respected. Where image_size is zero, + text_offset can be assumed to be 0x80000. + +- The flags field (introduced in v3.17) is a little-endian 64-bit field + composed as follows: + Bit 0: Kernel endianness. 1 if BE, 0 if LE. + Bits 1-63: Reserved. + +- When image_size is zero, a bootloader should attempt to keep as much + memory as possible free for use by the kernel immediately after the + end of the kernel image. The amount of space required will vary + depending on selected features, and is effectively unbound. + +The Image must be placed text_offset bytes from a 2MB aligned base +address near the start of usable system RAM and called there. Memory +below that base address is currently unusable by Linux, and therefore it +is strongly recommended that this location is the start of system RAM. +At least image_size bytes from the start of the image must be free for +use by the kernel. + +Any memory described to the kernel (even that below the 2MB aligned base +address) which is not marked as reserved from the kernel e.g. with a +memreserve region in the device tree) will be considered as available to +the kernel. Before jumping into the kernel, the following conditions must be met: diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index e048f2b..7b59c3d 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -108,9 +108,9 @@ efi_head: b stext // branch to kernel start, magic .long 0 // reserved #endif - .quad TEXT_OFFSET // Image load offset from start of RAM - .quad 0 // reserved - .quad 0 // reserved + .quad _kernel_offset_le // Image load offset from start of RAM, little-endian + .quad _kernel_size_le // Effective size of kernel image, little-endian + .quad _kernel_flags_le // Informative flags, little-endian .quad 0 // reserved .quad 0 // reserved .quad 0 // reserved diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h new file mode 100644 index 0000000..8fae075 --- /dev/null +++ b/arch/arm64/kernel/image.h @@ -0,0 +1,62 @@ +/* + * Linker script macros to generate Image header fields. + * + * Copyright (C) 2014 ARM Ltd. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + */ +#ifndef __ASM_IMAGE_H +#define __ASM_IMAGE_H + +#ifndef LINKER_SCRIPT +#error This file should only be included in vmlinux.lds.S +#endif + +/* + * There aren't any ELF relocations we can use to endian-swap values known only + * at link time (e.g. the subtraction of two symbol addresses), so we must get + * the linker to endian-swap certain values before emitting them. + */ +#ifdef CONFIG_CPU_BIG_ENDIAN +#define DATA_LE64(data) \ + ((((data) & 0x00000000000000ff) << 56) | \ + (((data) & 0x000000000000ff00) << 40) | \ + (((data) & 0x0000000000ff0000) << 24) | \ + (((data) & 0x00000000ff000000) << 8) | \ + (((data) & 0x000000ff00000000) >> 8) | \ + (((data) & 0x0000ff0000000000) >> 24) | \ + (((data) & 0x00ff000000000000) >> 40) | \ + (((data) & 0xff00000000000000) >> 56)) +#else +#define DATA_LE64(data) ((data) & 0xffffffffffffffff) +#endif + +#ifdef CONFIG_CPU_BIG_ENDIAN +#define __HEAD_FLAG_BE 1 +#else +#define __HEAD_FLAG_BE 0 +#endif + +#define __HEAD_FLAGS (__HEAD_FLAG_BE << 0) + +/* + * These will output as part of the Image header, which should be little-endian + * regardless of the endianness of the kernel. While constant values could be + * endian swapped in head.S, all are done here for consistency. + */ +#define HEAD_SYMBOLS \ + _kernel_size_le = DATA_LE64(_end - _text); \ + _kernel_offset_le = DATA_LE64(TEXT_OFFSET); \ + _kernel_flags_le = DATA_LE64(__HEAD_FLAGS); + +#endif /* __ASM_IMAGE_H */ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index c6648d3..a814768 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -9,6 +9,8 @@ #include #include +#include "image.h" + #define ARM_EXIT_KEEP(x) #define ARM_EXIT_DISCARD(x) x @@ -114,6 +116,8 @@ SECTIONS _end = .; STABS_DEBUG + + HEAD_SYMBOLS } /*