From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754198AbcCBOb6 (ORCPT ); Wed, 2 Mar 2016 09:31:58 -0500 Received: from mx2.suse.de ([195.135.220.15]:55273 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752869AbcCBOb4 (ORCPT ); Wed, 2 Mar 2016 09:31:56 -0500 Subject: Re: [PATCH v2 0/6] ARM64: meson: GXBaby (S905) and Vega S95 enablement To: Mark Rutland References: <1456886101-22967-1-git-send-email-afaerber@suse.de> <20160302135216.GB11670@leverpostej> Cc: linux-meson@googlegroups.com, Carlo Caione , linux-arm-kernel@lists.infradead.org, Matthias Brugger , Nicolas Saenz , =?UTF-8?Q?Andr=c3=a9_Przywara?= , Sudeep Holla , devicetree@vger.kernel.org, Catalin Marinas , Will Deacon , LKML From: =?UTF-8?Q?Andreas_F=c3=a4rber?= X-Enigmail-Draft-Status: N1110 Organization: SUSE Linux GmbH Message-ID: <56D6F958.2000109@suse.de> Date: Wed, 2 Mar 2016 15:31:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160302135216.GB11670@leverpostej> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 02.03.2016 um 14:52 schrieb Mark Rutland: > On Wed, Mar 02, 2016 at 03:34:55AM +0100, Andreas Färber wrote: >> Note: On the Vega S95 I need to change TEXT_OFFSET as follows, >> in order to avoid the vendor U-Boot overwriting itself (fwiu); >> for the Mini Mx that's reportedly not necessary. >> >> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile >> index 354d75402ace..b7cebdb8b1ce 100644 >> --- a/arch/arm64/Makefile >> +++ b/arch/arm64/Makefile >> @@ -62,7 +62,7 @@ head-y := arch/arm64/kernel/head.o >> ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y) >> TEXT_OFFSET := $(shell awk 'BEGIN {srand(); printf "0x%03x000\n", int(512 * rand())}') >> else >> -TEXT_OFFSET := 0x00080000 >> +TEXT_OFFSET := 0x01080000 >> endif >> >> # KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61) > > Absolute NAK to this. TEXT_OFFSET is not open for platform-specific > modification. Please read again. There is nothing to NAK here, it's a workaround for testing my patches on my device! Even my own git queue has it clearly labeled as "HACK:". Nothing you say here indicates that this is breaking any particular kernel feature or damaging the device, so unless you propose a different way to solve the problem I see no way around it for now. > Why can you not just load the Image 2MB higher regardless? Does the > U-Boot on this platform actually read TEXT_OFFSET and take it into > account? Yes, U-Boot checks the ELF(?) header and tries to copy the image to the indicated offset if it isn't loaded there already. The vendor's kernel has the adjusted offset and works; if I use unmodified mainline kernels then I get weird exceptions from before entering the kernel, my assumption being that U-Boot code gets overwritten. http://openlinux.amlogic.com:8000/download/ARM/u-boot/ This problem might go away if we had a proper upstream-based U-Boot; I'm not familiar enough with U-Boot to fix that myself and would hate to mess with U-Boot on eMMC, for lack of JTAG pins on this device. The Odroid-C2 (which I do not have access to yet) has instructions how to place U-Boot on an SD card, making it safer to experiment with. http://odroid.com/dokuwiki/doku.php?id=en:c2_partition_table >> This in turn runs into an apparent regression introduced with the >> text offset randomization: >> >> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S >> index 6ebd204da16a..afdec27c8871 100644 >> --- a/arch/arm64/kernel/head.S >> +++ b/arch/arm64/kernel/head.S >> @@ -48,7 +48,7 @@ >> #elif (PAGE_OFFSET & 0x1fffff) != 0 >> #error PAGE_OFFSET must be at least 2MB aligned >> #elif TEXT_OFFSET > 0x1fffff >> -#error TEXT_OFFSET must be less than 2MB >> +//#error TEXT_OFFSET must be less than 2MB >> #endif >> >> #define KERNEL_START _text > > This is not a regression. As above, TEXT_OFFSET is not supposed to be > modified in a platform-specific manner. It is in fact an unexplained behavioral change in http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=da57a369d3bc5cd61db90f7e9555840381db9b09 diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 3ba0fc0..69dafe9 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -37,8 +37,12 @@ #define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET) -#if (KERNEL_RAM_VADDR & 0xfffff) != 0x80000 -#error KERNEL_RAM_VADDR must start at 0xXXX80000 +#if (TEXT_OFFSET & 0xf) != 0 +#error TEXT_OFFSET must be at least 16B aligned +#elif (PAGE_OFFSET & 0xfffff) != 0 +#error PAGE_OFFSET must be at least 2MB aligned +#elif TEXT_OFFSET > 0xfffff +#error TEXT_OFFSET must be less than 2MB #endif .macro pgtbl, ttb0, ttb1, virt_to_phys As you can see, previously 0x1080000 was a valid value, and this regressed with the new randomization feature. It obviously works with the larger offset for me, so the "must be" seems questionable. Regards, Andreas -- SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton; HRB 21284 (AG Nürnberg)