From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751984Ab1ARV0W (ORCPT ); Tue, 18 Jan 2011 16:26:22 -0500 Received: from mail-vw0-f46.google.com ([209.85.212.46]:40366 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750961Ab1ARV0W (ORCPT ); Tue, 18 Jan 2011 16:26:22 -0500 Date: Tue, 18 Jan 2011 16:26:17 -0500 (EST) From: Nicolas Pitre X-X-Sender: nico@xanadu.home To: Grant Likely cc: linux-arm-kernel@lists.infradead.org, Russell King , Catalin Marinas , devicetree-discuss@lists.ozlabs.org, lkml , Olof Johansson , Jeremy Kerr , John Linn , Lennert Buijtenhek Subject: Re: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image In-Reply-To: <20110118202902.13011.68847.stgit@localhost6.localdomain6> Message-ID: References: <20110118195933.13011.56098.stgit@localhost6.localdomain6> <20110118202902.13011.68847.stgit@localhost6.localdomain6> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Jan 2011, Grant Likely wrote: > The dtb is passed to the kernel via register r2, which is the same > method that is used to pass an atags pointer. This patch modifies > __vet_atags to not clear r2 when it encounters a dtb image. > > Signed-off-by: Grant Likely > --- > arch/arm/kernel/head-common.S | 19 +++++++++++++------ > arch/arm/kernel/head.S | 8 ++++---- > 2 files changed, 17 insertions(+), 10 deletions(-) > > diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S > index 8f57515..d9a9105 100644 > --- a/arch/arm/kernel/head-common.S > +++ b/arch/arm/kernel/head-common.S > @@ -14,6 +14,7 @@ > #define ATAG_CORE 0x54410001 > #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) > #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2) > +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */ ARM can be big endian too. Would be nice to make this endian independent, or at least list this limitation in the commit log. > /* > * Exception handling. Something went wrong and we can't proceed. We > @@ -105,22 +106,28 @@ __lookup_machine_type_data: > > /* Determine validity of the r2 atags pointer. The heuristic requires > * that the pointer be aligned, in the first 16k of physical RAM and > - * that the ATAG_CORE marker is first and present. Future revisions > + * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE > + * is selected, then it will also accept a dtb pointer. Future revisions > * of this function may be more lenient with the physical address and > * may also be able to move the ATAGS block if necessary. > * > * r8 = machinfo > * > * Returns: > - * r2 either valid atags pointer, or zero > + * r2 either valid atags pointer, valid dtb pointer, or zero > * r5, r6 corrupted > */ > __vet_atags: > tst r2, #0x3 @ aligned? > bne 1f > > - ldr r5, [r2, #0] @ is first tag ATAG_CORE? > - cmp r5, #ATAG_CORE_SIZE > +#ifdef CONFIG_OF_FLATTREE > + ldr r5, [r2, #0] @ is it a DTB? > + ldr r6, =OF_DT_MAGIC > + cmp r5, r6 > + beq 2f > +#endif > + cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE? The "ldr r5 ..." is now done only within #ifdef CONFIG_OF_FLATTREE. So if CONFIG_OF_FLATTREE is undefined then r5 will contain garbage. Nicolas From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.pitre@linaro.org (Nicolas Pitre) Date: Tue, 18 Jan 2011 16:26:17 -0500 (EST) Subject: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image In-Reply-To: <20110118202902.13011.68847.stgit@localhost6.localdomain6> References: <20110118195933.13011.56098.stgit@localhost6.localdomain6> <20110118202902.13011.68847.stgit@localhost6.localdomain6> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 18 Jan 2011, Grant Likely wrote: > The dtb is passed to the kernel via register r2, which is the same > method that is used to pass an atags pointer. This patch modifies > __vet_atags to not clear r2 when it encounters a dtb image. > > Signed-off-by: Grant Likely > --- > arch/arm/kernel/head-common.S | 19 +++++++++++++------ > arch/arm/kernel/head.S | 8 ++++---- > 2 files changed, 17 insertions(+), 10 deletions(-) > > diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S > index 8f57515..d9a9105 100644 > --- a/arch/arm/kernel/head-common.S > +++ b/arch/arm/kernel/head-common.S > @@ -14,6 +14,7 @@ > #define ATAG_CORE 0x54410001 > #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) > #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2) > +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */ ARM can be big endian too. Would be nice to make this endian independent, or at least list this limitation in the commit log. > /* > * Exception handling. Something went wrong and we can't proceed. We > @@ -105,22 +106,28 @@ __lookup_machine_type_data: > > /* Determine validity of the r2 atags pointer. The heuristic requires > * that the pointer be aligned, in the first 16k of physical RAM and > - * that the ATAG_CORE marker is first and present. Future revisions > + * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE > + * is selected, then it will also accept a dtb pointer. Future revisions > * of this function may be more lenient with the physical address and > * may also be able to move the ATAGS block if necessary. > * > * r8 = machinfo > * > * Returns: > - * r2 either valid atags pointer, or zero > + * r2 either valid atags pointer, valid dtb pointer, or zero > * r5, r6 corrupted > */ > __vet_atags: > tst r2, #0x3 @ aligned? > bne 1f > > - ldr r5, [r2, #0] @ is first tag ATAG_CORE? > - cmp r5, #ATAG_CORE_SIZE > +#ifdef CONFIG_OF_FLATTREE > + ldr r5, [r2, #0] @ is it a DTB? > + ldr r6, =OF_DT_MAGIC > + cmp r5, r6 > + beq 2f > +#endif > + cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE? The "ldr r5 ..." is now done only within #ifdef CONFIG_OF_FLATTREE. So if CONFIG_OF_FLATTREE is undefined then r5 will contain garbage. Nicolas