From patchwork Mon Jun 20 14:37:56 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: tip-bot for Dave Martin X-Patchwork-Id: 897572 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p5KEirF9031536 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 20 Jun 2011 14:45:13 GMT Received: from canuck.infradead.org ([134.117.69.58]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QYfiZ-00079v-EX; Mon, 20 Jun 2011 14:44:47 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QYfiZ-000366-37; Mon, 20 Jun 2011 14:44:47 +0000 Received: from mail-wy0-f177.google.com ([74.125.82.177]) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QYfiW-00035n-O2 for linux-arm-kernel@lists.infradead.org; Mon, 20 Jun 2011 14:44:45 +0000 Received: by wyf23 with SMTP id 23so2929868wyf.36 for ; Mon, 20 Jun 2011 07:44:41 -0700 (PDT) Received: by 10.216.50.134 with SMTP id z6mr2085316web.52.1308580683908; Mon, 20 Jun 2011 07:38:03 -0700 (PDT) Received: from e200948.peterhouse.linaro.org (fw-lnat.cambridge.arm.com [217.140.96.63]) by mx.google.com with ESMTPS id d19sm3236166wbh.8.2011.06.20.07.38.02 (version=SSLv3 cipher=OTHER); Mon, 20 Jun 2011 07:38:03 -0700 (PDT) From: Dave Martin To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2] ARM: head, zImage: Always Enter the kernel in ARM state Date: Mon, 20 Jun 2011 15:37:56 +0100 Message-Id: <1308580676-30078-1-git-send-email-dave.martin@linaro.org> X-Mailer: git-send-email 1.7.4.1 X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.7.6 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110620_104445_083666_9DBB8535 X-CRM114-Status: GOOD ( 19.80 ) X-Spam-Score: -0.7 (/) X-Spam-Report: SpamAssassin version 3.3.1 on canuck.infradead.org summary: Content analysis details: (-0.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [74.125.82.177 listed in list.dnswl.org] Cc: Nicolas Pitre , patches@linaro.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Mon, 20 Jun 2011 14:45:14 +0000 (UTC) Currently, the documented kernel entry requirements are not explicit about whether the kernel should be entered in ARM or Thumb, leading to an ambiguitity about how to enter Thumb-2 kernels. As a result, the kernel is reliant on the zImage decompressor to enter the kernel proper in the correct instruction set state. This patch changes the boot entry protocol for head.S and Image to be the same as for zImage: in all cases, the kernel is now entered in ARM. Documentation/arm/Booting is updated to reflect this new policy. A different rule will be needed for Cortex-M class CPUs as and when support for those lands in mainline, since these CPUs don't support the ARM instruction set at all: a note is added to the effect that the kernel must be entered in Thumb on such systems. Signed-off-by: Dave Martin Acked-by: Nicolas Pitre --- Documentation/arm/Booting | 5 +++++ arch/arm/boot/compressed/head.S | 3 ++- arch/arm/kernel/head-nommu.S | 8 ++++++++ arch/arm/kernel/head.S | 8 ++++++++ 4 files changed, 23 insertions(+), 1 deletions(-) diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 4e686a2..a341d87 100644 --- a/Documentation/arm/Booting +++ b/Documentation/arm/Booting @@ -164,3 +164,8 @@ In either case, the following conditions must be met: - The boot loader is expected to call the kernel image by jumping directly to the first instruction of the kernel image. + On CPUs supporting the ARM instruction set, the entry must be + made in ARM state, even for a Thumb-2 kernel. + + On CPUs supporting only the Thumb instruction set such as + Cortex-M class CPUs, the entry must be made in Thumb state. diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index f9da419..51af709 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -353,7 +353,8 @@ not_relocated: mov r0, #0 mov r0, #0 @ must be zero mov r1, r7 @ restore architecture number mov r2, r8 @ restore atags pointer - mov pc, r4 @ call kernel + ARM( mov pc, r4 ) @ call kernel + THUMB( bx r4 ) @ entry point is always ARM .align 2 .type LC0, #object diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index 6b1e0ad..d46f259 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -32,8 +32,16 @@ * numbers for r1. * */ + .arm + __HEAD ENTRY(stext) + + THUMB( adr r9, BSYM(1f) ) @ Kernel is always entered in ARM. + THUMB( bx r9 ) @ If this is a Thumb-2 kernel, + THUMB( .thumb ) @ switch to Thumb now. + THUMB(1: ) + setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode @ and irqs disabled #ifndef CONFIG_CPU_CP15 diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index 278c1b0..742b610 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -71,8 +71,16 @@ * crap here - that's what the boot loader (or in extreme, well justified * circumstances, zImage) is for. */ + .arm + __HEAD ENTRY(stext) + + THUMB( adr r9, BSYM(1f) ) @ Kernel is always entered in ARM. + THUMB( bx r9 ) @ If this is a Thumb-2 kernel, + THUMB( .thumb ) @ switch to Thumb now. + THUMB(1: ) + setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode @ and irqs disabled mrc p15, 0, r9, c0, c0 @ get processor id