From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753078AbbIGOtM (ORCPT ); Mon, 7 Sep 2015 10:49:12 -0400 Received: from foss.arm.com ([217.140.101.70]:51205 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752590AbbIGOtJ (ORCPT ); Mon, 7 Sep 2015 10:49:09 -0400 Message-ID: <55EDA3D1.6020902@arm.com> Date: Mon, 07 Sep 2015 15:48:49 +0100 From: James Morse User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.6.0 MIME-Version: 1.0 To: Jungseok Lee CC: Catalin Marinas , Will Deacon , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 1/3] arm64: entry: Remove unnecessary calculation for S_SP in EL1h References: <1441376587-12979-1-git-send-email-jungseoklee85@gmail.com> <1441376587-12979-2-git-send-email-jungseoklee85@gmail.com> In-Reply-To: <1441376587-12979-2-git-send-email-jungseoklee85@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/09/15 15:23, Jungseok Lee wrote: > Under EL1h, S_SP data is not seen in kernel_exit. Thus, x21 calculation > is not needed in kernel_entry. Currently, S_SP information is vaild only > when sp_el0 is used. > > Signed-off-by: Jungseok Lee > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index e163518..d23ca0d 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -91,8 +91,6 @@ > get_thread_info tsk // Ensure MDSCR_EL1.SS is clear, > ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug > disable_step_tsk x19, x20 // exceptions when scheduling. > - .else > - add x21, sp, #S_FRAME_SIZE > .endif > mrs x22, elr_el1 > mrs x23, spsr_el1 > This sp value gets written to the struct pt_regs that is built on the stack, and passed to the fault handlers, see 'el1_sp_pc' in kernel/entry.S, which goes on to call do_sp_pc_abort() which prints this value out. (Other fault handlers may make decisions based on this value). It should be present and correct. Thanks, James