Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754786Ab2HUJDg (ORCPT ); Tue, 21 Aug 2012 05:03:36 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:39051 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753472Ab2HUJDa (ORCPT ); Tue, 21 Aug 2012 05:03:30 -0400 Date: Tue, 21 Aug 2012 09:58:19 +0100 From: Will Deacon To: Arnd Bergmann Cc: Catalin Marinas , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "ulrich.weigand@linaro.org" Subject: Re: [PATCH v2 23/31] arm64: Debugging support Message-ID: <20120821085819.GD28660@mudshark.cambridge.arm.com> References: <1344966752-16102-1-git-send-email-catalin.marinas@arm.com> <20120820090754.GB25864@mudshark.cambridge.arm.com> <20120820092744.GD25864@mudshark.cambridge.arm.com> <201208202010.59985.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201208202010.59985.arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1307 Lines: 31 On Mon, Aug 20, 2012 at 09:10:59PM +0100, Arnd Bergmann wrote: > On Monday 20 August 2012, Will Deacon wrote: > > On Mon, Aug 20, 2012 at 10:07:54AM +0100, Will Deacon wrote: > > > On Fri, Aug 17, 2012 at 08:06:07AM +0100, Arnd Bergmann wrote: > > > > Sorry for the dumb question, but why do you even need PTRACE_GET_THREAD_AREA > > > > for 64 bit tasks? I thought the thread pointer is a GPR, or is this just > > > > for compat tasks? > > > > > > The TLS is stored in a co-processor register which is read-only for > > > userspace. > > > > I should elaborate: the register is RW for AArch64 tasks, RO for aarch32 > > tasks (although that doesn't affect the need for the ptrace request). > > So can't you just /add/ that register to the GPR regset? We *could*, but it doesn't feel right to me. The TLS register: - Can only be manipulated by msr/mrs instructions - Is not part of the PCS - Is not accessed explicitly by user applications - Can not be written via ptrace so I think it sticks out like a sore thumb if we bundle it up with the GPRs. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/