From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Mon, 20 Aug 2012 10:27:44 +0100
Subject: [PATCH v2 23/31] arm64: Debugging support
In-Reply-To: <20120820090754.GB25864@mudshark.cambridge.arm.com>
References: <1344966752-16102-1-git-send-email-catalin.marinas@arm.com>
 <20120816104748.GI31784@mudshark.cambridge.arm.com>
 <201208161249.35008.arnd@arndb.de>
 <201208170706.07821.arnd@arndb.de>
 <20120820090754.GB25864@mudshark.cambridge.arm.com>
Message-ID: <20120820092744.GD25864@mudshark.cambridge.arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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).

Will