Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752580AbdGYPGV (ORCPT ); Tue, 25 Jul 2017 11:06:21 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:49068 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbdGYPGT (ORCPT ); Tue, 25 Jul 2017 11:06:19 -0400 Date: Tue, 25 Jul 2017 16:06:15 +0100 From: Dave Martin To: Mark Rutland Cc: linux-arch@vger.kernel.org, arnd@arndb.de, jiong.wang@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, christoffer.dall@linaro.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC 7/9] arm64: expose PAC bit positions via ptrace Message-ID: <20170725150612.GD6321@e103592.cambridge.arm.com> References: <1491232765-32501-1-git-send-email-mark.rutland@arm.com> <1491232765-32501-8-git-send-email-mark.rutland@arm.com> <20170725121145.GB6321@e103592.cambridge.arm.com> <20170725145903.GA20857@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725145903.GA20857@leverpostej> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1649 Lines: 46 On Tue, Jul 25, 2017 at 03:59:04PM +0100, Mark Rutland wrote: > On Tue, Jul 25, 2017 at 01:11:48PM +0100, Dave Martin wrote: > > On Mon, Apr 03, 2017 at 04:19:23PM +0100, Mark Rutland wrote: > > > +/* > > > + * The pointer bits used by a pointer authentication code. > > > + * If we were to use tagged pointers, bits 63:56 would also apply. > > > + */ > > > +#define ptrauth_pac_mask() GENMASK(54, VA_BITS) > > > > Tagged pointers _are_ enabled for userspace by default, no? > > Yes; I'd meant s/tagged/untagged/. > > I've corrected this to: > > /* > * The EL0 pointer bits used by a pointer authentication code. > * This is dependent on TBI0 being enabled, or bits 63:56 would also apply. > */ Yes, that's better. If we do enable untagged pointers for userspace at some point though, this is likely to be missed. I don't have a good answer to this. > > > diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h > > > index b59ee07..cae3d1e 100644 > > > --- a/include/uapi/linux/elf.h > > > +++ b/include/uapi/linux/elf.h > > > @@ -414,6 +414,7 @@ > > > #define NT_ARM_HW_BREAK 0x402 /* ARM hardware breakpoint registers */ > > > #define NT_ARM_HW_WATCH 0x403 /* ARM hardware watchpoint registers */ > > > #define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */ > > > +#define NT_ARM_PAC_MASK 0x405 /* ARM pointer authentication code masks */ > > > > The is the value tentatively assigned to NT_ARM_SVE. > > I must've generated this patch before I corrected this; my local branch > (and kernel.org) have 0x406 here. > > Sorry about that. Shame, I had a rant about pragmatism prepped and ready ;) Cheers ---Dave