From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932509AbcHISt6 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 9 Aug 2016 14:49:58 -0400
Received: from mx1.redhat.com ([209.132.183.28]:40268 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932207AbcHISt5 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Tue, 9 Aug 2016 14:49:57 -0400
Date: Tue, 9 Aug 2016 20:49:44 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Pratyush Anand <panand@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, linux@arm.linux.org.uk,
        catalin.marinas@arm.com, will.deacon@arm.com,
        linux-kernel@vger.kernel.org, wcohen@redhat.com, dave.long@linaro.org,
        steve.capper@linaro.org, srikar@linux.vnet.ibm.com,
        vijaya.kumar@caviumnetworks.com, Shi Yang <yang.shi@linaro.org>,
        Andre Przywara <andre.przywara@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Ashok Kumar <ashoks@broadcom.com>, James Morse <james.morse@arm.com>,
        Jungseok Lee <jungseoklee85@gmail.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>,
        Shaokun Zhang <zhangshaokun@hisilicon.com>,
        "Suzuki K. Poulose" <suzuki.poulose@arm.com>,
        Vladimir Murzin <vladimir.murzin@arm.com>
Subject: Re: [PATCH 5/5] arm64: Add uprobe support
Message-ID: <20160809184943.GA17112@redhat.com>
References: <cover.1470114993.git.panand@redhat.com> <abaac6ebaa5dd63889803ec568663bc8c8c65b02.1470114993.git.panand@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <abaac6ebaa5dd63889803ec568663bc8c8c65b02.1470114993.git.panand@redhat.com>
User-Agent: Mutt/1.5.18 (2008-05-17)
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 09 Aug 2016 18:49:56 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 08/02, Pratyush Anand wrote:
>
> This patch adds support for uprobe on ARM64 architecture.

I know nothing about ARM, so I can't actually review this change.
But it looks good to me ;)

Just one note,

> +int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	struct uprobe_task *utask = current->utask;
> +
> +	/* saved fault code is restored in post_xol */
> +	utask->autask.saved_fault_code = current->thread.fault_code;
> +
> +	/* An invalid fault code between pre/post xol event */
> +	current->thread.fault_code = UPROBE_INV_FAULT_CODE;
> +
> +	/* Instruction point to execute ol */
> +	instruction_pointer_set(regs, utask->xol_vaddr);
> +
> +	user_enable_single_step(current);

I don't think we want user_{enable,disable{_single_step in the long term,
please look at 9bd1190a11c9d2 "uprobes/x86: Do not (ab)use TIF_SINGLESTEP
/user_*_single_step() for single-stepping". it seems that ARM64 sets/clears
TIF_SINGLESTEP. You can also lool at saved_tf logic, probably ARM64 needs
the same.

However, I agree we can do this later and initial version can use these
ptrace helpers.

Oleg.