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 S1757508AbdEVIqO (ORCPT <rfc822;w@1wt.eu>);
        Mon, 22 May 2017 04:46:14 -0400
Received: from foss.arm.com ([217.140.101.70]:33168 "EHLO foss.arm.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752668AbdEVIqL (ORCPT <rfc822;Linux-kernel@vger.kernel.org>);
        Mon, 22 May 2017 04:46:11 -0400
Date: Mon, 22 May 2017 09:45:30 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: "Jin, Yao" <yao.jin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, acme@kernel.org,
        jolsa@kernel.org, mingo@redhat.com, alexander.shishkin@linux.intel.com,
        Linux-kernel@vger.kernel.org, ak@linux.intel.com, kan.liang@intel.com,
        yao.jin@intel.com, Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is
 specified
Message-ID: <20170522084529.GC1478@leverpostej>
References: <1495189152-5766-1-git-send-email-yao.jin@linux.intel.com>
 <20170519092905.yivnfjyhblm5wiap@hirez.programming.kicks-ass.net>
 <eba28230-5a96-fbfe-0fb3-191921839a72@linux.intel.com>
 <20170519121056.c45jbsfgcdjfuoow@hirez.programming.kicks-ass.net>
 <ae456a2e-a4c9-7cda-ab50-6135c53fe321@linux.intel.com>
 <20170519123648.p4tkt6xrt5xachuw@hirez.programming.kicks-ass.net>
 <6d82d33c-df7d-f1ea-979a-5898efe88528@linux.intel.com>
 <f67248f7-1ebd-98de-ae13-5ca3920d50e5@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <f67248f7-1ebd-98de-ae13-5ca3920d50e5@linux.intel.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, May 22, 2017 at 10:12:22AM +0800, Jin, Yao wrote:
> Hi Peter,
> 
> Maybe it's not very easy to move the skid checking to generic code
> because we don't have a common kernel_ip() available to determine if
> ip is a kernel address.
> 
> I was trying to move kernel_ip() from arch/x86/events/perf_event.h
> to generic code, but some difficulties I have:
> 
> For example, in new kernel_ip(), we may use many
> conditional-compilation for all arch, for example:
> 
> #ifdef CONFIG_X86_32
>     return ip > PAGE_OFFSET;
> #endif
> 
> #ifdef CONFIG_X86_64
>     return (long)ip < 0;
> #endif
> 
> #ifdef CONFIG_ARM....
> ......
> #ifdef CONFIG_MIPS....
> ......
> 
> But the code is being ugly and hard to maintain. And frankly I don't
> know kernel address space for all arch.
> 
> Any idea? Could we just do at x86 side this time?

Can we not check user_mode(regs) for all architectures?

!user_mode(regs) implies a kernel sample.

Thanks,
Mark.