linux-kernel - Re: [PATCH v16 10/13] arch/arm: enable task isolation functionality

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Message-ID: <557d6ff4-a52a-01d8-92fd-e971f28a8b39@mellanox.com>
Date:   Fri, 3 Nov 2017 13:27:49 -0400
From:   Chris Metcalf <cmetcalf@...lanox.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Christoph Lameter <cl@...ux.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Francis Giraldeau <francis.giraldeau@...il.com>
Subject: Re: [PATCH v16 10/13] arch/arm: enable task isolation functionality

On 11/3/2017 1:23 PM, Russell King - ARM Linux wrote:
> On Fri, Nov 03, 2017 at 01:04:49PM -0400, Chris Metcalf wrote:
>> From: Francis Giraldeau <francis.giraldeau@...il.com>
>>
>> This patch is a port of the task isolation functionality to the arm 32-bit
>> architecture. The task isolation needs an additional thread flag that
>> requires to change the entry assembly code to accept a bitfield larger than
>> one byte.  The constants _TIF_SYSCALL_WORK and _TIF_WORK_MASK are now
>> defined in the literal pool. The rest of the patch is straightforward and
>> reflects what is done on other architectures.
>>
>> To avoid problems with the tst instruction in the v7m build, we renumber
>> TIF_SECCOMP to bit 8 and let TIF_TASK_ISOLATION use bit 7.
> After a bit of digging (which could've been saved if our patch format
> contained information about what kernel version this patch was
> generated against) it turns out that this patch will not apply since
> commit 73ac5d6a2b6ac ("arm/syscalls: Check address limit on user-mode
> return") has been applied, which means the TIF numbers have changed
> as well as the assembly code that your patch touches.
>
> My guess is that this patch was generated from a 4.13 kernel, so
> misses the 4.14-rc1 changes.  Since we're potentially about to start
> the merge window for 4.15 this weekend, the timing of this doesn't
> work well either.

What patch failure did you see?  The patch is based against 4.14-rc4, so 
while
it's a few weeks out of date, it does include the commit you reference.

> Once 4.15-rc1 has been published, please rebase against that version
> and resend.

Sure.  I was hoping to eke out a little bit of attention from kernel 
developers
before the merge window actually opens :)

-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com