linux-kernel - Re: [PATCH] rseq/selftests: fix parametrized test with -fpie

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Message-ID: <44897232.11546.1538071328396.JavaMail.zimbra@efficios.com>
Date:   Thu, 27 Sep 2018 14:02:08 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     shuah kh <shuah.kh@...sung.com>
Cc:     rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Shuah Khan <shuahkh@....samsung.com>,
        linux-kselftest <linux-kselftest@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
        Chris Lameter <cl@...ux.com>, Ben Maurer <bmaurer@...com>,
        Josh Triplett <josh@...htriplett.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>,
        stable <stable@...r.kernel.org>, shuah <shuah@...nel.org>
Subject: Re: [PATCH] rseq/selftests: fix parametrized test with -fpie

----- On Sep 27, 2018, at 9:58 AM, Shuah Khan shuah.kh@...sung.com wrote:

> On 09/27/2018 07:22 AM, Steven Rostedt wrote:
>> On Tue, 25 Sep 2018 13:39:36 -0400 (EDT)
>> Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
>> 
>>> ----- On Sep 18, 2018, at 9:53 AM, Mathieu Desnoyers
>>> mathieu.desnoyers@...icios.com wrote:
>>>
>>>> On x86-64, the parametrized selftest code for rseq crashes with a
>>>> segmentation fault when compiled with -fpie. This happens when the
>>>> param_test binary is loaded at an address beyond 32-bit on x86-64.
>>>>
>>>> The issue is caused by use of a 32-bit register to hold the address
>>>> of the loop counter variable.
>>>>
>>>> Fix this by using a 64-bit register to calculate the address of the
>>>> loop counter variables as an offset from rip.
>>>
>>> Should this fix go through tip or the selftests tree ?
>>>
>> 
>> I usually have changes like this pulled through Shuah's tree with an
>> ack from the maintainer of the code that it tests.
>> 
>> -- Steve
>> 
> 
> Right that is what I prefer. I usually wait for an Ack. I can pull this
> in.

I am maintainer of the code that it tests as well, so being both author
of the selftest patch and giving an ack to it seems a bit silly. :) Other
rseq co-maintainers could weight in though: Peter, Paul, and Boqun.

Thanks,

Mathieu

> 
> thanks,
> -- Shuah
> 
> --
> Shuah Khan
> Sr. Linux Kernel Developer
> Open Source Innovation Group
> Samsung Research America(Silicon Valley)
> shuah.kh@...sung.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com