linux-kernel - Re: [RFC PATCH for 4.18] rseq: use __u64 for rseq

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Message-ID: <20180703164048.i2te5gjemcafqzwf@two.firstfloor.org>
Date:   Tue, 3 Jul 2018 09:40:48 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        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>,
        rostedt <rostedt@...dmis.org>,
        Josh Triplett <josh@...htriplett.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>, michal.simek@...inx.com,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [RFC PATCH for 4.18] rseq: use __u64 for rseq_cs fields,
 validate user inputs

> 
> So I think you're good... But yes, you raise an interresting point.

So it sounds like architectures that don't have an instruction atomic u64
*_user need to disable interrupts during the access, and somehow handle that
case when a page fault happens?

-Andi