linux-kernel - Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)

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Message-ID: <87imt8tha5.fsf@oldenburg2.str.redhat.com>
Date:   Fri, 14 Jun 2019 15:42:26 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     carlos <carlos@...hat.com>, Joseph Myers <joseph@...esourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        libc-alpha <libc-alpha@...rceware.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ben Maurer <bmaurer@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Rich Felker <dalias@...c.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>
Subject: Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)

* Mathieu Desnoyers:

> +  /* Publicize rseq registration ownership.  This must be performed
> +     after rtld re-relocation, before invoking constructors of
> +     preloaded libraries.  */
> +  rseq_init ();

Please add a comment that IFUNC resolvers do not see the initialized
value.  I think this is okay because we currently do not support access
to extern variables in IFUNC resolvers.

>    /* Do any necessary cleanups for the startup OS interface code.
>       We do these now so that no calls are made after rtld re-relocation
>       which might be resolved to different functions than we expect.
>
> It works fine now!

Great.

Thanks,
Florian