linux-kernel - Re: [PATCH glibc 5/9] glibc: Perform rseq(2) registration at C startup and thread creation (v17)

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Message-ID: <87k120vp90.fsf@mid.deneb.enyo.de>
Date:   Mon, 27 Apr 2020 18:59:23 +0200
From:   Florian Weimer <fw@...eb.enyo.de>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     libc-alpha <libc-alpha@...rceware.org>,
        Carlos O'Donell <carlos@...hat.com>,
        Rich Felker <dalias@...c.org>,
        linux-api <linux-api@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ben Maurer <bmaurer@...com>, Dave Watson <davejwatson@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul <paulmck@...ux.vnet.ibm.com>, Paul Turner <pjt@...gle.com>,
        Joseph Myers <joseph@...esourcery.com>
Subject: Re: [PATCH glibc 5/9] glibc: Perform rseq(2) registration at C startup and thread creation (v17)

* Mathieu Desnoyers:

> ----- On Apr 27, 2020, at 7:59 AM, Florian Weimer fw@...eb.enyo.de wrote:
>
>> * Mathieu Desnoyers via Libc-alpha:
>> 
>>> diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c
>>> index 1ac66d895d..30466afea0 100644
>>> --- a/elf/libc_early_init.c
>>> +++ b/elf/libc_early_init.c
>>> @@ -18,10 +18,13 @@
>>>  
>>>  #include <ctype.h>
>>>  #include <libc-early-init.h>
>>> +#include <rseq-internal.h>
>>>  
>>>  void
>>>  __libc_early_init (void)
>>>  {
>>>    /* Initialize ctype data.  */
>>>    __ctype_init ();
>>> +  /* Register rseq ABI to the kernel.   */
>>> +  (void) rseq_register_current_thread ();
>>>  }
>> 
>> I think the registration must be restricted to the primary namespace.
>> Otherwise, LD_AUDIT will register the area to the secondary libc (in
>> the audit module), not the primary libc for the entire process.
>> 
>> I think the easiest way to implement this for now is a flag argument
>> for __libc_early_init (as the upstream __libc_multiple_libcs is not
>> entirely accurate).  I will submit a patch.
>
> OK, once I get the patch, I will pick it up in my series.

There should be no need for that, it can be reviewed and committed
separately:

  <https://sourceware.org/pipermail/libc-alpha/2020-April/113182.html>