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From:   Florian Weimer <fw@deneb.enyo.de>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     libc-alpha <libc-alpha@sourceware.org>,
        Carlos O'Donell <carlos@redhat.com>,
        Rich Felker <dalias@libc.org>,
        linux-api <linux-api@vger.kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Will Deacon <will.deacon@arm.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ben Maurer <bmaurer@fb.com>, Dave Watson <davejwatson@fb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Paul <paulmck@linux.vnet.ibm.com>, Paul Turner <pjt@google.com>,
        Joseph Myers <joseph@codesourcery.com>
Subject: Re: [PATCH glibc 5/9] glibc: Perform rseq(2) registration at C startup and thread creation (v17)
References: <20200326155633.18236-1-mathieu.desnoyers@efficios.com>
        <20200326155633.18236-6-mathieu.desnoyers@efficios.com>
        <87ftcpxhpw.fsf@mid.deneb.enyo.de>
        <1660640739.70637.1588006030777.JavaMail.zimbra@efficios.com>
Date:   Mon, 27 Apr 2020 18:59:23 +0200
In-Reply-To: <1660640739.70637.1588006030777.JavaMail.zimbra@efficios.com>
        (Mathieu Desnoyers's message of "Mon, 27 Apr 2020 12:47:10 -0400
        (EDT)")
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* Mathieu Desnoyers:

> ----- On Apr 27, 2020, at 7:59 AM, Florian Weimer fw@deneb.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>