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

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Date:   Mon, 27 Apr 2020 12:47:10 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Florian Weimer <fw@...eb.enyo.de>
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)

----- 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.

Thanks,

Mathieu

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