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

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Florian Weimer <fw@deneb.enyo.de>
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)
Date: Mon, 27 Apr 2020 12:47:10 -0400 (EDT)	[thread overview]
Message-ID: <1660640739.70637.1588006030777.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <87ftcpxhpw.fsf@mid.deneb.enyo.de>

----- 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.

Thanks,

Mathieu

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