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

[Mathieu Desnoyers]

----- On Jun 14, 2019, at 3:42 PM, Florian Weimer fweimer@xxxxxxxxxx wrote:

> * 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 IFUNC resolvers happen to observe the __rseq_handled address that
was internal to ld.so ?

If so, we could simply initialize __rseq_handled twice: early before calling
IFUNC resolvers, and after ld.so re-relocation.

Thanks,

Mathieu


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