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

* 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 any necessary cleanups for the startup OS interface code.
      We do these now so that no calls are made after rtld re-relocation
      which might be resolved to different functions than we expect.

It works fine now!

Great.

Thanks,
Florian

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

* Mathieu Desnoyers:

quoted

+  /* 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