[PATCHv2] Fix float128 IFUNC relocations on ppc64le [BZ #21707]

[Nix]

On 8 Jul 2017, Tulio Magno Quites Machado Filho said this:

> diff --git a/csu/libc-start.c b/csu/libc-start.c
> index c2dd159..84b7f99 100644
> --- a/csu/libc-start.c
> +++ b/csu/libc-start.c
> @@ -188,12 +188,15 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
>  
>    ARCH_INIT_CPU_FEATURES ();
>  
> -  /* Perform IREL{,A} relocations.  */
> -  apply_irel ();
> -
>    /* The stack guard goes into the TCB, so initialize it early.  */
>    __libc_setup_tls ();
>  
> +  /* Perform IREL{,A} relocations.
> +     Note: the relocations must happen after TLS initialization so that
> +     IFUNC resolvers can benefit from thread-local storage, e.g. powerpc's
> +     hwcap and platform fields available in the TCB.  */
> +  apply_irel ();
> +
>    /* Set up the stack checker's canary.  */
>    uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
>  # ifdef THREAD_SET_STACK_GUARD

Note: I originally moved this above __libc_setup_tls() so that IFUNCs
could be stack-protected on statically-linked applications, but
subsequently found that this caused trouble with dynamically-linked
programs, so ended up de-protecting all the IFUNC resolvers anyway.
(See commit 003a27e8195470f470f4d9384ca70d4e9fc8bd1b.)

If this passes make check with --enable-stack-protector=all, I'm happy
with it.

-- 
NULL && (void)