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

[Florian Weimer]

On 07/05/2017 07:23 PM, Tulio Magno Quites Machado Filho wrote:

>    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 ();
> +

__libc_setup_tls calls memcpy and a lot of other stuff, so I'm not sure
if this change is correct on all architectures.

> +# libgcc requires __tcb_parse_hwcap_and_convert_at_platform when built with
> +# a binary128 type.  That symbol is provided by the loader on dynamically
> +# linked executables, forcing to link the loader after libgcc link.
> +f128-loader-link = $(as-needed) $(elf-objpfx)ld.so $(no-as-needed)

Why doesn't the regular linker invocation take care of this?  Will user
applications run into the same issue?

Thanks,
Florian