RFC: ld.so: Add DT_FLAGS_2 and DF_2_GNU_IFUNC [BZ #20019]

[Florian Weimer]

On 05/25/2018 10:26 PM, H.J. Lu wrote:
> +$(objpfx)tst-relocmod1b.so: $(objpfx)tst-relocmod1b.os \
> +			    $(objpfx)tst-relocmod1a.so
> +	$(LINK.o) -nostdlib -nostartfiles -shared -o $@ -Wl,-z,now \
> +		  $(filter-out $(shlib-lds),$^)

Does this still link against libc.so.6?  If not, then this is the bug.

> diff --git a/elf/tst-relocmod1a.c b/elf/tst-relocmod1a.c
> new file mode 100644
> index 0000000000..be9f8832b8
> --- /dev/null
> +++ b/elf/tst-relocmod1a.c
> @@ -0,0 +1,23 @@
> +/* Shared module to test for relocation over with IFUNC symbols.
> +   Copyright (C) 2018 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +<http://www.gnu.org/licenses/>.  */
> +
> +void
> +bar (char *dst, const char *src, unsigned int size)
> +{
> +  __builtin_memmove (dst, src, size);
> +}

What happens if you add an IFUNC resolver here?  Doesn't the problem 
return as before?

Thanks,
Florian