This change forces realignment of the stack pointer in __tls_get_addr, so
that binaries compiled by GCCs older than GCC 4.9:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
continue to work even if vector instructions are used in glibc which
require the ABI stack realignment.
__tls_get_addr_slow is added to handle the slow paths in the default
implementation of__tls_get_addr in elf/dl-tls.c. The new __tls_get_addr
calls __tls_get_addr_slow after realigning the stack. Internal calls
within ld.so go directly to the default implementation of __tls_get_addr
because they do not need stack realignment.
[BZ #21609]
* sysdeps/x86_64/Makefile (sysdep-dl-routines): Add tls_get_addr.
(gen-as-const-headers): Add rtld-offsets.sym.
* sysdeps/x86_64/dl-tls.c: New file.
* sysdeps/x86_64/rtld-offsets.sym: Likwise.
* sysdeps/x86_64/tls_get_addr.S: Likewise.
* sysdeps/x86_64/dl-tls.h: Add multiple inclusion guards.
* sysdeps/x86_64/tlsdesc.sym (TI_MODULE_OFFSET): New.
(TI_OFFSET_OFFSET): Likwise.
