aarch64: Add split-stack TCB fieldazanella/aarch64-split-stack

This patch adds split-stack support pointer guard on glibc for aarch64.
Different from other architectures (powerpc, s390) where the memory is
placed on TCB, aarch64 one is placed before thread pointer initial
position.  It has an advantage over extending TCB because for aarch64
TLS variable placement take in consideration tcbhead_t size and by
changing its value would require to also update the static linker
(and it would also add incompatibility with glibc and older linkers).

For aarch64 tcb direct access is fastest for thread local variable on
all mode and related TLS access.  It requires just a direct load with
displacement of -8 (since thread pointer points to tcbhead_t).

It also adds a loader symbol (__tcb_private_ss) to signal the existence
of the split stack guard area.

Checked on aarch64-linux-gnu.

	* sysdeps/aarch64/Makefile [$(subdir) = elf] (sysdeps-dl-routines):
	Add tcb-version.
	* sysdeps/aarch64/Versions [ld] (GLIBC_2.26): Add
	__libc_tcb_private_ss.
	* sysdeps/aarch64/nptl/tls.h (tcbprehead_t): New struct.
	(TLS_PRE_TCB_SIZE): Take tcbprehead_t in consideration.
	(TLS_DEFINE_INIT_TP): Likewise.
	(THREAD_SELF): Likewise.
	(DB_THREAD_SELF): Likewise.
	* sysdeps/aarch64/tcb-version.c: New file.
	* sysdeps/unix/sysv/linux/aarch64/ld.abilist (GLIBC_2.26): Add.
	(__libc_tcb_private_ss): Likewise.
	* sysdeps/aarch64/nptl/tcb-offsets.sym (PTHREAD_SIZEOF): Rename to
	PTHREAD_PRE_TCB_SIZE.

0 files changed, 0 insertions, 0 deletions