[PATCHi v2] aarch64: Add split-stack TCB field

[Florian Weimer]

On 02/13/2017 08:45 PM, Adhemerval Zanella wrote:
> +/* This is the size we need before TCB.  Check if there is room for
> +   tcbprehead_t in struct pthread's final padding and if not add it on
> +   required pre-tcb size.  */
> +# define TLS_PRE_TCB_SIZE \
> +  (sizeof (struct pthread)						\
> +   + (PTHREAD_STRUCT_END_PADDING < sizeof (tcbprehead_t)		\
> +      ? ALIGN_UP (sizeof (tcbprehead_t), sizeof (struct pthread))	\
> +      : 0))

How does this preserve the alignment of struct pthread?

It's also not clear to me how the “version control” aspect of 
__tcb_private_ss is supposed to work.  If the intent is to prevent 
loading of split-stack binaries with an older glibc, then a data symbol 
would be a safer choice.

Thanks,
Florian