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

[Carlos O'Donell]

On 02/14/2017 05:03 AM, Florian Weimer wrote:
> 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.

Why is a data symbol a safer choice?

I'm curious, because I recommended the design pattern that Adhemerval
is copying from the POWER example.

-- 
Cheers,
Carlos.