Re: TASK_UNMAPPED_BASE & stack location

[H. Peter Anvin]

Martin J. Bligh wrote:
>>>Is there any good reason we can't remove TASK_UNMAPPED_BASE, and just
>>>shove libraries directly above the program text? Red Hat seems to have
>>>patches to dynamically tune it on a per-processes basis anyway ...
>>>
>>>Moreover, can we put the stack back where it's meant to be, below the
>>>program text, in that wasted 128MB of virtual space? Who really wants 
>>>
>>>>128MB of stack anyway (and can't fix their app)?
>>
>>That space is NULL pointer trap zone.  NULL pointer trapping -> good.
> 
> 
> 128Mb of it? The bottom page, or even a few Mb, sure ... 
> but 128Mb seems somewhat excessive ...
> 

Perhaps, but large data structures can easily generate reasonably large
values when indirected.

	-hpa