Re: Getting rid of dynamic TASK_SIZE (on x86, at least)

[Andy Lutomirski]

On May 10, 2016 11:21 AM, "Oleg Nesterov" <oleg@xxxxxxxxxx> wrote:
>
> On 05/10, Andy Lutomirski wrote:
> >
> >  - xol_add_vma: This one is weird: uprobes really is doing something
> > behind the task's back, and the addresses need to be consistent with
> > the address width.  I'm not quite sure what to do here.
>
> It can use mm->task_size instead, plus this is just a hint. And perhaps
> mm->task_size should have more users, say get_unmapped_area...

Ick.  I hadn't noticed mm->task_size.  We have a *lot* of different
indicators of task size.  mm->task_size appears to have basically no
useful uses except maybe for ppc.

On x86, bitness can change without telling the kernel, and tasks
running in 64-bit mode can do 32-bit syscalls.

So maybe I should add mm->task_size to my list of things that would be
nice to remove.  Or maybe I'm just tilting at windmills.

>
> Not sure we should really get rid of dynamic TASK_SIZE completely, but
> personally I agree it looks a bit ugly.
>
> Oleg.
>