POWER: Unexpected fault when writing to brk-allocated memory

[Kirill A. Shutemov]

On Tue, Nov 07, 2017 at 12:26:12PM +0100, Florian Weimer wrote:
> On 11/07/2017 12:15 PM, Kirill A. Shutemov wrote:
> 
> > > First of all, using addr and MAP_FIXED to develop our heuristic can
> > > never really give unchanged ABI. It's an in-band signal. brk() is a
> > > good example that steadily keeps incrementing address, so depending
> > > on malloc usage and address space randomization, you will get a brk()
> > > that ends exactly at 128T, then the next one will be >
> > > DEFAULT_MAP_WINDOW, and it will switch you to 56 bit address space.
> > 
> > No, it won't. You will hit stack first.
> 
> That's not actually true on POWER in some cases.  See the process maps I
> posted here:
> 
>   <https://marc.info/?l=linuxppc-embedded&m=150988538106263&w=2>

Hm? I see that in all three cases the [stack] is the last mapping.
Do I miss something?

-- 
 Kirill A. Shutemov