[PATCH] powerpc/64e: Don't place the stack beyond TASK_SIZE

[Scott Wood]

On Tue, 2017-05-09 at 00:09 +1000, Michael Ellerman wrote:
> Scott Wood <oss at buserror.net> writes:
> 
> > Commit f4ea6dcb08ea ("powerpc/mm: Enable mappings above 128TB") increased
> > the task size on book3s, and introduced a mechanism to dynamically
> > control whether a task uses these larger addresses.  While the change to
> > the task size itself was ifdef-protected to only apply on book3s, the
> > change to STACK_TOP_USER64 was not.  On book3e, this had the effect of
> > trying to use addresses up to 128TiB for the stack despite a 64TiB task
> > size limit -- which broke 64-bit userspace producing the following errors:
> > 
> > Starting init: /sbin/init exists but couldn't execute it (error -14)
> > Starting init: /bin/sh exists but couldn't execute it (error -14)
> > Kernel panic - not syncing: No working init found.  Try passing init=
> > option to kernel. See Linux Documentation/admin-guide/init.rst for
> > guidance.
> 
> For some reason I am not seeing this on my p5020ds?
> 
> I just checked, it's definitely booting:
> 
>   [    0.000000] Linux version 4.11.0-gcc5-g13e0988 (kerkins at alpine1-p1)
> (gcc version 5.2.1 20151001 (GCC) ) #1 SMP Mon May 8 05:33:22 AEST 2017
>   [    0.000000] Using CoreNet Generic machine description
>   ...
>   [    3.216940] systemd[1]: Detected architecture ppc64.
>   ...
>   Debian GNU/Linux stretch/sid p5020ds ttyS0
>   
>   p5020ds login:
> 
> 
> Anyway patch looks good, I'll pull it in with the rest of your tree.

Are you using a 64-bit userspace?

-Scott