Re: [PATCH v3 04/11] arm64, mm: Move generic mmap layout functions to mm

[Christoph Hellwig]

On Thu, Apr 18, 2019 at 09:19:18AM -0500, Kees Cook wrote:
> On Thu, Apr 18, 2019 at 12:55 AM Alex Ghiti <alex@xxxxxxxx> wrote:
> > Regarding the help text, I agree that it does not seem to be frequent to
> > place
> > comment above config like that, I'll let Christoph and you decide what's
> > best. And I'll
> > add the possibility for the arch to define its own STACK_RND_MASK.
> 
> Yeah, I think it's very helpful to spell out the requirements for new
> architectures with these kinds of features in the help text (see
> SECCOMP_FILTER for example).

Spelling out the requirements sounds useful.  Abusing the help text
for an option for which no help text can be displayed it pointless.
Just make it a comment as Alex did in this patch, which makes whole
lot more sense.

> > Actually, I had to add those ifdefs for mmap_rnd_compat_bits, not
> > is_compat_task.
> 
> Oh! In that case, use CONFIG_HAVE_ARCH_MMAP_RND_BITS. :) Actually,
> what would be maybe cleaner would be to add mmap_rnd_bits_min/max
> consts set to 0 for the non-CONFIG_HAVE_ARCH_MMAP_RND_BITS case at the
> top of mm/mmap.c.

Lets do that in a second step.  The current series is already big
enough and a major improvement, even if there is much more to clean
up in this area still left.