Re: [PATCH v2 2/5] arm64, mm: Move generic mmap layout functions to mm

[Christoph Hellwig]

On Thu, Apr 04, 2019 at 01:51:25AM -0400, Alexandre Ghiti wrote:
> - fix the case where stack randomization should not be taken into
>   account.

Hmm.  This sounds a bit vague.  It might be better if something
considered a fix is split out to a separate patch with a good
description.

> +config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> +	bool
> +	help
> +	  This allows to use a set of generic functions to determine mmap base
> +	  address by giving priority to top-down scheme only if the process
> +	  is not in legacy mode (compat task, unlimited stack size or
> +	  sysctl_legacy_va_layout).

Given that this is an option that is just selected by other Kconfig
options the help text won't ever be shown.  I'd just move it into a
comment bove the definition.

> +#ifdef CONFIG_MMU
> +#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

I don't think we need the #ifdef CONFIG_MMU here,
CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT should only be selected
if the MMU is enabled to start with.

> +#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
> +unsigned long arch_mmap_rnd(void)

Now that a bunch of architectures use a version in common code
the arch_ prefix is a bit mislead.  Probably not worth changing
here, but some time in the future it could use a new name.