Re: [PATCH 1/4] arm64, mm: Move generic mmap layout functions to mm

[Alex Ghiti]

On 3/22/19 9:21 AM, Christoph Hellwig wrote:
> > It then introduces a new define ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> > that can be defined by other architectures to benefit from those functions.
> Can you make this a Kconfig option defined in arch/Kconfig or mm/Kconfig
> and selected by the architectures?


Yes, I will do.


> > -#ifndef STACK_RND_MASK
> > -#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))	/* 8MB of VA */
> > -#endif
> > -
> > -static unsigned long randomize_stack_top(unsigned long stack_top)
> > -{
> > -	unsigned long random_variable = 0;
> > -
> > -	if (current->flags & PF_RANDOMIZE) {
> > -		random_variable = get_random_long();
> > -		random_variable &= STACK_RND_MASK;
> > -		random_variable <<= PAGE_SHIFT;
> > -	}
> > -#ifdef CONFIG_STACK_GROWSUP
> > -	return PAGE_ALIGN(stack_top) + random_variable;
> > -#else
> > -	return PAGE_ALIGN(stack_top) - random_variable;
> > -#endif
> > -}
> > -
> Maybe the move of this function can be split into another prep patch,
> as it is only very lightly related?

Ok, that makes sense.

> > +#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
> > +	defined(ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)
> Not sure if it is wrÑtten down somehwere or just convention, but I
> general see cpp defined statements aligned with spaces to the
> one on the previous line.


Ok, I will fix that.


> Except for these nitpicks this looks very nice to me, thanks for doing
> this work!


Thanks :)