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

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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.

-#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))	/* 8MB of VA */
-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;
-	}
-	return PAGE_ALIGN(stack_top) + random_variable;
-	return PAGE_ALIGN(stack_top) - random_variable;
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) || \
Not sure if it is wrіtten 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 :)

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