[PATCH v2 1/1] powerpc: mm: support ARCH_MMAP_RND_BITS

[Kees Cook]

On Thu, Feb 2, 2017 at 9:11 PM, Bhupesh Sharma <bhsharma at redhat.com> wrote:
> powerpc: arch_mmap_rnd() uses hard-coded values, (23-PAGE_SHIFT) for
> 32-bit and (30-PAGE_SHIFT) for 64-bit, to generate the random offset
> for the mmap base address.
>
> This value represents a compromise between increased
> ASLR effectiveness and avoiding address-space fragmentation.
> Replace it with a Kconfig option, which is sensibly bounded, so that
> platform developers may choose where to place this compromise.
> Keep default values as new minimums.
>
> This patch makes sure that now powerpc mmap arch_mmap_rnd() approach
> is similar to other ARCHs like x86, arm64 and arm.
>
> Cc: Alexander Graf <agraf at suse.com>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Anatolij Gustschin <agust at denx.de>
> Cc: Alistair Popple <alistair at popple.id.au>
> Cc: Matt Porter <mporter at kernel.crashing.org>
> Cc: Vitaly Bordug <vitb at kernel.crashing.org>
> Cc: Scott Wood <oss at buserror.net>
> Cc: Kumar Gala <galak at kernel.crashing.org>
> Cc: Daniel Cashman <dcashman at android.com>
> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
> Reviewed-by: Kees Cook <keescook at chromium.org>

This " at " should be "@", but otherwise, yay v2! :)

-Kees

-- 
Kees Cook
Pixel Security