On Mon, Nov 23, 2015 at 10:55:16AM -0800, Daniel Cashman wrote:

On 11/23/2015 07:04 AM, Will Deacon wrote:

quoted

On Wed, Nov 18, 2015 at 03:20:07PM -0800, Daniel Cashman wrote:

quoted

+config ARCH_MMAP_RND_BITS_MAX
+       default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39

Where is ARCH_VA_BITS defined? We only have options like
ARM64_VA_BITS_39.

BTW, we no longer allow the 64K pages and 39-bit VA combination.

quoted

quoted

+       default 24 if ARCH_VA_BITS=39
+       default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42
+       default 27 if ARCH_VA_BITS=42
+       default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48
+       default 33 if ARCH_VA_BITS=48
+       default 15 if ARM64_64K_PAGES
+       default 19
+
+config ARCH_MMAP_RND_COMPAT_BITS_MIN
+       default 7 if ARM64_64K_PAGES
+       default 11

FYI: we now support 16k pages too, so this might need updating. It would
be much nicer if this was somehow computed rather than have the results
all open-coded like this.

Yes, I ideally wanted this to be calculated based on the different page
options and VA_BITS (which itself has a similar stanza), but I don't
know how to do that/if it is currently supported in Kconfig. This would
be even more desirable with the addition of 16K_PAGES, as with this
setup we have a combinatorial problem.

For KASan, we ended up calculating KASAN_SHADOW_OFFSET in
arch/arm64/Makefile. What would the formula be for the above
ARCH_MMAP_RND_BITS_MAX?

-- 
Catalin