On Fri, Nov 27, 2015 at 11:36:30AM +0300, Andrey Ryabinin wrote: > 2015-11-25 23:39 GMT+03:00 Daniel Cashman <dcashman@xxxxxxxxxxx>: > > On 11/25/2015 04:06 AM, Catalin Marinas wrote: > >> 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? > > > > The general formula I used ended up being: > > _max = floor(log(TASK_SIZE)) - log(PAGE_SIZE) - 3 > > For kasan, we calculate KASAN_SHADOW_OFFSET in Makefile, because we need to use > that value in Makefiles. > > For ARCH_MMAP_RND_COMPAT_BITS_MIN/MAX I don't see a reason why it has > to be in Kconfig. > Can't we just use your formula to #define ARCH_MMAP_RND_COMPAT_BITS_* > in some arch header? Because there is another option, ARCH_MMAP_RND_BITS depending on EXPERT which uses the MIN/MAX range defined per architecture. Since it's an expert feature, we could as well ignore the MIN/MAX in Kconfig and just add BUILD_BUG_ON checks to the code. This way we could simply define them in C files. Alternatively, add arithmetics support to kbuild ;). -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>