On Wed, Dec 05, 2018 at 04:41:41PM +0000, Steve Capper wrote: > We wish to introduce a 52-bit virtual address space for userspace but > maintain compatibility with software that assumes the maximum VA space > size is 48 bit. > > In order to achieve this, on 52-bit VA systems, we make mmap behave as > if it were running on a 48-bit VA system (unless userspace explicitly > requests a VA where addr[51:48] != 0). > > On a system running a 52-bit userspace we need TASK_SIZE to represent > the 52-bit limit as it is used in various places to distinguish between > kernelspace and userspace addresses. > > Thus we need a new limit for mmap, stack, ELF loader and EFI (which uses > TTBR0) to represent the non-extended VA space. > > This patch introduces DEFAULT_MAP_WINDOW and DEFAULT_MAP_WINDOW_64 and > switches the appropriate logic to use that instead of TASK_SIZE. > > Signed-off-by: Steve Capper <steve.capper@xxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
