• Steve Capper's avatar
    arm64: mm: Introduce DEFAULT_MAP_WINDOW · 363524d2
    Steve Capper authored
    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: default avatarSteve Capper <steve.capper@arm.com>
    Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    363524d2
processor.h 7.9 KB