• Steve Capper's avatar
    arm64: mm: Flip kernel VA space · 14c127c9
    Steve Capper authored
    In order to allow for a KASAN shadow that changes size at boot time, one
    must fix the KASAN_SHADOW_END for both 48 & 52-bit VAs and "grow" the
    start address. Also, it is highly desirable to maintain the same
    function addresses in the kernel .text between VA sizes. Both of these
    requirements necessitate us to flip the kernel address space halves s.t.
    the direct linear map occupies the lower addresses.
    
    This patch puts the direct linear map in the lower addresses of the
    kernel VA range and everything else in the higher ranges.
    
    We need to adjust:
     *) KASAN shadow region placement logic,
     *) KASAN_SHADOW_OFFSET computation logic,
     *) virt_to_phys, phys_to_virt checks,
     *) page table dumper.
    
    These are all small changes, that need to take place atomically, so they
    are bundled into this commit.
    
    As part of the re-arrangement, a guard region of 2MB (to preserve
    alignment for fixed map) is added after the vmemmap. Otherwise the
    vmemmap could intersect with IS_ERR pointers.
    Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarSteve Capper <steve.capper@arm.com>
    Signed-off-by: default avatarWill Deacon <will@kernel.org>
    14c127c9
pgtable.h 24.8 KB