• Ard Biesheuvel's avatar
    arm64/efi: Fix boot crash by not padding between EFI_MEMORY_RUNTIME regions · 0ce3cc00
    Ard Biesheuvel authored
    The new Properties Table feature introduced in UEFIv2.5 may
    split memory regions that cover PE/COFF memory images into
    separate code and data regions. Since these regions only differ
    in the type (runtime code vs runtime data) and the permission
    bits, but not in the memory type attributes (UC/WC/WT/WB), the
    spec does not require them to be aligned to 64 KB.
    Since the relative offset of PE/COFF .text and .data segments
    cannot be changed on the fly, this means that we can no longer
    pad out those regions to be mappable using 64 KB pages.
    Unfortunately, there is no annotation in the UEFI memory map
    that identifies data regions that were split off from a code
    region, so we must apply this logic to all adjacent runtime
    regions whose attributes only differ in the permission bits.
    So instead of rounding each memory region to 64 KB alignment at
    both ends, only round down regions that are not directly
    preceded by another runtime region with the same type
    attributes. Since the UEFI spec does not mandate that the memory
    map be sorted, this means we also need to sort it first.
    Note that this change will result in all EFI_MEMORY_RUNTIME
    regions whose start addresses are not aligned to the OS page
    size to be mapped with executable permissions (i.e., on kernels
    compiled with 64 KB pages). However, since these mappings are
    only active during the time that UEFI Runtime Services are being
    invoked, the window for abuse is rather small.
    Tested-by: default avatarMark Salter <msalter@redhat.com>
    Tested-by: Mark Rutland <mark.rutland@arm.com> [UEFI 2.4 only]
    Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
    Reviewed-by: default avatarMark Salter <msalter@redhat.com>
    Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
    Cc: <stable@vger.kernel.org> # v4.0+
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Leif Lindholm <leif.lindholm@linaro.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: linux-kernel@vger.kernel.org
    Link: http://lkml.kernel.org/r/1443218539-7610-3-git-send-email-matt@codeblueprint.co.uk
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
efi.c 8.67 KB