arm64/efi: Fix boot crash by not padding between EFI_MEMORY_RUNTIME regions

arm64/efi: Fix boot crash by not padding between EFI_MEMORY_RUNTIME regions

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: Mark Salter <msalter@redhat.com>
Tested-by: Mark Rutland <mark.rutland@arm.com> [UEFI 2.4 only]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Reviewed-by: Mark Salter <msalter@redhat.com>
Reviewed-by: Mark 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: Ingo Molnar <mingo@kernel.org>