[PATCH 0/2] Reserve page 0 for NULL pointer detection

["Wang, Jian J" <jian.j.wang@intel.com>]

When a boot loader examines the memory map, it can see that location 0
is available memory. If it chooses to use that memory, and
PcdNullPointerDetectionPropertyMask is enabled, use of memory in page 0
will cause an exception. This does occur when running the memtest86
program.

Leaving page 0 available is for legacy support purpose. Since we have
deprecated the support of legacy, the solution is just reserving it so
that it cannot be allocated for other uses.

Tests:
  - run memtest86 with PcdNullPointerDetectionPropertyMask set to 0x03
  - run memtest86 with PcdNullPointerDetectionPropertyMask set to 0x83
  - boot OVMF into Windows 7 with PcdNullPointerDetectionPropertyMask set to 0x83 

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1885
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>

Jian J Wang (2):
  MdeModulePkg/DxeIplPeim: reserve page 0 for NULL pointer detection
  MdeModulePkg/Core/Dxe: free page 0 after disabling NULL pointer
    detection

 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c   | 5 +++++
 MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 4 ++++
 MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c  | 4 ++++
 3 files changed, 13 insertions(+)

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2.17.1.windows.2