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...@intel.com> Cc: Liming Gao <liming....@intel.com> Cc: Ray Ni <ray...@intel.com> Cc: Hao A Wu <hao.a...@intel.com> Cc: Sean Brogan <sean.bro...@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(+) -- 2.17.1.windows.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#50060): https://edk2.groups.io/g/devel/message/50060 Mute This Topic: https://groups.io/mt/44036050/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
