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. 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> Signed-off-by: Jian J Wang <jian.j.w...@intel.com> --- MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 4 ++++ MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c | 4 ++++ 2 files changed, 8 insertions(+) diff --git a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c index 172d7cd1c6..6e8ca824d4 100644 --- a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c +++ b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c @@ -246,8 +246,12 @@ HandOffToDxeCore ( EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi; BOOLEAN BuildPageTablesIa32Pae; + // + // Clear page 0 and mark it as allocated if NULL pointer detection is enabled. + // if (IsNullDetectionEnabled ()) { ClearFirst4KPage (HobList.Raw); + BuildMemoryAllocationHob (0, EFI_PAGES_TO_SIZE (1), EfiBootServicesData); } Status = PeiServicesAllocatePages (EfiBootServicesData, EFI_SIZE_TO_PAGES (STACK_SIZE), &BaseOfStack); diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c index 2867610bff..f465eb1d8a 100644 --- a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c +++ b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c @@ -36,8 +36,12 @@ HandOffToDxeCore ( EFI_VECTOR_HANDOFF_INFO *VectorInfo; EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi; + // + // Clear page 0 and mark it as allocated if NULL pointer detection is enabled. + // if (IsNullDetectionEnabled ()) { ClearFirst4KPage (HobList.Raw); + BuildMemoryAllocationHob (0, EFI_PAGES_TO_SIZE (1), EfiBootServicesData); } // -- 2.17.1.windows.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#50061): https://edk2.groups.io/g/devel/message/50061 Mute This Topic: https://groups.io/mt/44036060/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
