The mechanism behind is to trigger a page fault exception at address 0. This can be made by disabling page 0 (0-4095) during page table setup. So this feature can only be available on platform with paging enabled.
Once this feature is enabled, any code, like CSM, which has to access memory in page 0 needs to enable this page temporarily in advance and disable it afterwards. PcdNullPointerDetectionPropertyMask is used to control and elaborate the use cases. For example, BIT7 of this PCD must be set for Windows 7 boot on Qemu if BIT0 set; or boot will fail. Cc: Star Zeng <[email protected]> Cc: Eric Dong <[email protected]> Cc: Laszlo Ersek <[email protected]> Cc: Jiewen Yao <[email protected]> Cc: Michael Kinney <[email protected]> Cc: Jordan Justen <[email protected]> Cc: Ayellet Wolman <[email protected]> Suggested-by: Ayellet Wolman <[email protected]> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Jian J Wang <[email protected]> Jian J Wang (5): MdeModulePkg/DxeIpl: Implement NULL pointer detection MdeModulePkg/Core/Dxe: Add EndOfDxe workaround for NULL pointer detection UefiCpuPkg/PiSmmCpuDxeSmm: Implement NULL pointer detection for SMM code IntelFrameworkModulePkg/Csm: Add code to bypass NULL pointer detection OvmfPkg/QemuVideoDxe: Bypass NULL pointer detection during VBE SHIM installing Wang, Jian J (1): MdeModulePkg/MdeModulePkg.dec,.uni: Add NULL pointer detection PCD .../Csm/BiosThunk/KeyboardDxe/BiosKeyboard.c | 101 ++++++++++++++ .../Csm/BiosThunk/KeyboardDxe/BiosKeyboard.h | 2 + .../Csm/BiosThunk/KeyboardDxe/KeyboardDxe.inf | 2 + .../Csm/LegacyBiosDxe/LegacyBda.c | 4 + .../Csm/LegacyBiosDxe/LegacyBios.c | 152 +++++++++++++++++++++ .../Csm/LegacyBiosDxe/LegacyBiosDxe.inf | 2 + .../Csm/LegacyBiosDxe/LegacyBiosInterface.h | 18 +++ .../Csm/LegacyBiosDxe/LegacyBootSupport.c | 23 +++- .../Csm/LegacyBiosDxe/LegacyPci.c | 17 ++- IntelFrameworkModulePkg/Csm/LegacyBiosDxe/Thunk.c | 27 +++- MdeModulePkg/Core/Dxe/DxeMain.inf | 1 + MdeModulePkg/Core/Dxe/Mem/Page.c | 4 +- MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 48 +++++++ MdeModulePkg/Core/DxeIplPeim/DxeIpl.h | 25 ++++ MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf | 1 + MdeModulePkg/Core/DxeIplPeim/DxeLoad.c | 65 +++++++++ MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 11 +- MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c | 2 + MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c | 31 ++++- MdeModulePkg/MdeModulePkg.dec | 13 ++ MdeModulePkg/MdeModulePkg.uni | 13 ++ OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf | 1 + OvmfPkg/QemuVideoDxe/VbeShim.c | 14 ++ UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c | 12 ++ UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 25 +++- UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf | 1 + UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c | 12 ++ 27 files changed, 606 insertions(+), 21 deletions(-) -- 2.14.1.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
