QemuVideoDxe driver will link VBE SHIM into page 0. If NULL pointer detection is enabled, this driver will fail to load. NULL pointer detection bypassing code is added to prevent such problem during boot.
Please note that Windows 7 will try to access VBE SHIM during boot if it's installed, and then cause boot failure. This can be fixed by setting BIT7 of PcdNullPointerDetectionPropertyMask to disable NULL pointer detection after EndOfDxe. As far as we know, there's no other OSs has such issue. > According to Laszlo, remove the code disabling/enabling the NULL pointer > detection but just ignore the installing if it's enabled 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]> --- OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf | 1 + OvmfPkg/QemuVideoDxe/VbeShim.c | 14 ++++++++++++++ 2 files changed, 15 insertions(+) diff --git a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf index 577e07b0a8..ff68c99e96 100644 --- a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf +++ b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf @@ -77,3 +77,4 @@ [Pcd] gOptionRomPkgTokenSpaceGuid.PcdDriverSupportedEfiVersion gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId + gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask diff --git a/OvmfPkg/QemuVideoDxe/VbeShim.c b/OvmfPkg/QemuVideoDxe/VbeShim.c index e45a08e887..8ba5522cde 100644 --- a/OvmfPkg/QemuVideoDxe/VbeShim.c +++ b/OvmfPkg/QemuVideoDxe/VbeShim.c @@ -75,6 +75,20 @@ InstallVbeShim ( UINTN Printed; VBE_MODE_INFO *VbeModeInfo; + if ((PcdGet8 (PcdNullPointerDetectionPropertyMask) & (BIT0|BIT7)) == BIT0) { + DEBUG (( + DEBUG_WARN, + "%a: page 0 protected, not installing VBE shim\n", + __FUNCTION__ + )); + DEBUG (( + DEBUG_WARN, + "%a: page 0 protection prevents Windows 7 from booting anyway\n", + __FUNCTION__ + )); + return; + } + Segment0 = 0x00000; SegmentC = 0xC0000; SegmentF = 0xF0000; -- 2.14.1.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
