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MdeModulePkg/DxeIpl: Implement NULL pointer detection

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NULL pointer detection is done by making use of paging mechanism of CPU.
During page table setup, if enabled, the first 4-K page (0-4095) will be
marked as NOT PRESENT. Any code which unintentionally access memory between
0-4095 will trigger a Page Fault exception which warns users that there's
potential illegal code in BIOS.

This also means that legacy code which has to access memory between 0-4095
should be cautious to temporarily disable this feature before the access
and re-enable it afterwards; or disalbe this feature at all.

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Ayellet Wolman <ayellet.wolman@intel.com>
Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
This commit is contained in:
Jian J Wang
2017-10-09 21:56:32 +08:00
committed by Eric Dong
parent f7e077768f
commit 9189ec20b9
6 changed files with 131 additions and 10 deletions
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17
MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
View File

@@ -123,7 +123,9 @@ Create4GPageTablesIa32Pae (
PageDirectoryPointerEntry->Bits.Present = 1;
for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512; IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PhysicalAddress += SIZE_2MB) {
if ((PhysicalAddress < StackBase + StackSize) && ((PhysicalAddress + SIZE_2MB) > StackBase)) {
if ((IsNullDetectionEnabled () && PhysicalAddress == 0)
|| ((PhysicalAddress < StackBase + StackSize)
&& ((PhysicalAddress + SIZE_2MB) > StackBase))) {
//
// Need to split this 2M page that covers stack range.
//
@@ -240,6 +242,10 @@ HandOffToDxeCore (
EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi;
BOOLEAN BuildPageTablesIa32Pae;
if (IsNullDetectionEnabled ()) {
ClearFirst4KPage (HobList.Raw);
}
Status = PeiServicesAllocatePages (EfiBootServicesData, EFI_SIZE_TO_PAGES (STACK_SIZE), &BaseOfStack);
ASSERT_EFI_ERROR (Status);
@@ -379,10 +385,15 @@ HandOffToDxeCore (
TopOfStack = (EFI_PHYSICAL_ADDRESS) (UINTN) ALIGN_POINTER (TopOfStack, CPU_STACK_ALIGNMENT);
PageTables = 0;
BuildPageTablesIa32Pae = (BOOLEAN) (PcdGetBool (PcdSetNxForStack) && IsIa32PaeSupport () && IsExecuteDisableBitAvailable ());
BuildPageTablesIa32Pae = (BOOLEAN) (IsIa32PaeSupport () &&
(IsNullDetectionEnabled () ||
(PcdGetBool (PcdSetNxForStack) &&
IsExecuteDisableBitAvailable ())));
if (BuildPageTablesIa32Pae) {
PageTables = Create4GPageTablesIa32Pae (BaseOfStack, STACK_SIZE);
EnableExecuteDisableBit ();
if (IsExecuteDisableBitAvailable ()) {
EnableExecuteDisableBit();
}
}
//