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MdeModulePkg/DxeIpl: Implement NULL pointer detection 

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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25
MdeModulePkg/Core/DxeIplPeim/DxeIpl.h
View File

@ -240,4 +240,29 @@ Decompress (
OUT UINTN *OutputSize
);
/**
Clear legacy memory located at the first 4K-page.
This function traverses the whole HOB list to check if memory from 0 to 4095
exists and has not been allocated, and then clear it if so.
@param HoStart The start of HobList passed to DxeCore.
**/
VOID
ClearFirst4KPage (
IN VOID *HobStart
);
/**
Return configure status of NULL pointer detection feature
@return TRUE NULL pointer detection feature is enabled
@return FALSE NULL pointer detection feature is disabled
**/
BOOLEAN
IsNullDetectionEnabled (
VOID
);
#endif

1
MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
View File

@ -115,6 +115,7 @@
[Pcd.IA32,Pcd.X64]
gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable ## SOMETIMES_CONSUMES
gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask ## CONSUMES
gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask ## CONSUMES
[Pcd.IA32,Pcd.X64,Pcd.ARM,Pcd.AARCH64]
gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack ## SOMETIMES_CONSUMES

1
MdeModulePkg/Core/DxeIplPeim/DxeLoad.c
View File

@ -825,3 +825,4 @@ UpdateStackHob (
Hob.Raw = GET_NEXT_HOB (Hob);
}
}

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();
}
}
//

4
MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c
View File

@ -42,6 +42,10 @@ HandOffToDxeCore (
EFI_VECTOR_HANDOFF_INFO *VectorInfo;
EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi;
if (IsNullDetectionEnabled ()) {
ClearFirst4KPage (HobList.Raw);
}
//
// Get Vector Hand-off Info PPI and build Guided HOB
//

93
MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
View File

@ -31,6 +31,68 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#include "DxeIpl.h"
#include "VirtualMemory.h"
/**
Clear legacy memory located at the first 4K-page, if available.
This function traverses the whole HOB list to check if memory from 0 to 4095
exists and has not been allocated, and then clear it if so.
@param HoStart The start of HobList passed to DxeCore.
**/
VOID
ClearFirst4KPage (
IN VOID *HobStart
)
{
EFI_PEI_HOB_POINTERS RscHob;
EFI_PEI_HOB_POINTERS MemHob;
BOOLEAN DoClear;
RscHob.Raw = HobStart;
MemHob.Raw = HobStart;
DoClear = FALSE;
//
// Check if page 0 exists and free
//
while ((RscHob.Raw = GetNextHob (EFI_HOB_TYPE_RESOURCE_DESCRIPTOR,
RscHob.Raw)) != NULL) {
if (RscHob.ResourceDescriptor->ResourceType == EFI_RESOURCE_SYSTEM_MEMORY &&
RscHob.ResourceDescriptor->PhysicalStart == 0) {
DoClear = TRUE;
//
// Make sure memory at 0-4095 has not been allocated.
//
while ((MemHob.Raw = GetNextHob (EFI_HOB_TYPE_MEMORY_ALLOCATION,
MemHob.Raw)) != NULL) {
if (MemHob.MemoryAllocation->AllocDescriptor.MemoryBaseAddress
< EFI_PAGE_SIZE) {
DoClear = FALSE;
break;
}
MemHob.Raw = GET_NEXT_HOB (MemHob);
}
break;
}
RscHob.Raw = GET_NEXT_HOB (RscHob);
}
if (DoClear) {
DEBUG ((DEBUG_INFO, "Clearing first 4K-page!\r\n"));
SetMem (NULL, EFI_PAGE_SIZE, 0);
}
return;
}
BOOLEAN
IsNullDetectionEnabled (
VOID
)
{
return ((PcdGet8 (PcdNullPointerDetectionPropertyMask) & BIT0) != 0);
}
/**
Enable Execute Disable Bit.
@ -90,8 +152,16 @@ Split2MPageTo4K (
//
PageTableEntry->Uint64 = (UINT64) PhysicalAddress4K | AddressEncMask;
PageTableEntry->Bits.ReadWrite = 1;
PageTableEntry->Bits.Present = 1;
if ((PhysicalAddress4K >= StackBase) && (PhysicalAddress4K < StackBase + StackSize)) {
if (IsNullDetectionEnabled () && PhysicalAddress4K == 0) {
PageTableEntry->Bits.Present = 0;
} else {
PageTableEntry->Bits.Present = 1;
}
if (PcdGetBool (PcdSetNxForStack)
&& (PhysicalAddress4K >= StackBase)
&& (PhysicalAddress4K < StackBase + StackSize)) {
//
// Set Nx bit for stack.
//
@ -137,9 +207,12 @@ Split1GPageTo2M (
PhysicalAddress2M = PhysicalAddress;
for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512; IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PhysicalAddress2M += SIZE_2MB) {
if ((PhysicalAddress2M < StackBase + StackSize) && ((PhysicalAddress2M + SIZE_2MB) > StackBase)) {
if ((IsNullDetectionEnabled () && PhysicalAddress2M == 0)
|| (PcdGetBool (PcdSetNxForStack)
&& (PhysicalAddress2M < StackBase + StackSize)
&& ((PhysicalAddress2M + SIZE_2MB) > StackBase))) {
//
// Need to split this 2M page that covers stack range.
// Need to split this 2M page that covers NULL or stack range.
//
Split2MPageTo4K (PhysicalAddress2M, (UINT64 *) PageDirectoryEntry, StackBase, StackSize);
} else {
@ -279,7 +352,10 @@ CreateIdentityMappingPageTables (
PageDirectory1GEntry = (VOID *) PageDirectoryPointerEntry;
for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512; IndexOfPageDirectoryEntries++, PageDirectory1GEntry++, PageAddress += SIZE_1GB) {
if (PcdGetBool (PcdSetNxForStack) && (PageAddress < StackBase + StackSize) && ((PageAddress + SIZE_1GB) > StackBase)) {
if ((IsNullDetectionEnabled () && PageAddress == 0)
|| (PcdGetBool (PcdSetNxForStack)
&& (PageAddress < StackBase + StackSize)
&& ((PageAddress + SIZE_1GB) > StackBase))) {
Split1GPageTo2M (PageAddress, (UINT64 *) PageDirectory1GEntry, StackBase, StackSize);
} else {
//
@ -308,9 +384,12 @@ CreateIdentityMappingPageTables (
PageDirectoryPointerEntry->Bits.Present = 1;
for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512; IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PageAddress += SIZE_2MB) {
if (PcdGetBool (PcdSetNxForStack) && (PageAddress < StackBase + StackSize) && ((PageAddress + SIZE_2MB) > StackBase)) {
if ((IsNullDetectionEnabled () && PageAddress == 0)
|| (PcdGetBool (PcdSetNxForStack)
&& (PageAddress < StackBase + StackSize)
&& ((PageAddress + SIZE_2MB) > StackBase))) {
//
// Need to split this 2M page that covers stack range.
// Need to split this 2M page that covers NULL or stack range.
//
Split2MPageTo4K (PageAddress, (UINT64 *) PageDirectoryEntry, StackBase, StackSize);
} else {