3.1.1 平衡二叉树中改变区块属性，并分裂区块保持属性一致:MmSplitRegion（）

MmSplitRegion函数

//改变区块属性，并分裂区块保持属性一致:

MmSplitRegion

//改变区块属性，并分裂区块保持属性一致:

PMM_REGION static
MmSplitRegion(PMM_REGION InitialRegion, PVOID InitialBaseAddress,PVOID StartAddress, ULONG Length, ULONG NewType,ULONG NewProtect, PMADDRESS_SPACE AddressSpace,PMM_ALTER_REGION_FUNC AlterFunc)
{PMM_REGION NewRegion1;PMM_REGION NewRegion2;ULONG InternalLength;/* Allocate this in front otherwise the failure case is too difficult. */NewRegion2 = ExAllocatePoolWithTag(NonPagedPool, sizeof(MM_REGION),TAG_MM_REGION);if (NewRegion2 == NULL){return(NULL);}/* Create the new region. */NewRegion1 = ExAllocatePoolWithTag(NonPagedPool, sizeof(MM_REGION),TAG_MM_REGION);if (NewRegion1 == NULL){ExFreePool(NewRegion2);return(NULL);}NewRegion1->Type = NewType;NewRegion1->Protect = NewProtect;InternalLength = ((char*)InitialBaseAddress + InitialRegion->Length) - (char*)StartAddress;InternalLength = min(InternalLength, Length);NewRegion1->Length = InternalLength;InsertAfterEntry(&InitialRegion->RegionListEntry,&NewRegion1->RegionListEntry);/** Call our helper function to do the changes on the addresses contained* in the initial region.*/AlterFunc(AddressSpace, StartAddress, InternalLength, InitialRegion->Type,InitialRegion->Protect, NewType, NewProtect);/** If necessary create a new region for the portion of the initial region* beyond the range of addresses to alter.*/if (((char*)InitialBaseAddress + InitialRegion->Length) > ((char*)StartAddress + Length)){NewRegion2->Type = InitialRegion->Type;NewRegion2->Protect = InitialRegion->Protect;NewRegion2->Length = ((char*)InitialBaseAddress + InitialRegion->Length) -((char*)StartAddress + Length);InsertAfterEntry(&NewRegion1->RegionListEntry,&NewRegion2->RegionListEntry);}else{ExFreePool(NewRegion2);}/* Either remove or shrink the initial region. */if (InitialBaseAddress == StartAddress){RemoveEntryList(&InitialRegion->RegionListEntry);ExFreePool(InitialRegion);}else{InitialRegion->Length = (char*)StartAddress - (char*)InitialBaseAddress;}return(NewRegion1);
}