diff --git a/BOOT/ENVIRON/INC/bootmgr.h b/BOOT/ENVIRON/INC/bootmgr.h
index 765e24f..5e79bb6 100644
--- a/BOOT/ENVIRON/INC/bootmgr.h
+++ b/BOOT/ENVIRON/INC/bootmgr.h
@@ -106,7 +106,7 @@ typedef struct {
     ULONG MdlOffset;
     ULONG DescriptorCount;
     ULONG DescriptorSize;
-    ULONG BasePageOffset;
+    ULONG FirstPageOffset;
 } BOOT_MEMORY_INFO, *PBOOT_MEMORY_INFO;
 
 //
@@ -154,11 +154,12 @@ typedef enum {
 typedef struct {
     LIST_ENTRY ListEntry;
 
-    ULONGLONG BasePage;
-    ULONG Pages;
+    ULONGLONG FirstPage;
+    ULONGLONG MappedFirstPage;
+    ULONG PageCount;
 
     ULONG Attributes;
-    ULONG Type;
+    MEMORY_TYPE Type;
 } MEMORY_DESCRIPTOR, *PMEMORY_DESCRIPTOR;
 
 typedef enum {
diff --git a/BOOT/ENVIRON/INC/mm.h b/BOOT/ENVIRON/INC/mm.h
index 876c7ff..59b58f5 100644
--- a/BOOT/ENVIRON/INC/mm.h
+++ b/BOOT/ENVIRON/INC/mm.h
@@ -18,12 +18,27 @@ Abstract:
 
 #include "bootlib.h"
 
+#define MDL_OPERATION_FLAGS_TRUNCATE 0x02
+
 NTSTATUS
 MmFwGetMemoryMap (
    IN OUT PMEMORY_DESCRIPTOR_LIST Mdl,
    IN ULONG Flags
    );
 
+BOOLEAN
+MmMdpHasPrecedence (
+    IN MEMORY_TYPE A,
+    IN MEMORY_TYPE B
+    );
+
+BOOLEAN
+MmMdpTruncateDescriptor (
+    IN PMEMORY_DESCRIPTOR_LIST Mdl,
+    IN PMEMORY_DESCRIPTOR Descriptor,
+    IN ULONG Flags
+    );
+
 NTSTATUS
 MmMdAddDescriptorToList (
     IN PMEMORY_DESCRIPTOR_LIST Mdl,
@@ -49,8 +64,8 @@ MmMdFreeList (
 
 PMEMORY_DESCRIPTOR
 MmMdInitDescriptor (
-    IN ULONGLONG BasePage,
-    IN ULONGLONG MappedBasePage,
+    IN ULONGLONG FirstPage,
+    IN ULONGLONG MappedFirstPage,
     IN ULONGLONG PageCount,
     IN ULONG Attributes,
     IN MEMORY_TYPE Type
diff --git a/BOOT/ENVIRON/LIB/EFI/efiinit.c b/BOOT/ENVIRON/LIB/EFI/efiinit.c
index 4fd294e..b20900f 100644
--- a/BOOT/ENVIRON/LIB/EFI/efiinit.c
+++ b/BOOT/ENVIRON/LIB/EFI/efiinit.c
@@ -654,12 +654,12 @@ Return Value:
     MemoryInfo->MdlOffset = sizeof(BOOT_MEMORY_INFO);
     MemoryInfo->DescriptorCount = 1;
     MemoryInfo->DescriptorSize = sizeof(MEMORY_DESCRIPTOR);
-    MemoryInfo->BasePageOffset = FIELD_OFFSET(MEMORY_DESCRIPTOR, BasePage);
+    MemoryInfo->FirstPageOffset = FIELD_OFFSET(MEMORY_DESCRIPTOR, FirstPage);
 
     MemoryDescriptor = (PMEMORY_DESCRIPTOR)(&EfiInitScratch[ScratchUsed]);
     ScratchUsed += sizeof(MEMORY_DESCRIPTOR);
-    MemoryDescriptor->BasePage = (UINTN)InputParameters->ImageBase >> PAGE_SHIFT;
-    MemoryDescriptor->Pages = ALIGN_UP(InputParameters->ImageSize, PAGE_SIZE) >> PAGE_SHIFT;
+    MemoryDescriptor->FirstPage = (UINTN)InputParameters->ImageBase >> PAGE_SHIFT;
+    MemoryDescriptor->PageCount = ALIGN_UP(InputParameters->ImageSize, PAGE_SIZE) >> PAGE_SHIFT;
     MemoryDescriptor->Attributes = MEMORY_ATTRIBUTE_WB;
     MemoryDescriptor->Type = MEMORY_TYPE_BOOT_APPLICATION;
 
diff --git a/BOOT/ENVIRON/LIB/EFI/efimm.c b/BOOT/ENVIRON/LIB/EFI/efimm.c
index 3ec6031..10c83c3 100644
--- a/BOOT/ENVIRON/LIB/EFI/efimm.c
+++ b/BOOT/ENVIRON/LIB/EFI/efimm.c
@@ -15,8 +15,266 @@ Abstract:
 
 #include "bootmgr.h"
 #include "efi.h"
+#include "efilib.h"
 #include "mm.h"
 
+#define _1MiB 1048576
+
+#define EFI_PAGE(NtPage) (((NtPage) << PAGE_SHIFT) >> EFI_PAGE_SHIFT)
+#define NT_PAGE(EfiPage) (((EfiPage) << EFI_PAGE_SHIFT) >> PAGE_SHIFT)
+
+extern EFI_BOOT_SERVICES *EfiBS;
+extern PBOOT_DEVICE BlpBootDevice;
+
+NTSTATUS
+EfiGetMemoryMap (
+    IN OUT UINTN *MemoryMapSize,
+    IN OUT EFI_MEMORY_DESCRIPTOR *MemoryMap,
+    IN OUT UINTN *MapKey,
+    IN OUT UINTN *DescriptorSize,
+    IN OUT UINT32 *DescriptorVersion
+    )
+
+/*++
+
+Routine Description:
+
+    Wrapper for EFI_BOOT_SERVICES.GetMemoryMap(). Gets the firmware memory map
+    and places it into a buffer.
+
+Arguments:
+
+    MemoryMapSize - pointer to the size of the buffer.
+
+    MemoryMap - pointer to the buffer to store the memory map in.
+
+    MapKey - ponter to the memory map key.
+
+    DescriptorSize - pointer to the size of each memory map descriptor.
+
+    DescriptorVersion - pointer to the version of memory map descriptors.
+
+Return Value:
+
+    STATUS_SUCCESS if successful,
+    Other NTSTATUS value if an error occurs.
+
+--*/
+
+{
+    return EfiGetNtStatusCode(
+        EfiBS->GetMemoryMap(
+            MemoryMapSize,
+            MemoryMap,
+            MapKey,
+            DescriptorSize,
+            DescriptorVersion
+        )
+    );
+}
+
+NTSTATUS
+EfiAllocatePages (
+    IN EFI_ALLOCATE_TYPE Type,
+    IN EFI_MEMORY_TYPE MemoryType,
+    IN UINTN Pages,
+    IN OUT EFI_PHYSICAL_ADDRESS *Memory
+    )
+
+/*++
+
+Routine Description:
+
+    Wrapper for EFI_BOOT_SERVICES.AllocatePages(). Allocates contiguous pages
+    of physical memory.
+
+Arguments:
+
+    Type - the type of allocation.
+
+    MemoryType - the type of memory to allocate.
+
+    Pages - the number of pages to allocate.
+
+    Memory - pointer to a physical address of the allocation.
+
+Return Value:
+
+    STATUS_SUCCESS if successful,
+    Other NTSTATUS value if an error occurs.
+
+--*/
+
+{
+    return EfiGetNtStatusCode(
+        EfiBS->AllocatePages(
+            Type,
+            MemoryType,
+            Pages,
+            Memory
+        )
+    );
+}
+
+NTSTATUS
+EfiFreePages (
+    IN EFI_PHYSICAL_ADDRESS Memory,
+    IN UINTN Pages
+    )
+
+/*++
+
+Routine Description:
+
+    Wrapper for EFI_BOOT_SERVICES.FreePages(). Frees contiguous pages
+    of physical memory.
+
+Arguments:
+
+    Memory - physical address of the pages to be freed.
+
+    Pages - the number of pages to free.
+
+Return Value:
+
+    STATUS_SUCCESS if successful,
+    Other NTSTATUS value if an error occurs.
+
+--*/
+
+{
+    return EfiGetNtStatusCode(
+        EfiBS->FreePages(
+            Memory,
+            Pages
+        )
+    );
+}
+
+MEMORY_TYPE
+BlMmTranslateEfiMemoryType (
+    IN EFI_MEMORY_TYPE EfiMemoryType
+    )
+
+/*++
+
+Routine Description:
+
+    Translates an EFI memory type to an NT memory type.
+
+Arguments:
+
+    EfiMemoryType - the EFI memory type.
+
+Return Value:
+
+    The NT memory type.
+
+--*/
+
+{
+    switch (EfiMemoryType) {
+    case EfiConventionalMemory:
+        return MEMORY_TYPE_FREE;
+    case EfiLoaderCode:
+    case EfiLoaderData:
+        return MEMORY_TYPE_BOOT_APPLICATION;
+    case EfiBootServicesCode:
+    case EfiBootServicesData:
+        return MEMORY_TYPE_BOOT_SERVICES;
+    case EfiRuntimeServicesCode:
+        return MEMORY_TYPE_RUNTIME_SERVICES_CODE;
+    case EfiRuntimeServicesData:
+        return MEMORY_TYPE_RUNTIME_SERVICES_DATA;
+    case EfiUnusableMemory:
+        return MEMORY_TYPE_UNUSABLE;
+    case EfiACPIReclaimMemory:
+        return MEMORY_TYPE_ACPI_RECLAIM;
+    case EfiACPIMemoryNVS:
+        return MEMORY_TYPE_ACPI_NVS;
+    case EfiMemoryMappedIO:
+        return MEMORY_TYPE_MMIO;
+    case EfiMemoryMappedIOPortSpace:
+        return MEMORY_TYPE_MMIO_PORT_SPACE;
+    case EfiPalCode:
+        return MEMORY_TYPE_PAL_CODE;
+    case EfiPersistentMemory:
+        return MEMORY_TYPE_PERSISTENT;
+    case EfiReservedMemoryType:
+    default:
+        if ((ULONG)EfiMemoryType < MAXLONG) {
+            return MEMORY_TYPE_RESERVED;
+        } else {
+            return (MEMORY_TYPE)EfiMemoryType;
+        }
+    }
+}
+
+ULONG
+MmFwpGetOsAttributeType (
+    IN UINT64 EfiAttributes
+    )
+
+/*++
+
+Routine Description:
+
+    Translates EFI memory descriptor attributes to NT memory descriptor attributes.
+
+Arguments:
+
+    EfiAttributes - the EFI attributes.
+
+Return Value:
+
+    The NT attributes.
+
+--*/
+
+{
+    ULONG NtAttributes;
+
+    NtAttributes = 0;
+
+    if (EfiAttributes & EFI_MEMORY_UC) {
+        NtAttributes |= MEMORY_ATTRIBUTE_UC;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_WC) {
+        NtAttributes |= MEMORY_ATTRIBUTE_WC;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_WT) {
+        NtAttributes |= MEMORY_ATTRIBUTE_WT;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_WB) {
+        NtAttributes |= MEMORY_ATTRIBUTE_WB;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_UCE) {
+        NtAttributes |= MEMORY_ATTRIBUTE_UCE;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_WP) {
+        NtAttributes |= MEMORY_ATTRIBUTE_WP;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_RP) {
+        NtAttributes |= MEMORY_ATTRIBUTE_RP;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_XP) {
+        NtAttributes |= MEMORY_ATTRIBUTE_XP;
+    }
+
+    if (EfiAttributes & EFI_MEMORY_RUNTIME) {
+        NtAttributes |= MEMORY_ATTRIBUTE_RUNTIME;
+    }
+
+    return NtAttributes;
+}
+
 NTSTATUS
 MmFwGetMemoryMap (
    IN OUT PMEMORY_DESCRIPTOR_LIST Mdl,
@@ -27,11 +285,13 @@ MmFwGetMemoryMap (
 
 Routine Description:
 
-    Converts an NT status code into an EFI status code.
+    Gets the memory map from EFI and converts it into an MDL.
 
 Arguments:
 
-    Status - The NT status code to be converted.
+    Mdl - Pointer to the MDL to store new descriptors in.
+
+    Flags - Unused.
 
 Return Value:
 
@@ -41,16 +301,288 @@ Return Value:
 --*/
 
 {
+    NTSTATUS Status;
+    UINTN EfiMapSize;
+    UINTN EfiMapKey;
+    UINTN EfiDescriptorSize;
+    UINT32 EfiDescriptorVersion;
+    UINTN PageCount, EfiPageCount;
+    EFI_PHYSICAL_ADDRESS EfiBuffer;
+    EFI_MEMORY_DESCRIPTOR *EfiMap;
+    BOOLEAN IsRamdisk;
+    MEMORY_TYPE MemoryType;
+    UINT64 EfiStartPage, EfiEndPage;
+    UINT64 EfiRamdiskStartPage, EfiRamdiskEndPage;
+    PMEMORY_DESCRIPTOR NtDescriptor;
+
     (VOID)Flags;
 
-    //
-    // Make sure Mdl is valid.
-    //
+    EfiBuffer = (EFI_PHYSICAL_ADDRESS)0;
+
     if (Mdl == NULL) {
         return STATUS_INVALID_PARAMETER;
     }
 
     MmMdFreeList(Mdl);
 
-    return STATUS_SUCCESS;
+    //
+    // Get the memory map from firmware.
+    // This is a "fake" call to actually just get
+    // the required buffer size and other info.
+    //
+    EfiMapSize = 0;
+    Status = EfiGetMemoryMap(&EfiMapSize, NULL, &EfiMapKey, &EfiDescriptorSize, &EfiDescriptorVersion);
+    if (Status != STATUS_BUFFER_TOO_SMALL) {
+        DebugPrint(L"MmFwGetMemoryMap(): EfiGetMemoryMap() failed\r\n");
+
+        //
+        // Make sure status is not successful, just in case
+        // EfiGetMemoryMap() somehow succeeded.
+        //
+        if (NT_SUCCESS(Status)) {
+            Status = STATUS_UNSUCCESSFUL;
+        }
+
+        goto exit;
+    }
+
+    EfiMapSize += 4 * EfiDescriptorSize;
+    PageCount = (ALIGN_UP(EfiMapSize, PAGE_SIZE) >> PAGE_SHIFT) + 1;
+    EfiPageCount = EFI_PAGE(PageCount);
+    Status = EfiAllocatePages(AllocateAnyPages, EfiLoaderData, EfiPageCount, &EfiBuffer);
+    if (!NT_SUCCESS(Status)) {
+        DebugPrint(L"MmFwGetMemoryMap(): EfiAllocatePages() failed\r\n");
+        goto exit;
+    }
+
+    EfiMap = (EFI_MEMORY_DESCRIPTOR *)EfiBuffer;
+    Status = EfiGetMemoryMap(&EfiMapSize, EfiMap, &EfiMapKey, &EfiDescriptorSize, &EfiDescriptorVersion);
+    if (!NT_SUCCESS(Status)) {
+        DebugPrint(L"MmFwGetMemoryMap(): EfiGetMemoryMap() failed\r\n");
+        goto exit;
+    }
+
+    if (EfiDescriptorSize < sizeof(EFI_MEMORY_DESCRIPTOR) || EfiMapSize % EfiDescriptorSize) {
+        DebugPrint(L"MmFwGetMemoryMap(): Invalid EFI descriptor/map sizes\r\n");
+        Status = STATUS_UNSUCCESSFUL;
+        goto exit;
+    }
+
+    if (BlpBootDevice->Type == BOOT_DEVICE_TYPE_BLOCK && BlpBootDevice->Block.Type == BOOT_BLOCK_DEVICE_TYPE_RAMDISK) {
+        IsRamdisk = TRUE;
+        EfiRamdiskStartPage = BlpBootDevice->Block.Ramdisk.ImageBase.QuadPart >> EFI_PAGE_SHIFT;
+        EfiRamdiskEndPage = EfiRamdiskStartPage + ((BlpBootDevice->Block.Ramdisk.ImageBase.QuadPart + BlpBootDevice->Block.Ramdisk.ImageSize) >> EFI_PAGE_SHIFT);
+    } else {
+        IsRamdisk = FALSE;
+    }
+
+    for (
+        ;
+        EfiMapSize > 0;
+        EfiMapSize -= EfiDescriptorSize,
+        EfiMap = (EFI_MEMORY_DESCRIPTOR *)((PUCHAR)EfiMap + EfiDescriptorSize)
+    ) {
+        //
+        // Skip desciptors with no pages.
+        //
+        if (EfiMap->NumberOfPages == 0) {
+            continue;
+        }
+
+        MemoryType = BlMmTranslateEfiMemoryType(EfiMap->Type);
+        if (MemoryType == MEMORY_TYPE_FREE) {
+            EfiStartPage = ALIGN_UP(EfiMap->PhysicalStart, EFI_PAGE_SIZE) >> EFI_PAGE_SHIFT;
+
+        } else {
+            EfiStartPage = EfiMap->PhysicalStart >> EFI_PAGE_SHIFT;
+        }
+        EfiEndPage = ALIGN_DOWN(EfiStartPage + EfiMap->NumberOfPages, EFI_PAGE(1));
+
+        //
+        // Regions under 1MiB are mapped differently.
+        //
+        if (EfiStartPage < (_1MiB >> EFI_PAGE_SHIFT)) {
+            //
+            // Reserve region at page 0.
+            //
+            if (EfiStartPage == 0) {
+                NtDescriptor = MmMdInitDescriptor(
+                    NT_PAGE(EfiStartPage),
+                    0,
+                    1,
+                    MmFwpGetOsAttributeType(EfiMap->Attribute),
+                    MEMORY_TYPE_RESERVED
+                );
+                if (NtDescriptor == NULL) {
+                    Status = STATUS_INSUFFICIENT_RESOURCES;
+                    goto exit;
+                }
+
+                Status = MmMdAddDescriptorToList(Mdl, NtDescriptor, MDL_OPERATION_FLAGS_TRUNCATE);
+                if (!NT_SUCCESS(Status)) {
+                    goto exit;
+                }
+
+                //
+                // Continue if this descriptor was only one page.
+                //
+                if (EfiEndPage == 1) {
+                    continue;
+                }
+            }
+
+            //
+            // For regions crossing over the 1MiB boundary,
+            // create two descriptors. One for <1MiB and one
+            // for over >=1MiB.
+            //
+            if (EfiEndPage > (_1MiB >> EFI_PAGE_SHIFT)) {
+                NtDescriptor = MmMdInitDescriptor(
+                    NT_PAGE(EfiStartPage),
+                    0,
+                    (_1MiB >> PAGE_SHIFT) - NT_PAGE(EfiStartPage),
+                    MmFwpGetOsAttributeType(EfiMap->Attribute),
+                    MemoryType
+                );
+                if (NtDescriptor == NULL) {
+                    Status = STATUS_INSUFFICIENT_RESOURCES;
+                    goto exit;
+                }
+
+                if (NtDescriptor->Type == MEMORY_TYPE_FREE) {
+                    NtDescriptor->Attributes |= MEMORY_ATTRIBUTE_BELOW_1MIB;
+                }
+
+                Status = MmMdAddDescriptorToList(Mdl, NtDescriptor, MDL_OPERATION_FLAGS_TRUNCATE);
+                if (!NT_SUCCESS(Status)) {
+                    goto exit;
+                }
+
+                //
+                // Continue to creating the >=1MiB mapping.
+                //
+                EfiStartPage = _1MiB >> EFI_PAGE_SHIFT;
+            }
+        }
+
+        if (IsRamdisk) {
+            if (
+                EfiStartPage <= EfiRamdiskStartPage
+                && EfiEndPage >= EfiRamdiskEndPage
+            ) {
+                if (NT_PAGE(EfiStartPage) < NT_PAGE(EfiRamdiskStartPage)) {
+                    NtDescriptor = MmMdInitDescriptor(
+                        NT_PAGE(EfiStartPage),
+                        0,
+                        NT_PAGE(EfiRamdiskStartPage) - NT_PAGE(EfiStartPage),
+                        MmFwpGetOsAttributeType(EfiMap->Attribute),
+                        MemoryType
+                    );
+                    if (NtDescriptor == NULL) {
+                        Status = STATUS_INSUFFICIENT_RESOURCES;
+                        goto exit;
+                    }
+
+                    Status = MmMdAddDescriptorToList(Mdl, NtDescriptor, MDL_OPERATION_FLAGS_TRUNCATE);
+                    if (!NT_SUCCESS(Status)) {
+                        goto exit;
+                    }
+                }
+
+                //
+                // Create a memory descriptor for the ramdisk.
+                //
+                NtDescriptor = MmMdInitDescriptor(
+                    NT_PAGE(EfiRamdiskStartPage),
+                    0,
+                    NT_PAGE(EfiRamdiskEndPage) - NT_PAGE(EfiRamdiskStartPage),
+                    MmFwpGetOsAttributeType(EfiMap->Attribute),
+                    MemoryType
+                );
+                if (NtDescriptor == NULL) {
+                    Status = STATUS_INSUFFICIENT_RESOURCES;
+                    goto exit;
+                }
+
+                Status = MmMdAddDescriptorToList(Mdl, NtDescriptor, MDL_OPERATION_FLAGS_TRUNCATE);
+                if (!NT_SUCCESS(Status)) {
+                    goto exit;
+                }
+
+                //
+                // Continue if there is no more memory to map inside the ramdisk.
+                //
+                if (NT_PAGE(EfiEndPage) <= NT_PAGE(EfiRamdiskEndPage)) {
+                    continue;
+                }
+
+                EfiStartPage = EFI_PAGE(NT_PAGE(EfiRamdiskEndPage - 1) + 1);
+            } else if (
+                NT_PAGE(EfiStartPage) < NT_PAGE(EfiRamdiskStartPage)
+                && NT_PAGE(EfiEndPage) > NT_PAGE(EfiRamdiskStartPage)
+            ) {
+                //
+                // Remove the region inside the start of the ramdisk.
+                //
+                EfiEndPage = EfiRamdiskStartPage;
+            } else if (
+                NT_PAGE(EfiStartPage) < NT_PAGE(EfiRamdiskEndPage)
+                && NT_PAGE(EfiEndPage) > NT_PAGE(EfiRamdiskEndPage)
+            ) {
+                //
+                // Remove the region inside the end of the ramdisk.
+                //
+                EfiStartPage = EfiRamdiskEndPage;
+            }
+
+            //
+            // Continue if the region is now empty.
+            //
+            if (NT_PAGE(EfiStartPage) == NT_PAGE(EfiEndPage)) {
+                continue;
+            }
+        }
+
+        //
+        // Create a memory descriptor for the region.
+        //
+        NtDescriptor = MmMdInitDescriptor(
+            NT_PAGE(EfiStartPage),
+            0,
+            NT_PAGE(EfiEndPage) - NT_PAGE(EfiStartPage),
+            MmFwpGetOsAttributeType(EfiMap->Attribute),
+            MemoryType
+        );
+        if (NtDescriptor == NULL) {
+            Status = STATUS_INSUFFICIENT_RESOURCES;
+            goto exit;
+        }
+
+        //
+        // Set attribute if below 1MiB.
+        //
+        if (NtDescriptor->Type == MEMORY_TYPE_FREE && EfiEndPage <= (_1MiB >> EFI_PAGE_SHIFT)) {
+            NtDescriptor->Attributes |= MEMORY_ATTRIBUTE_BELOW_1MIB;
+        }
+
+        Status = MmMdAddDescriptorToList(Mdl, NtDescriptor, MDL_OPERATION_FLAGS_TRUNCATE);
+        if (!NT_SUCCESS(Status)) {
+            goto exit;
+        }
+    }
+
+    //
+    // TODO: Account for possible MDL changes due to EfiFreePages(EfiBuffer).
+    //
+
+exit:
+    if (EfiBuffer) {
+        EfiFreePages(EfiBuffer, EfiPageCount);
+    }
+
+    if (!NT_SUCCESS(Status)) {
+        MmMdFreeList(Mdl);
+    }
+
+    return Status;
 }
\ No newline at end of file
diff --git a/BOOT/ENVIRON/LIB/MM/mm.c b/BOOT/ENVIRON/LIB/MM/mm.c
index 703f0c0..d86074a 100644
--- a/BOOT/ENVIRON/LIB/MM/mm.c
+++ b/BOOT/ENVIRON/LIB/MM/mm.c
@@ -32,11 +32,11 @@ Routine Description:
 
 Arguments:
 
-    MemoryInfo - pointer to the memory info structure.
+    MemoryInfo - Pointer to the memory info.
 
-    TranslationType - the current translation type being used.
+    TranslationType - The current translation type.
 
-    LibraryParameters - pointer to the library parameters structure.
+    LibraryParameters - Pointer to the library parameters.
 
 Return Value:
 
diff --git a/BOOT/ENVIRON/LIB/MM/mmmd.c b/BOOT/ENVIRON/LIB/MM/mmmd.c
index 9205983..19bc153 100644
--- a/BOOT/ENVIRON/LIB/MM/mmmd.c
+++ b/BOOT/ENVIRON/LIB/MM/mmmd.c
@@ -22,10 +22,316 @@ Abstract:
 MEMORY_DESCRIPTOR MmStaticMemoryDescriptors[MAX_STATIC_DESCRIPTOR_COUNT];
 
 PMEMORY_DESCRIPTOR MmGlobalMemoryDescriptors;
-ULONG MmGlobalMemoryDescriptorCount;
+ULONG MmGlobalMemoryDescriptorCount, MmGlobalMemoryDescriptorsUsed;
 
 PMEMORY_DESCRIPTOR MmDynamicMemoryDescriptors;
-ULONG MmDynamicMemoryDescriptorCount;
+ULONG MmDynamicMemoryDescriptorCount, MmDynamicMemoryDescriptorsUsed;
+
+BOOLEAN
+MmMdpHasPrecedence (
+    IN MEMORY_TYPE A,
+    IN MEMORY_TYPE B
+    )
+
+/*++
+
+Routine Description:
+
+    Compares two memory types to determine which has precedence.
+
+Arguments:
+
+    A - memory type A.
+
+    B - memory type B.
+
+Return Value:
+
+    TRUE if A has precedence over B, or if neither has precedence.
+    FALSE if B has precedence over A.
+
+--*/
+
+{
+    ULONG ClassA, ClassB;
+
+    ClassA = A >> 28;
+    ClassB = B >> 28;
+
+    if (B == MEMORY_TYPE_FREE) {
+        return TRUE;
+    }
+
+    if (A == MEMORY_TYPE_FREE) {
+        return FALSE;
+    }
+
+    if (ClassA > 0x0F) {
+        return TRUE;
+    }
+
+    if (ClassB > 0x0F) {
+        return FALSE;
+    }
+
+    if (ClassA != 0x0F) {
+        return (ClassB != 0x0F && (ClassA == 0x0D || ClassB != 0x0D)) ? TRUE:FALSE;
+    }
+
+    if (ClassB != 0x0F) {
+        return TRUE;
+    }
+
+    //
+    // TODO: Incomplete.
+    //
+    ConsolePrint(L"MmMdpHasPrecedence() is incomplete\r\n");
+    return TRUE;
+}
+
+BOOLEAN
+MmMdpTruncateDescriptor (
+    IN PMEMORY_DESCRIPTOR_LIST Mdl,
+    IN PMEMORY_DESCRIPTOR Descriptor,
+    IN ULONG Flags
+    )
+
+/*++
+
+Routine Description:
+
+    Trunactes a memory descriptor that overlaps
+    with adjacent descriptors.
+
+Arguments:
+
+    Mdl - The MDL containing Descriptor.
+
+    Descriptor - The descriptor to truncate.
+
+Return Value:
+
+    TRUE if Descriptor was deleted from Mdl.
+
+--*/
+
+{
+    PMEMORY_DESCRIPTOR PrevDescriptor, NextDescriptor, NewDescriptor;
+    ULONGLONG DescriptorEnd, PrevDescriptorEnd, NextDescriptorEnd;
+    ULONGLONG MappedFirstPage;
+    ULONGLONG Change;
+
+    PrevDescriptor = (PMEMORY_DESCRIPTOR)Descriptor->ListEntry.Blink;
+    NextDescriptor = (PMEMORY_DESCRIPTOR)Descriptor->ListEntry.Flink;
+
+    DescriptorEnd = Descriptor->FirstPage + Descriptor->PageCount;
+    PrevDescriptorEnd = PrevDescriptor->FirstPage + PrevDescriptor->PageCount;
+    NextDescriptorEnd = NextDescriptor->FirstPage + NextDescriptor->PageCount;
+
+    //
+    // Check if overlapping with previous descriptor.
+    //
+    if (Descriptor->ListEntry.Blink != Mdl->Head && Descriptor->FirstPage < PrevDescriptorEnd) {
+        if (MmMdpHasPrecedence(Descriptor->Type, PrevDescriptor->Type)) {
+            PrevDescriptor->PageCount = Descriptor->FirstPage - PrevDescriptor->FirstPage;
+
+            if (DescriptorEnd < PrevDescriptorEnd) {
+                if (PrevDescriptor->MappedFirstPage) {
+                    MappedFirstPage = PrevDescriptor->MappedFirstPage + DescriptorEnd - PrevDescriptor->FirstPage;
+                } else {
+                    MappedFirstPage = 0;
+                }
+
+                NewDescriptor = MmMdInitDescriptor(
+                    DescriptorEnd,
+                    MappedFirstPage,
+                    PrevDescriptorEnd - DescriptorEnd,
+                    PrevDescriptor->Attributes,
+                    PrevDescriptor->Type
+                );
+                if (NewDescriptor != NULL) {
+                    MmMdAddDescriptorToList(Mdl, NewDescriptor, Flags);
+                }
+            }
+
+            //
+            // Delete and free the previous
+            // descriptor if it is now empty.
+            //
+            if (PrevDescriptor->PageCount == 0) {
+                MmMdRemoveDescriptorFromList(Mdl, PrevDescriptor);
+                MmMdFreeDescriptor(PrevDescriptor);
+            }
+        } else {
+            //
+            // Remove if completely overlapping.
+            //
+            if (DescriptorEnd <= PrevDescriptorEnd) {
+                MmMdRemoveDescriptorFromList(Mdl, Descriptor);
+                MmMdFreeDescriptor(Descriptor);
+                return TRUE;
+            }
+
+            //
+            // Otherwise, move the descriptor.
+            //
+            Change = PrevDescriptorEnd - Descriptor->FirstPage;
+            Descriptor->FirstPage += Change;
+            Descriptor->PageCount -= Change;
+            if (Descriptor->MappedFirstPage) {
+                Descriptor->MappedFirstPage += Change;
+            }
+        }
+    }
+
+    //
+    // Check if overlapping with next descriptor.
+    //
+    if (Descriptor->ListEntry.Flink != Mdl->Head && NextDescriptor->FirstPage < DescriptorEnd) {
+        if (MmMdpHasPrecedence(NextDescriptor->Type, Descriptor->Type)) {
+            Descriptor->PageCount = NextDescriptor->FirstPage - Descriptor->FirstPage;
+
+            if (NextDescriptorEnd < DescriptorEnd) {
+                if (Descriptor->MappedFirstPage) {
+                    MappedFirstPage = Descriptor->MappedFirstPage + NextDescriptorEnd - Descriptor->FirstPage;
+                } else {
+                    MappedFirstPage = 0;
+                }
+
+                NewDescriptor = MmMdInitDescriptor(
+                    NextDescriptorEnd,
+                    MappedFirstPage,
+                    DescriptorEnd - NextDescriptorEnd,
+                    Descriptor->Attributes,
+                    Descriptor->Type
+                );
+                if (NewDescriptor != NULL) {
+                    MmMdAddDescriptorToList(Mdl, NewDescriptor, Flags);
+                }
+            }
+
+            //
+            // Delete and free the previous
+            // descriptor if it is now empty.
+            //
+            if (Descriptor->PageCount == 0) {
+                MmMdRemoveDescriptorFromList(Mdl, Descriptor);
+                MmMdFreeDescriptor(Descriptor);
+            }
+        } else {
+            //
+            // Remove if completely overlapping.
+            //
+            if (NextDescriptorEnd <= DescriptorEnd) {
+                MmMdRemoveDescriptorFromList(Mdl, NextDescriptor);
+                MmMdFreeDescriptor(NextDescriptor);
+                return TRUE;
+            }
+
+            //
+            // Otherwise, move the next descriptor.
+            //
+            Change = DescriptorEnd - NextDescriptor->FirstPage;
+            NextDescriptor->FirstPage += Change;
+            NextDescriptor->PageCount -= Change;
+            if (NextDescriptor->MappedFirstPage) {
+                NextDescriptor->MappedFirstPage += Change;
+            }
+        }
+    }
+
+    return FALSE;
+}
+
+NTSTATUS
+MmMdAddDescriptorToList (
+    IN PMEMORY_DESCRIPTOR_LIST Mdl,
+    IN PMEMORY_DESCRIPTOR Descriptor,
+    IN ULONG Flags
+    )
+
+/*++
+
+Routine Description:
+
+    Adds a descriptor to a MDL.
+
+Arguments:
+
+    Mdl - the MDL to add Descriptor to.
+
+    Descriptor - the descriptor to add to Mdl.
+
+Return Value:
+
+    STATUS_SUCCESS if successful,
+    STATUS_INVALID_PARAMETER if Mdl or Descriptor are invalid.
+
+--*/
+
+{
+    PLIST_ENTRY Entry;
+    PMEMORY_DESCRIPTOR CurrentDescriptor;
+
+    if (Mdl == NULL || Descriptor == NULL) {
+        return STATUS_INVALID_PARAMETER;
+    }
+
+    if (Mdl->Current) {
+        if (Descriptor->FirstPage < ((PMEMORY_DESCRIPTOR)Mdl->Current)->FirstPage) {
+            Entry = Mdl->Head->Flink;
+        } else {
+            Entry = Mdl->Current;
+        }
+    } else {
+        Entry = Mdl->Head->Flink;
+    }
+
+    //
+    // Search for an existing descriptor for this region.
+    //
+    while (Entry != Mdl->Head) {
+        CurrentDescriptor = (PMEMORY_DESCRIPTOR)Entry;
+
+        if (
+            Descriptor->FirstPage >= CurrentDescriptor->FirstPage && (Descriptor->FirstPage != CurrentDescriptor->FirstPage
+            || !MmMdpHasPrecedence(Descriptor->Type, CurrentDescriptor->Type))
+        ) {
+            Entry = Entry->Flink;
+            continue;
+        }
+
+        //
+        // Insert descriptor into the list
+        // right before the current entry.
+        //
+        Descriptor->ListEntry.Blink = Entry->Blink;
+        Descriptor->ListEntry.Flink = Entry;
+        Entry->Blink->Flink = &Descriptor->ListEntry;
+        Entry->Blink = &Descriptor->ListEntry;
+
+        //
+        // Truncate overlapping descriptors
+        // into one larger descriptor.
+        //
+        if (Flags & MDL_OPERATION_FLAGS_TRUNCATE) {
+            MmMdpTruncateDescriptor(Mdl, Descriptor, Flags);
+        }
+
+        return STATUS_SUCCESS;
+    }
+
+    //
+    // If there are no existing descriptors for this region
+    // (or the list is empty), insert and truncate the descriptor.
+    //
+    InsertTailList(Mdl->Head, &Descriptor->ListEntry);
+    if (Flags & MDL_OPERATION_FLAGS_TRUNCATE) {
+        MmMdpTruncateDescriptor(Mdl, Descriptor, Flags);
+    }
+
+    return STATUS_SUCCESS;
+}
 
 VOID
 MmMdRemoveDescriptorFromList (
@@ -55,10 +361,6 @@ Return Value:
     PLIST_ENTRY Blink;
 
     Blink = Descriptor->ListEntry.Blink;
-
-    //
-    // Remove the descriptor from the MDL.
-    //
     RemoveEntryList(&Descriptor->ListEntry);
 
     //
@@ -129,7 +431,7 @@ Return Value:
     // Free the descriptor from the heap.
     // TODO: Use BlMmFreeHeap()
     //
-    ConsolePrint(L"Cannot free memory descriptor: BlMmFreeHeap() is not implemented\r\n");
+    ConsolePrint(L"MmMdFreeDescriptor(): need BlMmFreeHeap() to free descriptor\r\n");
     return STATUS_NOT_IMPLEMENTED;
     // return BlMmFreeHeap(Descriptor);
 }
@@ -147,7 +449,7 @@ Routine Description:
 
 Arguments:
 
-    Mdl - the MDL to free.
+    Mdl - the MDL.
 
 Return Value:
 
@@ -166,6 +468,56 @@ Return Value:
     }
 }
 
+PMEMORY_DESCRIPTOR
+MmMdInitDescriptor (
+    IN ULONGLONG FirstPage,
+    IN ULONGLONG MappedFirstPage,
+    IN ULONGLONG PageCount,
+    IN ULONG Attributes,
+    IN MEMORY_TYPE Type
+    )
+
+/*++
+
+Routine Description:
+
+    Initializes a memory descriptor.
+
+Arguments:
+
+    FirstPage - The first page in the region.
+
+    MappedFirstPage - The first page in the mapping.
+
+    Attributes - Memory attributes of the region.
+
+    Type - Memory type of the region.
+
+Return Value:
+
+    Pointer to the memory descriptor,
+    NULL if an error occurs.
+
+--*/
+
+{
+    PMEMORY_DESCRIPTOR Descriptor;
+
+    if (MmGlobalMemoryDescriptorsUsed >= MmGlobalMemoryDescriptorCount) {
+        return NULL;
+    }
+
+    Descriptor = &MmGlobalMemoryDescriptors[MmGlobalMemoryDescriptorsUsed++];
+    Descriptor->FirstPage = FirstPage;
+    Descriptor->MappedFirstPage = MappedFirstPage;
+    Descriptor->PageCount = PageCount;
+    Descriptor->Attributes = Attributes;
+    Descriptor->Type = Type;
+    InitializeListHead(&Descriptor->ListEntry);
+
+    return Descriptor;
+}
+
 VOID
 MmMdInitialize (
     IN ULONG Unused,
@@ -201,6 +553,7 @@ Return Value:
     //
     MmGlobalMemoryDescriptors = &MmStaticMemoryDescriptors[0];
     MmGlobalMemoryDescriptorCount = MAX_STATIC_DESCRIPTOR_COUNT;
+    MmGlobalMemoryDescriptorsUsed = 0;
     RtlZeroMemory(MmGlobalMemoryDescriptors, MAX_STATIC_DESCRIPTOR_COUNT * sizeof(MEMORY_DESCRIPTOR));
     DebugPrintf(L"Global memory descriptor count: %x\r\n", MmGlobalMemoryDescriptorCount);
 }
diff --git a/BOOT/ENVIRON/LIB/MM/mmpa.c b/BOOT/ENVIRON/LIB/MM/mmpa.c
index 10b3992..41c103a 100644
--- a/BOOT/ENVIRON/LIB/MM/mmpa.c
+++ b/BOOT/ENVIRON/LIB/MM/mmpa.c
@@ -44,7 +44,7 @@ Routine Description:
 
 Arguments:
 
-    Mdl - the MDL to initialize.
+    Mdl - Pointer to the MDL.
 
 Return Value:
 
@@ -72,9 +72,9 @@ Routine Description:
 
 Arguments:
 
-    MemoryInfo - pointer to the memory info structure.
+    MemoryInfo - Pointer to the memory info structure.
 
-    MinimumAllocation - minimum amount of pages to grow the pool by at a time.
+    MinimumAllocation - Minimum amount of pages to grow the pool by at a time.
 
 Return Value: