[NTOSKRNL]

[reactos.git] / ntoskrnl / mm / ARM3 / mminit.c

/*
 * PROJECT:         ReactOS Kernel
 * LICENSE:         BSD - See COPYING.ARM in the top level directory
 * FILE:            ntoskrnl/mm/ARM3/mminit.c
 * PURPOSE:         ARM Memory Manager Initialization
 * PROGRAMMERS:     ReactOS Portable Systems Group
 */

/* INCLUDES *******************************************************************/

#include <ntoskrnl.h>
#define NDEBUG
#include <debug.h>

#line 15 "ARM³::INIT"
#define MODULE_INVOLVED_IN_ARM3
#include "miarm.h"

/* GLOBALS ********************************************************************/

//
// These are all registry-configurable, but by default, the memory manager will
// figure out the most appropriate values.
//
ULONG MmMaximumNonPagedPoolPercent;
ULONG MmSizeOfNonPagedPoolInBytes;
ULONG MmMaximumNonPagedPoolInBytes;

/* Some of the same values, in pages */
PFN_NUMBER MmMaximumNonPagedPoolInPages;

//
// These numbers describe the discrete equation components of the nonpaged
// pool sizing algorithm.
//
// They are described on http://support.microsoft.com/default.aspx/kb/126402/ja
// along with the algorithm that uses them, which is implemented later below.
//
ULONG MmMinimumNonPagedPoolSize = 256 * 1024;
ULONG MmMinAdditionNonPagedPoolPerMb = 32 * 1024;
ULONG MmDefaultMaximumNonPagedPool = 1024 * 1024; 
ULONG MmMaxAdditionNonPagedPoolPerMb = 400 * 1024;

//
// The memory layout (and especially variable names) of the NT kernel mode
// components can be a bit hard to twig, especially when it comes to the non
// paged area.
//
// There are really two components to the non-paged pool:
//
// - The initial nonpaged pool, sized dynamically up to a maximum.
// - The expansion nonpaged pool, sized dynamically up to a maximum.
//
// The initial nonpaged pool is physically continuous for performance, and
// immediately follows the PFN database, typically sharing the same PDE. It is
// a very small resource (32MB on a 1GB system), and capped at 128MB.
//
// Right now we call this the "ARM³ Nonpaged Pool" and it begins somewhere after
// the PFN database (which starts at 0xB0000000).
//
// The expansion nonpaged pool, on the other hand, can grow much bigger (400MB 
// for a 1GB system). On ARM³ however, it is currently capped at 128MB.
//
// The address where the initial nonpaged pool starts is aptly named
// MmNonPagedPoolStart, and it describes a range of MmSizeOfNonPagedPoolInBytes
// bytes.
//
// Expansion nonpaged pool starts at an address described by the variable called
// MmNonPagedPoolExpansionStart, and it goes on for MmMaximumNonPagedPoolInBytes
// minus MmSizeOfNonPagedPoolInBytes bytes, always reaching MmNonPagedPoolEnd
// (because of the way it's calculated) at 0xFFBE0000.
//
// Initial nonpaged pool is allocated and mapped early-on during boot, but what
// about the expansion nonpaged pool? It is instead composed of special pages
// which belong to what are called System PTEs. These PTEs are the matter of a
// later discussion, but they are also considered part of the "nonpaged" OS, due
// to the fact that they are never paged out -- once an address is described by
// a System PTE, it is always valid, until the System PTE is torn down.
//
// System PTEs are actually composed of two "spaces", the system space proper,
// and the nonpaged pool expansion space. The latter, as we've already seen, 
// begins at MmNonPagedPoolExpansionStart. Based on the number of System PTEs
// that the system will support, the remaining address space below this address
// is used to hold the system space PTEs. This address, in turn, is held in the
// variable named MmNonPagedSystemStart, which itself is never allowed to go
// below 0xEB000000 (thus creating an upper bound on the number of System PTEs).
//
// This means that 330MB are reserved for total nonpaged system VA, on top of
// whatever the initial nonpaged pool allocation is.
//
// The following URLs, valid as of April 23rd, 2008, support this evidence:
//
// http://www.cs.miami.edu/~burt/journal/NT/memory.html
// http://www.ditii.com/2007/09/28/windows-memory-management-x86-virtual-address-space/
//
PVOID MmNonPagedSystemStart;
PVOID MmNonPagedPoolStart;
PVOID MmNonPagedPoolExpansionStart;
PVOID MmNonPagedPoolEnd = MI_NONPAGED_POOL_END;

//
// This is where paged pool starts by default
//
PVOID MmPagedPoolStart = MI_PAGED_POOL_START;
PVOID MmPagedPoolEnd;

//
// And this is its default size
//
ULONG MmSizeOfPagedPoolInBytes = MI_MIN_INIT_PAGED_POOLSIZE;
PFN_NUMBER MmSizeOfPagedPoolInPages = MI_MIN_INIT_PAGED_POOLSIZE / PAGE_SIZE;

//
// Session space starts at 0xBFFFFFFF and grows downwards
// By default, it includes an 8MB image area where we map win32k and video card
// drivers, followed by a 4MB area containing the session's working set. This is
// then followed by a 20MB mapped view area and finally by the session's paged
// pool, by default 16MB.
// 
// On a normal system, this results in session space occupying the region from
// 0xBD000000 to 0xC0000000
//
// See miarm.h for the defines that determine the sizing of this region. On an
// NT system, some of these can be configured through the registry, but we don't
// support that yet.
//
PVOID MiSessionSpaceEnd;    // 0xC0000000
PVOID MiSessionImageEnd;    // 0xC0000000
PVOID MiSessionImageStart;  // 0xBF800000
PVOID MiSessionViewStart;   // 0xBE000000
PVOID MiSessionPoolEnd;     // 0xBE000000
PVOID MiSessionPoolStart;   // 0xBD000000
PVOID MmSessionBase;        // 0xBD000000
ULONG MmSessionSize;
ULONG MmSessionViewSize;
ULONG MmSessionPoolSize;
ULONG MmSessionImageSize;

/*
 * These are the PTE addresses of the boundaries carved out above
 */
PMMPTE MiSessionImagePteStart;
PMMPTE MiSessionImagePteEnd;
PMMPTE MiSessionBasePte;
PMMPTE MiSessionLastPte;

//
// The system view space, on the other hand, is where sections that are memory
// mapped into "system space" end up.
//
// By default, it is a 16MB region.
//
PVOID MiSystemViewStart;
ULONG MmSystemViewSize;

//
// A copy of the system page directory (the page directory associated with the
// System process) is kept (double-mapped) by the manager in order to lazily
// map paged pool PDEs into external processes when they fault on a paged pool
// address.
//
PFN_NUMBER MmSystemPageDirectory[PD_COUNT];
PMMPTE MmSystemPagePtes;

//
// The system cache starts right after hyperspace. The first few pages are for
// keeping track of the system working set list.
//
// This should be 0xC0C00000 -- the cache itself starts at 0xC1000000
//
PMMWSL MmSystemCacheWorkingSetList = MI_SYSTEM_CACHE_WS_START;

//
// Windows NT seems to choose between 7000, 11000 and 50000
// On systems with more than 32MB, this number is then doubled, and further
// aligned up to a PDE boundary (4MB).
//
ULONG MmNumberOfSystemPtes;

//
// This is how many pages the PFN database will take up
// In Windows, this includes the Quark Color Table, but not in ARM³
//
ULONG MxPfnAllocation;

//
// Unlike the old ReactOS Memory Manager, ARM³ (and Windows) does not keep track
// of pages that are not actually valid physical memory, such as ACPI reserved
// regions, BIOS address ranges, or holes in physical memory address space which
// could indicate device-mapped I/O memory.
//
// In fact, the lack of a PFN entry for a page usually indicates that this is
// I/O space instead.
//
// A bitmap, called the PFN bitmap, keeps track of all page frames by assigning
// a bit to each. If the bit is set, then the page is valid physical RAM.
//
RTL_BITMAP MiPfnBitMap;

//
// This structure describes the different pieces of RAM-backed address space
//
PPHYSICAL_MEMORY_DESCRIPTOR MmPhysicalMemoryBlock;

//
// This is where we keep track of the most basic physical layout markers
//
ULONG MmNumberOfPhysicalPages, MmHighestPhysicalPage, MmLowestPhysicalPage = -1;

//
// The total number of pages mapped by the boot loader, which include the kernel
// HAL, boot drivers, registry, NLS files and other loader data structures is
// kept track of here. This depends on "LoaderPagesSpanned" being correct when
// coming from the loader.
//
// This number is later aligned up to a PDE boundary.
//
ULONG MmBootImageSize;

//
// These three variables keep track of the core separation of address space that
// exists between kernel mode and user mode.
//
ULONG MmUserProbeAddress;
PVOID MmHighestUserAddress;
PVOID MmSystemRangeStart;

/* And these store the respective highest PTE/PDE address */
PMMPTE MiHighestUserPte;
PMMPDE MiHighestUserPde;

/* These variables define the system cache address space */
PVOID MmSystemCacheStart;
PVOID MmSystemCacheEnd;
MMSUPPORT MmSystemCacheWs;

//
// This is where hyperspace ends (followed by the system cache working set)
//
PVOID MmHyperSpaceEnd;

//
// Page coloring algorithm data
//
ULONG MmSecondaryColors;
ULONG MmSecondaryColorMask;

//
// Actual (registry-configurable) size of a GUI thread's stack
//
ULONG MmLargeStackSize = KERNEL_LARGE_STACK_SIZE;

//
// Before we have a PFN database, memory comes straight from our physical memory
// blocks, which is nice because it's guaranteed contiguous and also because once
// we take a page from here, the system doesn't see it anymore.
// However, once the fun is over, those pages must be re-integrated back into
// PFN society life, and that requires us keeping a copy of the original layout
// so that we can parse it later.
//
PMEMORY_ALLOCATION_DESCRIPTOR MxFreeDescriptor;
MEMORY_ALLOCATION_DESCRIPTOR MxOldFreeDescriptor;

/*
 * For each page's worth bytes of L2 cache in a given set/way line, the zero and
 * free lists are organized in what is called a "color".
 *
 * This array points to the two lists, so it can be thought of as a multi-dimensional
 * array of MmFreePagesByColor[2][MmSecondaryColors]. Since the number is dynamic,
 * we describe the array in pointer form instead.
 *
 * On a final note, the color tables themselves are right after the PFN database.
 */
C_ASSERT(FreePageList == 1);
PMMCOLOR_TABLES MmFreePagesByColor[FreePageList + 1];

/* An event used in Phase 0 before the rest of the system is ready to go */
KEVENT MiTempEvent;

/* All the events used for memory threshold notifications */
PKEVENT MiLowMemoryEvent;
PKEVENT MiHighMemoryEvent;
PKEVENT MiLowPagedPoolEvent;
PKEVENT MiHighPagedPoolEvent;
PKEVENT MiLowNonPagedPoolEvent;
PKEVENT MiHighNonPagedPoolEvent;

/* The actual thresholds themselves, in page numbers */
PFN_NUMBER MmLowMemoryThreshold;
PFN_NUMBER MmHighMemoryThreshold;
PFN_NUMBER MiLowPagedPoolThreshold;
PFN_NUMBER MiHighPagedPoolThreshold;
PFN_NUMBER MiLowNonPagedPoolThreshold;
PFN_NUMBER MiHighNonPagedPoolThreshold;

/*
 * This number determines how many free pages must exist, at minimum, until we
 * start trimming working sets and flushing modified pages to obtain more free
 * pages.
 *
 * This number changes if the system detects that this is a server product
 */
PFN_NUMBER MmMinimumFreePages = 26;

/* 
 * This number indicates how many pages we consider to be a low limit of having
 * "plenty" of free memory.
 *
 * It is doubled on systems that have more than 63MB of memory
 */
PFN_NUMBER MmPlentyFreePages = 400;

/* These values store the type of system this is (small, med, large) and if server */
ULONG MmProductType;
MM_SYSTEMSIZE MmSystemSize;

/*
 * These values store the cache working set minimums and maximums, in pages
 *
 * The minimum value is boosted on systems with more than 24MB of RAM, and cut
 * down to only 32 pages on embedded (<24MB RAM) systems.
 *
 * An extra boost of 2MB is given on systems with more than 33MB of RAM.
 */
PFN_NUMBER MmSystemCacheWsMinimum = 288;
PFN_NUMBER MmSystemCacheWsMaximum = 350;

/* FIXME: Move to cache/working set code later */
BOOLEAN MmLargeSystemCache;

/* PRIVATE FUNCTIONS **********************************************************/

//
// In Bavaria, this is probably a hate crime
//
VOID
FASTCALL
MiSyncARM3WithROS(IN PVOID AddressStart,
                  IN PVOID AddressEnd)
{
    //
    // Puerile piece of junk-grade carbonized horseshit puss sold to the lowest bidder
    //
    ULONG Pde = MiGetPdeOffset(AddressStart);
    while (Pde <= MiGetPdeOffset(AddressEnd))
    {
        //
        // This both odious and heinous
        //
        extern ULONG MmGlobalKernelPageDirectory[];
        MmGlobalKernelPageDirectory[Pde] = ((PULONG)PDE_BASE)[Pde];
        Pde++;
    }
}

PFN_NUMBER
NTAPI
MxGetNextPage(IN PFN_NUMBER PageCount)
{
    PFN_NUMBER Pfn;
 
    /* Make sure we have enough pages */
    if (PageCount > MxFreeDescriptor->PageCount)
    {
        /* Crash the system */
        KeBugCheckEx(INSTALL_MORE_MEMORY,
                     MmNumberOfPhysicalPages,
                     MxFreeDescriptor->PageCount,
                     MxOldFreeDescriptor.PageCount,
                     PageCount);
    }
    
    /* Use our lowest usable free pages */
    Pfn = MxFreeDescriptor->BasePage;
    MxFreeDescriptor->BasePage += PageCount;
    MxFreeDescriptor->PageCount -= PageCount;
    return Pfn;
}

VOID
NTAPI
MiComputeColorInformation(VOID)
{
    ULONG L2Associativity;
    
    /* Check if no setting was provided already */
    if (!MmSecondaryColors)
    {
        /* Get L2 cache information */
        L2Associativity = KiGetSecondLevelDCacheSize();
        
        /* The number of colors is the number of cache bytes by set/way */
        MmSecondaryColors = KiGetSecondLevelDCacheSize();
        if (L2Associativity) MmSecondaryColors /= L2Associativity;
    }
    
    /* Now convert cache bytes into pages */
    MmSecondaryColors >>= PAGE_SHIFT;
    if (!MmSecondaryColors)
    {
        /* If there was no cache data from the KPCR, use the default colors */
        MmSecondaryColors = MI_SECONDARY_COLORS;
    }
    else
    {
        /* Otherwise, make sure there aren't too many colors */
        if (MmSecondaryColors > MI_MAX_SECONDARY_COLORS)
        {
            /* Set the maximum */
            MmSecondaryColors = MI_MAX_SECONDARY_COLORS;
        }
        
        /* Make sure there aren't too little colors */
        if (MmSecondaryColors < MI_MIN_SECONDARY_COLORS)
        {
            /* Set the default */
            MmSecondaryColors = MI_SECONDARY_COLORS;
        }
        
        /* Finally make sure the colors are a power of two */
        if (MmSecondaryColors & (MmSecondaryColors - 1))
        {
            /* Set the default */
            MmSecondaryColors = MI_SECONDARY_COLORS;
        }
    }
    
    /* Compute the mask and store it */
    MmSecondaryColorMask = MmSecondaryColors - 1;
    KeGetCurrentPrcb()->SecondaryColorMask = MmSecondaryColorMask;    
}

VOID
NTAPI
MiInitializeColorTables(VOID)
{
    ULONG i;
    PMMPTE PointerPte, LastPte;
    MMPTE TempPte = ValidKernelPte;
    
    /* The color table starts after the ARM3 PFN database */
    MmFreePagesByColor[0] = (PMMCOLOR_TABLES)&MmPfnDatabase[1][MmHighestPhysicalPage + 1];
    
    /* Loop the PTEs. We have two color tables for each secondary color */
    PointerPte = MiAddressToPte(&MmFreePagesByColor[0][0]);
    LastPte = MiAddressToPte((ULONG_PTR)MmFreePagesByColor[0] +
                             (2 * MmSecondaryColors * sizeof(MMCOLOR_TABLES))
                             - 1);
    while (PointerPte <= LastPte)
    {
        /* Check for valid PTE */
        if (PointerPte->u.Hard.Valid == 0)
        {
            /* Get a page and map it */
            TempPte.u.Hard.PageFrameNumber = MxGetNextPage(1);
            ASSERT(TempPte.u.Hard.Valid == 1);
            *PointerPte = TempPte;
            
            /* Zero out the page */
            RtlZeroMemory(MiPteToAddress(PointerPte), PAGE_SIZE);
        }
        
        /* Next */
        PointerPte++;
    }
    
    /* Now set the address of the next list, right after this one */
    MmFreePagesByColor[1] = &MmFreePagesByColor[0][MmSecondaryColors];
    
    /* Now loop the lists to set them up */
    for (i = 0; i < MmSecondaryColors; i++)
    {
        /* Set both free and zero lists for each color */
        MmFreePagesByColor[ZeroedPageList][i].Flink = 0xFFFFFFFF;
        MmFreePagesByColor[ZeroedPageList][i].Blink = (PVOID)0xFFFFFFFF;
        MmFreePagesByColor[ZeroedPageList][i].Count = 0;
        MmFreePagesByColor[FreePageList][i].Flink = 0xFFFFFFFF;
        MmFreePagesByColor[FreePageList][i].Blink = (PVOID)0xFFFFFFFF;
        MmFreePagesByColor[FreePageList][i].Count = 0;
    }
}

BOOLEAN
NTAPI
MiIsRegularMemory(IN PLOADER_PARAMETER_BLOCK LoaderBlock,
                  IN PFN_NUMBER Pfn)
{
    PLIST_ENTRY NextEntry;
    PMEMORY_ALLOCATION_DESCRIPTOR MdBlock;

    /* Loop the memory descriptors */
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        /* Get the memory descriptor */
        MdBlock = CONTAINING_RECORD(NextEntry,
                                    MEMORY_ALLOCATION_DESCRIPTOR,
                                    ListEntry);

        /* Check if this PFN could be part of the block */
        if (Pfn >= (MdBlock->BasePage))
        {
            /* Check if it really is part of the block */
            if (Pfn < (MdBlock->BasePage + MdBlock->PageCount))
            {
                /* Check if the block is actually memory we don't map */
                if ((MdBlock->MemoryType == LoaderFirmwarePermanent) ||
                    (MdBlock->MemoryType == LoaderBBTMemory) ||
                    (MdBlock->MemoryType == LoaderSpecialMemory))
                {
                    /* We don't need PFN database entries for this memory */
                    break;
                }

                /* This is memory we want to map */
                return TRUE;
            }
        }
        else
        {
            /* Blocks are ordered, so if it's not here, it doesn't exist */
            break;
        }

        /* Get to the next descriptor */
        NextEntry = MdBlock->ListEntry.Flink;
    }

    /* Check if this PFN is actually from our free memory descriptor */
    if ((Pfn >= MxOldFreeDescriptor.BasePage) &&
        (Pfn < MxOldFreeDescriptor.BasePage + MxOldFreeDescriptor.PageCount))
    {
        /* We use these pages for initial mappings, so we do want to count them */
        return TRUE;
    }

    /* Otherwise this isn't memory that we describe or care about */
    return FALSE;
}

VOID
NTAPI
MiMapPfnDatabase(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
{
    ULONG FreePage, FreePageCount, PagesLeft, BasePage, PageCount;
    PLIST_ENTRY NextEntry;
    PMEMORY_ALLOCATION_DESCRIPTOR MdBlock;
    PMMPTE PointerPte, LastPte;
    MMPTE TempPte = ValidKernelPte;
    
    /* Get current page data, since we won't be using MxGetNextPage as it would corrupt our state */
    FreePage = MxFreeDescriptor->BasePage;
    FreePageCount = MxFreeDescriptor->PageCount;
    PagesLeft = 0;
    
    /* Loop the memory descriptors */
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        /* Get the descriptor */
        MdBlock = CONTAINING_RECORD(NextEntry,
                                    MEMORY_ALLOCATION_DESCRIPTOR,
                                    ListEntry);
        if ((MdBlock->MemoryType == LoaderFirmwarePermanent) ||
            (MdBlock->MemoryType == LoaderBBTMemory) ||
            (MdBlock->MemoryType == LoaderSpecialMemory))
        {
            /* These pages are not part of the PFN database */
            NextEntry = MdBlock->ListEntry.Flink;
            continue;
        }
        
        /* Next, check if this is our special free descriptor we've found */
        if (MdBlock == MxFreeDescriptor)
        {
            /* Use the real numbers instead */
            BasePage = MxOldFreeDescriptor.BasePage;
            PageCount = MxOldFreeDescriptor.PageCount;
        }
        else
        {
            /* Use the descriptor's numbers */
            BasePage = MdBlock->BasePage;
            PageCount = MdBlock->PageCount;
        }
        
        /* Get the PTEs for this range */
        PointerPte = MiAddressToPte(&MmPfnDatabase[0][BasePage]);
        LastPte = MiAddressToPte(((ULONG_PTR)&MmPfnDatabase[0][BasePage + PageCount]) - 1);
        DPRINT("MD Type: %lx Base: %lx Count: %lx\n", MdBlock->MemoryType, BasePage, PageCount);
        
        /* Loop them */
        while (PointerPte <= LastPte)
        {
            /* We'll only touch PTEs that aren't already valid */
            if (PointerPte->u.Hard.Valid == 0)
            {
                /* Use the next free page */
                TempPte.u.Hard.PageFrameNumber = FreePage;
                ASSERT(FreePageCount != 0);
                
                /* Consume free pages */
                FreePage++;
                FreePageCount--;
                if (!FreePageCount)
                {
                    /* Out of memory */
                    KeBugCheckEx(INSTALL_MORE_MEMORY,
                                 MmNumberOfPhysicalPages,
                                 FreePageCount,
                                 MxOldFreeDescriptor.PageCount,
                                 1);
                }
                
                /* Write out this PTE */
                PagesLeft++;
                ASSERT(PointerPte->u.Hard.Valid == 0);
                ASSERT(TempPte.u.Hard.Valid == 1);
                *PointerPte = TempPte;
                
                /* Zero this page */
                RtlZeroMemory(MiPteToAddress(PointerPte), PAGE_SIZE);
            }
            
            /* Next! */
            PointerPte++;
        }
        
        /* Get the PTEs for this range */
        PointerPte = MiAddressToPte(&MmPfnDatabase[1][BasePage]);
        LastPte = MiAddressToPte(((ULONG_PTR)&MmPfnDatabase[1][BasePage + PageCount]) - 1);
        DPRINT("MD Type: %lx Base: %lx Count: %lx\n", MdBlock->MemoryType, BasePage, PageCount);
        
        /* Loop them */
        while (PointerPte <= LastPte)
        {
            /* We'll only touch PTEs that aren't already valid */
            if (PointerPte->u.Hard.Valid == 0)
            {
                /* Use the next free page */
                TempPte.u.Hard.PageFrameNumber = FreePage;
                ASSERT(FreePageCount != 0);
                
                /* Consume free pages */
                FreePage++;
                FreePageCount--;
                if (!FreePageCount)
                {
                    /* Out of memory */
                    KeBugCheckEx(INSTALL_MORE_MEMORY,
                                 MmNumberOfPhysicalPages,
                                 FreePageCount,
                                 MxOldFreeDescriptor.PageCount,
                                 1);
                }
                
                /* Write out this PTE */
                PagesLeft++;
                ASSERT(PointerPte->u.Hard.Valid == 0);
                ASSERT(TempPte.u.Hard.Valid == 1);
                *PointerPte = TempPte;
                
                /* Zero this page */
                RtlZeroMemory(MiPteToAddress(PointerPte), PAGE_SIZE);
            }
            
            /* Next! */
            PointerPte++;
        }
        
        /* Do the next address range */
        NextEntry = MdBlock->ListEntry.Flink;
    }
    
    /* Now update the free descriptors to consume the pages we used up during the PFN allocation loop */
    MxFreeDescriptor->BasePage = FreePage;
    MxFreeDescriptor->PageCount = FreePageCount;
}

VOID
NTAPI
MiBuildPfnDatabaseFromPages(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
{
    PMMPDE PointerPde;
    PMMPTE PointerPte;
    ULONG i, Count, j;
    PFN_NUMBER PageFrameIndex, StartupPdIndex, PtePageIndex;
    PMMPFN Pfn1, Pfn2;
    ULONG_PTR BaseAddress = 0;
    
    /* PFN of the startup page directory */
    StartupPdIndex = PFN_FROM_PTE(MiAddressToPde(PDE_BASE));
    
    /* Start with the first PDE and scan them all */
    PointerPde = MiAddressToPde(NULL);
    Count = PD_COUNT * PDE_COUNT;
    for (i = 0; i < Count; i++)
    {
        /* Check for valid PDE */
        if (PointerPde->u.Hard.Valid == 1)
        {
            /* Get the PFN from it */
            PageFrameIndex = PFN_FROM_PTE(PointerPde);
            
            /* Do we want a PFN entry for this page? */
            if (MiIsRegularMemory(LoaderBlock, PageFrameIndex))
            {
                /* Yes we do, set it up */
                Pfn1 = MI_PFN_TO_PFNENTRY(PageFrameIndex);
                Pfn1->u4.PteFrame = StartupPdIndex;
                Pfn1->PteAddress = (PMMPTE)PointerPde;
                Pfn1->u2.ShareCount++;
                Pfn1->u3.e2.ReferenceCount = 1;
                Pfn1->u3.e1.PageLocation = ActiveAndValid;
                Pfn1->u3.e1.CacheAttribute = MiNonCached;
            }
            else
            {
                /* No PFN entry */
                Pfn1 = NULL;
            }
            
            /* Now get the PTE and scan the pages */
            PointerPte = MiAddressToPte(BaseAddress);
            for (j = 0; j < PTE_COUNT; j++)
            {
                /* Check for a valid PTE */
                if (PointerPte->u.Hard.Valid == 1)
                {
                    /* Increase the shared count of the PFN entry for the PDE */
                    ASSERT(Pfn1 != NULL);
                    Pfn1->u2.ShareCount++;
                    
                    /* Now check if the PTE is valid memory too */
                    PtePageIndex = PFN_FROM_PTE(PointerPte);
                    if (MiIsRegularMemory(LoaderBlock, PtePageIndex))
                    {
                        /*
                         * Only add pages above the end of system code or pages
                         * that are part of nonpaged pool
                         */
                        if ((BaseAddress >= 0xA0000000) ||
                            ((BaseAddress >= (ULONG_PTR)MmNonPagedPoolStart) &&
                             (BaseAddress < (ULONG_PTR)MmNonPagedPoolStart +
                                            MmSizeOfNonPagedPoolInBytes)))
                        {
                            /* Get the PFN entry and make sure it too is valid */
                            Pfn2 = MI_PFN_TO_PFNENTRY(PtePageIndex);
                            if ((MmIsAddressValid(Pfn2)) &&
                                (MmIsAddressValid(Pfn2 + 1)))
                            {
                                /* Setup the PFN entry */
                                Pfn2->u4.PteFrame = PageFrameIndex;
                                Pfn2->PteAddress = PointerPte;
                                Pfn2->u2.ShareCount++;
                                Pfn2->u3.e2.ReferenceCount = 1;
                                Pfn2->u3.e1.PageLocation = ActiveAndValid;
                                Pfn2->u3.e1.CacheAttribute = MiNonCached;
                            }
                        }
                    }
                }
                
                /* Next PTE */
                PointerPte++;
                BaseAddress += PAGE_SIZE;
            }
        }
        else
        {
            /* Next PDE mapped address */
            BaseAddress += PDE_MAPPED_VA;
        }
        
        /* Next PTE */
        PointerPde++;
    }
}

VOID
NTAPI
MiBuildPfnDatabaseZeroPage(VOID)
{
    PMMPFN Pfn1;
    PMMPDE PointerPde;
    
    /* Grab the lowest page and check if it has no real references */
    Pfn1 = MI_PFN_TO_PFNENTRY(MmLowestPhysicalPage);
    if (!(MmLowestPhysicalPage) && !(Pfn1->u3.e2.ReferenceCount))
    {
        /* Make it a bogus page to catch errors */
        PointerPde = MiAddressToPde(0xFFFFFFFF);
        Pfn1->u4.PteFrame = PFN_FROM_PTE(PointerPde);
        Pfn1->PteAddress = (PMMPTE)PointerPde;
        Pfn1->u2.ShareCount++;
        Pfn1->u3.e2.ReferenceCount = 0xFFF0;
        Pfn1->u3.e1.PageLocation = ActiveAndValid;
        Pfn1->u3.e1.CacheAttribute = MiNonCached;
    } 
}

VOID
NTAPI
MiBuildPfnDatabaseFromLoaderBlock(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
{
    PLIST_ENTRY NextEntry;
    PFN_NUMBER PageCount = 0;
    PMEMORY_ALLOCATION_DESCRIPTOR MdBlock;
    PFN_NUMBER PageFrameIndex;
    PMMPFN Pfn1;
    PMMPTE PointerPte;
    PMMPDE PointerPde;
    
    /* Now loop through the descriptors */
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        /* Get the current descriptor */
        MdBlock = CONTAINING_RECORD(NextEntry,
                                    MEMORY_ALLOCATION_DESCRIPTOR,
                                    ListEntry);

        /* Read its data */
        PageCount = MdBlock->PageCount;
        PageFrameIndex = MdBlock->BasePage;

        /* Don't allow memory above what the PFN database is mapping */
        if (PageFrameIndex > MmHighestPhysicalPage)
        {
            /* Since they are ordered, everything past here will be larger */
            break;
        }

        /* On the other hand, the end page might be higher up... */
        if ((PageFrameIndex + PageCount) > (MmHighestPhysicalPage + 1))
        {
            /* In which case we'll trim the descriptor to go as high as we can */
            PageCount = MmHighestPhysicalPage + 1 - PageFrameIndex;
            MdBlock->PageCount = PageCount;
            
            /* But if there's nothing left to trim, we got too high, so quit */
            if (!PageCount) break;
        }

        /* Now check the descriptor type */
        switch (MdBlock->MemoryType)
        {
            /* Check for bad RAM */
            case LoaderBad:
            
                DPRINT1("You have damaged RAM modules. Stopping boot\n");
                while (TRUE);
                break;

            /* Check for free RAM */
            case LoaderFree:
            case LoaderLoadedProgram:
            case LoaderFirmwareTemporary:
            case LoaderOsloaderStack:

                /* Get the last page of this descriptor. Note we loop backwards */
                PageFrameIndex += PageCount - 1;
                Pfn1 = MI_PFN_TO_PFNENTRY(PageFrameIndex);
                while (PageCount--)
                {
                    /* If the page really has no references, mark it as free */
                    if (!Pfn1->u3.e2.ReferenceCount)
                    {
                        Pfn1->u3.e1.CacheAttribute = MiNonCached;
                        //MiInsertPageInFreeList(PageFrameIndex);
                    }

                    /* Go to the next page */
                    Pfn1--;
                    PageFrameIndex--;
                }
                
                /* Done with this block */
                break;

            /* Check for pages that are invisible to us */
            case LoaderFirmwarePermanent:
            case LoaderSpecialMemory:
            case LoaderBBTMemory:

                /* And skip them */
                break;

            default:

                /* Map these pages with the KSEG0 mapping that adds 0x80000000 */
                PointerPte = MiAddressToPte(KSEG0_BASE + (PageFrameIndex << PAGE_SHIFT));
                Pfn1 = MI_PFN_TO_PFNENTRY(PageFrameIndex);
                while (PageCount--)
                {
                    /* Check if the page is really unused */
                    PointerPde = MiAddressToPde(KSEG0_BASE + (PageFrameIndex << PAGE_SHIFT));
                    if (!Pfn1->u3.e2.ReferenceCount)
                    {
                        /* Mark it as being in-use */
                        Pfn1->u4.PteFrame = PFN_FROM_PTE(PointerPde);
                        Pfn1->PteAddress = PointerPte;
                        Pfn1->u2.ShareCount++;
                        Pfn1->u3.e2.ReferenceCount = 1;
                        Pfn1->u3.e1.PageLocation = ActiveAndValid;
                        Pfn1->u3.e1.CacheAttribute = MiNonCached;
                        
                        /* Check for RAM disk page */
                        if (MdBlock->MemoryType == LoaderXIPRom)
                        {
                            /* Make it a pseudo-I/O ROM mapping */
                            Pfn1->u1.Flink = 0;
                            Pfn1->u2.ShareCount = 0;
                            Pfn1->u3.e2.ReferenceCount = 0;
                            Pfn1->u3.e1.PageLocation = 0;
                            Pfn1->u3.e1.Rom = 1;
                            Pfn1->u4.InPageError = 0;
                            Pfn1->u3.e1.PrototypePte = 1;
                        }
                    }
                    
                    /* Advance page structures */
                    Pfn1++;
                    PageFrameIndex++;
                    PointerPte++;
                }
                break;
        }

        /* Next descriptor entry */
        NextEntry = MdBlock->ListEntry.Flink;
    }
}

VOID
NTAPI
MiBuildPfnDatabaseSelf(VOID)
{
    PMMPTE PointerPte, LastPte;
    PMMPFN Pfn1;
    
    /* Loop the PFN database page */
    PointerPte = MiAddressToPte(MI_PFN_TO_PFNENTRY(MmLowestPhysicalPage));
    LastPte = MiAddressToPte(MI_PFN_TO_PFNENTRY(MmHighestPhysicalPage));
    while (PointerPte <= LastPte)
    {
        /* Make sure the page is valid */
        if (PointerPte->u.Hard.Valid == 1)
        {
            /* Get the PFN entry and just mark it referenced */
            Pfn1 = MI_PFN_TO_PFNENTRY(PointerPte->u.Hard.PageFrameNumber);
            Pfn1->u2.ShareCount = 1;
            Pfn1->u3.e2.ReferenceCount = 1;
        }
        
        /* Next */
        PointerPte++;
    }
}

VOID
NTAPI
MiInitializePfnDatabase(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
{
    /* Scan memory and start setting up PFN entries */
    MiBuildPfnDatabaseFromPages(LoaderBlock);
    
    /* Add the zero page */
    MiBuildPfnDatabaseZeroPage();
    
    /* Scan the loader block and build the rest of the PFN database */
    MiBuildPfnDatabaseFromLoaderBlock(LoaderBlock);
    
    /* Finally add the pages for the PFN database itself */ 
    MiBuildPfnDatabaseSelf();
}

VOID
NTAPI
MiAdjustWorkingSetManagerParameters(IN BOOLEAN Client)
{
    /* This function needs to do more work, for now, we tune page minimums */
    
    /* Check for a system with around 64MB RAM or more */
    if (MmNumberOfPhysicalPages >= (63 * _1MB) / PAGE_SIZE)
    {
        /* Double the minimum amount of pages we consider for a "plenty free" scenario */
        MmPlentyFreePages *= 2;
    }
}

VOID
NTAPI
MiNotifyMemoryEvents(VOID)
{
    /* Are we in a low-memory situation? */
    if (MmAvailablePages < MmLowMemoryThreshold)
    {
        /* Clear high, set low  */
        if (KeReadStateEvent(MiHighMemoryEvent)) KeClearEvent(MiHighMemoryEvent);
        if (!KeReadStateEvent(MiLowMemoryEvent)) KeSetEvent(MiLowMemoryEvent, 0, FALSE);
    }
    else if (MmAvailablePages < MmHighMemoryThreshold)
    {
        /* We are in between, clear both */
        if (KeReadStateEvent(MiHighMemoryEvent)) KeClearEvent(MiHighMemoryEvent);
        if (KeReadStateEvent(MiLowMemoryEvent)) KeClearEvent(MiLowMemoryEvent);
    }
    else
    {
        /* Clear low, set high  */
        if (KeReadStateEvent(MiLowMemoryEvent)) KeClearEvent(MiLowMemoryEvent);
        if (!KeReadStateEvent(MiHighMemoryEvent)) KeSetEvent(MiHighMemoryEvent, 0, FALSE);
    }
}

NTSTATUS
NTAPI
MiCreateMemoryEvent(IN PUNICODE_STRING Name,
                    OUT PKEVENT *Event)
{
    PACL Dacl;
    HANDLE EventHandle;
    ULONG DaclLength;
    NTSTATUS Status;
    OBJECT_ATTRIBUTES ObjectAttributes;
    SECURITY_DESCRIPTOR SecurityDescriptor;

    /* Create the SD */
    Status = RtlCreateSecurityDescriptor(&SecurityDescriptor,
                                         SECURITY_DESCRIPTOR_REVISION);
    if (!NT_SUCCESS(Status)) return Status;

    /* One ACL with 3 ACEs, containing each one SID */
    DaclLength = sizeof(ACL) +
                 3 * sizeof(ACCESS_ALLOWED_ACE) +
                 RtlLengthSid(SeLocalSystemSid) +
                 RtlLengthSid(SeAliasAdminsSid) +
                 RtlLengthSid(SeWorldSid);

    /* Allocate space for the DACL */
    Dacl = ExAllocatePoolWithTag(PagedPool, DaclLength, 'lcaD');
    if (!Dacl) return STATUS_INSUFFICIENT_RESOURCES;

    /* Setup the ACL inside it */
    Status = RtlCreateAcl(Dacl, DaclLength, ACL_REVISION);
    if (!NT_SUCCESS(Status)) goto CleanUp;
    
    /* Add query rights for everyone */
    Status = RtlAddAccessAllowedAce(Dacl,
                                    ACL_REVISION,
                                    SYNCHRONIZE | EVENT_QUERY_STATE | READ_CONTROL,
                                    SeWorldSid);
    if (!NT_SUCCESS(Status)) goto CleanUp;
    
    /* Full rights for the admin */
    Status = RtlAddAccessAllowedAce(Dacl,
                                    ACL_REVISION,
                                    EVENT_ALL_ACCESS,
                                    SeAliasAdminsSid);
    if (!NT_SUCCESS(Status)) goto CleanUp;
    
    /* As well as full rights for the system */
    Status = RtlAddAccessAllowedAce(Dacl,
                                    ACL_REVISION,
                                    EVENT_ALL_ACCESS,
                                    SeLocalSystemSid);
    if (!NT_SUCCESS(Status)) goto CleanUp;
  
    /* Set this DACL inside the SD */
    Status = RtlSetDaclSecurityDescriptor(&SecurityDescriptor,
                                          TRUE,
                                          Dacl,
                                          FALSE);
    if (!NT_SUCCESS(Status)) goto CleanUp;
  
    /* Setup the event attributes, making sure it's a permanent one */
    InitializeObjectAttributes(&ObjectAttributes,
                               Name,
                               OBJ_KERNEL_HANDLE | OBJ_PERMANENT,
                               NULL,
                               &SecurityDescriptor);

    /* Create the event */
    Status = ZwCreateEvent(&EventHandle,
                           EVENT_ALL_ACCESS,
                           &ObjectAttributes,
                           NotificationEvent,
                           FALSE);
CleanUp:
    /* Free the DACL */
    ExFreePool(Dacl);

    /* Check if this is the success path */
    if (NT_SUCCESS(Status))
    {
        /* Add a reference to the object, then close the handle we had */
        Status = ObReferenceObjectByHandle(EventHandle,
                                           EVENT_MODIFY_STATE,
                                           ExEventObjectType,
                                           KernelMode,
                                           (PVOID*)Event,
                                           NULL);
        ZwClose (EventHandle);                     
    }

    /* Return status */
    return Status;
}

BOOLEAN
NTAPI
MiInitializeMemoryEvents(VOID)
{
    UNICODE_STRING LowString = RTL_CONSTANT_STRING(L"\\KernelObjects\\LowMemoryCondition");
    UNICODE_STRING HighString = RTL_CONSTANT_STRING(L"\\KernelObjects\\HighMemoryCondition");
    UNICODE_STRING LowPagedPoolString = RTL_CONSTANT_STRING(L"\\KernelObjects\\LowPagedPoolCondition");
    UNICODE_STRING HighPagedPoolString = RTL_CONSTANT_STRING(L"\\KernelObjects\\HighPagedPoolCondition");
    UNICODE_STRING LowNonPagedPoolString = RTL_CONSTANT_STRING(L"\\KernelObjects\\LowNonPagedPoolCondition");
    UNICODE_STRING HighNonPagedPoolString = RTL_CONSTANT_STRING(L"\\KernelObjects\\HighNonPagedPoolCondition");
    NTSTATUS Status;

    /* Check if we have a registry setting */
    if (MmLowMemoryThreshold)
    {
        /* Convert it to pages */
        MmLowMemoryThreshold *= (_1MB / PAGE_SIZE);
    }
    else
    {
        /* The low memory threshold is hit when we don't consider that we have "plenty" of free pages anymore */
        MmLowMemoryThreshold = MmPlentyFreePages;

        /* More than one GB of memory? */
        if (MmNumberOfPhysicalPages > 0x40000)
        {
            /* Start at 32MB, and add another 16MB for each GB */
            MmLowMemoryThreshold = (32 * _1MB) / PAGE_SIZE;
            MmLowMemoryThreshold += ((MmNumberOfPhysicalPages - 0x40000) >> 7);
        }
        else if (MmNumberOfPhysicalPages > 0x8000)
        {
            /* For systems with > 128MB RAM, add another 4MB for each 128MB */
            MmLowMemoryThreshold += ((MmNumberOfPhysicalPages - 0x8000) >> 5);
        }

        /* Don't let the minimum threshold go past 64MB */
        MmLowMemoryThreshold = min(MmLowMemoryThreshold, (64 * _1MB) / PAGE_SIZE);
    }

    /* Check if we have a registry setting */
    if (MmHighMemoryThreshold)
    {
        /* Convert it into pages */
        MmHighMemoryThreshold *= (_1MB / PAGE_SIZE);
    }
    else
    {
        /* Otherwise, the default is three times the low memory threshold */
        MmHighMemoryThreshold = 3 * MmLowMemoryThreshold;
        ASSERT(MmHighMemoryThreshold > MmLowMemoryThreshold);
    }

    /* Make sure high threshold is actually higher than the low */
    MmHighMemoryThreshold = max(MmHighMemoryThreshold, MmLowMemoryThreshold);

    /* Create the memory events for all the thresholds */
    Status = MiCreateMemoryEvent(&LowString, &MiLowMemoryEvent);
    if (!NT_SUCCESS(Status)) return FALSE;
    Status = MiCreateMemoryEvent(&HighString, &MiHighMemoryEvent);
    if (!NT_SUCCESS(Status)) return FALSE;
    Status = MiCreateMemoryEvent(&LowPagedPoolString, &MiLowPagedPoolEvent);
    if (!NT_SUCCESS(Status)) return FALSE;
    Status = MiCreateMemoryEvent(&HighPagedPoolString, &MiHighPagedPoolEvent);
    if (!NT_SUCCESS(Status)) return FALSE;
    Status = MiCreateMemoryEvent(&LowNonPagedPoolString, &MiLowNonPagedPoolEvent);
    if (!NT_SUCCESS(Status)) return FALSE;
    Status = MiCreateMemoryEvent(&HighNonPagedPoolString, &MiHighNonPagedPoolEvent);
    if (!NT_SUCCESS(Status)) return FALSE;

    /* Now setup the pool events */
    MiInitializePoolEvents();

    /* Set the initial event state */
    MiNotifyMemoryEvents();
    return TRUE;
}

VOID
NTAPI
MiAddHalIoMappings(VOID)
{
    PVOID BaseAddress;
    PMMPTE PointerPde;
    PMMPTE PointerPte;
    ULONG i, j, PdeCount;
    PFN_NUMBER PageFrameIndex;

    /* HAL Heap address -- should be on a PDE boundary */
    BaseAddress = (PVOID)0xFFC00000;
    ASSERT(MiAddressToPteOffset(BaseAddress) == 0);

    /* Check how many PDEs the heap has */
    PointerPde = MiAddressToPde(BaseAddress);
    PdeCount = PDE_COUNT - MiGetPdeOffset(BaseAddress);
    for (i = 0; i < PdeCount; i++)
    {
        /* Does the HAL own this mapping? */
        if ((PointerPde->u.Hard.Valid == 1) &&
            (PointerPde->u.Hard.LargePage == 0))
        {
            /* Get the PTE for it and scan each page */
            PointerPte = MiAddressToPte(BaseAddress);
            for (j = 0 ; j < PTE_COUNT; j++)
            {
                /* Does the HAL own this page? */
                if (PointerPte->u.Hard.Valid == 1)
                {
                    /* Is the HAL using it for device or I/O mapped memory? */
                    PageFrameIndex = PFN_FROM_PTE(PointerPte);
                    if (!MiGetPfnEntry(PageFrameIndex))
                    {
                        /* FIXME: For PAT, we need to track I/O cache attributes for coherency */
                        DPRINT1("HAL I/O Mapping at %p is unsafe\n", BaseAddress);
                    }
                }

                /* Move to the next page */
                BaseAddress = (PVOID)((ULONG_PTR)BaseAddress + PAGE_SIZE);
                PointerPte++;
            }
        }
        else
        {
            /* Move to the next address */
            BaseAddress = (PVOID)((ULONG_PTR)BaseAddress + PDE_MAPPED_VA);
        }

        /* Move to the next PDE */
        PointerPde++;
    }
}

VOID
NTAPI
MmDumpArmPfnDatabase(VOID)
{
    ULONG i;
    PMMPFN Pfn1;
    PCHAR Consumer = "Unknown";
    KIRQL OldIrql;
    ULONG ActivePages = 0, FreePages = 0, OtherPages = 0;
    
    KeRaiseIrql(HIGH_LEVEL, &OldIrql);
    
    //
    // Loop the PFN database
    //
    for (i = 0; i <= MmHighestPhysicalPage; i++)
    {
        Pfn1 = MI_PFN_TO_PFNENTRY(i);
        if (!Pfn1) continue;
        
        //
        // Get the page location
        //
        switch (Pfn1->u3.e1.PageLocation)
        {
            case ActiveAndValid:
                
                Consumer = "Active and Valid";
                ActivePages++;
                break;
                
            case FreePageList:
                
                Consumer = "Free Page List";
                FreePages++;
                break;
                
            default:
                
                Consumer = "Other (ASSERT!)";
                OtherPages++;
                break;
        }
                
        //
        // Pretty-print the page
        //
        DbgPrint("0x%08p:\t%20s\t(%02d.%02d) [%08p-%08p])\n",
                 i << PAGE_SHIFT,
                 Consumer,
                 Pfn1->u3.e2.ReferenceCount,
                 Pfn1->u2.ShareCount,
                 Pfn1->PteAddress,
                 Pfn1->u4.PteFrame);
    }
    
    DbgPrint("Active:               %d pages\t[%d KB]\n", ActivePages,  (ActivePages    << PAGE_SHIFT) / 1024);
    DbgPrint("Free:                 %d pages\t[%d KB]\n", FreePages,    (FreePages      << PAGE_SHIFT) / 1024);
    DbgPrint("Other:                %d pages\t[%d KB]\n", OtherPages,   (OtherPages     << PAGE_SHIFT) / 1024);
    
    KeLowerIrql(OldIrql);
}

PFN_NUMBER
NTAPI
MiPagesInLoaderBlock(IN PLOADER_PARAMETER_BLOCK LoaderBlock,
                     IN PBOOLEAN IncludeType)
{
    PLIST_ENTRY NextEntry;
    PFN_NUMBER PageCount = 0;
    PMEMORY_ALLOCATION_DESCRIPTOR MdBlock;
    
    //
    // Now loop through the descriptors
    //
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        //
        // Grab each one, and check if it's one we should include
        //
        MdBlock = CONTAINING_RECORD(NextEntry,
                                    MEMORY_ALLOCATION_DESCRIPTOR,
                                    ListEntry);
        if ((MdBlock->MemoryType < LoaderMaximum) &&
            (IncludeType[MdBlock->MemoryType]))
        {
            //
            // Add this to our running total
            //
            PageCount += MdBlock->PageCount;
        }
        
        //
        // Try the next descriptor
        //
        NextEntry = MdBlock->ListEntry.Flink;
    }
    
    //
    // Return the total
    //
    return PageCount;
}

PPHYSICAL_MEMORY_DESCRIPTOR
NTAPI
MmInitializeMemoryLimits(IN PLOADER_PARAMETER_BLOCK LoaderBlock,
                         IN PBOOLEAN IncludeType)
{
    PLIST_ENTRY NextEntry;
    ULONG Run = 0, InitialRuns = 0;
    PFN_NUMBER NextPage = -1, PageCount = 0;
    PPHYSICAL_MEMORY_DESCRIPTOR Buffer, NewBuffer;
    PMEMORY_ALLOCATION_DESCRIPTOR MdBlock;
    
    //
    // Scan the memory descriptors
    //
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        //
        // For each one, increase the memory allocation estimate
        //
        InitialRuns++;
        NextEntry = NextEntry->Flink;
    }
    
    //
    // Allocate the maximum we'll ever need
    //
    Buffer = ExAllocatePoolWithTag(NonPagedPool,
                                   sizeof(PHYSICAL_MEMORY_DESCRIPTOR) +
                                   sizeof(PHYSICAL_MEMORY_RUN) *
                                   (InitialRuns - 1),
                                   'lMmM');
    if (!Buffer) return NULL;

    //
    // For now that's how many runs we have
    //
    Buffer->NumberOfRuns = InitialRuns;
    
    //
    // Now loop through the descriptors again
    //
    NextEntry = LoaderBlock->MemoryDescriptorListHead.Flink;
    while (NextEntry != &LoaderBlock->MemoryDescriptorListHead)
    {
        //
        // Grab each one, and check if it's one we should include
        //
        MdBlock = CONTAINING_RECORD(NextEntry,
                                    MEMORY_ALLOCATION_DESCRIPTOR,
                                    ListEntry);
        if ((MdBlock->MemoryType < LoaderMaximum) &&
            (IncludeType[MdBlock->MemoryType]))
        {
            //
            // Add this to our running total
            //
            PageCount += MdBlock->PageCount;
            
            //
            // Check if the next page is described by the next descriptor
            //            
            if (MdBlock->BasePage == NextPage)
            {
                //
                // Combine it into the same physical run
                //
                ASSERT(MdBlock->PageCount != 0);
                Buffer->Run[Run - 1].PageCount += MdBlock->PageCount;
                NextPage += MdBlock->PageCount;
            }
            else
            {
                //
                // Otherwise just duplicate the descriptor's contents
                //
                Buffer->Run[Run].BasePage = MdBlock->BasePage;
                Buffer->Run[Run].PageCount = MdBlock->PageCount;
                NextPage = Buffer->Run[Run].BasePage + Buffer->Run[Run].PageCount;
                
                //
                // And in this case, increase the number of runs
                //
                Run++;
            }
        }
        
        //
        // Try the next descriptor
        //
        NextEntry = MdBlock->ListEntry.Flink;
    }
    
    //
    // We should not have been able to go past our initial estimate
    //
    ASSERT(Run <= Buffer->NumberOfRuns);

    //
    // Our guess was probably exaggerated...
    //
    if (InitialRuns > Run)
    {
        //
        // Allocate a more accurately sized buffer
        //
        NewBuffer = ExAllocatePoolWithTag(NonPagedPool,
                                          sizeof(PHYSICAL_MEMORY_DESCRIPTOR) +
                                          sizeof(PHYSICAL_MEMORY_RUN) *
                                          (Run - 1),
                                          'lMmM');
        if (NewBuffer)
        {
            //
            // Copy the old buffer into the new, then free it
            //
            RtlCopyMemory(NewBuffer->Run,
                          Buffer->Run,
                          sizeof(PHYSICAL_MEMORY_RUN) * Run);
            ExFreePool(Buffer);
            
            //
            // Now use the new buffer
            //
            Buffer = NewBuffer;
        }
    }
    
    //
    // Write the final numbers, and return it
    //
    Buffer->NumberOfRuns = Run;
    Buffer->NumberOfPages = PageCount;
    return Buffer;
}

VOID
NTAPI
MiBuildPagedPool(VOID)
{
    PMMPTE PointerPte;
    PMMPDE PointerPde;
    MMPTE TempPte = ValidKernelPte;
    MMPDE TempPde = ValidKernelPde;
    PFN_NUMBER PageFrameIndex;
    KIRQL OldIrql;
    ULONG Size, BitMapSize;
    
    //
    // Get the page frame number for the system page directory
    //
    PointerPte = MiAddressToPte(PDE_BASE);
    ASSERT(PD_COUNT == 1);
    MmSystemPageDirectory[0] = PFN_FROM_PTE(PointerPte);
    
    //
    // Allocate a system PTE which will hold a copy of the page directory
    //
    PointerPte = MiReserveSystemPtes(1, SystemPteSpace);
    ASSERT(PointerPte);
    MmSystemPagePtes = MiPteToAddress(PointerPte);

    //
    // Make this system PTE point to the system page directory.
    // It is now essentially double-mapped. This will be used later for lazy
    // evaluation of PDEs accross process switches, similarly to how the Global
    // page directory array in the old ReactOS Mm is used (but in a less hacky
    // way).
    //
    TempPte = ValidKernelPte;
    ASSERT(PD_COUNT == 1);
    TempPte.u.Hard.PageFrameNumber = MmSystemPageDirectory[0];
    ASSERT(PointerPte->u.Hard.Valid == 0);
    ASSERT(TempPte.u.Hard.Valid == 1);
    *PointerPte = TempPte;

    //
    // Let's get back to paged pool work: size it up.
    // By default, it should be twice as big as nonpaged pool.
    //
    MmSizeOfPagedPoolInBytes = 2 * MmMaximumNonPagedPoolInBytes;
    if (MmSizeOfPagedPoolInBytes > ((ULONG_PTR)MmNonPagedSystemStart -
                                    (ULONG_PTR)MmPagedPoolStart))
    {
        //
        // On the other hand, we have limited VA space, so make sure that the VA
        // for paged pool doesn't overflow into nonpaged pool VA. Otherwise, set
        // whatever maximum is possible.
        //
        MmSizeOfPagedPoolInBytes = (ULONG_PTR)MmNonPagedSystemStart -
                                   (ULONG_PTR)MmPagedPoolStart;
    }

    //
    // Get the size in pages and make sure paged pool is at least 32MB.
    //
    Size = MmSizeOfPagedPoolInBytes;
    if (Size < MI_MIN_INIT_PAGED_POOLSIZE) Size = MI_MIN_INIT_PAGED_POOLSIZE;
    Size = BYTES_TO_PAGES(Size);

    //
    // Now check how many PTEs will be required for these many pages.
    //
    Size = (Size + (1024 - 1)) / 1024;

    //
    // Recompute the page-aligned size of the paged pool, in bytes and pages.
    //
    MmSizeOfPagedPoolInBytes = Size * PAGE_SIZE * 1024;
    MmSizeOfPagedPoolInPages = MmSizeOfPagedPoolInBytes >> PAGE_SHIFT;

    //
    // Let's be really sure this doesn't overflow into nonpaged system VA
    //
    ASSERT((MmSizeOfPagedPoolInBytes + (ULONG_PTR)MmPagedPoolStart) <= 
           (ULONG_PTR)MmNonPagedSystemStart);

    //
    // This is where paged pool ends
    //
    MmPagedPoolEnd = (PVOID)(((ULONG_PTR)MmPagedPoolStart +
                              MmSizeOfPagedPoolInBytes) - 1);

    //
    // So now get the PDE for paged pool and zero it out
    //
    PointerPde = MiAddressToPde(MmPagedPoolStart);
    RtlZeroMemory(PointerPde,
                  (1 + MiAddressToPde(MmPagedPoolEnd) - PointerPde) * sizeof(MMPTE));

    //
    // Next, get the first and last PTE
    //
    PointerPte = MiAddressToPte(MmPagedPoolStart);
    MmPagedPoolInfo.FirstPteForPagedPool = PointerPte;
    MmPagedPoolInfo.LastPteForPagedPool = MiAddressToPte(MmPagedPoolEnd);

    //
    // Lock the PFN database
    //
    OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);

    //
    // Allocate a page and map the first paged pool PDE
    //
    PageFrameIndex = MmAllocPage(MC_NPPOOL);
    TempPde.u.Hard.PageFrameNumber = PageFrameIndex;
    ASSERT(PointerPde->u.Hard.Valid == 0);
    ASSERT(TempPde.u.Hard.Valid == 1);
    *PointerPde = TempPde;

    //
    // Release the PFN database lock
    //
    KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);

    //
    // We only have one PDE mapped for now... at fault time, additional PDEs
    // will be allocated to handle paged pool growth. This is where they'll have
    // to start.
    //
    MmPagedPoolInfo.NextPdeForPagedPoolExpansion = (PMMPTE)(PointerPde + 1);

    //
    // We keep track of each page via a bit, so check how big the bitmap will
    // have to be (make sure to align our page count such that it fits nicely
    // into a 4-byte aligned bitmap.
    //
    // We'll also allocate the bitmap header itself part of the same buffer.
    //
    Size = Size * 1024;
    ASSERT(Size == MmSizeOfPagedPoolInPages);
    BitMapSize = Size;
    Size = sizeof(RTL_BITMAP) + (((Size + 31) / 32) * sizeof(ULONG));

    //
    // Allocate the allocation bitmap, which tells us which regions have not yet
    // been mapped into memory
    //
    MmPagedPoolInfo.PagedPoolAllocationMap = ExAllocatePoolWithTag(NonPagedPool,
                                                                   Size,
                                                                   '  mM');
    ASSERT(MmPagedPoolInfo.PagedPoolAllocationMap);

    //
    // Initialize it such that at first, only the first page's worth of PTEs is
    // marked as allocated (incidentially, the first PDE we allocated earlier).
    //
    RtlInitializeBitMap(MmPagedPoolInfo.PagedPoolAllocationMap,
                        (PULONG)(MmPagedPoolInfo.PagedPoolAllocationMap + 1),
                        BitMapSize);
    RtlSetAllBits(MmPagedPoolInfo.PagedPoolAllocationMap);
    RtlClearBits(MmPagedPoolInfo.PagedPoolAllocationMap, 0, 1024);

    //
    // We have a second bitmap, which keeps track of where allocations end.
    // Given the allocation bitmap and a base address, we can therefore figure
    // out which page is the last page of that allocation, and thus how big the
    // entire allocation is.
    //
    MmPagedPoolInfo.EndOfPagedPoolBitmap = ExAllocatePoolWithTag(NonPagedPool,
                                                                 Size,
                                                                 '  mM');
    ASSERT(MmPagedPoolInfo.EndOfPagedPoolBitmap);
    RtlInitializeBitMap(MmPagedPoolInfo.EndOfPagedPoolBitmap,
                        (PULONG)(MmPagedPoolInfo.EndOfPagedPoolBitmap + 1),
                        BitMapSize);

    //
    // Since no allocations have been made yet, there are no bits set as the end
    //
    RtlClearAllBits(MmPagedPoolInfo.EndOfPagedPoolBitmap);

    //
    // Initialize paged pool.
    //
    InitializePool(PagedPool, 0);

    /* Default low threshold of 30MB or one fifth of paged pool */
    MiLowPagedPoolThreshold = (30 * _1MB) >> PAGE_SHIFT;
    MiLowPagedPoolThreshold = min(MiLowPagedPoolThreshold, Size / 5);

    /* Default high threshold of 60MB or 25% */
    MiHighPagedPoolThreshold = (60 * _1MB) >> PAGE_SHIFT;
    MiHighPagedPoolThreshold = min(MiHighPagedPoolThreshold, (Size * 2) / 5);
    ASSERT(MiLowPagedPoolThreshold < MiHighPagedPoolThreshold);
}

NTSTATUS
NTAPI
MmArmInitSystem(IN ULONG Phase,
                IN PLOADER_PARAMETER_BLOCK LoaderBlock)
{
    ULONG i;
    BOOLEAN IncludeType[LoaderMaximum];
    PVOID Bitmap;
    PPHYSICAL_MEMORY_RUN Run;
    PFN_NUMBER PageCount;
    
    //
    // Instantiate memory that we don't consider RAM/usable
    // We use the same exclusions that Windows does, in order to try to be
    // compatible with WinLDR-style booting
    //
    for (i = 0; i < LoaderMaximum; i++) IncludeType[i] = TRUE;
    IncludeType[LoaderBad] = FALSE;
    IncludeType[LoaderFirmwarePermanent] = FALSE;
    IncludeType[LoaderSpecialMemory] = FALSE;
    IncludeType[LoaderBBTMemory] = FALSE;
    if (Phase == 0)
    {
        /* Initialize the phase 0 temporary event */
        KeInitializeEvent(&MiTempEvent, NotificationEvent, FALSE);

        /* Set all the events to use the temporary event for now */
        MiLowMemoryEvent = &MiTempEvent;
        MiHighMemoryEvent = &MiTempEvent;
        MiLowPagedPoolEvent = &MiTempEvent;
        MiHighPagedPoolEvent = &MiTempEvent;
        MiLowNonPagedPoolEvent = &MiTempEvent;
        MiHighNonPagedPoolEvent = &MiTempEvent;
        
        //
        // Define the basic user vs. kernel address space separation
        //
        MmSystemRangeStart = (PVOID)KSEG0_BASE;
        MmUserProbeAddress = (ULONG_PTR)MmSystemRangeStart - 0x10000;
        MmHighestUserAddress = (PVOID)(MmUserProbeAddress - 1);
        
        /* Highest PTE and PDE based on the addresses above */
        MiHighestUserPte = MiAddressToPte(MmHighestUserAddress);
        MiHighestUserPde = MiAddressToPde(MmHighestUserAddress);
        
        //
        // Get the size of the boot loader's image allocations and then round
        // that region up to a PDE size, so that any PDEs we might create for
        // whatever follows are separate from the PDEs that boot loader might've
        // already created (and later, we can blow all that away if we want to).
        //
        MmBootImageSize = KeLoaderBlock->Extension->LoaderPagesSpanned;
        MmBootImageSize *= PAGE_SIZE;
        MmBootImageSize = (MmBootImageSize + PDE_MAPPED_VA - 1) & ~(PDE_MAPPED_VA - 1);
        ASSERT((MmBootImageSize % PDE_MAPPED_VA) == 0);
        
        //
        // Set the size of session view, pool, and image
        //
        MmSessionSize = MI_SESSION_SIZE;
        MmSessionViewSize = MI_SESSION_VIEW_SIZE;
        MmSessionPoolSize = MI_SESSION_POOL_SIZE;
        MmSessionImageSize = MI_SESSION_IMAGE_SIZE;
        
        //
        // Set the size of system view
        //
        MmSystemViewSize = MI_SYSTEM_VIEW_SIZE;
        
        //
        // This is where it all ends
        //
        MiSessionImageEnd = (PVOID)PTE_BASE;
        
        //
        // This is where we will load Win32k.sys and the video driver
        //
        MiSessionImageStart = (PVOID)((ULONG_PTR)MiSessionImageEnd -
                                      MmSessionImageSize);
        
        //
        // So the view starts right below the session working set (itself below
        // the image area)
        //
        MiSessionViewStart = (PVOID)((ULONG_PTR)MiSessionImageEnd -
                                     MmSessionImageSize -
                                     MI_SESSION_WORKING_SET_SIZE - 
                                     MmSessionViewSize);
        
        //
        // Session pool follows
        //
        MiSessionPoolEnd = MiSessionViewStart;
        MiSessionPoolStart = (PVOID)((ULONG_PTR)MiSessionPoolEnd -
                                     MmSessionPoolSize);
        
        //
        // And it all begins here
        //
        MmSessionBase = MiSessionPoolStart;
        
        //
        // Sanity check that our math is correct
        //
        ASSERT((ULONG_PTR)MmSessionBase + MmSessionSize == PTE_BASE);
        
        //
        // Session space ends wherever image session space ends
        //
        MiSessionSpaceEnd = MiSessionImageEnd;
        
        //
        // System view space ends at session space, so now that we know where
        // this is, we can compute the base address of system view space itself.
        //
        MiSystemViewStart = (PVOID)((ULONG_PTR)MmSessionBase -
                                    MmSystemViewSize);

        /* Compute the PTE addresses for all the addresses we carved out */
        MiSessionImagePteStart = MiAddressToPte(MiSessionImageStart);
        MiSessionImagePteEnd = MiAddressToPte(MiSessionImageEnd);
        MiSessionBasePte = MiAddressToPte(MmSessionBase);
        MiSessionLastPte = MiAddressToPte(MiSessionSpaceEnd);
                                    
        /* Initialize the user mode image list */
        InitializeListHead(&MmLoadedUserImageList);
        
        /* Initialize the paged pool mutex */
        KeInitializeGuardedMutex(&MmPagedPoolMutex);
        
        /* Initialize the Loader Lock */
        KeInitializeMutant(&MmSystemLoadLock, FALSE);        
                                    
        //
        // Count physical pages on the system
        //
        PageCount = MiPagesInLoaderBlock(LoaderBlock, IncludeType);
        
        //
        // Check if this is a machine with less than 19MB of RAM
        //
        if (PageCount < MI_MIN_PAGES_FOR_SYSPTE_TUNING)
        {
            //
            // Use the very minimum of system PTEs
            //
            MmNumberOfSystemPtes = 7000;
        }
        else
        {
            //
            // Use the default, but check if we have more than 32MB of RAM
            //
            MmNumberOfSystemPtes = 11000;
            if (PageCount > MI_MIN_PAGES_FOR_SYSPTE_BOOST)
            {
                //
                // Double the amount of system PTEs
                //
                MmNumberOfSystemPtes <<= 1;
            }
        }
        
        DPRINT("System PTE count has been tuned to %d (%d bytes)\n",
               MmNumberOfSystemPtes, MmNumberOfSystemPtes * PAGE_SIZE);
        
        /* Initialize the platform-specific parts */       
        MiInitMachineDependent(LoaderBlock);
        
        //
        // Sync us up with ReactOS Mm
        //
        MiSyncARM3WithROS(MmNonPagedSystemStart, (PVOID)((ULONG_PTR)MmNonPagedPoolEnd - 1));
        MiSyncARM3WithROS(MmPfnDatabase[0], (PVOID)((ULONG_PTR)MmNonPagedPoolStart + MmSizeOfNonPagedPoolInBytes - 1));
        MiSyncARM3WithROS((PVOID)HYPER_SPACE, (PVOID)(HYPER_SPACE + PAGE_SIZE - 1));
      
        //
        // Build the physical memory block
        //
        MmPhysicalMemoryBlock = MmInitializeMemoryLimits(LoaderBlock,
                                                         IncludeType);
         
        //
        // Allocate enough buffer for the PFN bitmap
        // Align it up to a 32-bit boundary
        //
        Bitmap = ExAllocatePoolWithTag(NonPagedPool,
                                       (((MmHighestPhysicalPage + 1) + 31) / 32) * 4,
                                       '  mM');
        if (!Bitmap)
        {
            //
            // This is critical
            //
            KeBugCheckEx(INSTALL_MORE_MEMORY,
                         MmNumberOfPhysicalPages,
                         MmLowestPhysicalPage,
                         MmHighestPhysicalPage,
                         0x101);
        }
        
        //
        // Initialize it and clear all the bits to begin with
        //
        RtlInitializeBitMap(&MiPfnBitMap,
                            Bitmap,
                            MmHighestPhysicalPage + 1);
        RtlClearAllBits(&MiPfnBitMap);
        
        //
        // Loop physical memory runs
        //
        for (i = 0; i < MmPhysicalMemoryBlock->NumberOfRuns; i++)
        {
            //
            // Get the run
            //
            Run = &MmPhysicalMemoryBlock->Run[i];
            DPRINT("PHYSICAL RAM [0x%08p to 0x%08p]\n",
                   Run->BasePage << PAGE_SHIFT,
                   (Run->BasePage + Run->PageCount) << PAGE_SHIFT);

            //
            // Make sure it has pages inside it
            //
            if (Run->PageCount)
            {
                //
                // Set the bits in the PFN bitmap
                //
                RtlSetBits(&MiPfnBitMap, Run->BasePage, Run->PageCount);
            }
        }
        
        /* Look for large page cache entries that need caching */
        MiSyncCachedRanges();

        /* Loop for HAL Heap I/O device mappings that need coherency tracking */
        MiAddHalIoMappings();

        /* Set the initial resident page count */
        MmResidentAvailablePages = MmAvailablePages - 32;

        /* Initialize large page structures on PAE/x64, and MmProcessList on x86 */
        MiInitializeLargePageSupport();

        /* Check if the registry says any drivers should be loaded with large pages */
        MiInitializeDriverLargePageList();

        /* Relocate the boot drivers into system PTE space and fixup their PFNs */
        MiReloadBootLoadedDrivers(LoaderBlock);

        /* FIXME: Call out into Driver Verifier for initialization  */

        /* Check how many pages the system has */
        if (MmNumberOfPhysicalPages <= (13 * _1MB))
        {
            /* Set small system */
            MmSystemSize = MmSmallSystem;
        }
        else if (MmNumberOfPhysicalPages <= (19 * _1MB))
        {
            /* Set small system and add 100 pages for the cache */
            MmSystemSize = MmSmallSystem;
            MmSystemCacheWsMinimum += 100;
        }
        else
        {
            /* Set medium system and add 400 pages for the cache */
            MmSystemSize = MmMediumSystem;
            MmSystemCacheWsMinimum += 400;
        }
        
        /* Check for less than 24MB */
        if (MmNumberOfPhysicalPages < ((24 * _1MB) / PAGE_SIZE))
        {
            /* No more than 32 pages */
            MmSystemCacheWsMinimum = 32;
        }

        /* Check for more than 32MB */
        if (MmNumberOfPhysicalPages >= ((32 * _1MB) / PAGE_SIZE))
        {
            /* Check for product type being "Wi" for WinNT */
            if (MmProductType == '\0i\0W')
            {
                /* Then this is a large system */
                MmSystemSize = MmLargeSystem;
            }
            else
            {
                /* For servers, we need 64MB to consider this as being large */
                if (MmNumberOfPhysicalPages >= ((64 * _1MB) / PAGE_SIZE))
                {
                    /* Set it as large */
                    MmSystemSize = MmLargeSystem;
                }
            }
        }
        
        /* Check for more than 33 MB */
        if (MmNumberOfPhysicalPages > ((33 * _1MB) / PAGE_SIZE))
        {
            /* Add another 500 pages to the cache */
            MmSystemCacheWsMinimum += 500;
        }
        
        /* Now setup the shared user data fields */
        ASSERT(SharedUserData->NumberOfPhysicalPages == 0);
        SharedUserData->NumberOfPhysicalPages = MmNumberOfPhysicalPages;
        SharedUserData->LargePageMinimum = 0;

        /* Check for workstation (Wi for WinNT) */
        if (MmProductType == '\0i\0W')
        {
            /* Set Windows NT Workstation product type */
            SharedUserData->NtProductType = NtProductWinNt;
            MmProductType = 0;
        }
        else
        {
            /* Check for LanMan server */
            if (MmProductType == '\0a\0L')
            {
                /* This is a domain controller */
                SharedUserData->NtProductType = NtProductLanManNt;
            }
            else
            {
                /* Otherwise it must be a normal server */
                SharedUserData->NtProductType = NtProductServer;
            }

            /* Set the product type, and make the system more aggressive with low memory */
            MmProductType = 1;
            MmMinimumFreePages = 81;
        }

        /* Update working set tuning parameters */
        MiAdjustWorkingSetManagerParameters(!MmProductType);

        /* Finetune the page count by removing working set and NP expansion */
        MmResidentAvailablePages -= MiExpansionPoolPagesInitialCharge;
        MmResidentAvailablePages -= MmSystemCacheWsMinimum;
        MmResidentAvailableAtInit = MmResidentAvailablePages;
        if (MmResidentAvailablePages <= 0)
        {
            /* This should not happen */
            DPRINT1("System cache working set too big\n");
            return FALSE;
        }
        
        /* Size up paged pool and build the shadow system page directory */
        MiBuildPagedPool();
    }
    
    //
    // Always return success for now
    //
    return STATUS_SUCCESS;
}

/* EOF */