reactos/reactos/ntoskrnl/mm/hypermap.c

/*
 * PROJECT:         ReactOS Kernel
 * LICENSE:         BSD - See COPYING.ARM in the top level directory
 * FILE:            ntoskrnl/mm/hypermap.c
 * PURPOSE:         Hyperspace Mapping Functionality
 * PROGRAMMERS:     ReactOS Portable Systems Group
 */

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

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

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

PMMPTE MmFirstReservedMappingPte, MmLastReservedMappingPte;
MMPTE HyperTemplatePte;
PEPROCESS HyperProcess;
KIRQL HyperIrql;

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

PVOID
NTAPI
MiMapPageInHyperSpace(IN PEPROCESS Process,
                      IN PFN_NUMBER Page,
                      IN PKIRQL OldIrql)
{
    MMPTE TempPte;
    PMMPTE PointerPte;
    PFN_NUMBER Offset;
    PVOID Address;

    /* Never accept page 0 */
    ASSERT(Page != 0);

    /* Build the PTE */
    TempPte = HyperTemplatePte;
    TempPte.u.Hard.PageFrameNumber = Page;

    /* Pick the first hyperspace PTE */
    PointerPte = MmFirstReservedMappingPte;

    /* Acquire the hyperlock */
    ASSERT(Process == PsGetCurrentProcess());
    KeAcquireSpinLock(&Process->HyperSpaceLock, OldIrql);

    /* Now get the first free PTE */
    Offset = PFN_FROM_PTE(PointerPte);
    if (!Offset)
    {
        /* Reset the PTEs */
        Offset = MI_HYPERSPACE_PTES;
        KeFlushProcessTb();
    }

    /* Prepare the next PTE */
    PointerPte->u.Hard.PageFrameNumber = Offset - 1;

    /* Write the current PTE */
    PointerPte += Offset;
    ASSERT(PointerPte->u.Hard.Valid == 0);
    ASSERT(TempPte.u.Hard.Valid == 1);
    *PointerPte = TempPte;

    /* Return the address */
    Address = (PVOID)((ULONG_PTR)PointerPte << 10);
    return Address;
}

VOID
NTAPI
MiUnmapPageInHyperSpace(IN PEPROCESS Process,
                        IN PVOID Address,
                        IN KIRQL OldIrql)
{
    ASSERT(Process == PsGetCurrentProcess());

    /* Blow away the mapping */
    MiAddressToPte(Address)->u.Long = 0;

    /* Release the hyperlock */
    ASSERT(KeGetCurrentIrql() == DISPATCH_LEVEL);
    KeReleaseSpinLock(&Process->HyperSpaceLock, OldIrql);
}

PVOID
NTAPI
MiMapPageToZeroInHyperSpace(IN PFN_NUMBER Page)
{
    MMPTE TempPte;
    PMMPTE PointerPte;
    PVOID Address; 

    /* Never accept page 0 */
    ASSERT(Page != 0);

    /* Build the PTE */
    TempPte = HyperTemplatePte;
    TempPte.u.Hard.PageFrameNumber = Page;

    /* Get the Zero PTE and its address */
    PointerPte = MiAddressToPte(MI_ZERO_PTE);
    Address = (PVOID)((ULONG_PTR)PointerPte << 10);

    /* Invalidate the old address */
    __invlpg(Address);

    /* Write the current PTE */
    TempPte.u.Hard.PageFrameNumber = Page;
    *PointerPte = TempPte;

    /* Return the address */
    return Address;
}