[CMAKE]
[reactos.git] / ntoskrnl / mm / ARM3 / pagfault.c
index c391a0a..50304da 100644 (file)
@@ -27,12 +27,30 @@ MiCheckVirtualAddress(IN PVOID VirtualAddress,
                       OUT PMMVAD *ProtoVad)
 {
     PMMVAD Vad;
+    PMMPTE PointerPte;
     
     /* No prototype/section support for now */
     *ProtoVad = NULL;
     
-    /* Only valid for user VADs for now */
-    ASSERT(VirtualAddress <= MM_HIGHEST_USER_ADDRESS);
+    /* Check if this is a page table address */
+    if (MI_IS_PAGE_TABLE_ADDRESS(VirtualAddress))
+    {
+        /* This should never happen, as these addresses are handled by the double-maping */
+        if (((PMMPTE)VirtualAddress >= MiAddressToPte(MmPagedPoolStart)) &&
+            ((PMMPTE)VirtualAddress <= MmPagedPoolInfo.LastPteForPagedPool))
+        {
+            /* Fail such access */
+            *ProtectCode = MM_NOACCESS;
+            return NULL;
+        }
+        
+        /* Return full access rights */
+        *ProtectCode = MM_READWRITE;
+        return NULL;
+    }
+    
+    /* Should not be a session address */
+    ASSERT(MI_IS_SESSION_ADDRESS(VirtualAddress) == FALSE);
     
     /* Special case for shared data */
     if (PAGE_ALIGN(VirtualAddress) == (PVOID)USER_SHARED_DATA)
@@ -50,15 +68,33 @@ MiCheckVirtualAddress(IN PVOID VirtualAddress,
         *ProtectCode = MM_NOACCESS;
         return NULL;
     }
-    
-    /* This must be a TEB/PEB VAD */
-    ASSERT(Vad->u.VadFlags.PrivateMemory == TRUE);
-    ASSERT(Vad->u.VadFlags.MemCommit == TRUE);
+
+    /* This must be a VM VAD */
     ASSERT(Vad->u.VadFlags.VadType == VadNone);
     
-    /* Return the protection on it */
-    *ProtectCode = Vad->u.VadFlags.Protection;
-    return NULL;
+    /* Check if it's a section, or just an allocation */
+    if (Vad->u.VadFlags.PrivateMemory == TRUE)
+    {
+        /* This must be a TEB/PEB VAD */
+        ASSERT(Vad->u.VadFlags.MemCommit == TRUE);
+        *ProtectCode = Vad->u.VadFlags.Protection;
+        return NULL;
+    }
+    else
+    {
+        /* Return the proto VAD */
+        ASSERT(Vad->u2.VadFlags2.ExtendableFile == 0);
+        *ProtoVad = Vad;
+        
+        /* Get the prototype PTE for this page */
+        PointerPte = (((ULONG_PTR)VirtualAddress >> PAGE_SHIFT) - Vad->StartingVpn) + Vad->FirstPrototypePte;
+        ASSERT(PointerPte <= Vad->LastContiguousPte);
+        ASSERT(PointerPte != NULL);
+        
+        /* Return the Prototype PTE and the protection for the page mapping */
+        *ProtectCode = Vad->u.VadFlags.Protection;
+        return PointerPte;
+    }
 }
  
 NTSTATUS
@@ -107,16 +143,11 @@ MiCheckPdeForPagedPool(IN PVOID Address)
 #ifdef _M_AMD64
         ASSERT(FALSE);
 #else
-        /* This seems to be making the assumption that one PDE is one page long */
-        C_ASSERT(PAGE_SIZE == (PD_COUNT * (sizeof(MMPTE) * PDE_COUNT)));
-        
         //
         // Copy it from our double-mapped system page directory
         //
         InterlockedExchangePte(PointerPde,
-                               MmSystemPagePtes[((ULONG_PTR)PointerPde &
-                                                 (PAGE_SIZE - 1)) /
-                                                sizeof(MMPTE)].u.Long);
+                               MmSystemPagePtes[((ULONG_PTR)PointerPde & (SYSTEM_PD_SIZE - 1)) / sizeof(MMPTE)].u.Long);
 #endif
     }
     
@@ -179,16 +210,16 @@ MiResolveDemandZeroFault(IN PVOID Address,
                          IN PEPROCESS Process,
                          IN KIRQL OldIrql)
 {
-    PFN_NUMBER PageFrameNumber;
+    PFN_NUMBER PageFrameNumber = 0;
     MMPTE TempPte;
-    BOOLEAN NeedZero = FALSE;
+    BOOLEAN NeedZero = FALSE, HaveLock = FALSE;
+    ULONG Color;
     DPRINT("ARM3 Demand Zero Page Fault Handler for address: %p in process: %p\n",
             Address,
             Process);
     
     /* Must currently only be called by paging path */
-    ASSERT(OldIrql == MM_NOIRQL);
-    if (Process)
+    if ((Process) && (OldIrql == MM_NOIRQL))
     {
         /* Sanity check */
         ASSERT(MI_IS_PAGE_TABLE_ADDRESS(PointerPte));
@@ -196,27 +227,66 @@ MiResolveDemandZeroFault(IN PVOID Address,
         /* No forking yet */
         ASSERT(Process->ForkInProgress == NULL);
         
+        /* Get process color */
+        Color = MI_GET_NEXT_PROCESS_COLOR(Process);
+        ASSERT(Color != 0xFFFFFFFF);
+        
         /* We'll need a zero page */
         NeedZero = TRUE;
     }
+    else
+    {
+        /* Check if we need a zero page */
+        NeedZero = (OldIrql != MM_NOIRQL);
         
-    //
-    // Lock the PFN database
-    //
-    OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
-    ASSERT(PointerPte->u.Hard.Valid == 0);
+        /* Get the next system page color */
+        Color = MI_GET_NEXT_COLOR();
+    }
+
+    /* Check if the PFN database should be acquired */
+    if (OldIrql == MM_NOIRQL)
+    {
+        /* Acquire it and remember we should release it after */
+        OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+        HaveLock = TRUE;
+    }
     
-    /* Get a page */
-    PageFrameNumber = MiRemoveAnyPage(0);
-    DPRINT("New pool page: %lx\n", PageFrameNumber);
+    /* We either manually locked the PFN DB, or already came with it locked */
+    ASSERT(KeGetCurrentIrql() == DISPATCH_LEVEL);
+    
+    /* Do we need a zero page? */
+    ASSERT(PointerPte->u.Hard.Valid == 0);
+    if ((NeedZero) && (Process))
+    {
+        /* Try to get one, if we couldn't grab a free page and zero it */
+        PageFrameNumber = MiRemoveZeroPageSafe(Color);
+        if (PageFrameNumber)
+        {
+            /* We got a genuine zero page, stop worrying about it */
+            NeedZero = FALSE;
+        }
+        else
+        {
+            /* We'll need a free page and zero it manually */
+            PageFrameNumber = MiRemoveAnyPage(Color);
+        }
+    }
+    else if (!NeedZero)
+    {
+        /* Process or system doesn't want a zero page, grab anything */
+        PageFrameNumber = MiRemoveAnyPage(Color);
+    }
+    else
+    {
+        /* System wants a zero page, obtain one */
+        PageFrameNumber = MiRemoveZeroPage(Color);
+    }
     
     /* Initialize it */
     MiInitializePfn(PageFrameNumber, PointerPte, TRUE);
     
-    //
-    // Release PFN lock
-    //
-    KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
+    /* Release PFN lock if needed */
+    if (HaveLock) KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
     
     //
     // Increment demand zero faults
@@ -267,24 +337,53 @@ MiCompleteProtoPteFault(IN BOOLEAN StoreInstruction,
                         IN PMMPFN Pfn1)
 {
     MMPTE TempPte;
+    PMMPTE OriginalPte;
+    ULONG Protection;
     PFN_NUMBER PageFrameIndex;
     
     /* Must be called with an valid prototype PTE, with the PFN lock held */
     ASSERT(KeGetCurrentIrql() == DISPATCH_LEVEL);
     ASSERT(PointerProtoPte->u.Hard.Valid == 1);
     
-    /* Quick-n-dirty */
-    ASSERT(PointerPte->u.Soft.PageFileHigh == 0xFFFFF);
-    
     /* Get the page */
     PageFrameIndex = PFN_FROM_PTE(PointerProtoPte);
+    
+    /* Get the PFN entry and set it as a prototype PTE */
+    Pfn1 = MiGetPfnEntry(PageFrameIndex);
+    Pfn1->u3.e1.PrototypePte = 1;
+    
+    /* FIXME: Increment the share count for the page table */
+    
+    /* Check where we should be getting the protection information from */
+    if (PointerPte->u.Soft.PageFileHigh == MI_PTE_LOOKUP_NEEDED)
+    {
+        /* Get the protection from the PTE, there's no real Proto PTE data */
+        Protection = PointerPte->u.Soft.Protection;
+    }
+    else
+    {
+        /* Get the protection from the original PTE link */
+        OriginalPte = &Pfn1->OriginalPte;
+        Protection = OriginalPte->u.Soft.Protection;
+    }
 
     /* Release the PFN lock */
     KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
     
-    /* Build the user PTE */
-    ASSERT(Address < MmSystemRangeStart);
-    MI_MAKE_HARDWARE_PTE_USER(&TempPte, PointerPte, MM_READONLY, PageFrameIndex);
+    /* Remove caching bits */
+    Protection &= ~(MM_NOCACHE | MM_NOACCESS);
+    
+    /* Check if this is a kernel or user address */
+    if (Address < MmSystemRangeStart)
+    {
+        /* Build the user PTE */
+        MI_MAKE_HARDWARE_PTE_USER(&TempPte, PointerPte, Protection, PageFrameIndex);
+    }
+    else
+    {
+        /* Build the kernel PTE */
+        MI_MAKE_HARDWARE_PTE(&TempPte, PointerPte, Protection, PageFrameIndex);
+    }
     
     /* Write the PTE */
     MI_WRITE_VALID_PTE(PointerPte, TempPte);
@@ -309,25 +408,56 @@ MiResolveProtoPteFault(IN BOOLEAN StoreInstruction,
     MMPTE TempPte;
     PMMPFN Pfn1;
     PFN_NUMBER PageFrameIndex;
+    NTSTATUS Status;
     
     /* Must be called with an invalid, prototype PTE, with the PFN lock held */
     ASSERT(KeGetCurrentIrql() == DISPATCH_LEVEL);
     ASSERT(PointerPte->u.Hard.Valid == 0);
     ASSERT(PointerPte->u.Soft.Prototype == 1);
 
-    /* Read the prototype PTE -- it must be valid since we only handle shared data */
+    /* Read the prototype PTE and check if it's valid */
     TempPte = *PointerProtoPte;
-    ASSERT(TempPte.u.Hard.Valid == 1);
+    if (TempPte.u.Hard.Valid == 1)
+    {
+        /* One more user of this mapped page */
+        PageFrameIndex = PFN_FROM_PTE(&TempPte);
+        Pfn1 = MiGetPfnEntry(PageFrameIndex);
+        Pfn1->u2.ShareCount++;
     
-    /* One more user of this mapped page */
-    PageFrameIndex = PFN_FROM_PTE(&TempPte);
-    Pfn1 = MiGetPfnEntry(PageFrameIndex);
-    Pfn1->u2.ShareCount++;
+        /* Call it a transition */
+        InterlockedIncrement(&KeGetCurrentPrcb()->MmTransitionCount);
+    
+        /* Complete the prototype PTE fault -- this will release the PFN lock */
+        return MiCompleteProtoPteFault(StoreInstruction,
+                                       Address,
+                                       PointerPte,
+                                       PointerProtoPte,
+                                       OldIrql,
+                                       NULL);
+    }
+    
+    /* Make sure there's some protection mask */
+    if (TempPte.u.Long == 0)
+    {
+        /* Release the lock */
+        DPRINT1("Access on reserved section?\n");
+        KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
+        return STATUS_ACCESS_VIOLATION;
+    }
     
-    /* Call it a transition */
-    InterlockedIncrement(&KeGetCurrentPrcb()->MmTransitionCount);
+    /* This is the only thing we support right now */
+    ASSERT(TempPte.u.Soft.PageFileHigh == 0);
+    ASSERT(TempPte.u.Proto.ReadOnly == 0);
+    ASSERT(PointerPte > MiHighestUserPte);
+    ASSERT(TempPte.u.Soft.Prototype == 0);
+    ASSERT(TempPte.u.Soft.Transition == 0);
+
+    /* Resolve the demand zero fault */
+    Status = MiResolveDemandZeroFault(Address, PointerProtoPte, Process, OldIrql);
+    ASSERT(NT_SUCCESS(Status));
     
     /* Complete the prototype PTE fault -- this will release the PFN lock */
+    ASSERT(PointerPte->u.Hard.Valid == 0);
     return MiCompleteProtoPteFault(StoreInstruction,
                                    Address,
                                    PointerPte,
@@ -372,39 +502,75 @@ MiDispatchFault(IN BOOLEAN StoreInstruction,
     {
         /* This should never happen */
         ASSERT(!MI_IS_PHYSICAL_ADDRESS(PointerProtoPte));
+        
+        /* Check if this is a kernel-mode address */
+        SuperProtoPte = MiAddressToPte(PointerProtoPte);
+        if (Address >= MmSystemRangeStart)
+        {
+            /* Lock the PFN database */
+            LockIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
             
-        /* We currently only handle the shared user data PTE path */
-        ASSERT(Address < MmSystemRangeStart);
-        ASSERT(PointerPte->u.Soft.Prototype == 1);
-        ASSERT(PointerPte->u.Soft.PageFileHigh == 0xFFFFF);
-        ASSERT(Vad == NULL);
+            /* Has the PTE been made valid yet? */
+            if (!SuperProtoPte->u.Hard.Valid)
+            {
+                UNIMPLEMENTED;
+                while (TRUE);
+            }
+            else
+            {
+                /* Resolve the fault -- this will release the PFN lock */
+                ASSERT(PointerPte->u.Hard.Valid == 0);
+                Status = MiResolveProtoPteFault(StoreInstruction,
+                                                Address,
+                                                PointerPte,
+                                                PointerProtoPte,
+                                                NULL,
+                                                NULL,
+                                                NULL,
+                                                Process,
+                                                LockIrql,
+                                                TrapInformation);
+                ASSERT(Status == STATUS_SUCCESS);
+
+                /* Complete this as a transition fault */
+                ASSERT(OldIrql == KeGetCurrentIrql());
+                ASSERT(OldIrql <= APC_LEVEL);
+                ASSERT(KeAreAllApcsDisabled() == TRUE);
+                return Status;
+            }
+        }
+        else
+        {
+            /* We currently only handle very limited paths */
+            ASSERT(PointerPte->u.Soft.Prototype == 1);
+            ASSERT(PointerPte->u.Soft.PageFileHigh == MI_PTE_LOOKUP_NEEDED);
         
-        /* Lock the PFN database */
-        LockIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+            /* Lock the PFN database */
+            LockIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
         
-        /* For the shared data page, this should be true */
-        SuperProtoPte = MiAddressToPte(PointerProtoPte);
-        ASSERT(SuperProtoPte->u.Hard.Valid == 1);
-        ASSERT(TempPte.u.Hard.Valid == 0);
-
-        /* Resolve the fault -- this will release the PFN lock */
-        Status = MiResolveProtoPteFault(StoreInstruction,
-                                        Address,
-                                        PointerPte,
-                                        PointerProtoPte,
-                                        NULL,
-                                        NULL,
-                                        NULL,
-                                        Process,
-                                        LockIrql,
-                                        TrapInformation);
-        ASSERT(Status == STATUS_SUCCESS);
-
-        /* Complete this as a transition fault */
-        ASSERT(OldIrql == KeGetCurrentIrql());
-        ASSERT(OldIrql <= APC_LEVEL);
-        ASSERT(KeAreAllApcsDisabled() == TRUE);
-        return STATUS_PAGE_FAULT_TRANSITION;
+            /* For our current usage, this should be true */
+            ASSERT(SuperProtoPte->u.Hard.Valid == 1);
+            ASSERT(TempPte.u.Hard.Valid == 0);
+
+            /* Resolve the fault -- this will release the PFN lock */
+            Status = MiResolveProtoPteFault(StoreInstruction,
+                                            Address,
+                                            PointerPte,
+                                            PointerProtoPte,
+                                            NULL,
+                                            NULL,
+                                            NULL,
+                                            Process,
+                                            LockIrql,
+                                            TrapInformation);
+            ASSERT(Status == STATUS_SUCCESS);
+
+            /* Complete this as a transition fault */
+            ASSERT(OldIrql == KeGetCurrentIrql());
+            ASSERT(OldIrql <= APC_LEVEL);
+            ASSERT(KeAreAllApcsDisabled() == TRUE);
+            return STATUS_PAGE_FAULT_TRANSITION;
+        }
     }
     
     //
@@ -453,7 +619,7 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
                  IN PVOID TrapInformation)
 {
     KIRQL OldIrql = KeGetCurrentIrql(), LockIrql;
-    PMMPTE PointerPte, ProtoPte;
+    PMMPTE PointerPte, ProtoPte = NULL;
     PMMPDE PointerPde;
     MMPTE TempPte;
     PETHREAD CurrentThread;
@@ -463,6 +629,7 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
     ULONG ProtectionCode;
     PMMVAD Vad;
     PFN_NUMBER PageFrameIndex;
+    ULONG Color;
     DPRINT("ARM3 FAULT AT: %p\n", Address);
     
     //
@@ -492,7 +659,7 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
     //
     // Check for kernel fault
     //
-    if (Address >= MmSystemRangeStart)
+    while (Address >= MmSystemRangeStart)
     {
         //
         // What are you even DOING here?
@@ -568,25 +735,16 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
         //
         if (MI_IS_PAGE_TABLE_OR_HYPER_ADDRESS(Address))
         {
-            //
-            // This might happen...not sure yet
-            //
-            DPRINT1("FAULT ON PAGE TABLES: %p %lx %lx!\n", Address, *PointerPte, *PointerPde);
 #if (_MI_PAGING_LEVELS == 2) 
-            //
-            // Map in the page table
-            //
+            /* Could be paged pool access from a new process -- synchronize the page directories */
             if (MiCheckPdeForPagedPool(Address) == STATUS_WAIT_1)
             {
                 DPRINT1("PAGE TABLES FAULTED IN!\n");
                 return STATUS_SUCCESS;
             }
 #endif
-            //
-            // Otherwise the page table doesn't actually exist
-            //
-            DPRINT1("FAILING\n");
-            return STATUS_ACCESS_VIOLATION;
+            /* Otherwise this could be a commit of a virtual address */
+            break;
         }
         
         /* In this path, we are using the system working set */
@@ -628,9 +786,6 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
         /* Check one kind of prototype PTE */
         if (TempPte.u.Soft.Prototype)
         {
-            /* The one used for protected pool... */
-            ASSERT(MmProtectFreedNonPagedPool == TRUE);
-            
             /* Make sure protected pool is on, and that this is a pool address */
             if ((MmProtectFreedNonPagedPool) &&
                 (((Address >= MmNonPagedPoolStart) &&
@@ -646,12 +801,43 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
                              Mode,
                              4);
             }
+            
+            /* Get the prototype PTE! */
+            ProtoPte = MiProtoPteToPte(&TempPte);
         }
+        else
+        {        
+            //
+            // We don't implement transition PTEs
+            //
+            ASSERT(TempPte.u.Soft.Transition == 0);
         
-        //
-        // We don't implement transition PTEs
-        //
-        ASSERT(TempPte.u.Soft.Transition == 0);
+            /* Check for no-access PTE */
+            if (TempPte.u.Soft.Protection == MM_NOACCESS)
+            {
+                /* Bad boy, bad boy, whatcha gonna do, whatcha gonna do when ARM3 comes for you! */
+                KeBugCheckEx(PAGE_FAULT_IN_NONPAGED_AREA,
+                             (ULONG_PTR)Address,
+                             StoreInstruction,
+                             (ULONG_PTR)TrapInformation,
+                             1);
+            }
+        }
+        
+        /* Check for demand page */
+        if ((StoreInstruction) && !(ProtoPte) && !(TempPte.u.Hard.Valid))
+        {
+            /* Get the protection code */
+            if (!(TempPte.u.Soft.Protection & MM_READWRITE))
+            {
+                /* Bad boy, bad boy, whatcha gonna do, whatcha gonna do when ARM3 comes for you! */
+                KeBugCheckEx(ATTEMPTED_WRITE_TO_READONLY_MEMORY,
+                             (ULONG_PTR)Address,
+                             TempPte.u.Long,
+                             (ULONG_PTR)TrapInformation,
+                             14);
+            }
+        }
         
         //
         // Now do the real fault handling
@@ -659,7 +845,7 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
         Status = MiDispatchFault(StoreInstruction,
                                  Address,
                                  PointerPte,
-                                 NULL,
+                                 ProtoPte,
                                  FALSE,
                                  NULL,
                                  TrapInformation,
@@ -690,7 +876,6 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
 #endif
 
     /* First things first, is the PDE valid? */
-    ASSERT(PointerPde != MiAddressToPde(PTE_BASE));
     ASSERT(PointerPde->u.Hard.LargePage == 0);
     if (PointerPde->u.Hard.Valid == 0)
     {
@@ -725,11 +910,55 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
         ASSERT(PointerPde->u.Hard.Valid == 1);
     }
 
-    /* Now capture the PTE. We only handle cases where it's totally empty */
+    /* Now capture the PTE. Ignore virtual faults for now */
     TempPte = *PointerPte;
-    ASSERT(TempPte.u.Long == 0);
+    ASSERT(TempPte.u.Hard.Valid == 0);
+    
+    /* Quick check for demand-zero */
+    if (TempPte.u.Long == (MM_READWRITE << MM_PTE_SOFTWARE_PROTECTION_BITS))
+    {
+        /* Resolve the fault */
+        MiResolveDemandZeroFault(Address,
+                                 PointerPte,
+                                 CurrentProcess,
+                                 MM_NOIRQL);
+
+        /* Return the status */
+        MiUnlockProcessWorkingSet(CurrentProcess, CurrentThread);
+        return STATUS_PAGE_FAULT_DEMAND_ZERO;
+    }
+    
+    /* Get protection and check if it's a prototype PTE */
+    ProtectionCode = TempPte.u.Soft.Protection;
+    ASSERT(TempPte.u.Soft.Prototype == 0);
+    
+    /* Check for non-demand zero PTE */
+    if (TempPte.u.Long != 0)
+    {
+        /* This is a page fault, check for valid protection */
+        ASSERT(ProtectionCode != 0x100);
+        
+        /* FIXME: Run MiAccessCheck */
+        
+        /* Dispatch the fault */
+        Status = MiDispatchFault(StoreInstruction,
+                                 Address,
+                                 PointerPte,
+                                 NULL,
+                                 FALSE,
+                                 PsGetCurrentProcess(),
+                                 TrapInformation,
+                                 NULL);
+                                 
+        /* Return the status */
+        ASSERT(NT_SUCCESS(Status));
+        ASSERT(KeGetCurrentIrql() <= APC_LEVEL);
+        MiUnlockProcessWorkingSet(CurrentProcess, CurrentThread);
+        return Status;
+    }
 
     /* Check if this address range belongs to a valid allocation (VAD) */
+    ASSERT(TempPte.u.Long == 0);
     ProtoPte = MiCheckVirtualAddress(Address, &ProtectionCode, &Vad);
     if (ProtectionCode == MM_NOACCESS)
     {
@@ -756,19 +985,25 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
 
         /* Lock the PFN database since we're going to grab a page */
         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+        
+        /* Try to get a zero page */
+        Color = MI_GET_NEXT_PROCESS_COLOR(CurrentProcess);
+        PageFrameIndex = MiRemoveZeroPageSafe(Color);
+        if (!PageFrameIndex)
+        {
+            /* Grab a page out of there. Later we should grab a colored zero page */
+            PageFrameIndex = MiRemoveAnyPage(Color);
+            ASSERT(PageFrameIndex);
 
-        /* Grab a page out of there. Later we should grab a colored zero page */
-        PageFrameIndex = MiRemoveAnyPage(0);
-        ASSERT(PageFrameIndex);
-
-        /* Release the lock since we need to do some zeroing */
-        KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
+            /* Release the lock since we need to do some zeroing */
+            KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
 
-        /* Zero out the page, since it's for user-mode */
-        MiZeroPfn(PageFrameIndex);
+            /* Zero out the page, since it's for user-mode */
+            MiZeroPfn(PageFrameIndex);
 
-        /* Grab the lock again so we can initialize the PFN entry */
-        OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+            /* Grab the lock again so we can initialize the PFN entry */
+            OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+        }
 
         /* Initialize the PFN entry now */
         MiInitializePfn(PageFrameIndex, PointerPte, 1);
@@ -808,8 +1043,9 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
     }
     else
     {
-        /* The only "prototype PTE" we support is the shared user data path */
-        ASSERT(ProtectionCode == MM_READONLY);
+        /* No guard page support yet */
+        ASSERT((ProtectionCode & MM_DECOMMIT) == 0);
+        ASSERT(ProtectionCode != 0x100);
         
         /* Write the prototype PTE */
         TempPte = PrototypePte;
@@ -827,7 +1063,7 @@ MmArmAccessFault(IN BOOLEAN StoreInstruction,
                                  Vad);
         ASSERT(Status == STATUS_PAGE_FAULT_TRANSITION);
         ASSERT(PointerPte->u.Hard.Valid == 1);
-        ASSERT(PointerPte->u.Hard.PageFrameNumber == MmSharedUserDataPte->u.Hard.PageFrameNumber);
+        ASSERT(PointerPte->u.Hard.PageFrameNumber != 0);
     }
     
     /* Release the working set */