From 3e04cabe4eceb72c51d4ce658b7e86aeab86ec98 Mon Sep 17 00:00:00 2001
From: ReactOS Portable Systems Group <ros-arm-bringup@svn.reactos.org>
Date: Mon, 27 Jul 2009 02:13:19 +0000
Subject: [PATCH] - Create a double-mapping PTE for the shared user data region
 and fault it in whenever a process touches that address. - Remove the old
 hack which used the PCR's page frame number to create a fake PTE each time to
 reference it, basing on the fact that the shared user data region was on the
 same page as the PCR on certain architectures.

svn path=/trunk/; revision=42252
---
 reactos/ntoskrnl/mm/mmfault.c | 12 +++---------
 reactos/ntoskrnl/mm/mminit.c  | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/reactos/ntoskrnl/mm/mmfault.c b/reactos/ntoskrnl/mm/mmfault.c
index 490e77c314c..c954b07498e 100644
--- a/reactos/ntoskrnl/mm/mmfault.c
+++ b/reactos/ntoskrnl/mm/mmfault.c
@@ -150,7 +150,7 @@ MmNotPresentFault(KPROCESSOR_MODE Mode,
    MEMORY_AREA* MemoryArea;
    NTSTATUS Status;
    BOOLEAN Locked = FromMdl;
-   PFN_TYPE Pfn;
+   extern PMMPTE MmSharedUserDataPte;
 
    DPRINT("MmNotPresentFault(Mode %d, Address %x)\n", Mode, Address);
 
@@ -228,14 +228,8 @@ MmNotPresentFault(KPROCESSOR_MODE Mode,
             break;
 
          case MEMORY_AREA_SHARED_DATA:
-            Pfn = MmGetPhysicalAddress((PVOID)PCR).LowPart >> PAGE_SHIFT;
-            Pfn++;
-            Status =
-               MmCreateVirtualMapping(PsGetCurrentProcess(),
-                                      (PVOID)PAGE_ROUND_DOWN(Address),
-                                      PAGE_READONLY,
-                                      &Pfn,
-                                      1);
+              *MiAddressToPte(USER_SHARED_DATA) = *MmSharedUserDataPte;
+              Status = STATUS_SUCCESS;
             break;
 
          default:
diff --git a/reactos/ntoskrnl/mm/mminit.c b/reactos/ntoskrnl/mm/mminit.c
index b6702b18406..5d332a2864a 100644
--- a/reactos/ntoskrnl/mm/mminit.c
+++ b/reactos/ntoskrnl/mm/mminit.c
@@ -48,6 +48,7 @@ MemType[] =
 PBOOLEAN Mm64BitPhysicalAddress = FALSE;
 ULONG MmReadClusterSize;
 MM_STATS MmStats;
+PMMPTE MmSharedUserDataPte;
 PMMSUPPORT MmKernelAddressSpace;
 extern KMUTANT MmSystemLoadLock;
 extern ULONG MmBootImageSize;
@@ -181,6 +182,11 @@ NTAPI
 MmInitSystem(IN ULONG Phase,
              IN PLOADER_PARAMETER_BLOCK LoaderBlock)
 {
+    extern MMPTE HyperTemplatePte;
+    PMMPTE PointerPte;
+    MMPTE TempPte = HyperTemplatePte;
+    PFN_NUMBER PageFrameNumber;
+    
     if (Phase == 0)
     {
         /* Initialize Mm bootstrap */
@@ -210,6 +216,31 @@ MmInitSystem(IN ULONG Phase,
         MmInitSectionImplementation();
         MmInitPagingFile();
         
+        //
+        // Create a PTE to double-map the shared data section. We allocate it
+        // from paged pool so that we can't fault when trying to touch the PTE
+        // itself (to map it), since paged pool addresses will already be mapped
+        // by the fault handler.
+        //
+        MmSharedUserDataPte = ExAllocatePoolWithTag(PagedPool,
+                                                    sizeof(MMPTE),
+                                                    '  mM');
+        if (!MmSharedUserDataPte) return FALSE;
+        
+        //
+        // Now get the PTE for shared data, and read the PFN that holds it
+        //
+        PointerPte = MiAddressToPte(KI_USER_SHARED_DATA);
+        ASSERT(PointerPte->u.Hard.Valid == 1);
+        PageFrameNumber = PFN_FROM_PTE(PointerPte);
+        
+        //
+        // Now write a copy of it
+        //
+        TempPte.u.Hard.Owner = 1;
+        TempPte.u.Hard.PageFrameNumber = PageFrameNumber;
+        *MmSharedUserDataPte = TempPte;
+        
         /*
          * Unmap low memory
          */