Expose PFN database lookup via GetPfnEntry

xtoskrnl/includes/mm/pfn.hh

@@ -31,6 +31,7 @@ namespace MM
             STATIC XTAPI VOID ComputePfnDatabaseSize(VOID);
             STATIC XTAPI ULONGLONG GetNumberOfPhysicalPages(VOID);
             STATIC XTAPI PFN_NUMBER GetPfnDatabaseSize(VOID);
+            STATIC XTAPI PMMPFN GetPfnEntry(IN PFN_NUMBER Pfn);
             STATIC XTAPI VOID ScanMemoryDescriptors(VOID);
 
         private:

xtoskrnl/mm/pfn.cc

@@ -105,6 +105,36 @@ MM::Pfn::GetPfnDatabaseSize(VOID)
     return PfnDatabaseSize;
 }
 
+/**
+ * Retrieves a pointer to the PFN database entry for a given physical page.
+ *
+ * @param Pfn
+ *        The Page Frame Number (PFN) to look up.
+ *
+ * @return This routine returns a pointer to the MMPFN structure for the given PFN, or NULLPTR if the PFN is invalid.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+PMMPFN
+MM::Pfn::GetPfnEntry(IN PFN_NUMBER Pfn)
+{
+    PMMMEMORY_LAYOUT MemoryLayout;
+
+    /* Validate that the PFN is within the range of managed physical memory */
+    if(Pfn > HighestPhysicalPage)
+    {
+        /* The requested page number is outside the bounds, return NULLPTR */
+        return NULLPTR;
+    }
+
+    /* Get the memory layout */
+    MemoryLayout = MM::Manager::GetMemoryLayout();
+
+    /* Calculate the address of the PFN entry by indexing into the PFN database array and return it */
+    return &((PMMPFN)MemoryLayout->PfnDatabaseAddress)[Pfn];
+}
+
 /**
  * Increments the global count of available pages.
  *