Extract PFN management into separate module

2025-12-13 20:42:48 +01:00
parent 237f6a2974
commit 783a9eea3a
9 changed files with 130 additions and 149 deletions
--- a/xtoskrnl/mm/pfn.cc
+++ b/xtoskrnl/mm/pfn.cc
@@ -0,0 +1,89 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtoskrnl/mm/pfn.cc
+ * DESCRIPTION:     Physical Frame Number (PFN) support
+ * DEVELOPERS:      Aiken Harris <harraiken91@gmail.com>
+ *                  Rafal Kupiec <belliash@codingworkshop.eu.org>
+ */
+
+#include <xtos.hh>
+
+
+/**
+ * Scans memory descriptors provided by the boot loader.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+VOID
+MM::Pfn::ScanMemoryDescriptors(VOID)
+{
+    PLIST_ENTRY LoaderMemoryDescriptors, MemoryMappings;
+    PLOADER_MEMORY_DESCRIPTOR MemoryDescriptor;
+    PFN_NUMBER FreePages;
+
+    /* Initially, set number of free pages to 0 */
+    FreePages = 0;
+
+    /* Get a list of memory descriptors provided by the boot loader */
+    LoaderMemoryDescriptors = KE::BootInformation::GetMemoryDescriptors();
+
+    /* Iterate through memory mappings provided by the boot loader */
+    MemoryMappings = LoaderMemoryDescriptors->Flink;
+    while(MemoryMappings != LoaderMemoryDescriptors)
+    {
+        /* Get memory descriptor */
+        MemoryDescriptor = CONTAIN_RECORD(MemoryMappings, LOADER_MEMORY_DESCRIPTOR, ListEntry);
+
+        /* Check if memory type is invisible or cached */
+        if(VerifyMemoryTypeInvisible(MemoryDescriptor->MemoryType) ||
+           (MemoryDescriptor->MemoryType == LoaderHardwareCachedMemory))
+        {
+            /* Skip this mapping */
+            MemoryMappings = MemoryMappings->Flink;
+            continue;
+        }
+
+        /* Make sure that memory type is not bad */
+        if(MemoryDescriptor->MemoryType != LoaderBad)
+        {
+            /* Increment number of physical pages */
+            NumberOfPhysicalPages += MemoryDescriptor->PageCount;
+        }
+
+        /* Find lowest physical page */
+        if(MemoryDescriptor->BasePage < LowestPhysicalPage)
+        {
+            /* Update lowest physical page */
+            LowestPhysicalPage = MemoryDescriptor->BasePage;
+        }
+
+        /* Find highest physical page */
+        if(MemoryDescriptor->BasePage + MemoryDescriptor->PageCount > HighestPhysicalPage)
+        {
+            /* Update highest physical page */
+            HighestPhysicalPage = (MemoryDescriptor->BasePage + MemoryDescriptor->PageCount) - 1;
+        }
+
+        /* Check if memory type should be considered as free */
+        if(VerifyMemoryTypeFree(MemoryDescriptor->MemoryType))
+        {
+            /* Check if this descriptor contains more free pages */
+            if(MemoryDescriptor->PageCount >= FreePages)
+            {
+                /* Update free descriptor */
+                FreePages = MemoryDescriptor->PageCount;
+                FreeDescriptor = MemoryDescriptor;
+            }
+        }
+
+        /* Get next memory descriptor */
+        MemoryMappings = MemoryMappings->Flink;
+    }
+
+    /* Store original free descriptor */
+    RTL::Memory::CopyMemory(&OldFreeDescriptor, FreeDescriptor, sizeof(LOADER_MEMORY_DESCRIPTOR));
+}