feat: completely functional PMM

2026-04-26 15:12:04 +04:00
parent 785a61b451
commit 55335013a9
4 changed files with 78 additions and 9 deletions
@@ -1,4 +1,8 @@
 #include <VM/PMM.h>
+#include <Lib/String.h>
+
+extern char _kernelStart[];
+extern char _kernelEnd[];

 static inline Size BitmapGetByteIndex(Address address) {
    return (address / kVMPageSize) / kVMBlocksPerByte;
@@ -20,3 +24,60 @@ static inline void BitmapUnset(MemoryPointer bitmap, Address address) {
    bitmap[BitmapGetByteIndex(address)] &= ~(1U << BitmapGetBitOffset(address));
 }

+static MemoryPointer sPMMBitmap;
+static Size sPMMBitmapSize;
+static Size sPMMTotalPages;
+
+void PMMInitialize(VMBootMemoryMap* bootMap) {
+    UInt32 vIndex = bootMap->reservedCount;
+    bootMap->reserved[vIndex].base = 0x0;
+    bootMap->reserved[vIndex].size = bootMap->totalRAM.base; 
+    bootMap->reservedCount++;
+    
+    UInt32 kIndex = bootMap->reservedCount;
+    bootMap->reserved[kIndex].base = (Address)_kernelStart;
+    bootMap->reserved[kIndex].size = (Address)_kernelEnd - (Address)_kernelStart;
+    bootMap->reservedCount++;
+
+    sPMMTotalPages = bootMap->totalRAM.size / kVMPageSize;
+    sPMMBitmapSize = sPMMTotalPages / kVMBlocksPerByte;
+    sPMMBitmap = (MemoryPointer)_kernelEnd;
+
+    StringSet(sPMMBitmap, 0, sPMMBitmapSize);
+
+    UInt32 bIndex = bootMap->reservedCount;
+    bootMap->reserved[bIndex].base = (Address)sPMMBitmap;
+    bootMap->reserved[bIndex].size = sPMMBitmapSize;
+    bootMap->reservedCount++;
+
+    for (Size i = 0; i < bootMap->reservedCount; i++) {
+        Address regionBase = bootMap->reserved[i].base;
+        Size regionSize = bootMap->reserved[i].size;
+
+        Size pagesToReserve = (regionSize + kVMPageSize - 1) / kVMPageSize;
+
+        for (Size p = 0; p < pagesToReserve; p++) {
+            Address pageAdress = regionBase + (p * kVMPageSize);
+            BitmapSet(sPMMBitmap, pageAdress);
+        }
+    }
+}
+
+Pointer PMMAllocatePage() {
+    for (Size i = 0; i < sPMMBitmapSize; i++) {
+        if (sPMMBitmap[i] == 0xFF) continue;
+        for (Size bit = 0; bit < kVMBlocksPerByte; bit++) {
+            if ((sPMMBitmap[i] & (1 << bit)) == 0) {
+                Address address = (i * kVMBlocksPerByte + bit) * kVMPageSize;
+                BitmapSet(sPMMBitmap, address);
+                return (Pointer)address;
+            }
+        }
+    }
+
+    return nullptr;
+}
+
+void PMMFreePage(Address address) {
+    BitmapUnset(sPMMBitmap, address);
+}