fix(vmm): make MMU bring-up and kernel mappings reliable

2026-04-26 23:41:57 +04:00
parent b56b55e4b3
commit 5d010f7fb2
8 changed files with 167 additions and 13 deletions
@@ -0,0 +1,101 @@
+#include <VM/Heap.h>
+#include <VM/PMM.h>
+#include <VM/VMM.h>
+#include <Lib/String.h>
+#include <OS/Panic.h>
+
+static VMHeapBlockHeader* sVMHeapListHead = nullptr;
+
+static void CombineForward(VMHeapBlockHeader* current) {
+    if (!current->next || !current->next->isFree) return;
+    current->size += sizeof(VMHeapBlockHeader) + current->next->size;
+    current->next = current->next->next;
+    if (current->next) current->next->previous = current; // what the fuck
+}
+
+void HeapInitialize() {
+    Address heapStart = kKernelHeapStart;
+
+    for (UInt64 i = 0; i < kHeapSizePages; i++) {
+        Address physical = (Address)PMMAllocatePage();
+        if (!physical) OSPanic("OOM during heap init");
+
+        Address virtual = heapStart + (i * kVMPageSize);
+        VMMMapPage(gVMKernelL0Table, physical, virtual, kPTENormalMem | kPTEAccessRW | kPTEPrivNX | kPTEUserNX);
+    }
+
+    sVMHeapListHead = (VMHeapBlockHeader*)heapStart;
+    sVMHeapListHead->magic = kHeapBlockHeaderMagic;
+    sVMHeapListHead->size = (kHeapSizePages * kVMPageSize) - sizeof(VMHeapBlockHeader);
+    sVMHeapListHead->isFree = true;
+    sVMHeapListHead->next = nullptr;
+    sVMHeapListHead->previous = nullptr;
+}
+
+Pointer HeapAllocate(Size size) {
+    if (size == 0) return nullptr;
+    Size alignedSize = (size + 15) & ~15;
+
+    VMHeapBlockHeader* current = sVMHeapListHead;
+    while (current) {
+        if (current->isFree && current->size >= alignedSize) {
+            if (current->size > alignedSize + sizeof(VMHeapBlockHeader) + 16) {
+                VMHeapBlockHeader* new_block = (VMHeapBlockHeader*)((Address)current + sizeof(VMHeapBlockHeader) + alignedSize);
+                new_block->size = current->size - alignedSize - sizeof(VMHeapBlockHeader);
+                new_block->isFree = true;
+                new_block->next = current->next;
+                new_block->previous = current;
+                new_block->magic = kHeapBlockHeaderMagic;
+                
+                if (current->next) current->next->previous = new_block;
+                current->next = new_block;
+                current->size = alignedSize;
+            }
+            current->isFree = false;
+            return (Pointer)((Address)current + sizeof(VMHeapBlockHeader));
+        }
+        current = current->next;
+    }
+
+    return nullptr;
+}
+
+void HeapFree(Pointer pointer) {
+    if (!pointer) return;
+
+    VMHeapBlockHeader* current = (VMHeapBlockHeader*)((Address)pointer - sizeof(VMHeapBlockHeader));
+    if (current->magic != kHeapBlockHeaderMagic) return;
+    
+    current->isFree = true;
+    if (current->next && current->next->isFree) CombineForward(current);
+    if (current->previous && current->previous->isFree) CombineForward(current->previous);
+}
+
+Pointer HeapResize(Pointer pointer, Size newSize) {
+    if (!pointer) return HeapAllocate(newSize);
+    if (newSize == 0) { 
+        HeapFree(pointer); 
+        return nullptr; 
+    }
+
+    Size alignedSize = (newSize + 15) & ~15;
+
+    VMHeapBlockHeader* current = (VMHeapBlockHeader*)((Address)pointer - sizeof(VMHeapBlockHeader));
+    if (current->size >= alignedSize) {
+        return pointer;
+    }
+
+    if (current->next && current->next->isFree &&
+        (current->size + sizeof(VMHeapBlockHeader) + current->next->size) >= alignedSize) {
+            CombineForward(current);
+            return pointer;
+    }
+
+    Pointer newPointer = HeapAllocate(newSize);
+    if (newPointer) {
+        MemoryCopy(newPointer, pointer, current->size);
+        HeapFree(pointer);
+    }
+
+    return newPointer;
+}