Added a PhysicalMemoryManager class.

Stores a linkedlist of free blocks of PhysicalMemory.

zion/memory/physical_memory.cpp

@@ -15,6 +15,69 @@ struct BootstrapMemory {
 static BootstrapMemory gBootstrap;
 static bool gBootstrapEnabled = false;
 
+class PhysicalMemoryManager {
+ public:
+  // Reads the memory map and takes
+  // control of the available regions.
+  PhysicalMemoryManager() {
+    const limine_memmap_response& memmap = boot::GetMemoryMap();
+    for (uint64_t i = 0; i < memmap.entry_count; i++) {
+      const limine_memmap_entry& entry = *memmap.entries[i];
+      if (entry.type == 0) {
+        uint64_t base = entry.base;
+        uint64_t size = entry.length;
+        if (base == gBootstrap.init_page) {
+          base = gBootstrap.next_page;
+          uint64_t bootstrap_used = gBootstrap.next_page - gBootstrap.init_page;
+          dbgln("[PMM] Taking over from bootstrap, used: %x", bootstrap_used);
+          size -= bootstrap_used;
+        }
+        AddMemoryRegion(base, size);
+      }
+    }
+  }
+
+  uint64_t AllocatePage() {
+    if (front_ == nullptr) {
+      panic("No available memory regions.");
+    }
+
+    if (front_->num_pages == 0) {
+      panic("Bad state, empty memory block.");
+    }
+
+    uint64_t page = front_->base;
+    front_->base += 0x1000;
+    front_->num_pages--;
+    if (front_->num_pages == 0) {
+      MemBlock* temp = front_;
+      front_ = front_->next;
+      delete temp;
+    }
+    return page;
+  }
+  void FreePage(uint64_t page) { AddMemoryRegion(page, 0x1000); }
+
+ private:
+  void AddMemoryRegion(uint64_t base, uint64_t size) {
+    MemBlock* block = new MemBlock{
+        .next = front_,
+        .base = base,
+        .num_pages = size >> 12,
+    };
+    front_ = block;
+  }
+  struct MemBlock {
+    MemBlock* next = nullptr;
+    uint64_t base = 0;
+    uint64_t num_pages = 0;
+  };
+
+  MemBlock* front_ = nullptr;
+};
+
+static PhysicalMemoryManager* gPmm = nullptr;
+
 };  // namespace
 
 void InitBootstrapPageAllocation() {
@@ -36,11 +99,18 @@ void InitBootstrapPageAllocation() {
   }
 }
 
+void InitPhysicalMemoryManager() { gPmm = new PhysicalMemoryManager(); }
+
 uint64_t AllocatePage() {
+  if (gPmm != nullptr) {
+    return gPmm->AllocatePage();
+  }
   if (!gBootstrapEnabled) {
     panic("No Bootstrap Memory Manager");
   }
 
+  dbgln("[PMM] Boostrap Alloc!");
+
   uint64_t page = gBootstrap.next_page;
   if (page == gBootstrap.max_page) {
     panic("Bootstrap Memory Manager OOM");

zion/zion.cpp

@@ -14,7 +14,8 @@ extern "C" void zion() {
 
   phys_mem::InitBootstrapPageAllocation();
   KernelHeap heap(0xFFFFFFFF'40000000, 0xFFFFFFFF'80000000);
-  heap.Allocate(1);
+  phys_mem::InitPhysicalMemoryManager();
+  heap.Allocate(0x2000);
 
   dbgln("Sleeping!");
   while (1)