feat: start adding physical memory allocator

kernel/include/memory/allocator.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include "memory/pointer.h"
+#include "process/process.h"
+#include "util/optional.h"
+#include "init/multiboot2.h"
+
+constexpr const size_t page_size = 4096;
+
+struct PhysicalAllocator {
+public:
+    struct allocation_t {
+        paddr_t ptr;
+        size_t page_count;
+    };
+    struct entry_t {
+        uint64_t page_count;
+        pid_t owner;
+    };
+    static void init(const multiboot::tag_mmap* multiboot_info);
+    static PhysicalAllocator& getInstance();
+    allocation_t allocPages(size_t page_count, pid_t owner);
+    void free(allocation_t ptr);
+    void force(allocation_t ptr, pid_t owner);
+    entry_t getOwner(paddr_t from);
+private:
+    struct Page {
+        optional<Page*> next;
+        entry_t entries[255];
+        void forceEntry(entry_t entry);
+        void cleanup();
+        void compact();
+    };
+    static_assert(sizeof(Page) == page_size);
+    Page* storage;    
+};
+

kernel/include/memory/pointer.h

@@ -7,13 +7,12 @@ constexpr uint64_t high_base = 0xFFFF800000000000;
 #define read_symbol(symbol) [](){uint64_t res; asm volatile("movabsq $" symbol ", %0": "=r"(res)); return res;}()
 
 struct paddr_t {
-uint64_t address;
-
-template<typename T>
-T* access() {
-    return reinterpret_cast<T*>(address+high_base);
-}
+    uint64_t address;
 
+    template<typename T>
+    T* access() {
+        return reinterpret_cast<T*>(address+high_base);
+    }
 };
 
 inline void* operator new(size_t, void* p) {

kernel/include/memory/sections.h

@@ -17,3 +17,14 @@ void for_each_reserved_section(Fn&& fn) {
     for (auto* s = __reserved_ranges_start__; s < __reserved_ranges_end__; ++s)
         fn(*s);
 }
+
+inline bool is_in_reserved_section(paddr_t ptr, size_t size = 1) {
+    bool res = false;
+    for_each_reserved_section([&](const KernelSection& section) {
+        if (ptr.address < section.phys_end().address &&
+            section.phys_start().address < ptr.address + size) {
+            res = true;
+        }
+    });
+    return res;
+}