fix: various kernel bug fixes

kernel/src/Memory/Paging.hpp

@@ -117,6 +117,12 @@ public:
         // Skips MMIO/WC pages (WriteThrough or CacheDisabled set in PTE).
         static void FreeUserHalf(std::uint64_t pml4Phys);
 
+        // Validate that every page in the given user range is mapped with
+        // user permissions. If requireWrite is true, all pages must also be
+        // writable.
+        static bool IsUserRangeAccessible(std::uint64_t pml4Phys, std::uint64_t virtualAddress,
+                                          std::uint64_t size, bool requireWrite = false);
+
         // Identity-map EFI runtime service regions so firmware code can
         // reference its own data at physical addresses.
         void MapEfiRuntime(limine_efi_memmap_response* efiMemmap);