feat: overhaul userspace heap and virtual memory

kernel/src/Memory/Paging.hpp

@@ -104,6 +104,17 @@ public:
         // Map a page into an arbitrary PML4 (specified by physical address) with User bit set.
         static bool MapUserIn(std::uint64_t pml4Phys, std::uint64_t physicalAddress, std::uint64_t virtualAddress);
 
+        // Map ordinary user memory with explicit leaf permissions. Read access
+        // is implied by x86 paging; writable and executable are independent.
+        static bool MapUserInPermissions(std::uint64_t pml4Phys,
+                                         std::uint64_t physicalAddress,
+                                         std::uint64_t virtualAddress,
+                                         bool writable, bool executable);
+
+        // Change leaf permissions on an existing user page.
+        static bool ProtectUserIn(std::uint64_t pml4Phys, std::uint64_t virtualAddress,
+                                  bool writable, bool executable);
+
         // Map a page into an arbitrary PML4 with User + Write-Combining attributes.
         static bool MapUserInWC(std::uint64_t pml4Phys, std::uint64_t physicalAddress, std::uint64_t virtualAddress);