fix: kernel concurrency, interrupt context, and user VA safety

kernel/src/CppLib/Spinlock.cpp

@@ -7,18 +7,29 @@
 #include "Spinlock.hpp"
 
 namespace kcp {
-    void Spinlock::Acquire() {
+    uint64_t Spinlock::AcquireIrqSave() {
         uint64_t flags;
         asm volatile("pushfq; pop %0; cli" : "=r"(flags) :: "memory");
         while (atomic_flag.test_and_set(std::memory_order_acquire)) {
             asm volatile("pause");
         }
-        savedFlags = flags;
+        return flags;
     }
 
-    void Spinlock::Release() {
-        uint64_t flags = savedFlags;
+    void Spinlock::ReleaseIrqRestore(uint64_t flags) {
         atomic_flag.clear(std::memory_order_release);
         asm volatile("push %0; popfq" :: "r"(flags) : "memory");
     }
-};
+
+    void Spinlock::ReleaseIrqNoRestore() {
+        atomic_flag.clear(std::memory_order_release);
+    }
+
+    void Spinlock::Acquire() {
+        savedFlags = AcquireIrqSave();
+    }
+
+    void Spinlock::Release() {
+        ReleaseIrqRestore(savedFlags);
+    }
+};