make bluescreen demo more general for paging

c_os/user/demo/BlueScreenDemo.cc

@@ -1,20 +0,0 @@
-#include "user/demo/BlueScreenDemo.h"
-#include "kernel/Paging.h"
-
-void BlueScreenDemo::run() {
-    kout << "Trigger Bluescreen, if you can read this it didn't work" << endl;
-
-    // BlueScreen 1
-    // asm("int $3");
-
-    // BlueScreen 2
-    unsigned int* page = pg_alloc_page();
-    *page = 42;
-    pg_write_protect_page(page);
-    invalidate_tlb_entry(page); // If we don't invalidate after first access the write protection
-                                // won't work as no lookup is performed (address in tlb)
-    *page = 42; // We map logical to physical 1:1 so no need to do any lookup
-                // If tlb is invalidated this access produces a pagefault
-
-    scheduler.exit();
-}

c_os/user/demo/BlueScreenDemo.h

@@ -1,16 +0,0 @@
-#ifndef BlueScreenDemo_include__
-#define BlueScreenDemo_include__
-
-#include "kernel/Globals.h"
-#include "kernel/threads/Thread.h"
-
-class BlueScreenDemo : public Thread {
-public:
-    BlueScreenDemo(const BlueScreenDemo& copy) = delete;
-
-    BlueScreenDemo() : Thread("BlueScreenDemo") {}
-
-    void run() override;
-};
-
-#endif

c_os/user/demo/PagingDemo.cc

@@ -0,0 +1,51 @@
+#include "user/demo/PagingDemo.h"
+#include "kernel/Paging.h"
+
+void PagingDemo::writeprotect_page() {
+    kout << "Accessing a writeprotected page triggers bluescreen,\nif you can read this it didn't work" << endl;
+
+    // BlueScreen 1
+    // asm("int $3");
+
+    // BlueScreen 2
+    log.info() << "Allocating page" << endl;
+    unsigned int* page = pg_alloc_page();
+    *page = 42;
+    log.info() << "Writeprotecting page..." << endl;
+    pg_write_protect_page(page);
+
+    log.info() << "Accessing writeprotected page" << endl;
+    *page = 42; // We map logical to physical 1:1 so no need to do any lookup
+
+    // No free because bluescreen
+}
+
+void PagingDemo::notpresent_page() {
+    kout << "Produces pagefault, if you can read this it didn't work" << endl;
+
+    log.info() << "Allocating page" << endl;
+    unsigned int* page = pg_alloc_page();
+    *page = 42;
+
+    log.info() << "Marking page notpresent..." << endl;
+    pg_notpresent_page(page);
+
+    log.info() << "Accessing page" << endl;
+    kout << "Page not accessible: " << *page << endl;
+
+    // No free because bluescreen
+}
+
+void PagingDemo::run() {
+    kout << "Press w for writeprotect demo, n for notpresent demo" << endl;
+    switch(listener.waitForKeyEvent()) {
+    case 'w':
+        writeprotect_page();
+        break;
+    case 'n':
+        notpresent_page();
+        break;
+    }
+
+    scheduler.exit();
+}

c_os/user/demo/PagingDemo.h

@@ -0,0 +1,30 @@
+#ifndef BlueScreenDemo_include__
+#define BlueScreenDemo_include__
+
+#include "kernel/Globals.h"
+#include "kernel/threads/Thread.h"
+#include "user/event/KeyEventListener.h"
+
+class PagingDemo: public Thread {
+private:
+    void writeprotect_page();
+    void free_page();
+    void notpresent_page();
+
+    KeyEventListener listener;
+
+public:
+    PagingDemo(const PagingDemo& copy) = delete;
+
+    PagingDemo(): Thread("PagingDemo"), listener(tid) {
+        kevman.subscribe(listener);
+    }
+
+    ~PagingDemo() override {
+        kevman.unsubscribe(listener);
+    }
+
+    void run() override;
+};
+
+#endif