Kernel: Ensure proper locking when mutating boot console cursor

The BootFramebufferConsole highly depends on using the m_lock spinlock,
therefore setting and changing the cursor state should be done under
that spinlock too to avoid crashing.

Kernel/Graphics/Console/BootFramebufferConsole.cpp

@@ -71,6 +71,31 @@ void BootFramebufferConsole::write(size_t x, size_t y, char ch, Color background
         GenericFramebufferConsoleImpl::write(x, y, ch, background, foreground, critical);
 }
 
+void BootFramebufferConsole::set_cursor(size_t x, size_t y)
+{
+    // Note: To ensure we don't trigger a deadlock, let's assert in
+    // case we already locked the spinlock, so we know there's a bug
+    // in the call path.
+    VERIFY(!m_lock.is_locked());
+    SpinlockLocker lock(m_lock);
+    hide_cursor();
+    m_x = x;
+    m_y = y;
+    show_cursor();
+}
+
+void BootFramebufferConsole::hide_cursor()
+{
+    VERIFY(m_lock.is_locked());
+    GenericFramebufferConsoleImpl::hide_cursor();
+}
+
+void BootFramebufferConsole::show_cursor()
+{
+    VERIFY(m_lock.is_locked());
+    GenericFramebufferConsoleImpl::show_cursor();
+}
+
 u8* BootFramebufferConsole::framebuffer_data()
 {
     VERIFY(m_lock.is_locked());

Kernel/Graphics/Console/BootFramebufferConsole.h

@@ -30,6 +30,11 @@ public:
     BootFramebufferConsole(PhysicalAddress framebuffer_addr, size_t width, size_t height, size_t pitch);
 #endif
 
+private:
+    virtual void set_cursor(size_t x, size_t y) override;
+    virtual void hide_cursor() override;
+    virtual void show_cursor() override;
+
 protected:
     virtual void clear_glyph(size_t x, size_t y) override;