kernel: Add /dev/full

kernel/CMakeLists.txt

@@ -47,6 +47,7 @@ set(SOURCES
     src/fs/devices/DeviceRegistry.cpp
     src/fs/devices/NullDevice.cpp
     src/fs/devices/ZeroDevice.cpp
+    src/fs/devices/FullDevice.cpp
     src/fs/devices/ConsoleDevice.cpp
     src/fs/devices/FramebufferDevice.cpp
     src/fs/InitRD.cpp

kernel/src/fs/devices/DeviceRegistry.cpp

@@ -3,6 +3,7 @@
 #include "fs/VFS.h"
 #include "fs/devices/ConsoleDevice.h"
 #include "fs/devices/FramebufferDevice.h"
+#include "fs/devices/FullDevice.h"
 #include "fs/devices/NullDevice.h"
 #include "fs/devices/ZeroDevice.h"
 #include "fs/tmpfs/FileSystem.h"
@@ -69,6 +70,7 @@ namespace DeviceRegistry
 
         NullDevice::create();
         ZeroDevice::create();
+        FullDevice::create();
         ConsoleDevice::create();
         FramebufferDevice::create();
 

kernel/src/fs/devices/FullDevice.cpp

@@ -0,0 +1,7 @@
+#include "fs/devices/FullDevice.h"
+
+Result<void> FullDevice::create()
+{
+    auto device = (SharedPtr<Device>)TRY(make_shared<FullDevice>());
+    return DeviceRegistry::register_special_device(DeviceRegistry::Memory, 2, device, "full");
+}

kernel/src/fs/devices/FullDevice.h

@@ -0,0 +1,28 @@
+#pragma once
+#include "fs/devices/DeviceRegistry.h"
+
+class FullDevice : public Device
+{
+  public:
+    // Initializer for DeviceRegistry.
+    static Result<void> create();
+
+    Result<usize> read(u8* buf, usize, usize length) const override
+    {
+        __builtin_memset(buf, 0, length);
+
+        return length;
+    }
+
+    Result<usize> write(const u8*, usize, usize) override
+    {
+        return err(ENOSPC);
+    }
+
+    bool blocking() const override
+    {
+        return false;
+    }
+
+    virtual ~FullDevice() = default;
+};