Kernel: Make SharedMemory inherit from File.

Kernel/File.h

@@ -27,6 +27,7 @@ public:
 
     virtual bool is_seekable() const { return false; }
 
+    virtual bool is_shared_memory() const { return false; }
     virtual bool is_device() const { return false; }
     virtual bool is_tty() const { return false; }
     virtual bool is_master_pty() const { return false; }

Kernel/FileSystem/FileDescriptor.cpp

@@ -23,11 +23,6 @@ Retained<FileDescriptor> FileDescriptor::create(RetainPtr<File>&& file)
     return adopt(*new FileDescriptor(move(file)));
 }
 
-Retained<FileDescriptor> FileDescriptor::create(RetainPtr<SharedMemory>&& shared_memory)
-{
-    return adopt(*new FileDescriptor(move(shared_memory)));
-}
-
 Retained<FileDescriptor> FileDescriptor::create(RetainPtr<Socket>&& socket, SocketRole role)
 {
     return adopt(*new FileDescriptor(move(socket), role));
@@ -53,11 +48,6 @@ FileDescriptor::FileDescriptor(RetainPtr<File>&& file)
 {
 }
 
-FileDescriptor::FileDescriptor(RetainPtr<SharedMemory>&& shared_memory)
-    : m_shared_memory(move(shared_memory))
-{
-}
-
 FileDescriptor::FileDescriptor(RetainPtr<Socket>&& socket, SocketRole role)
     : m_socket(move(socket))
 {
@@ -448,3 +438,22 @@ KResult FileDescriptor::truncate(off_t length)
     ASSERT(is_shared_memory());
     return shared_memory()->truncate(length);
 }
+
+bool FileDescriptor::is_shared_memory() const
+{
+    return m_file && m_file->is_shared_memory();
+}
+
+SharedMemory* FileDescriptor::shared_memory()
+{
+    if (!is_shared_memory())
+        return nullptr;
+    return static_cast<SharedMemory*>(m_file.ptr());
+}
+
+const SharedMemory* FileDescriptor::shared_memory() const
+{
+    if (!is_shared_memory())
+        return nullptr;
+    return static_cast<const SharedMemory*>(m_file.ptr());
+}

Kernel/FileSystem/FileDescriptor.h

@@ -9,7 +9,6 @@
 #include <AK/Retainable.h>
 #include <AK/Badge.h>
 #include <Kernel/Net/Socket.h>
-#include <Kernel/SharedMemory.h>
 
 class File;
 class TTY;
@@ -17,13 +16,13 @@ class MasterPTY;
 class Process;
 class Region;
 class CharacterDevice;
+class SharedMemory;
 
 class FileDescriptor : public Retainable<FileDescriptor> {
 public:
     static Retained<FileDescriptor> create(RetainPtr<Socket>&&, SocketRole = SocketRole::None);
     static Retained<FileDescriptor> create(RetainPtr<Inode>&&);
     static Retained<FileDescriptor> create(RetainPtr<File>&&);
-    static Retained<FileDescriptor> create(RetainPtr<SharedMemory>&&);
     static Retained<FileDescriptor> create_pipe_writer(FIFO&);
     static Retained<FileDescriptor> create_pipe_reader(FIFO&);
     ~FileDescriptor();
@@ -85,9 +84,9 @@ public:
     FIFO::Direction fifo_direction() { return m_fifo_direction; }
 
     bool is_fsfile() const;
-    bool is_shared_memory() const { return m_shared_memory; }
-    SharedMemory* shared_memory() { return m_shared_memory.ptr(); }
-    const SharedMemory* shared_memory() const { return m_shared_memory.ptr(); }
+    bool is_shared_memory() const;
+    SharedMemory* shared_memory();
+    const SharedMemory* shared_memory() const;
 
     ByteBuffer& generator_cache() { return m_generator_cache; }
 
@@ -103,7 +102,6 @@ private:
     FileDescriptor(RetainPtr<Socket>&&, SocketRole);
     explicit FileDescriptor(RetainPtr<Inode>&&);
     explicit FileDescriptor(RetainPtr<File>&&);
-    explicit FileDescriptor(RetainPtr<SharedMemory>&&);
     FileDescriptor(FIFO&, FIFO::Direction);
 
     RetainPtr<Inode> m_inode;
@@ -122,8 +120,6 @@ private:
     RetainPtr<FIFO> m_fifo;
     FIFO::Direction m_fifo_direction { FIFO::Neither };
 
-    RetainPtr<SharedMemory> m_shared_memory;
-
     bool m_closed { false };
 };
 

Kernel/SharedMemory.cpp

@@ -67,3 +67,24 @@ KResult SharedMemory::truncate(int length)
     ASSERT_NOT_REACHED();
     return KResult(-ENOTIMPL);
 }
+
+String SharedMemory::absolute_path() const
+{
+    return String::format("shm:%u", this);
+}
+
+int SharedMemory::read(Process&, byte* buffer, int buffer_size)
+{
+    UNUSED_PARAM(buffer);
+    UNUSED_PARAM(buffer_size);
+    // FIXME: Implement.
+    ASSERT_NOT_REACHED();
+}
+
+int SharedMemory::write(Process&, const byte* data, int data_size)
+{
+    UNUSED_PARAM(data);
+    UNUSED_PARAM(data_size);
+    // FIXME: Implement.
+    ASSERT_NOT_REACHED();
+}

Kernel/SharedMemory.h

@@ -5,14 +5,15 @@
 #include <AK/AKString.h>
 #include <Kernel/KResult.h>
 #include <Kernel/UnixTypes.h>
+#include <Kernel/File.h>
 
 class VMObject;
 
-class SharedMemory : public Retainable<SharedMemory> {
+class SharedMemory : public File {
 public:
     static KResultOr<Retained<SharedMemory>> open(const String& name, int flags, mode_t);
     static KResult unlink(const String& name);
-    ~SharedMemory();
+    virtual ~SharedMemory() override;
 
     String name() const { return m_name; }
     KResult truncate(off_t);
@@ -22,6 +23,15 @@ public:
     gid_t gid() const { return m_gid; }
 
 private:
+    // ^File
+    virtual bool can_read(Process&) const override { return true; }
+    virtual bool can_write(Process&) const override { return true; }
+    virtual int read(Process&, byte*, int) override;
+    virtual int write(Process&, const byte*, int) override;
+    virtual String absolute_path() const override;
+    virtual const char* class_name() const override { return "SharedMemory"; }
+    virtual bool is_shared_memory() const override { return true; }
+
     SharedMemory(const String& name, uid_t, gid_t, mode_t);
 
     String m_name;