Kernel: Reading from a slave PTY should give EOF if master PTY is closed.

Kernel/MasterPTY.cpp

@@ -69,3 +69,12 @@ bool MasterPTY::can_write_from_slave() const
 {
     return m_buffer.bytes_in_write_buffer() < 4096;
 }
+
+void MasterPTY::close()
+{
+    if (retain_count() == 2) {
+        // After the closing FileDescriptor dies, slave is the only thing keeping me alive.
+        // From this point, let's consider ourselves closed.
+        m_closed = true;
+    }
+}

Kernel/MasterPTY.h

@@ -11,24 +11,25 @@ public:
     explicit MasterPTY(unsigned index);
     virtual ~MasterPTY() override;
 
-    // ^CharacterDevice
-    virtual ssize_t read(Process&, byte*, size_t) override;
-    virtual ssize_t write(Process&, const byte*, size_t) override;
-    virtual bool can_read(Process&) const override;
-    virtual bool can_write(Process&) const override;
-    virtual bool is_master_pty() const override { return true; }
-
     unsigned index() const { return m_index; }
     String pts_name() const;
     void on_slave_write(const byte*, size_t);
     bool can_write_from_slave() const;
     void notify_slave_closed(Badge<SlavePTY>);
+    bool is_closed() const { return m_closed; }
 
 private:
     // ^CharacterDevice
+    virtual ssize_t read(Process&, byte*, size_t) override;
+    virtual ssize_t write(Process&, const byte*, size_t) override;
+    virtual bool can_read(Process&) const override;
+    virtual bool can_write(Process&) const override;
+    virtual void close() override;
+    virtual bool is_master_pty() const override { return true; }
     virtual const char* class_name() const override { return "MasterPTY"; }
 
     RetainPtr<SlavePTY> m_slave;
     unsigned m_index;
+    bool m_closed { false };
     DoubleBuffer m_buffer;
 };

Kernel/SlavePTY.cpp

@@ -43,6 +43,20 @@ bool SlavePTY::can_write(Process&) const
     return m_master->can_write_from_slave();
 }
 
+bool SlavePTY::can_read(Process& process) const
+{
+    if (m_master->is_closed())
+        return true;
+    return TTY::can_read(process);
+}
+
+ssize_t SlavePTY::read(Process& process, byte* buffer, size_t size)
+{
+    if (m_master->is_closed())
+        return 0;
+    return TTY::read(process, buffer, size);
+}
+
 void SlavePTY::close()
 {
     m_master->notify_slave_closed(Badge<SlavePTY>());

Kernel/SlavePTY.h

@@ -20,6 +20,8 @@ private:
     virtual void on_tty_write(const byte*, size_t) override;
 
     // ^CharacterDevice
+    virtual bool can_read(Process&) const override;
+    virtual ssize_t read(Process&, byte*, size_t) override;
     virtual bool can_write(Process&) const override;
     virtual const char* class_name() const override { return "SlavePTY"; }
     virtual void close() override;

Userland/sh.cpp

@@ -410,6 +410,8 @@ int main(int argc, char** argv)
     for (;;) {
         char keybuf[16];
         ssize_t nread = read(0, keybuf, sizeof(keybuf));
+        if (nread == 0)
+            return 0;
         if (nread < 0) {
             if (errno == EINTR) {
                 ASSERT(g->was_interrupted);