Kernel: Fix pseudo terminal writability

kernel/include/kernel/Terminal/PseudoTerminal.h

@@ -27,10 +27,12 @@ namespace Kernel
 		BAN::ErrorOr<size_t> write_impl(off_t, BAN::ConstByteSpan) override;
 
 		bool can_read_impl() const override { SpinLockGuard _(m_buffer_lock); return m_buffer_size > 0; }
-		bool can_write_impl() const override { SpinLockGuard _(m_buffer_lock); return m_buffer_size < m_buffer->size(); }
+		bool can_write_impl() const override { return true; }
 		bool has_error_impl() const override { return false; }
 		bool has_hungup_impl() const override { return !m_slave.valid(); }
 
+		void on_close(int) override;
+
 		BAN::ErrorOr<long> ioctl_impl(int, void*) override;
 
 	private:
@@ -48,6 +50,7 @@ namespace Kernel
 
 		const dev_t m_rdev;
 
+		friend class PseudoTerminalSlave;
 		friend class BAN::RefPtr<PseudoTerminalMaster>;
 	};
 
@@ -62,8 +65,11 @@ namespace Kernel
 		void clear() override;
 
 	protected:
+		bool master_has_closed() const override { return !m_master.valid(); }
+
 		bool putchar_impl(uint8_t ch) override;
 
+		bool can_write_impl() const override;
 		bool has_hungup_impl() const override { return !m_master.valid(); }
 
 		BAN::ErrorOr<long> ioctl_impl(int, void*) override;

kernel/include/kernel/Terminal/Serial.h

@@ -42,18 +42,19 @@ namespace Kernel
 	public:
 		static BAN::ErrorOr<BAN::RefPtr<SerialTTY>> create(Serial);
 
-		virtual uint32_t width() const override;
+		uint32_t width() const override;
-		virtual uint32_t height() const override;
+		uint32_t height() const override;
 
-		virtual void clear() override { putchar_impl('\e'); putchar_impl('['); putchar_impl('2'); putchar_impl('J'); }
+		void clear() override { putchar_impl('\e'); putchar_impl('['); putchar_impl('2'); putchar_impl('J'); }
 
-		virtual void update() override;
+		void update() override;
 
-		virtual void handle_irq() override;
+		void handle_irq() override;
 
 	protected:
-		virtual BAN::StringView name() const override { return m_name; }
+		BAN::StringView name() const override { return m_name; }
-		virtual bool putchar_impl(uint8_t) override;
+		bool putchar_impl(uint8_t) override;
+		bool can_write_impl() const override { return true; }
 
 	private:
 		SerialTTY(Serial);

kernel/include/kernel/Terminal/TTY.h

@@ -66,18 +66,19 @@ namespace Kernel
 		virtual BAN::ErrorOr<long> ioctl_impl(int, void*) override;
 
 		virtual bool can_read_impl() const override { return m_output.flush; }
-		virtual bool can_write_impl() const override { return true; }
 		virtual bool has_error_impl() const override { return false; }
 		virtual bool has_hungup_impl() const override { return false; }
 
+		virtual bool master_has_closed() const { return false; }
+
 	protected:
 		TTY(termios termios, mode_t mode, uid_t uid, gid_t gid);
 
 		virtual bool putchar_impl(uint8_t ch) = 0;
-		virtual void update_cursor() {}
+		virtual void after_write() {}
 
-		virtual BAN::ErrorOr<size_t> read_impl(off_t, BAN::ByteSpan) override;
+		virtual BAN::ErrorOr<size_t> read_impl(off_t, BAN::ByteSpan) final override;
-		virtual BAN::ErrorOr<size_t> write_impl(off_t, BAN::ConstByteSpan) override;
+		virtual BAN::ErrorOr<size_t> write_impl(off_t, BAN::ConstByteSpan) final override;
 
 	private:
 		bool putchar(uint8_t ch);
@@ -110,6 +111,7 @@ namespace Kernel
 
 	protected:
 		RecursiveSpinLock m_write_lock;
+		ThreadBlocker m_write_blocker;
 	};
 
 }

kernel/include/kernel/Terminal/VirtualTTY.h

@@ -17,17 +17,18 @@ namespace Kernel
 	public:
 		static BAN::ErrorOr<BAN::RefPtr<VirtualTTY>> create(BAN::RefPtr<TerminalDriver>);
 
-		virtual BAN::ErrorOr<void> set_font(LibFont::Font&&) override;
+		BAN::ErrorOr<void> set_font(LibFont::Font&&) override;
 
-		virtual uint32_t height() const override { return m_height; }
+		uint32_t height() const override { return m_height; }
-		virtual uint32_t width() const override { return m_width; }
+		uint32_t width() const override { return m_width; }
 
-		virtual void clear() override;
+		void clear() override;
 
 	protected:
-		virtual BAN::StringView name() const override { return m_name; }
+		BAN::StringView name() const override { return m_name; }
-		virtual bool putchar_impl(uint8_t ch) override;
+		bool putchar_impl(uint8_t ch) override;
-		void update_cursor() override;
+		bool can_write_impl() const override { return true; }
+		void after_write() override;
 
 	private:
 		VirtualTTY(BAN::RefPtr<TerminalDriver>);

kernel/kernel/OpenFileDescriptorSet.cpp

@@ -360,7 +360,7 @@ namespace Kernel
 		{
 			LockGuard _(inode->m_mutex);
 			if (is_nonblock && !inode->can_read())
-				return 0;
+				return BAN::Error::from_errno(EAGAIN);
 			nread = TRY(inode->read(offset, buffer));
 		}
 
@@ -395,7 +395,7 @@ namespace Kernel
 		{
 			LockGuard _(inode->m_mutex);
 			if (is_nonblock && !inode->can_write())
-				return BAN::Error::from_errno(EWOULDBLOCK);
+				return BAN::Error::from_errno(EAGAIN);
 			nwrite = TRY(inode->write(offset, buffer));
 		}
 

kernel/kernel/Terminal/PseudoTerminal.cpp

@@ -130,6 +130,9 @@ namespace Kernel
 		m_buffer_size -= to_copy;
 		m_buffer_tail = (m_buffer_tail + to_copy) % m_buffer->size();
 
+		if (auto slave = m_slave.lock())
+			slave->m_write_blocker.unblock();
+
 		epoll_notify(EPOLLOUT);
 
 		return to_copy;
@@ -139,12 +142,18 @@ namespace Kernel
 	{
 		auto slave = m_slave.lock();
 		if (!slave)
-			return BAN::Error::from_errno(ENODEV);
+			return BAN::Error::from_errno(EIO);
 		for (size_t i = 0; i < buffer.size(); i++)
 			slave->handle_input_byte(buffer[i]);
 		return buffer.size();
 	}
 
+	void PseudoTerminalMaster::on_close(int)
+	{
+		if (auto slave = m_slave.lock())
+			slave->m_write_blocker.unblock();
+	}
+
 	BAN::ErrorOr<long> PseudoTerminalMaster::ioctl_impl(int request, void* argument)
 	{
 		auto slave = m_slave.lock();
@@ -186,6 +195,15 @@ namespace Kernel
 		return false;
 	}
 
+	bool PseudoTerminalSlave::can_write_impl() const
+	{
+		auto master = m_master.lock();
+		if (!master)
+			return false;
+		SpinLockGuard _(master->m_buffer_lock);
+		return master->m_buffer_size < master->m_buffer->size();
+	}
+
 	BAN::ErrorOr<long> PseudoTerminalSlave::ioctl_impl(int request, void* argument)
 	{
 		switch (request)

kernel/kernel/Terminal/TTY.cpp

@@ -219,7 +219,7 @@ namespace Kernel
 			auto* ptr = reinterpret_cast<const uint8_t*>(ansi_c_str);
 			while (*ptr)
 				handle_input_byte(*ptr++);
-			update_cursor();
+			after_write();
 		}
 	}
 
@@ -297,12 +297,8 @@ namespace Kernel
 
 		if (should_append)
 		{
-			// FIXME: don't ignore these bytes
 			if (m_output.bytes >= m_output.buffer.size())
-			{
-				dwarnln("TTY input full");
 				return;
-			}
 			m_output.buffer[m_output.bytes++] = ch;
 		}
 
@@ -405,6 +401,8 @@ namespace Kernel
 
 		if (m_output.bytes == 0)
 		{
+			if (master_has_closed())
+				return 0;
 			m_output.flush = false;
 			return 0;
 		}
@@ -431,6 +429,13 @@ namespace Kernel
 
 	BAN::ErrorOr<size_t> TTY::write_impl(off_t, BAN::ConstByteSpan buffer)
 	{
+		while (!can_write_impl())
+		{
+			if (master_has_closed())
+				return BAN::Error::from_errno(EIO);
+			TRY(Thread::current().block_or_eintr_indefinite(m_write_blocker, &m_mutex));
+		}
+
 		size_t written = 0;
 
 		{
@@ -438,7 +443,7 @@ namespace Kernel
 			for (; written < buffer.size(); written++)
 				if (!putchar(buffer[written]))
 					break;
-			update_cursor();
+			after_write();
 		}
 
 		if (can_write_impl())
@@ -452,7 +457,7 @@ namespace Kernel
 		ASSERT(s_tty);
 		SpinLockGuard _(s_tty->m_write_lock);
 		s_tty->putchar(ch);
-		s_tty->update_cursor();
+		s_tty->after_write();
 	}
 
 	bool TTY::is_initialized()

kernel/kernel/Terminal/VirtualTTY.cpp

@@ -577,7 +577,7 @@ namespace Kernel
 		return true;
 	}
 
-	void VirtualTTY::update_cursor()
+	void VirtualTTY::after_write()
 	{
 		if (m_cursor_shown != m_last_cursor_shown)
 			m_terminal_driver->set_cursor_shown(m_cursor_shown);