genode/base-hw/include/base/pager.h

/*
 * \brief  Paging framework
 * \author Martin Stein
 * \date   2013-11-07
 */

/*
 * Copyright (C) 2013 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _BASE__PAGER_H_
#define _BASE__PAGER_H_

/* Genode includes */
#include <base/thread.h>
#include <base/object_pool.h>
#include <base/signal.h>
#include <pager/capability.h>

/* base-hw includes */
#include <placement_new.h>

namespace Genode
{
	class Cap_session;

	/**
	 * Translation of a virtual page frame
	 */
	struct Mapping;

	/**
	 * Interface between the generic paging system and the base-hw backend
	 */
	class Ipc_pager;

	/**
	 * Represents a faulter and its paging context
	 */
	class Pager_object;

	/**
	 * Paging entry point that manages a pool of pager objects
	 */
	class Pager_entrypoint;

	/**
	 * A thread that processes one page fault of a pager object at a time
	 */
	class Pager_activation_base;

	/**
	 * Pager-activation base with custom stack size
	 */
	template <unsigned STACK_SIZE> class Pager_activation;
}

struct Genode::Mapping
{
	addr_t   virt_address;
	addr_t   phys_address;
	bool     write_combined;
	bool     io_mem;
	unsigned size_log2;
	bool     writable;

	/**
	 * Constructor for invalid mappings
	 */
	Mapping();

	/**
	 * Constructor for valid mappings
	 */
	Mapping(addr_t const va, addr_t const pa, bool const wc,
	        bool const io, unsigned const sl2, bool const w);

	/**
	 * Prepare for the application of the mapping
	 */
	void prepare_map_operation();
};

class Genode::Ipc_pager
{
	protected:

		/**
		 * Page-fault data that is read from the faulters thread registers
		 */
		struct Fault_thread_regs
		{
			addr_t pd;
			addr_t ip;
			addr_t addr;
			addr_t writes;
			addr_t signal;
		};

		Fault_thread_regs _fault;
		Mapping           _mapping;

	public:

		/**
		 * Instruction pointer of current page fault
		 */
		addr_t fault_ip() const;

		/**
		 * Faulter-local fault address of current page fault
		 */
		addr_t fault_addr() const;

		/**
		 * Access direction of current page fault
		 */
		bool is_write_fault() const;

		/**
		 * Input mapping data as reply to current page fault
		 */
		void set_reply_mapping(Mapping m);
};

class Genode::Pager_object : public Object_pool<Pager_object>::Entry,
                             public Signal_context
{
	friend class Pager_entrypoint;

	private:

		Signal_context_capability _signal_context_cap;
		Thread_capability         _thread_cap;
		bool                      _signal_valid;
		char                      _signal_buf[sizeof(Signal)];
		unsigned const            _badge;

		/**
		 * Remember an incoming fault for handling
		 *
		 * \param s  fault signal
		 */
		void _take_fault(Signal const & s)
		{
			new (_signal_buf) Signal(s);
			_signal_valid = 1;
		}

		/**
		 * End handling of current fault
		 */
		void _end_fault()
		{
			_signal()->~Signal();
			_signal_valid = 0;
		}

		/**
		 * End handling of current fault if there is one
		 */
		void _end_fault_if_pending()
		{
			if (_signal_valid) { _end_fault(); }
		}


		/***************
		 ** Accessors **
		 ***************/

		Signal * _signal() const;

	public:

		/**
		 * Constructor
		 *
		 * \param badge  user identifaction of pager object
		 */
		Pager_object(unsigned const badge, Affinity::Location);

		/**
		 * The faulter has caused a fault and awaits paging
		 *
		 * \param s  signal that communicated the fault
		 */
		void fault_occured(Signal const & s) { _take_fault(s); }

		/**
		 * Current fault has been resolved so resume faulter
		 */
		void fault_resolved() { _end_fault(); }

		/**
		 * User identification of pager object
		 */
		unsigned badge() const { return _badge; }

		/**
		 * Resume faulter
		 */
		void wake_up();

		/**
		 * Unnecessary as base-hw doesn't use exception handlers
		 */
		void exception_handler(Signal_context_capability);

		/**
		 * Install information that is necessary to handle page faults
		 *
		 * \param c  linkage between signal context and a signal receiver
		 * \param p  linkage between pager object and a pager entry-point
		 */
		void start_paging(Signal_context_capability const & c,
		                  Pager_capability const & p)
		{
			_signal_context_cap = c;
			Object_pool<Pager_object>::Entry::cap(p);
		}

		/**
		 * Uninstall paging information and cancel unresolved faults
		 */
		void stop_paging()
		{
			Object_pool<Pager_object>::Entry::cap(Native_capability());
			_signal_context_cap = Signal_context_capability();
			_end_fault_if_pending();
		}


		/******************
		 ** Pure virtual **
		 ******************/

		/**
		 * Request a mapping that resolves a fault directly
		 *
		 * \param p  offers the fault data and receives mapping data
		 *
		 * \retval   0  succeeded
		 * \retval !=0  fault can't be received directly
		 */
		virtual int pager(Ipc_pager & p) = 0;


		/***************
		 ** Accessors **
		 ***************/

		Thread_capability thread_cap() const;

		void thread_cap(Thread_capability const & c);

		unsigned signal_context_id() const;
};

class Genode::Pager_activation_base : public Thread_base,
                                      public Signal_receiver,
                                      public Ipc_pager
{
	private:

		Native_capability  _cap;
		Lock               _cap_valid;
		Pager_entrypoint * _ep;

	public:

		/**
		 * Constructor
		 *
		 * \param name        name of the new thread
		 * \param stack_size  stack size of the new thread
		 */
		Pager_activation_base(char const * const name,
		                      size_t const stack_size);

		/**
		 * Bring current mapping data into effect
		 *
		 * \retval  0  succeeded
		 * \retval -1  failed
		 */
		int apply_mapping();


		/**********************
		 ** Thread interface **
		 **********************/

		void entry();


		/***************
		 ** Accessors **
		 ***************/

		Native_capability cap();

		void ep(Pager_entrypoint * const ep);
};

class Genode::Pager_entrypoint : public Object_pool<Pager_object>
{
	private:

		Pager_activation_base * const _activation;

	public:

		/**
		 * Constructor
		 *
		 * \param a  activation that shall handle the objects of the entrypoint
		 */
		Pager_entrypoint(Cap_session *, Pager_activation_base * const a);

		/**
		 * Associate pager object 'obj' with entry point
		 */
		Pager_capability manage(Pager_object * const obj);

		/**
		 * Dissolve pager object 'obj' from entry point
		 */
		void dissolve(Pager_object * const obj);
};

template <unsigned STACK_SIZE>
class Genode::Pager_activation : public Pager_activation_base
{
	public:

		/**
		 * Constructor
		 */
		Pager_activation()
		:
			Pager_activation_base("pager_activation", STACK_SIZE)
		{
			start();
		}
};

#endif /* _BASE__PAGER_H_ */