br_manager

// vi:set ft=cpp: -*- Mode: C++ -*-
/*
 * (c) 2014 Alexander Warg <alexander.warg@kernkonzept.com>
 *
 * This file is part of TUD:OS and distributed under the terms of the
 * GNU General Public License 2.
 * Please see the COPYING-GPL-2 file for details.
 *
 * As a special exception, you may use this file as part of a free software
 * library without restriction.  Specifically, if other files instantiate
 * templates or use macros or inline functions from this file, or you compile
 * this file and link it with other files to produce an executable, this
 * file does not by itself cause the resulting executable to be covered by
 * the GNU General Public License.  This exception does not however
 * invalidate any other reasons why the executable file might be covered by
 * the GNU General Public License.
 */
 
#pragma once
 
#include <l4/re/util/cap_alloc>
#include <l4/sys/cxx/ipc_server_loop>
#include <l4/cxx/ipc_timeout_queue>
#include <l4/sys/assert.h>
 
namespace L4Re { namespace Util {
 
class Br_manager : public L4::Ipc_svr::Server_iface
{
private:
  enum { _mem = 0, _ports = 0 };
  enum { Brs_per_timeout = sizeof(l4_kernel_clock_t) / sizeof(l4_umword_t) };
 
public:
  Br_manager() : _caps(0), _cap_flags(L4_RCV_ITEM_LOCAL_ID) {}
 
  Br_manager(Br_manager const &) = delete;
  Br_manager &operator = (Br_manager const &) = delete;
 
  Br_manager(Br_manager &&) = delete;
  Br_manager &operator = (Br_manager &&) = delete;
 
  ~Br_manager()
  {
    // Slots for received capabilities are placed at the beginning of the
    // (shadowed) buffer registers. Free those.
    for (unsigned i = 0; i < _caps; ++i)
      cap_alloc.free(L4::Cap<void>(_brs[i] & L4_CAP_MASK));
  }
 
  /*
   * This implementation dynamically manages assignment of buffer registers for
   * the necessary amount of receive buffers allocated by all calls to this
   * function.
   */
  int alloc_buffer_demand(Demand const &d) override
  {
    using L4::Ipc::Small_buf;
 
    // memory and IO port receive windows currently not supported
    if (d.mem || d.ports)
      return -L4_EINVAL;
 
    // take extra buffers for a possible timeout and for a zero terminator
    if (d.caps + d.mem * 2 + d.ports * 2 + Brs_per_timeout + 1
        > L4_UTCB_GENERIC_BUFFERS_SIZE)
      return -L4_ERANGE;
 
    if (d.caps > _caps)
      {
        while (_caps < d.caps)
          {
            L4::Cap<void> cap = cap_alloc.alloc();
            if (!cap)
              return -L4_ENOMEM;
 
            reinterpret_cast<Small_buf&>(_brs[_caps])
              = Small_buf(cap.cap(), _cap_flags);
            ++_caps;
          }
        _brs[_caps] = 0;
      }
 
    return L4_EOK;
  }
 
 
  L4::Cap<void> get_rcv_cap(int i) const override
  {
    if (i < 0 || i >= _caps)
      return L4::Cap<void>::Invalid;
 
    return L4::Cap<void>(_brs[i] & L4_CAP_MASK);
  }
 
  int realloc_rcv_cap(int i) override
  {
    using L4::Ipc::Small_buf;
 
    if (i < 0 || i >= _caps)
      return -L4_EINVAL;
 
    L4::Cap<void> cap = cap_alloc.alloc();
    if (!cap)
      return -L4_ENOMEM;
 
    reinterpret_cast<Small_buf&>(_brs[i])
      = Small_buf(cap.cap(), _cap_flags);
 
    return L4_EOK;
  }
 
  void set_rcv_cap_flags(unsigned long flags)
  {
    l4_assert(_caps == 0);
 
    _cap_flags = flags;
  }
 
  int add_timeout(L4::Ipc_svr::Timeout *, l4_kernel_clock_t) override
  { return -L4_ENOSYS; }
 
  int remove_timeout(L4::Ipc_svr::Timeout *) override
  { return -L4_ENOSYS; }
 
  void setup_wait(l4_utcb_t *utcb, L4::Ipc_svr::Reply_mode)
  {
    l4_buf_regs_t *br = l4_utcb_br_u(utcb);
    br->bdr = 0;
    for (unsigned i = 0; i <= _caps; ++i)
      br->br[i] = _brs[i];
  }
 
protected:
  unsigned first_free_br() const
  {
    // The last BR (64-bit) or the last two BRs (32-bit); this is constant.
    return L4_UTCB_GENERIC_BUFFERS_SIZE - Brs_per_timeout;
    // We could also do the following dynamic approach:
    // return _caps + _mem + _ports + 1
  }
 
private:
  unsigned short _caps;
  unsigned long _cap_flags;
 
  l4_umword_t _brs[L4_UTCB_GENERIC_BUFFERS_SIZE];
};
 
struct Br_manager_hooks
: L4::Ipc_svr::Ignore_errors,
  L4::Ipc_svr::Default_timeout,
  L4::Ipc_svr::Compound_reply,
  Br_manager
{};
 
struct Br_manager_timeout_hooks :
  public L4::Ipc_svr::Timeout_queue_hooks<Br_manager_timeout_hooks, Br_manager>,
  public L4::Ipc_svr::Ignore_errors
{
public:
  static l4_kernel_clock_t now()
  { return l4_kip_clock(l4re_kip()); }
};
 
}}