block_device_mgr.h

/*
 * Copyright (C) 2018-2020, 2022 Kernkonzept GmbH.
 * Author(s): Sarah Hoffmann <sarah.hoffmann@kernkonzept.com>
 *            Manuel von Oltersdorff-Kalettka <manuel.kalettka@kernkonzept.com>
 *
 * This file is distributed under the terms of the GNU General Public
 * License, version 2.  Please see the COPYING-GPL-2 file for details.
 */
#pragma once
 
#include <cassert>
#include <cstring>
#include <memory>
#include <string>
#include <vector>
 
#include <l4/cxx/ref_ptr>
#include <l4/cxx/ref_ptr_list>
#include <l4/cxx/unique_ptr>
#include <l4/re/error_helper>
#include <l4/sys/factory>
#include <l4/sys/cxx/ipc_epiface>
 
#include <l4/libblock-device/debug.h>
#include <l4/libblock-device/errand.h>
#include <l4/libblock-device/partition.h>
#include <l4/libblock-device/part_device.h>
#include <l4/libblock-device/virtio_client.h>
#include <l4/libblock-device/scheduler.h>
 
namespace Block_device {
 
template <typename DEV>
struct Simple_factory
{
  using Device_type = DEV;
  using Client_type = Virtio_client<Device_type>;
 
  static cxx::unique_ptr<Client_type>
  create_client(cxx::Ref_ptr<Device_type> const &dev,
                unsigned numds, bool readonly)
  { return cxx::make_unique<Client_type>(dev, numds, readonly); }
};
 
template <typename BASE_DEV>
struct Partitionable_factory
{
  using Device_type = BASE_DEV;
  using Client_type = Virtio_client<Device_type>;
 
  static cxx::unique_ptr<Client_type>
  create_client(cxx::Ref_ptr<Device_type> const &dev,
                unsigned numds, bool readonly)
  {
    return cxx::make_unique<Client_type>(dev, numds, readonly);
  }
 
  static cxx::Ref_ptr<Device_type>
  create_partition(cxx::Ref_ptr<Device_type> const &dev, unsigned partition_id,
                   Partition_info const &pi)
  {
    return cxx::Ref_ptr<Device_type>(
        new Partitioned_device<Device_type>(dev, partition_id, pi));
  }
};
 
 
template <typename DEV, typename FACTORY = Simple_factory<DEV>,
          typename SCHEDULER = Rr_scheduler<typename FACTORY::Device_type>>
class Device_mgr
{
  using Device_factory_type = FACTORY;
  using Client_type = typename Device_factory_type::Client_type;
  using Device_type = typename Device_factory_type::Device_type;
  using Scheduler_type = SCHEDULER;
 
  using Ds_vector = std::vector<L4::Cap<L4Re::Dataspace>>;
 
  using Pairing_callback = std::function<void(Device_type *)>;
 
  struct Pending_client
  {
    std::string device_id;
    L4::Cap<L4::Rcv_endpoint> gate;
    int num_ds;
    bool readonly;
 
    bool enable_trusted_ds_validation;
 
    std::shared_ptr<Ds_vector const> trusted_dataspaces;
 
    Pairing_callback pairing_cb;
 
    Pending_client() = default;
 
    Pending_client(L4::Cap<L4::Rcv_endpoint> g, std::string const &dev, int ds,
                   bool ro, bool enable_trusted_ds_validation,
                   std::shared_ptr<Ds_vector const> trusted_dataspaces,
                   Pairing_callback cb)
    : device_id(dev), gate(g), num_ds(ds), readonly(ro),
      enable_trusted_ds_validation(enable_trusted_ds_validation),
      trusted_dataspaces(trusted_dataspaces), pairing_cb(cb)
    {}
  };
 
  class Connection : public cxx::Ref_obj_list_item<Connection>
  {
  public:
    explicit Connection(Device_mgr *mgr, cxx::Ref_ptr<Device_type> &&dev)
    : _shutdown_state(Shutdown_type::Running),
      _device(cxx::move(dev)),
      _mgr(mgr)
    {}
 
    L4::Cap<void> cap() const
    { return _interface ? _interface->obj_cap() : L4::Cap<void>(); }
 
    void start_disk_scan(Errand::Callback const &callback)
    {
      _device->start_device_scan(
        [=]()
          {
            scan_disk_partitions(callback, 0);
          });
    }
 
    void unregister_interfaces(L4::Registry_iface *registry) const
    {
      if (_interface)
        registry->unregister_obj(_interface.get());
 
      for (auto *sub : _subs)
        sub->unregister_interfaces(registry);
    }
 
    int create_interface_for(Pending_client *c, L4::Registry_iface *registry)
    {
      if (_shutdown_state != Shutdown_type::Running)
        return -L4_EIO;
 
      if (_interface)
        return contains_device(c->device_id) ? -L4_EBUSY : -L4_ENODEV;
 
      // check for match in partitions
 
      bool busy = false;
      for (auto *sub : _subs)
        {
          if (sub->_interface)
            busy = true;
 
          int ret = sub->create_interface_for(c, registry);
 
          if (ret != -L4_ENODEV) // includes L4_EOK
            return ret;
        }
 
      if (!match_hid(c->device_id))
        return -L4_ENODEV;
 
      if (busy)
        return -L4_EBUSY;
 
      auto clt = Device_factory_type::create_client(_device, c->num_ds,
                                                    c->readonly);
 
      clt->add_trusted_dataspaces(c->trusted_dataspaces);
      if (c->enable_trusted_ds_validation)
        clt->enable_trusted_ds_validation();
 
      if (c->gate.is_valid())
        {
          if (!clt->register_obj(registry, c->gate).is_valid())
            return -L4_ENOMEM;
        }
      else
        {
          c->gate = L4::cap_reinterpret_cast<L4::Rcv_endpoint>(
                      clt->register_obj(registry));
          if (!c->gate.is_valid())
            return -L4_ENOMEM;
        }
 
      _mgr->_scheduler->add_client(clt.get());
      _interface.reset(clt.release());
 
      // Let it be known that the client and the device paired
      if (c->pairing_cb)
        c->pairing_cb(_device.get());
      return L4_EOK;
    }
 
    void check_clients(L4::Registry_iface *registry)
    {
      if (_interface)
        {
          if (_interface->obj_cap() && !_interface->obj_cap().validate().label())
            remove_client(registry);
 
          return;
        }
 
      // Sub-devices only need to be checked when the parent device was free.
      for (auto *sub : _subs)
        sub->check_clients(registry);
    }
 
    void shutdown_event(Shutdown_type type)
    {
      // Set new shutdown state
      _shutdown_state = type;
      for (auto const &sub: _subs)
        sub->shutdown_event(type);
      if (_interface)
        _interface->shutdown_event(type);
    }
 
  private:
    template <typename T = Device_factory_type>
    auto scan_disk_partitions(Errand::Callback const &callback, int)
     -> decltype((T::create_partition)(cxx::Ref_ptr<Device_type>(), 0, Partition_info()), void())
    {
      auto reader = cxx::make_ref_obj<Partition_reader<Device_type>>(_device.get());
      // The reference to reader will be captured in the lambda passed to
      // reader's own read() method. At the same time, reader will store
      // the reference to the lambda.
      reader->read(
        [=]()
          {
            l4_size_t sz = reader->table_size();
 
            for (l4_size_t i = 1; i <= sz; ++i)
              {
                Partition_info info;
                if (reader->get_partition(i, &info) < 0)
                  continue;
 
                auto conn = cxx::make_ref_obj<Connection>(
                  _mgr,
                  Device_factory_type::create_partition(_device, i, info));
                _subs.push_front(std::move(conn));
              }
 
            callback();
 
            // Prolong the life-span of reader until we are sure the reader is
            // not currently invoked (i.e. capture the last reference to it in
            // an independent timeout callback).
            Errand::schedule([reader](){}, 0);
          });
    }
 
    template <typename T = Device_factory_type>
    void scan_disk_partitions(Errand::Callback const &callback, long)
    { callback(); }
 
    void remove_client(L4::Registry_iface *registry)
    {
      assert(_interface);
 
      // This operation is idempotent.
      _interface->shutdown_event(Shutdown_type::Client_gone);
 
      if (_interface->busy())
        {
          Dbg::trace().printf("Deferring dead client removal.\n");
 
          // Cannot remove the client while it still has active I/O requests.
          // This means that the device did not abort its inflight requests in
          // its reset() callback. It is still desirable though to wait for
          // those requests to finish and defer the dead client removal until
          // later.
          Errand::schedule([this, registry]() { remove_client(registry); },
                           10000);
          return;
        }
 
      _interface->unregister_obj(registry);
      _mgr->_scheduler->remove_client(_interface.get());
      _interface.reset();
    }
 
    bool contains_device(std::string const &name) const
    {
      if (match_hid(name))
        return true;
 
      for (auto *sub : _subs)
        if (sub->contains_device(name))
          return true;
 
      return false;
    }
 
    bool match_hid(std::string const &name) const
    { return _device->match_hid(cxx::String(name.c_str(), name.length())); }
 
 
    Shutdown_type _shutdown_state;
    cxx::Ref_ptr<Device_type> _device;
    cxx::unique_ptr<Client_type> _interface;
    cxx::Ref_ptr_list<Connection> _subs;
 
    Device_mgr *_mgr;
  };
 
public:
  Device_mgr(L4::Registry_iface *registry)
  : _registry(registry)
  {
    _scheduler = cxx::make_unique<Scheduler_type>(registry);
  }
 
  virtual ~Device_mgr()
  {
    for (auto *c : _connpts)
      c->unregister_interfaces(_registry);
  }
 
  int add_static_client(L4::Cap<L4::Rcv_endpoint> client, const char *device,
                        int partno, int num_ds, bool readonly = false,
                        Pairing_callback cb = nullptr,
                        bool enable_trusted_ds_validation = false,
                        std::shared_ptr<Ds_vector const> trusted_dataspaces
                          = nullptr)
  {
    char _buf[30];
    const char *buf;
 
    if (partno == 0)
      {
        Err().printf("Invalid partition number 0.\n");
        return -L4_ENODEV;
      }
 
    if (partno != -1)
      {
        /* Could we avoid to make a string here and parsing this again
         * deeper in the stack? */
        snprintf(_buf, sizeof(_buf), "%s:%d", device, partno);
        buf = _buf;
      }
    else
      buf = device;
 
    _pending_clients.emplace_back(client, buf, num_ds, readonly,
                                  enable_trusted_ds_validation,
                                  trusted_dataspaces, cb);
 
    return L4_EOK;
  }
 
  int create_dynamic_client(std::string const &device, int partno, int num_ds,
                            L4::Cap<void> *cap, bool readonly = false,
                            Pairing_callback cb = nullptr,
                            bool enable_trusted_ds_validation = false,
                            std::shared_ptr<Ds_vector const> trusted_dataspaces
                              = nullptr)
  {
    Pending_client clt;
 
    // Maximum number of dataspaces that can be registered.
    clt.num_ds = num_ds;
 
    clt.readonly = readonly;
 
    clt.device_id = device;
 
    clt.pairing_cb = cb;
 
    clt.trusted_dataspaces = trusted_dataspaces;
 
    clt.enable_trusted_ds_validation = enable_trusted_ds_validation;
 
    if (partno > 0)
      {
        clt.device_id += ':';
        clt.device_id += std::to_string(partno);
      }
 
    for (auto *c : _connpts)
      {
        int ret = c->create_interface_for(&clt, _registry);
 
        if (ret == -L4_ENODEV)
          continue;
 
        if (ret < 0)
          return ret;
 
        // found the requested device
        *cap = clt.gate;
        return L4_EOK;
      }
 
    return -L4_ENODEV;
  }
 
  void check_clients()
  {
    for (auto *c : _connpts)
      c->check_clients(_registry);
  }
 
  void add_disk(cxx::Ref_ptr<Device_type> &&device, Errand::Callback const &callback)
  {
    auto conn = cxx::make_ref_obj<Connection>(this, std::move(device));
 
    conn->start_disk_scan(
      [=]()
        {
          _connpts.push_front(conn);
          connect_static_clients(conn.get());
          callback();
        });
  }
 
  void shutdown_event(Shutdown_type type)
  {
    l4_assert(type != Client_gone);
    l4_assert(type != Client_shutdown);
 
    for (auto const &con : _connpts)
      con->shutdown_event(type);
  }
 
private:
  void connect_static_clients(Connection *con)
  {
    for (auto &c : _pending_clients)
      {
        Dbg::trace().printf("Checking existing client %s\n", c.device_id.c_str());
        if (!c.gate.is_valid())
          continue;
 
        int ret = con->create_interface_for(&c, _registry);
 
        if (ret == L4_EOK)
          {
            c.gate = L4::Cap<L4::Rcv_endpoint>();
            // There might be other clients waiting for other partitions.
            // Continue search.
            continue;
          }
 
        if (ret != -L4_ENODEV)
          break;
      }
  }
 
 
  L4::Registry_iface *_registry;
  cxx::Ref_ptr_list<Connection> _connpts;
  std::vector<Pending_client> _pending_clients;
  cxx::unique_ptr<Scheduler_type> _scheduler;
};
 
} // name space