text: /*
   * QEMU Random Number Generator Backend
   *
   * Copyright IBM, Corp. 2012
   *
   * Authors:
   *  Anthony Liguori   <aliguori@us.ibm.com>
   *
   * This work is licensed under the terms of the GNU GPL, version 2 or later.
   * See the COPYING file in the top-level directory.
   */
  
  #include "qemu/osdep.h"
  #include "sysemu/rng-random.h"
  #include "sysemu/rng.h"
  #include "qapi/error.h"
  #include "qapi/qmp/qerror.h"
  #include "qemu/main-loop.h"
  #include "qemu/module.h"
  
  struct RngRandom
  {
      RngBackend parent;
  
      int fd;
      char *filename;
  };
  
  /**
   * A simple and incomplete backend to request entropy from /dev/random.
   *
   * This backend exposes an additional "filename" property that can be used to
   * set the filename to use to open the backend.
   */
  
  static void entropy_available(void *opaque)
  {
      RngRandom *s = RNG_RANDOM(opaque);
  
      while (!QSIMPLEQ_EMPTY(&s->parent.requests)) {
          RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
          ssize_t len;
  
          len = read(s->fd, req->data, req->size);
          if (len < 0 && errno == EAGAIN) {
              return;
          }
          g_assert(len != -1);
  
          req->receive_entropy(req->opaque, req->data, len);
  
          rng_backend_finalize_request(&s->parent, req);
      }
  
      /* We've drained all requests, the fd handler can be reset. */
      qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
  }
  
  static void rng_random_request_entropy(RngBackend *b, RngRequest *req)
  {
      RngRandom *s = RNG_RANDOM(b);
  
      if (QSIMPLEQ_EMPTY(&s->parent.requests)) {
          /* If there are no pending requests yet, we need to
           * install our fd handler. */
          qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
      }
  }
  
  static void rng_random_opened(RngBackend *b, Error **errp)
  {
      RngRandom *s = RNG_RANDOM(b);
  
      if (s->filename == NULL) {
          error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                     "filename", "a valid filename");
      } else {
          s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK);
          if (s->fd == -1) {
              error_setg_file_open(errp, errno, s->filename);
          }
      }
  }
  
  static char *rng_random_get_filename(Object *obj, Error **errp)
  {
      RngRandom *s = RNG_RANDOM(obj);
  
      return g_strdup(s->filename);
  }
  
  static void rng_random_set_filename(Object *obj, const char *filename,
                                   Error **errp)
  {
      RngBackend *b = RNG_BACKEND(obj);
      RngRandom *s = RNG_RANDOM(obj);
  
      if (b->opened) {
          error_setg(errp, QERR_PERMISSION_DENIED);
          return;
      }
  
      g_free(s->filename);
      s->filename = g_strdup(filename);
  }
  
  static void rng_random_init(Object *obj)
  {
      RngRandom *s = RNG_RANDOM(obj);
  
      object_property_add_str(obj, "filename",
                              rng_random_get_filename,
                              rng_random_set_filename,
                              NULL);
  
      s->filename = g_strdup("/dev/urandom");
      s->fd = -1;
  }
  
  static void rng_random_finalize(Object *obj)
  {
      RngRandom *s = RNG_RANDOM(obj);
  
      if (s->fd != -1) {
          qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
          qemu_close(s->fd);
      }
  
      g_free(s->filename);
  }
  
  static void rng_random_class_init(ObjectClass *klass, void *data)
  {
      RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
  
      rbc->request_entropy = rng_random_request_entropy;
      rbc->opened = rng_random_opened;
  }
  
  static const TypeInfo rng_random_info = {
      .name = TYPE_RNG_RANDOM,
      .parent = TYPE_RNG_BACKEND,
      .instance_size = sizeof(RngRandom),
      .class_init = rng_random_class_init,
      .instance_init = rng_random_init,
      .instance_finalize = rng_random_finalize,
  };
  
  static void register_types(void)
  {
      type_register_static(&rng_random_info);
  }
  
  type_init(register_types);
  