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/*
* 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_old(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);
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;
object_class_property_add_str(klass, "filename",
rng_random_get_filename,
rng_random_set_filename);
}
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);
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