The filename can be overridden but it expects a non-blocking source of entropy.
A typical invocation would be:
qemu -object rng-urandom,id=rng0 -device virtio-rng-pci,rng=rng0
Signed-off-by: Anthony Liguori <aligu...@us.ibm.com>
---
backends/Makefile.objs | 2 +-
backends/rng-urandom.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 145 insertions(+), 1 deletions(-)
create mode 100644 backends/rng-urandom.c
diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index 06e08c7..423c9df 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -1 +1 @@
-common-obj-y += rng.o
+common-obj-y += rng.o rng-urandom.o
diff --git a/backends/rng-urandom.c b/backends/rng-urandom.c
new file mode 100644
index 0000000..7fbe886
--- /dev/null
+++ b/backends/rng-urandom.c
@@ -0,0 +1,144 @@
+/*
+ * QEMU Random Number Generator Backend
+ *
+ * Copyright IBM, Corp. 2012
+ *
+ * Authors:
+ * Anthony Liguori <aligu...@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/rng.h"
+#include "qerror.h"
+
+#define TYPE_RNG_URANDOM "rng-urandom"
+#define RNG_URANDOM(obj) OBJECT_CHECK(RndURandom, (obj), TYPE_RNG_URANDOM)
+
+typedef struct RndURandom
+{
+ RngBackend parent;
+
+ int fd;
+ char *filename;
+ GSList *pending_data;
+} RndURandom;
+
+/**
+ * A simple and incomplete backend to request entropy from /dev/urandom.
+ *
+ * This backend exposes an additional "filename" property that can be used to
+ * set the filename to use to open the backend.
+ */
+static void rng_urandom_request_entropy(RngBackend *b, size_t size,
+ EntropyReceiveFunc *receive_entropy,
+ void *opaque)
+{
+ RndURandom *s = RNG_URANDOM(b);
+ uint8_t data[size];
+ ssize_t ret;
+
+ g_assert(s->fd != -1);
+
+ do {
+ ret = read(s->fd, data, size);
+ } while (ret == -1 && errno == EINTR);
+
+ g_assert(ret != -1);
+
+ /* FIXME: needs to be done via a BH */
+ receive_entropy(opaque, data, ret);
+}
+
+static void rng_urandom_opened(RngBackend *b, Error **errp)
+{
+ RndURandom *s = RNG_URANDOM(b);
+
+ if (s->filename == NULL) {
+ error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+ "filename", "a valid filename");
+ } else {
+ s->fd = open(s->filename, O_RDONLY);
+
+ if (s->fd == -1) {
+ error_set(errp, QERR_OPEN_FILE_FAILED, s->filename);
+ }
+ }
+}
+
+static char *rng_urandom_get_filename(Object *obj, Error **errp)
+{
+ RndURandom *s = RNG_URANDOM(obj);
+
+ if (s->filename) {
+ return g_strdup(s->filename);
+ }
+
+ return NULL;
+}
+
+static void rng_urandom_set_filename(Object *obj, const char *filename,
+ Error **errp)
+{
+ RngBackend *b = RNG_BACKEND(obj);
+ RndURandom *s = RNG_URANDOM(obj);
+
+ if (b->opened) {
+ error_set(errp, QERR_PERMISSION_DENIED);
+ return;
+ }
+
+ if (s->filename) {
+ g_free(s->filename);
+ }
+
+ s->filename = g_strdup(filename);
+}
+
+static void rng_urandom_init(Object *obj)
+{
+ RndURandom *s = RNG_URANDOM(obj);
+
+ object_property_add_str(obj, "filename",
+ rng_urandom_get_filename,
+ rng_urandom_set_filename,
+ NULL);
+
+ s->filename = g_strdup("/dev/urandom");
+}
+
+static void rng_urandom_finalize(Object *obj)
+{
+ RndURandom *s = RNG_URANDOM(obj);
+
+ if (s->fd != -1) {
+ close(s->fd);
+ }
+
+ g_free(s->filename);
+}
+
+static void rng_urandom_class_init(ObjectClass *klass, void *data)
+{
+ RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
+
+ rbc->request_entropy = rng_urandom_request_entropy;
+ rbc->opened = rng_urandom_opened;
+}
+
+static TypeInfo rng_urandom_info = {
+ .name = TYPE_RNG_URANDOM,
+ .parent = TYPE_RNG_BACKEND,
+ .instance_size = sizeof(RndURandom),
+ .class_init = rng_urandom_class_init,
+ .instance_init = rng_urandom_init,
+ .instance_finalize = rng_urandom_finalize,
+};
+
+static void register_types(void)
+{
+ type_register_static(&rng_urandom_info);
+}
+
+type_init(register_types);
--
1.7.5.4
