rng-builtin: add an RNG backend that uses qemu_guest_getrandom()

Add a new RNG backend using QEMU builtin getrandom function.

It can be created and used with something like:

    ... -object rng-builtin,id=rng0 -device virtio-rng,rng=rng0 ...

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20190820160615.14616-2-lvivier@redhat.com>

2 files changed, 79 insertions, 1 deletions

diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index 981e8e122f..f0691116e8 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -1,4 +1,4 @@
-common-obj-y += rng.o rng-egd.o
+common-obj-y += rng.o rng-egd.o rng-builtin.o
 common-obj-$(CONFIG_POSIX) += rng-random.o
 
 common-obj-$(CONFIG_TPM) += tpm.o
diff --git a/backends/rng-builtin.c b/backends/rng-builtin.c
new file mode 100644
index 0000000000..3381d47174
--- /dev/null
+++ b/backends/rng-builtin.c
@@ -0,0 +1,78 @@
+/*
+ * QEMU Builtin Random Number Generator Backend
+ *
+ * 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.h"
+#include "qemu/main-loop.h"
+#include "qemu/guest-random.h"
+
+#define TYPE_RNG_BUILTIN "rng-builtin"
+#define RNG_BUILTIN(obj) OBJECT_CHECK(RngBuiltin, (obj), TYPE_RNG_BUILTIN)
+
+typedef struct RngBuiltin {
+    RngBackend parent;
+    QEMUBH *bh;
+} RngBuiltin;
+
+static void rng_builtin_receive_entropy_bh(void *opaque)
+{
+    RngBuiltin *s = opaque;
+
+    while (!QSIMPLEQ_EMPTY(&s->parent.requests)) {
+        RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
+
+        qemu_guest_getrandom_nofail(req->data, req->size);
+
+        req->receive_entropy(req->opaque, req->data, req->size);
+
+        rng_backend_finalize_request(&s->parent, req);
+    }
+}
+
+static void rng_builtin_request_entropy(RngBackend *b, RngRequest *req)
+{
+    RngBuiltin *s = RNG_BUILTIN(b);
+
+    qemu_bh_schedule(s->bh);
+}
+
+static void rng_builtin_init(Object *obj)
+{
+    RngBuiltin *s = RNG_BUILTIN(obj);
+
+    s->bh = qemu_bh_new(rng_builtin_receive_entropy_bh, s);
+}
+
+static void rng_builtin_finalize(Object *obj)
+{
+    RngBuiltin *s = RNG_BUILTIN(obj);
+
+    qemu_bh_delete(s->bh);
+}
+
+static void rng_builtin_class_init(ObjectClass *klass, void *data)
+{
+    RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
+
+    rbc->request_entropy = rng_builtin_request_entropy;
+}
+
+static const TypeInfo rng_builtin_info = {
+    .name = TYPE_RNG_BUILTIN,
+    .parent = TYPE_RNG_BACKEND,
+    .instance_size = sizeof(RngBuiltin),
+    .instance_init = rng_builtin_init,
+    .instance_finalize = rng_builtin_finalize,
+    .class_init = rng_builtin_class_init,
+};
+
+static void register_types(void)
+{
+    type_register_static(&rng_builtin_info);
+}
+
+type_init(register_types);