rng-egd: introduce EGD compliant RNG backend

This backend talks EGD to a CharDriverState.  A typical way to invoke this would
be:

qemu -chardev socket,host=localhost,port=1024,id=chr0 \
     -object rng-egd,chardev=chr0,id=egd0 \
     -device virtio-rng-pci,rng=egd0

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

2 files changed, 216 insertions, 1 deletions

diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index 23ca19b..875eebc 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -1 +1 @@
-common-obj-y += rng.o rng-random.o
+common-obj-y += rng.o rng-random.o rng-egd.o
diff --git a/backends/rng-egd.c b/backends/rng-egd.c
new file mode 100644
index 0000000..ec58358
--- /dev/null
+++ b/backends/rng-egd.c
@@ -0,0 +1,215 @@
+/*
+ * 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/rng.h"
+#include "qemu-char.h"
+#include "qerror.h"
+#include "hw/qdev.h" /* just for DEFINE_PROP_CHR */
+
+#define TYPE_RNG_EGD "rng-egd"
+#define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)
+
+typedef struct RngEgd
+{
+    RngBackend parent;
+
+    CharDriverState *chr;
+    char *chr_name;
+
+    GSList *requests;
+} RngEgd;
+
+typedef struct RngRequest
+{
+    EntropyReceiveFunc *receive_entropy;
+    uint8_t *data;
+    void *opaque;
+    size_t offset;
+    size_t size;
+} RngRequest;
+
+static void rng_egd_request_entropy(RngBackend *b, size_t size,
+                                    EntropyReceiveFunc *receive_entropy,
+                                    void *opaque)
+{
+    RngEgd *s = RNG_EGD(b);
+    RngRequest *req;
+
+    req = g_malloc(sizeof(*req));
+
+    req->offset = 0;
+    req->size = size;
+    req->receive_entropy = receive_entropy;
+    req->opaque = opaque;
+    req->data = g_malloc(req->size);
+
+    while (size > 0) {
+        uint8_t header[2];
+        uint8_t len = MIN(size, 255);
+
+        /* synchronous entropy request */
+        header[0] = 0x02;
+        header[1] = len;
+
+        qemu_chr_fe_write(s->chr, header, sizeof(header));
+
+        size -= len;
+    }
+
+    s->requests = g_slist_append(s->requests, req);
+}
+
+static void rng_egd_free_request(RngRequest *req)
+{
+    g_free(req->data);
+    g_free(req);
+}
+
+static int rng_egd_chr_can_read(void *opaque)
+{
+    RngEgd *s = RNG_EGD(opaque);
+    GSList *i;
+    int size = 0;
+
+    for (i = s->requests; i; i = i->next) {
+        RngRequest *req = i->data;
+        size += req->size - req->offset;
+    }
+
+    return size;
+}
+
+static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
+{
+    RngEgd *s = RNG_EGD(opaque);
+
+    while (size > 0 && s->requests) {
+        RngRequest *req = s->requests->data;
+        int len = MIN(size, req->size - req->offset);
+
+        memcpy(req->data + req->offset, buf, len);
+        req->offset += len;
+        size -= len;
+
+        if (req->offset == req->size) {
+            s->requests = g_slist_remove_link(s->requests, s->requests);
+
+            req->receive_entropy(req->opaque, req->data, req->size);
+
+            rng_egd_free_request(req);
+        }
+    }
+}
+
+static void rng_egd_cancel_requests(RngBackend *b)
+{
+    RngEgd *s = RNG_EGD(b);
+
+    /* We simply delete the list of pending requests.  If there is data in the 
+     * queue waiting to be read, this is okay, because there will always be
+     * more data than we requested originally
+     */
+    g_slist_free_full(s->requests,
+                      (GDestroyNotify)rng_egd_free_request);
+    s->requests = NULL;
+}
+
+static void rng_egd_opened(RngBackend *b, Error **errp)
+{
+    RngEgd *s = RNG_EGD(b);
+
+    if (s->chr_name == NULL) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+                  "chardev", "a valid character device");
+        return;
+    }
+
+    s->chr = qemu_chr_find(s->chr_name);
+    if (s->chr == NULL) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, s->chr_name);
+        return;
+    }
+
+    /* FIXME we should resubmit pending requests when the CDS reconnects. */
+    qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
+                          NULL, s);
+}
+
+static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
+{
+    RngBackend *b = RNG_BACKEND(obj);
+    RngEgd *s = RNG_EGD(b);
+
+    if (b->opened) {
+        error_set(errp, QERR_PERMISSION_DENIED);
+    } else {
+        g_free(s->chr_name);
+        s->chr_name = g_strdup(value);
+    }
+}
+
+static char *rng_egd_get_chardev(Object *obj, Error **errp)
+{
+    RngEgd *s = RNG_EGD(obj);
+
+    if (s->chr && s->chr->label) {
+        return g_strdup(s->chr->label);
+    }
+
+    return NULL;
+}
+
+static void rng_egd_init(Object *obj)
+{
+    object_property_add_str(obj, "chardev",
+                            rng_egd_get_chardev, rng_egd_set_chardev,
+                            NULL);
+}
+
+static void rng_egd_finalize(Object *obj)
+{
+    RngEgd *s = RNG_EGD(obj);
+
+    if (s->chr) {
+        qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
+    }
+
+    g_free(s->chr_name);
+
+    g_slist_free_full(s->requests, (GDestroyNotify)rng_egd_free_request);
+    s->requests = NULL;
+}
+
+static void rng_egd_class_init(ObjectClass *klass, void *data)
+{
+    RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
+
+    rbc->request_entropy = rng_egd_request_entropy;
+    rbc->cancel_requests = rng_egd_cancel_requests;
+    rbc->opened = rng_egd_opened;
+}
+
+static TypeInfo rng_egd_info = {
+    .name = TYPE_RNG_EGD,
+    .parent = TYPE_RNG_BACKEND,
+    .instance_size = sizeof(RngEgd),
+    .class_init = rng_egd_class_init,
+    .instance_init = rng_egd_init,
+    .instance_finalize = rng_egd_finalize,
+};
+
+static void register_types(void)
+{
+    type_register_static(&rng_egd_info);
+}
+
+type_init(register_types);