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>
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5c74521d24
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1da2738f55
backends
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common-obj-y += rng.o rng-random.o
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common-obj-y += rng.o rng-random.o rng-egd.o
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215
backends/rng-egd.c
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215
backends/rng-egd.c
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/*
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* QEMU Random Number Generator Backend
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*
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* Copyright IBM, Corp. 2012
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/rng.h"
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#include "qemu-char.h"
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#include "qerror.h"
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#include "hw/qdev.h" /* just for DEFINE_PROP_CHR */
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#define TYPE_RNG_EGD "rng-egd"
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#define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)
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typedef struct RngEgd
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{
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RngBackend parent;
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CharDriverState *chr;
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char *chr_name;
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GSList *requests;
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} RngEgd;
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typedef struct RngRequest
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{
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EntropyReceiveFunc *receive_entropy;
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uint8_t *data;
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void *opaque;
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size_t offset;
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size_t size;
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} RngRequest;
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static void rng_egd_request_entropy(RngBackend *b, size_t size,
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EntropyReceiveFunc *receive_entropy,
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void *opaque)
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{
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RngEgd *s = RNG_EGD(b);
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RngRequest *req;
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req = g_malloc(sizeof(*req));
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req->offset = 0;
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req->size = size;
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req->receive_entropy = receive_entropy;
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req->opaque = opaque;
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req->data = g_malloc(req->size);
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while (size > 0) {
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uint8_t header[2];
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uint8_t len = MIN(size, 255);
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/* synchronous entropy request */
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header[0] = 0x02;
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header[1] = len;
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qemu_chr_fe_write(s->chr, header, sizeof(header));
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size -= len;
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}
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s->requests = g_slist_append(s->requests, req);
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}
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static void rng_egd_free_request(RngRequest *req)
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{
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g_free(req->data);
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g_free(req);
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}
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static int rng_egd_chr_can_read(void *opaque)
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{
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RngEgd *s = RNG_EGD(opaque);
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GSList *i;
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int size = 0;
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for (i = s->requests; i; i = i->next) {
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RngRequest *req = i->data;
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size += req->size - req->offset;
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}
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return size;
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}
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static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
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{
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RngEgd *s = RNG_EGD(opaque);
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while (size > 0 && s->requests) {
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RngRequest *req = s->requests->data;
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int len = MIN(size, req->size - req->offset);
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memcpy(req->data + req->offset, buf, len);
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req->offset += len;
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size -= len;
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if (req->offset == req->size) {
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s->requests = g_slist_remove_link(s->requests, s->requests);
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req->receive_entropy(req->opaque, req->data, req->size);
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rng_egd_free_request(req);
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}
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}
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}
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static void rng_egd_cancel_requests(RngBackend *b)
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{
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RngEgd *s = RNG_EGD(b);
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/* We simply delete the list of pending requests. If there is data in the
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* queue waiting to be read, this is okay, because there will always be
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* more data than we requested originally
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*/
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g_slist_free_full(s->requests,
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(GDestroyNotify)rng_egd_free_request);
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s->requests = NULL;
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}
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static void rng_egd_opened(RngBackend *b, Error **errp)
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{
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RngEgd *s = RNG_EGD(b);
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if (s->chr_name == NULL) {
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error_set(errp, QERR_INVALID_PARAMETER_VALUE,
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"chardev", "a valid character device");
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return;
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}
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s->chr = qemu_chr_find(s->chr_name);
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if (s->chr == NULL) {
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error_set(errp, QERR_DEVICE_NOT_FOUND, s->chr_name);
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return;
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}
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/* FIXME we should resubmit pending requests when the CDS reconnects. */
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qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
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NULL, s);
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}
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static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
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{
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RngBackend *b = RNG_BACKEND(obj);
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RngEgd *s = RNG_EGD(b);
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if (b->opened) {
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error_set(errp, QERR_PERMISSION_DENIED);
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} else {
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g_free(s->chr_name);
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s->chr_name = g_strdup(value);
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}
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}
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static char *rng_egd_get_chardev(Object *obj, Error **errp)
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{
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RngEgd *s = RNG_EGD(obj);
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if (s->chr && s->chr->label) {
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return g_strdup(s->chr->label);
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}
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return NULL;
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}
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static void rng_egd_init(Object *obj)
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{
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object_property_add_str(obj, "chardev",
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rng_egd_get_chardev, rng_egd_set_chardev,
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NULL);
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}
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static void rng_egd_finalize(Object *obj)
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{
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RngEgd *s = RNG_EGD(obj);
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if (s->chr) {
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qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
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}
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g_free(s->chr_name);
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g_slist_free_full(s->requests, (GDestroyNotify)rng_egd_free_request);
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s->requests = NULL;
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}
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static void rng_egd_class_init(ObjectClass *klass, void *data)
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{
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RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
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rbc->request_entropy = rng_egd_request_entropy;
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rbc->cancel_requests = rng_egd_cancel_requests;
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rbc->opened = rng_egd_opened;
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}
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static TypeInfo rng_egd_info = {
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.name = TYPE_RNG_EGD,
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.parent = TYPE_RNG_BACKEND,
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.instance_size = sizeof(RngEgd),
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.class_init = rng_egd_class_init,
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.instance_init = rng_egd_init,
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.instance_finalize = rng_egd_finalize,
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};
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static void register_types(void)
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{
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type_register_static(&rng_egd_info);
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}
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type_init(register_types);
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