backends/rng-egd.c

   1 /*
   2  * QEMU Random Number Generator Backend
   3  *
   4  * Copyright IBM, Corp. 2012
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu/rng.h"
  14 #include "char/char.h"
  15 #include "qapi/qmp/qerror.h"
  16 #include "hw/qdev.h" /* just for DEFINE_PROP_CHR */
  17
  18 #define TYPE_RNG_EGD "rng-egd"
  19 #define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)
  20
  21 typedef struct RngEgd
  22 {
  23     RngBackend parent;
  24
  25     CharDriverState *chr;
  26     char *chr_name;
  27
  28     GSList *requests;
  29 } RngEgd;
  30
  31 typedef struct RngRequest
  32 {
  33     EntropyReceiveFunc *receive_entropy;
  34     uint8_t *data;
  35     void *opaque;
  36     size_t offset;
  37     size_t size;
  38 } RngRequest;
  39
  40 static void rng_egd_request_entropy(RngBackend *b, size_t size,
  41                                     EntropyReceiveFunc *receive_entropy,
  42                                     void *opaque)
  43 {
  44     RngEgd *s = RNG_EGD(b);
  45     RngRequest *req;
  46
  47     req = g_malloc(sizeof(*req));
  48
  49     req->offset = 0;
  50     req->size = size;
  51     req->receive_entropy = receive_entropy;
  52     req->opaque = opaque;
  53     req->data = g_malloc(req->size);
  54
  55     while (size > 0) {
  56         uint8_t header[2];
  57         uint8_t len = MIN(size, 255);
  58
  59         /* synchronous entropy request */
  60         header[0] = 0x02;
  61         header[1] = len;
  62
  63         qemu_chr_fe_write(s->chr, header, sizeof(header));
  64
  65         size -= len;
  66     }
  67
  68     s->requests = g_slist_append(s->requests, req);
  69 }
  70
  71 static void rng_egd_free_request(RngRequest *req)
  72 {
  73     g_free(req->data);
  74     g_free(req);
  75 }
  76
  77 static int rng_egd_chr_can_read(void *opaque)
  78 {
  79     RngEgd *s = RNG_EGD(opaque);
  80     GSList *i;
  81     int size = 0;
  82
  83     for (i = s->requests; i; i = i->next) {
  84         RngRequest *req = i->data;
  85         size += req->size - req->offset;
  86     }
  87
  88     return size;
  89 }
  90
  91 static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
  92 {
  93     RngEgd *s = RNG_EGD(opaque);
  94
  95     while (size > 0 && s->requests) {
  96         RngRequest *req = s->requests->data;
  97         int len = MIN(size, req->size - req->offset);
  98
  99         memcpy(req->data + req->offset, buf, len);
 100         req->offset += len;
 101         size -= len;
 102
 103         if (req->offset == req->size) {
 104             s->requests = g_slist_remove_link(s->requests, s->requests);
 105
 106             req->receive_entropy(req->opaque, req->data, req->size);
 107
 108             rng_egd_free_request(req);
 109         }
 110     }
 111 }
 112
 113 static void rng_egd_free_requests(RngEgd *s)
 114 {
 115     GSList *i;
 116
 117     for (i = s->requests; i; i = i->next) {
 118         rng_egd_free_request(i->data);
 119     }
 120
 121     g_slist_free(s->requests);
 122     s->requests = NULL;
 123 }
 124
 125 static void rng_egd_cancel_requests(RngBackend *b)
 126 {
 127     RngEgd *s = RNG_EGD(b);
 128
 129     /* We simply delete the list of pending requests.  If there is data in the
 130      * queue waiting to be read, this is okay, because there will always be
 131      * more data than we requested originally
 132      */
 133     rng_egd_free_requests(s);
 134 }
 135
 136 static void rng_egd_opened(RngBackend *b, Error **errp)
 137 {
 138     RngEgd *s = RNG_EGD(b);
 139
 140     if (s->chr_name == NULL) {
 141         error_set(errp, QERR_INVALID_PARAMETER_VALUE,
 142                   "chardev", "a valid character device");
 143         return;
 144     }
 145
 146     s->chr = qemu_chr_find(s->chr_name);
 147     if (s->chr == NULL) {
 148         error_set(errp, QERR_DEVICE_NOT_FOUND, s->chr_name);
 149         return;
 150     }
 151
 152     /* FIXME we should resubmit pending requests when the CDS reconnects. */
 153     qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
 154                           NULL, s);
 155 }
 156
 157 static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
 158 {
 159     RngBackend *b = RNG_BACKEND(obj);
 160     RngEgd *s = RNG_EGD(b);
 161
 162     if (b->opened) {
 163         error_set(errp, QERR_PERMISSION_DENIED);
 164     } else {
 165         g_free(s->chr_name);
 166         s->chr_name = g_strdup(value);
 167     }
 168 }
 169
 170 static char *rng_egd_get_chardev(Object *obj, Error **errp)
 171 {
 172     RngEgd *s = RNG_EGD(obj);
 173
 174     if (s->chr && s->chr->label) {
 175         return g_strdup(s->chr->label);
 176     }
 177
 178     return NULL;
 179 }
 180
 181 static void rng_egd_init(Object *obj)
 182 {
 183     object_property_add_str(obj, "chardev",
 184                             rng_egd_get_chardev, rng_egd_set_chardev,
 185                             NULL);
 186 }
 187
 188 static void rng_egd_finalize(Object *obj)
 189 {
 190     RngEgd *s = RNG_EGD(obj);
 191
 192     if (s->chr) {
 193         qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
 194     }
 195
 196     g_free(s->chr_name);
 197
 198     rng_egd_free_requests(s);
 199 }
 200
 201 static void rng_egd_class_init(ObjectClass *klass, void *data)
 202 {
 203     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 204
 205     rbc->request_entropy = rng_egd_request_entropy;
 206     rbc->cancel_requests = rng_egd_cancel_requests;
 207     rbc->opened = rng_egd_opened;
 208 }
 209
 210 static const TypeInfo rng_egd_info = {
 211     .name = TYPE_RNG_EGD,
 212     .parent = TYPE_RNG_BACKEND,
 213     .instance_size = sizeof(RngEgd),
 214     .class_init = rng_egd_class_init,
 215     .instance_init = rng_egd_init,
 216     .instance_finalize = rng_egd_finalize,
 217 };
 218
 219 static void register_types(void)
 220 {
 221     type_register_static(&rng_egd_info);
 222 }
 223
 224 type_init(register_types);