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/osdep.h"
  14 #include "sysemu/rng.h"
  15 #include "sysemu/char.h"
  16 #include "qapi/qmp/qerror.h"
  17 #include "hw/qdev.h" /* just for DEFINE_PROP_CHR */
  18
  19 #define TYPE_RNG_EGD "rng-egd"
  20 #define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)
  21
  22 typedef struct RngEgd
  23 {
  24     RngBackend parent;
  25
  26     CharDriverState *chr;
  27     char *chr_name;
  28
  29     GSList *requests;
  30 } RngEgd;
  31
  32 typedef struct RngRequest
  33 {
  34     EntropyReceiveFunc *receive_entropy;
  35     uint8_t *data;
  36     void *opaque;
  37     size_t offset;
  38     size_t size;
  39 } RngRequest;
  40
  41 static void rng_egd_request_entropy(RngBackend *b, size_t size,
  42                                     EntropyReceiveFunc *receive_entropy,
  43                                     void *opaque)
  44 {
  45     RngEgd *s = RNG_EGD(b);
  46     RngRequest *req;
  47
  48     req = g_malloc(sizeof(*req));
  49
  50     req->offset = 0;
  51     req->size = size;
  52     req->receive_entropy = receive_entropy;
  53     req->opaque = opaque;
  54     req->data = g_malloc(req->size);
  55
  56     while (size > 0) {
  57         uint8_t header[2];
  58         uint8_t len = MIN(size, 255);
  59
  60         /* synchronous entropy request */
  61         header[0] = 0x02;
  62         header[1] = len;
  63
  64         qemu_chr_fe_write(s->chr, header, sizeof(header));
  65
  66         size -= len;
  67     }
  68
  69     s->requests = g_slist_append(s->requests, req);
  70 }
  71
  72 static void rng_egd_free_request(RngRequest *req)
  73 {
  74     g_free(req->data);
  75     g_free(req);
  76 }
  77
  78 static int rng_egd_chr_can_read(void *opaque)
  79 {
  80     RngEgd *s = RNG_EGD(opaque);
  81     GSList *i;
  82     int size = 0;
  83
  84     for (i = s->requests; i; i = i->next) {
  85         RngRequest *req = i->data;
  86         size += req->size - req->offset;
  87     }
  88
  89     return size;
  90 }
  91
  92 static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
  93 {
  94     RngEgd *s = RNG_EGD(opaque);
  95     size_t buf_offset = 0;
  96
  97     while (size > 0 && s->requests) {
  98         RngRequest *req = s->requests->data;
  99         int len = MIN(size, req->size - req->offset);
 100
 101         memcpy(req->data + req->offset, buf + buf_offset, len);
 102         buf_offset += len;
 103         req->offset += len;
 104         size -= len;
 105
 106         if (req->offset == req->size) {
 107             s->requests = g_slist_remove_link(s->requests, s->requests);
 108
 109             req->receive_entropy(req->opaque, req->data, req->size);
 110
 111             rng_egd_free_request(req);
 112         }
 113     }
 114 }
 115
 116 static void rng_egd_free_requests(RngEgd *s)
 117 {
 118     GSList *i;
 119
 120     for (i = s->requests; i; i = i->next) {
 121         rng_egd_free_request(i->data);
 122     }
 123
 124     g_slist_free(s->requests);
 125     s->requests = NULL;
 126 }
 127
 128 static void rng_egd_cancel_requests(RngBackend *b)
 129 {
 130     RngEgd *s = RNG_EGD(b);
 131
 132     /* We simply delete the list of pending requests.  If there is data in the
 133      * queue waiting to be read, this is okay, because there will always be
 134      * more data than we requested originally
 135      */
 136     rng_egd_free_requests(s);
 137 }
 138
 139 static void rng_egd_opened(RngBackend *b, Error **errp)
 140 {
 141     RngEgd *s = RNG_EGD(b);
 142
 143     if (s->chr_name == NULL) {
 144         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
 145                    "chardev", "a valid character device");
 146         return;
 147     }
 148
 149     s->chr = qemu_chr_find(s->chr_name);
 150     if (s->chr == NULL) {
 151         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
 152                   "Device '%s' not found", s->chr_name);
 153         return;
 154     }
 155
 156     if (qemu_chr_fe_claim(s->chr) != 0) {
 157         error_setg(errp, QERR_DEVICE_IN_USE, s->chr_name);
 158         return;
 159     }
 160
 161     /* FIXME we should resubmit pending requests when the CDS reconnects. */
 162     qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
 163                           NULL, s);
 164 }
 165
 166 static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
 167 {
 168     RngBackend *b = RNG_BACKEND(obj);
 169     RngEgd *s = RNG_EGD(b);
 170
 171     if (b->opened) {
 172         error_setg(errp, QERR_PERMISSION_DENIED);
 173     } else {
 174         g_free(s->chr_name);
 175         s->chr_name = g_strdup(value);
 176     }
 177 }
 178
 179 static char *rng_egd_get_chardev(Object *obj, Error **errp)
 180 {
 181     RngEgd *s = RNG_EGD(obj);
 182
 183     if (s->chr && s->chr->label) {
 184         return g_strdup(s->chr->label);
 185     }
 186
 187     return NULL;
 188 }
 189
 190 static void rng_egd_init(Object *obj)
 191 {
 192     object_property_add_str(obj, "chardev",
 193                             rng_egd_get_chardev, rng_egd_set_chardev,
 194                             NULL);
 195 }
 196
 197 static void rng_egd_finalize(Object *obj)
 198 {
 199     RngEgd *s = RNG_EGD(obj);
 200
 201     if (s->chr) {
 202         qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
 203         qemu_chr_fe_release(s->chr);
 204     }
 205
 206     g_free(s->chr_name);
 207
 208     rng_egd_free_requests(s);
 209 }
 210
 211 static void rng_egd_class_init(ObjectClass *klass, void *data)
 212 {
 213     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 214
 215     rbc->request_entropy = rng_egd_request_entropy;
 216     rbc->cancel_requests = rng_egd_cancel_requests;
 217     rbc->opened = rng_egd_opened;
 218 }
 219
 220 static const TypeInfo rng_egd_info = {
 221     .name = TYPE_RNG_EGD,
 222     .parent = TYPE_RNG_BACKEND,
 223     .instance_size = sizeof(RngEgd),
 224     .class_init = rng_egd_class_init,
 225     .instance_init = rng_egd_init,
 226     .instance_finalize = rng_egd_finalize,
 227 };
 228
 229 static void register_types(void)
 230 {
 231     type_register_static(&rng_egd_info);
 232 }
 233
 234 type_init(register_types);