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