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