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/error.h"
  17 #include "qapi/qmp/qerror.h"
  18 #include "hw/qdev.h" /* just for DEFINE_PROP_CHR */
  19
  20 #define TYPE_RNG_EGD "rng-egd"
  21 #define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)
  22
  23 typedef struct RngEgd
  24 {
  25     RngBackend parent;
  26
  27     CharDriverState *chr;
  28     char *chr_name;
  29 } RngEgd;
  30
  31 static void rng_egd_request_entropy(RngBackend *b, RngRequest *req)
  32 {
  33     RngEgd *s = RNG_EGD(b);
  34     size_t size = req->size;
  35
  36     while (size > 0) {
  37         uint8_t header[2];
  38         uint8_t len = MIN(size, 255);
  39
  40         /* synchronous entropy request */
  41         header[0] = 0x02;
  42         header[1] = len;
  43
  44         qemu_chr_fe_write(s->chr, header, sizeof(header));
  45
  46         size -= len;
  47     }
  48 }
  49
  50 static int rng_egd_chr_can_read(void *opaque)
  51 {
  52     RngEgd *s = RNG_EGD(opaque);
  53     RngRequest *req;
  54     int size = 0;
  55
  56     QSIMPLEQ_FOREACH(req, &s->parent.requests, next) {
  57         size += req->size - req->offset;
  58     }
  59
  60     return size;
  61 }
  62
  63 static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
  64 {
  65     RngEgd *s = RNG_EGD(opaque);
  66     size_t buf_offset = 0;
  67
  68     while (size > 0 && !QSIMPLEQ_EMPTY(&s->parent.requests)) {
  69         RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
  70         int len = MIN(size, req->size - req->offset);
  71
  72         memcpy(req->data + req->offset, buf + buf_offset, len);
  73         buf_offset += len;
  74         req->offset += len;
  75         size -= len;
  76
  77         if (req->offset == req->size) {
  78             req->receive_entropy(req->opaque, req->data, req->size);
  79
  80             rng_backend_finalize_request(&s->parent, req);
  81         }
  82     }
  83 }
  84
  85 static void rng_egd_opened(RngBackend *b, Error **errp)
  86 {
  87     RngEgd *s = RNG_EGD(b);
  88
  89     if (s->chr_name == NULL) {
  90         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
  91                    "chardev", "a valid character device");
  92         return;
  93     }
  94
  95     s->chr = qemu_chr_find(s->chr_name);
  96     if (s->chr == NULL) {
  97         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
  98                   "Device '%s' not found", s->chr_name);
  99         return;
 100     }
 101
 102     if (qemu_chr_fe_claim(s->chr) != 0) {
 103         error_setg(errp, QERR_DEVICE_IN_USE, s->chr_name);
 104         return;
 105     }
 106
 107     /* FIXME we should resubmit pending requests when the CDS reconnects. */
 108     qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
 109                           NULL, s);
 110 }
 111
 112 static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
 113 {
 114     RngBackend *b = RNG_BACKEND(obj);
 115     RngEgd *s = RNG_EGD(b);
 116
 117     if (b->opened) {
 118         error_setg(errp, QERR_PERMISSION_DENIED);
 119     } else {
 120         g_free(s->chr_name);
 121         s->chr_name = g_strdup(value);
 122     }
 123 }
 124
 125 static char *rng_egd_get_chardev(Object *obj, Error **errp)
 126 {
 127     RngEgd *s = RNG_EGD(obj);
 128
 129     if (s->chr && s->chr->label) {
 130         return g_strdup(s->chr->label);
 131     }
 132
 133     return NULL;
 134 }
 135
 136 static void rng_egd_init(Object *obj)
 137 {
 138     object_property_add_str(obj, "chardev",
 139                             rng_egd_get_chardev, rng_egd_set_chardev,
 140                             NULL);
 141 }
 142
 143 static void rng_egd_finalize(Object *obj)
 144 {
 145     RngEgd *s = RNG_EGD(obj);
 146
 147     if (s->chr) {
 148         qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
 149         qemu_chr_fe_release(s->chr);
 150     }
 151
 152     g_free(s->chr_name);
 153 }
 154
 155 static void rng_egd_class_init(ObjectClass *klass, void *data)
 156 {
 157     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 158
 159     rbc->request_entropy = rng_egd_request_entropy;
 160     rbc->opened = rng_egd_opened;
 161 }
 162
 163 static const TypeInfo rng_egd_info = {
 164     .name = TYPE_RNG_EGD,
 165     .parent = TYPE_RNG_BACKEND,
 166     .instance_size = sizeof(RngEgd),
 167     .class_init = rng_egd_class_init,
 168     .instance_init = rng_egd_init,
 169     .instance_finalize = rng_egd_finalize,
 170 };
 171
 172 static void register_types(void)
 173 {
 174     type_register_static(&rng_egd_info);
 175 }
 176
 177 type_init(register_types);