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         /* XXX this blocks entire thread. Rewrite to use
  45          * qemu_chr_fe_write and background I/O callbacks */
  46         qemu_chr_fe_write_all(s->chr, header, sizeof(header));
  47
  48         size -= len;
  49     }
  50 }
  51
  52 static int rng_egd_chr_can_read(void *opaque)
  53 {
  54     RngEgd *s = RNG_EGD(opaque);
  55     RngRequest *req;
  56     int size = 0;
  57
  58     QSIMPLEQ_FOREACH(req, &s->parent.requests, next) {
  59         size += req->size - req->offset;
  60     }
  61
  62     return size;
  63 }
  64
  65 static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
  66 {
  67     RngEgd *s = RNG_EGD(opaque);
  68     size_t buf_offset = 0;
  69
  70     while (size > 0 && !QSIMPLEQ_EMPTY(&s->parent.requests)) {
  71         RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
  72         int len = MIN(size, req->size - req->offset);
  73
  74         memcpy(req->data + req->offset, buf + buf_offset, len);
  75         buf_offset += len;
  76         req->offset += len;
  77         size -= len;
  78
  79         if (req->offset == req->size) {
  80             req->receive_entropy(req->opaque, req->data, req->size);
  81
  82             rng_backend_finalize_request(&s->parent, req);
  83         }
  84     }
  85 }
  86
  87 static void rng_egd_opened(RngBackend *b, Error **errp)
  88 {
  89     RngEgd *s = RNG_EGD(b);
  90
  91     if (s->chr_name == NULL) {
  92         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
  93                    "chardev", "a valid character device");
  94         return;
  95     }
  96
  97     s->chr = qemu_chr_find(s->chr_name);
  98     if (s->chr == NULL) {
  99         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
 100                   "Device '%s' not found", s->chr_name);
 101         return;
 102     }
 103
 104     if (qemu_chr_fe_claim(s->chr) != 0) {
 105         error_setg(errp, QERR_DEVICE_IN_USE, s->chr_name);
 106         return;
 107     }
 108
 109     /* FIXME we should resubmit pending requests when the CDS reconnects. */
 110     qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,
 111                           NULL, s);
 112 }
 113
 114 static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
 115 {
 116     RngBackend *b = RNG_BACKEND(obj);
 117     RngEgd *s = RNG_EGD(b);
 118
 119     if (b->opened) {
 120         error_setg(errp, QERR_PERMISSION_DENIED);
 121     } else {
 122         g_free(s->chr_name);
 123         s->chr_name = g_strdup(value);
 124     }
 125 }
 126
 127 static char *rng_egd_get_chardev(Object *obj, Error **errp)
 128 {
 129     RngEgd *s = RNG_EGD(obj);
 130
 131     if (s->chr && s->chr->label) {
 132         return g_strdup(s->chr->label);
 133     }
 134
 135     return NULL;
 136 }
 137
 138 static void rng_egd_init(Object *obj)
 139 {
 140     object_property_add_str(obj, "chardev",
 141                             rng_egd_get_chardev, rng_egd_set_chardev,
 142                             NULL);
 143 }
 144
 145 static void rng_egd_finalize(Object *obj)
 146 {
 147     RngEgd *s = RNG_EGD(obj);
 148
 149     if (s->chr) {
 150         qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
 151         qemu_chr_fe_release(s->chr);
 152     }
 153
 154     g_free(s->chr_name);
 155 }
 156
 157 static void rng_egd_class_init(ObjectClass *klass, void *data)
 158 {
 159     RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
 160
 161     rbc->request_entropy = rng_egd_request_entropy;
 162     rbc->opened = rng_egd_opened;
 163 }
 164
 165 static const TypeInfo rng_egd_info = {
 166     .name = TYPE_RNG_EGD,
 167     .parent = TYPE_RNG_BACKEND,
 168     .instance_size = sizeof(RngEgd),
 169     .class_init = rng_egd_class_init,
 170     .instance_init = rng_egd_init,
 171     .instance_finalize = rng_egd_finalize,
 172 };
 173
 174 static void register_types(void)
 175 {
 176     type_register_static(&rng_egd_info);
 177 }
 178
 179 type_init(register_types);