1 /* 2 * Randomness driver for virtio 3 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 18 */ 19 20 #include <linux/err.h> 21 #include <linux/hw_random.h> 22 #include <linux/scatterlist.h> 23 #include <linux/spinlock.h> 24 #include <linux/virtio.h> 25 #include <linux/virtio_rng.h> 26 #include <linux/module.h> 27 28 static DEFINE_IDA(rng_index_ida); 29 30 struct virtrng_info { 31 struct hwrng hwrng; 32 struct virtqueue *vq; 33 struct completion have_data; 34 char name[25]; 35 unsigned int data_avail; 36 int index; 37 bool busy; 38 bool hwrng_register_done; 39 bool hwrng_removed; 40 }; 41 42 static void random_recv_done(struct virtqueue *vq) 43 { 44 struct virtrng_info *vi = vq->vdev->priv; 45 46 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ 47 if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) 48 return; 49 50 complete(&vi->have_data); 51 } 52 53 /* The host will fill any buffer we give it with sweet, sweet randomness. */ 54 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size) 55 { 56 struct scatterlist sg; 57 58 sg_init_one(&sg, buf, size); 59 60 /* There should always be room for one buffer. */ 61 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL); 62 63 virtqueue_kick(vi->vq); 64 } 65 66 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) 67 { 68 int ret; 69 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 70 71 if (vi->hwrng_removed) 72 return -ENODEV; 73 74 if (!vi->busy) { 75 vi->busy = true; 76 init_completion(&vi->have_data); 77 register_buffer(vi, buf, size); 78 } 79 80 if (!wait) 81 return 0; 82 83 ret = wait_for_completion_killable(&vi->have_data); 84 if (ret < 0) 85 return ret; 86 87 vi->busy = false; 88 89 return vi->data_avail; 90 } 91 92 static void virtio_cleanup(struct hwrng *rng) 93 { 94 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 95 96 if (vi->busy) 97 wait_for_completion(&vi->have_data); 98 } 99 100 static int probe_common(struct virtio_device *vdev) 101 { 102 int err, index; 103 struct virtrng_info *vi = NULL; 104 105 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); 106 if (!vi) 107 return -ENOMEM; 108 109 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); 110 if (index < 0) { 111 err = index; 112 goto err_ida; 113 } 114 sprintf(vi->name, "virtio_rng.%d", index); 115 init_completion(&vi->have_data); 116 117 vi->hwrng = (struct hwrng) { 118 .read = virtio_read, 119 .cleanup = virtio_cleanup, 120 .priv = (unsigned long)vi, 121 .name = vi->name, 122 .quality = 1000, 123 }; 124 vdev->priv = vi; 125 126 /* We expect a single virtqueue. */ 127 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); 128 if (IS_ERR(vi->vq)) { 129 err = PTR_ERR(vi->vq); 130 goto err_find; 131 } 132 133 return 0; 134 135 err_find: 136 ida_simple_remove(&rng_index_ida, index); 137 err_ida: 138 kfree(vi); 139 return err; 140 } 141 142 static void remove_common(struct virtio_device *vdev) 143 { 144 struct virtrng_info *vi = vdev->priv; 145 146 vi->hwrng_removed = true; 147 vi->data_avail = 0; 148 complete(&vi->have_data); 149 vdev->config->reset(vdev); 150 vi->busy = false; 151 if (vi->hwrng_register_done) 152 hwrng_unregister(&vi->hwrng); 153 vdev->config->del_vqs(vdev); 154 ida_simple_remove(&rng_index_ida, vi->index); 155 kfree(vi); 156 } 157 158 static int virtrng_probe(struct virtio_device *vdev) 159 { 160 return probe_common(vdev); 161 } 162 163 static void virtrng_remove(struct virtio_device *vdev) 164 { 165 remove_common(vdev); 166 } 167 168 static void virtrng_scan(struct virtio_device *vdev) 169 { 170 struct virtrng_info *vi = vdev->priv; 171 int err; 172 173 err = hwrng_register(&vi->hwrng); 174 if (!err) 175 vi->hwrng_register_done = true; 176 } 177 178 #ifdef CONFIG_PM_SLEEP 179 static int virtrng_freeze(struct virtio_device *vdev) 180 { 181 remove_common(vdev); 182 return 0; 183 } 184 185 static int virtrng_restore(struct virtio_device *vdev) 186 { 187 int err; 188 189 err = probe_common(vdev); 190 if (!err) { 191 struct virtrng_info *vi = vdev->priv; 192 193 /* 194 * Set hwrng_removed to ensure that virtio_read() 195 * does not block waiting for data before the 196 * registration is complete. 197 */ 198 vi->hwrng_removed = true; 199 err = hwrng_register(&vi->hwrng); 200 if (!err) { 201 vi->hwrng_register_done = true; 202 vi->hwrng_removed = false; 203 } 204 } 205 206 return err; 207 } 208 #endif 209 210 static struct virtio_device_id id_table[] = { 211 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, 212 { 0 }, 213 }; 214 215 static struct virtio_driver virtio_rng_driver = { 216 .driver.name = KBUILD_MODNAME, 217 .driver.owner = THIS_MODULE, 218 .id_table = id_table, 219 .probe = virtrng_probe, 220 .remove = virtrng_remove, 221 .scan = virtrng_scan, 222 #ifdef CONFIG_PM_SLEEP 223 .freeze = virtrng_freeze, 224 .restore = virtrng_restore, 225 #endif 226 }; 227 228 module_virtio_driver(virtio_rng_driver); 229 MODULE_DEVICE_TABLE(virtio, id_table); 230 MODULE_DESCRIPTION("Virtio random number driver"); 231 MODULE_LICENSE("GPL"); 232