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 43 static void random_recv_done(struct virtqueue *vq) 44 { 45 struct virtrng_info *vi = vq->vdev->priv; 46 47 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ 48 if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) 49 return; 50 51 complete(&vi->have_data); 52 } 53 54 /* The host will fill any buffer we give it with sweet, sweet randomness. */ 55 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size) 56 { 57 struct scatterlist sg; 58 59 sg_init_one(&sg, buf, size); 60 61 /* There should always be room for one buffer. */ 62 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL); 63 64 virtqueue_kick(vi->vq); 65 } 66 67 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) 68 { 69 int ret; 70 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 71 72 if (vi->hwrng_removed) 73 return -ENODEV; 74 75 if (!vi->busy) { 76 vi->busy = true; 77 init_completion(&vi->have_data); 78 register_buffer(vi, buf, size); 79 } 80 81 if (!wait) 82 return 0; 83 84 ret = wait_for_completion_killable(&vi->have_data); 85 if (ret < 0) 86 return ret; 87 88 vi->busy = false; 89 90 return vi->data_avail; 91 } 92 93 static void virtio_cleanup(struct hwrng *rng) 94 { 95 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 96 97 if (vi->busy) 98 wait_for_completion(&vi->have_data); 99 } 100 101 static int probe_common(struct virtio_device *vdev) 102 { 103 int err, index; 104 struct virtrng_info *vi = NULL; 105 106 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); 107 if (!vi) 108 return -ENOMEM; 109 110 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); 111 if (index < 0) { 112 kfree(vi); 113 return index; 114 } 115 sprintf(vi->name, "virtio_rng.%d", index); 116 init_completion(&vi->have_data); 117 118 vi->hwrng = (struct hwrng) { 119 .read = virtio_read, 120 .cleanup = virtio_cleanup, 121 .priv = (unsigned long)vi, 122 .name = vi->name, 123 .quality = 1000, 124 }; 125 vdev->priv = vi; 126 127 /* We expect a single virtqueue. */ 128 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); 129 if (IS_ERR(vi->vq)) { 130 err = PTR_ERR(vi->vq); 131 vi->vq = NULL; 132 kfree(vi); 133 ida_simple_remove(&rng_index_ida, index); 134 return err; 135 } 136 137 return 0; 138 } 139 140 static void remove_common(struct virtio_device *vdev) 141 { 142 struct virtrng_info *vi = vdev->priv; 143 144 vi->hwrng_removed = true; 145 vi->data_avail = 0; 146 complete(&vi->have_data); 147 vdev->config->reset(vdev); 148 vi->busy = false; 149 if (vi->hwrng_register_done) 150 hwrng_unregister(&vi->hwrng); 151 vdev->config->del_vqs(vdev); 152 ida_simple_remove(&rng_index_ida, vi->index); 153 kfree(vi); 154 } 155 156 static int virtrng_probe(struct virtio_device *vdev) 157 { 158 return probe_common(vdev); 159 } 160 161 static void virtrng_remove(struct virtio_device *vdev) 162 { 163 remove_common(vdev); 164 } 165 166 static void virtrng_scan(struct virtio_device *vdev) 167 { 168 struct virtrng_info *vi = vdev->priv; 169 int err; 170 171 err = hwrng_register(&vi->hwrng); 172 if (!err) 173 vi->hwrng_register_done = true; 174 } 175 176 #ifdef CONFIG_PM_SLEEP 177 static int virtrng_freeze(struct virtio_device *vdev) 178 { 179 remove_common(vdev); 180 return 0; 181 } 182 183 static int virtrng_restore(struct virtio_device *vdev) 184 { 185 return probe_common(vdev); 186 } 187 #endif 188 189 static struct virtio_device_id id_table[] = { 190 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, 191 { 0 }, 192 }; 193 194 static struct virtio_driver virtio_rng_driver = { 195 .driver.name = KBUILD_MODNAME, 196 .driver.owner = THIS_MODULE, 197 .id_table = id_table, 198 .probe = virtrng_probe, 199 .remove = virtrng_remove, 200 .scan = virtrng_scan, 201 #ifdef CONFIG_PM_SLEEP 202 .freeze = virtrng_freeze, 203 .restore = virtrng_restore, 204 #endif 205 }; 206 207 module_virtio_driver(virtio_rng_driver); 208 MODULE_DEVICE_TABLE(virtio, id_table); 209 MODULE_DESCRIPTION("Virtio random number driver"); 210 MODULE_LICENSE("GPL"); 211