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 }; 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->busy) { 72 vi->busy = true; 73 init_completion(&vi->have_data); 74 register_buffer(vi, buf, size); 75 } 76 77 if (!wait) 78 return 0; 79 80 ret = wait_for_completion_killable(&vi->have_data); 81 if (ret < 0) 82 return ret; 83 84 vi->busy = false; 85 86 return vi->data_avail; 87 } 88 89 static void virtio_cleanup(struct hwrng *rng) 90 { 91 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 92 93 if (vi->busy) 94 wait_for_completion(&vi->have_data); 95 } 96 97 static int probe_common(struct virtio_device *vdev) 98 { 99 int err, index; 100 struct virtrng_info *vi = NULL; 101 102 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); 103 if (!vi) 104 return -ENOMEM; 105 106 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); 107 if (index < 0) { 108 kfree(vi); 109 return index; 110 } 111 sprintf(vi->name, "virtio_rng.%d", index); 112 init_completion(&vi->have_data); 113 114 vi->hwrng = (struct hwrng) { 115 .read = virtio_read, 116 .cleanup = virtio_cleanup, 117 .priv = (unsigned long)vi, 118 .name = vi->name, 119 .quality = 1000, 120 }; 121 vdev->priv = vi; 122 123 /* We expect a single virtqueue. */ 124 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); 125 if (IS_ERR(vi->vq)) { 126 err = PTR_ERR(vi->vq); 127 vi->vq = NULL; 128 kfree(vi); 129 ida_simple_remove(&rng_index_ida, index); 130 return err; 131 } 132 133 return 0; 134 } 135 136 static void remove_common(struct virtio_device *vdev) 137 { 138 struct virtrng_info *vi = vdev->priv; 139 140 vdev->config->reset(vdev); 141 vi->busy = false; 142 if (vi->hwrng_register_done) 143 hwrng_unregister(&vi->hwrng); 144 vdev->config->del_vqs(vdev); 145 ida_simple_remove(&rng_index_ida, vi->index); 146 kfree(vi); 147 } 148 149 static int virtrng_probe(struct virtio_device *vdev) 150 { 151 return probe_common(vdev); 152 } 153 154 static void virtrng_remove(struct virtio_device *vdev) 155 { 156 remove_common(vdev); 157 } 158 159 static void virtrng_scan(struct virtio_device *vdev) 160 { 161 struct virtrng_info *vi = vdev->priv; 162 int err; 163 164 err = hwrng_register(&vi->hwrng); 165 if (!err) 166 vi->hwrng_register_done = true; 167 } 168 169 #ifdef CONFIG_PM_SLEEP 170 static int virtrng_freeze(struct virtio_device *vdev) 171 { 172 remove_common(vdev); 173 return 0; 174 } 175 176 static int virtrng_restore(struct virtio_device *vdev) 177 { 178 return probe_common(vdev); 179 } 180 #endif 181 182 static struct virtio_device_id id_table[] = { 183 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, 184 { 0 }, 185 }; 186 187 static struct virtio_driver virtio_rng_driver = { 188 .driver.name = KBUILD_MODNAME, 189 .driver.owner = THIS_MODULE, 190 .id_table = id_table, 191 .probe = virtrng_probe, 192 .remove = virtrng_remove, 193 .scan = virtrng_scan, 194 #ifdef CONFIG_PM_SLEEP 195 .freeze = virtrng_freeze, 196 .restore = virtrng_restore, 197 #endif 198 }; 199 200 module_virtio_driver(virtio_rng_driver); 201 MODULE_DEVICE_TABLE(virtio, id_table); 202 MODULE_DESCRIPTION("Virtio random number driver"); 203 MODULE_LICENSE("GPL"); 204