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 virtio_device *vdev; 32 struct hwrng hwrng; 33 struct virtqueue *vq; 34 unsigned int data_avail; 35 struct completion have_data; 36 bool busy; 37 char name[25]; 38 int index; 39 }; 40 41 static bool probe_done; 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 /* 73 * Don't ask host for data till we're setup. This call can 74 * happen during hwrng_register(), after commit d9e7972619. 75 */ 76 if (unlikely(!probe_done)) 77 return 0; 78 79 if (!vi->busy) { 80 vi->busy = true; 81 init_completion(&vi->have_data); 82 register_buffer(vi, buf, size); 83 } 84 85 if (!wait) 86 return 0; 87 88 ret = wait_for_completion_killable(&vi->have_data); 89 if (ret < 0) 90 return ret; 91 92 vi->busy = false; 93 94 return vi->data_avail; 95 } 96 97 static void virtio_cleanup(struct hwrng *rng) 98 { 99 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 100 101 if (vi->busy) 102 wait_for_completion(&vi->have_data); 103 } 104 105 static int probe_common(struct virtio_device *vdev) 106 { 107 int err, index; 108 struct virtrng_info *vi = NULL; 109 110 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); 111 if (!vi) 112 return -ENOMEM; 113 114 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); 115 if (index < 0) { 116 kfree(vi); 117 return index; 118 } 119 sprintf(vi->name, "virtio_rng.%d", index); 120 init_completion(&vi->have_data); 121 122 vi->hwrng = (struct hwrng) { 123 .read = virtio_read, 124 .cleanup = virtio_cleanup, 125 .priv = (unsigned long)vi, 126 .name = vi->name, 127 }; 128 vdev->priv = vi; 129 130 /* We expect a single virtqueue. */ 131 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); 132 if (IS_ERR(vi->vq)) { 133 err = PTR_ERR(vi->vq); 134 vi->vq = NULL; 135 kfree(vi); 136 ida_simple_remove(&rng_index_ida, index); 137 return err; 138 } 139 140 err = hwrng_register(&vi->hwrng); 141 if (err) { 142 vdev->config->del_vqs(vdev); 143 vi->vq = NULL; 144 kfree(vi); 145 ida_simple_remove(&rng_index_ida, index); 146 return err; 147 } 148 149 probe_done = true; 150 return 0; 151 } 152 153 static void remove_common(struct virtio_device *vdev) 154 { 155 struct virtrng_info *vi = vdev->priv; 156 vdev->config->reset(vdev); 157 vi->busy = false; 158 hwrng_unregister(&vi->hwrng); 159 vdev->config->del_vqs(vdev); 160 ida_simple_remove(&rng_index_ida, vi->index); 161 kfree(vi); 162 } 163 164 static int virtrng_probe(struct virtio_device *vdev) 165 { 166 return probe_common(vdev); 167 } 168 169 static void virtrng_remove(struct virtio_device *vdev) 170 { 171 remove_common(vdev); 172 } 173 174 #ifdef CONFIG_PM_SLEEP 175 static int virtrng_freeze(struct virtio_device *vdev) 176 { 177 remove_common(vdev); 178 return 0; 179 } 180 181 static int virtrng_restore(struct virtio_device *vdev) 182 { 183 return probe_common(vdev); 184 } 185 #endif 186 187 static struct virtio_device_id id_table[] = { 188 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, 189 { 0 }, 190 }; 191 192 static struct virtio_driver virtio_rng_driver = { 193 .driver.name = KBUILD_MODNAME, 194 .driver.owner = THIS_MODULE, 195 .id_table = id_table, 196 .probe = virtrng_probe, 197 .remove = virtrng_remove, 198 #ifdef CONFIG_PM_SLEEP 199 .freeze = virtrng_freeze, 200 .restore = virtrng_restore, 201 #endif 202 }; 203 204 module_virtio_driver(virtio_rng_driver); 205 MODULE_DEVICE_TABLE(virtio, id_table); 206 MODULE_DESCRIPTION("Virtio random number driver"); 207 MODULE_LICENSE("GPL"); 208