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 void random_recv_done(struct virtqueue *vq) 42 { 43 struct virtrng_info *vi = vq->vdev->priv; 44 45 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ 46 if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) 47 return; 48 49 complete(&vi->have_data); 50 } 51 52 /* The host will fill any buffer we give it with sweet, sweet randomness. */ 53 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size) 54 { 55 struct scatterlist sg; 56 57 sg_init_one(&sg, buf, size); 58 59 /* There should always be room for one buffer. */ 60 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL); 61 62 virtqueue_kick(vi->vq); 63 } 64 65 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) 66 { 67 int ret; 68 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 69 70 if (!vi->busy) { 71 vi->busy = true; 72 init_completion(&vi->have_data); 73 register_buffer(vi, buf, size); 74 } 75 76 if (!wait) 77 return 0; 78 79 ret = wait_for_completion_killable(&vi->have_data); 80 if (ret < 0) 81 return ret; 82 83 vi->busy = false; 84 85 return vi->data_avail; 86 } 87 88 static void virtio_cleanup(struct hwrng *rng) 89 { 90 struct virtrng_info *vi = (struct virtrng_info *)rng->priv; 91 92 if (vi->busy) 93 wait_for_completion(&vi->have_data); 94 } 95 96 static int probe_common(struct virtio_device *vdev) 97 { 98 int err, index; 99 struct virtrng_info *vi = NULL; 100 101 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); 102 if (!vi) 103 return -ENOMEM; 104 105 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); 106 if (index < 0) { 107 kfree(vi); 108 return index; 109 } 110 sprintf(vi->name, "virtio_rng.%d", index); 111 init_completion(&vi->have_data); 112 113 vi->hwrng = (struct hwrng) { 114 .read = virtio_read, 115 .cleanup = virtio_cleanup, 116 .priv = (unsigned long)vi, 117 .name = vi->name, 118 }; 119 vdev->priv = vi; 120 121 /* We expect a single virtqueue. */ 122 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); 123 if (IS_ERR(vi->vq)) { 124 err = PTR_ERR(vi->vq); 125 vi->vq = NULL; 126 kfree(vi); 127 ida_simple_remove(&rng_index_ida, index); 128 return err; 129 } 130 131 err = hwrng_register(&vi->hwrng); 132 if (err) { 133 vdev->config->del_vqs(vdev); 134 vi->vq = NULL; 135 kfree(vi); 136 ida_simple_remove(&rng_index_ida, index); 137 return err; 138 } 139 140 return 0; 141 } 142 143 static void remove_common(struct virtio_device *vdev) 144 { 145 struct virtrng_info *vi = vdev->priv; 146 vdev->config->reset(vdev); 147 vi->busy = false; 148 hwrng_unregister(&vi->hwrng); 149 vdev->config->del_vqs(vdev); 150 ida_simple_remove(&rng_index_ida, vi->index); 151 kfree(vi); 152 } 153 154 static int virtrng_probe(struct virtio_device *vdev) 155 { 156 return probe_common(vdev); 157 } 158 159 static void virtrng_remove(struct virtio_device *vdev) 160 { 161 remove_common(vdev); 162 } 163 164 #ifdef CONFIG_PM_SLEEP 165 static int virtrng_freeze(struct virtio_device *vdev) 166 { 167 remove_common(vdev); 168 return 0; 169 } 170 171 static int virtrng_restore(struct virtio_device *vdev) 172 { 173 return probe_common(vdev); 174 } 175 #endif 176 177 static struct virtio_device_id id_table[] = { 178 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, 179 { 0 }, 180 }; 181 182 static struct virtio_driver virtio_rng_driver = { 183 .driver.name = KBUILD_MODNAME, 184 .driver.owner = THIS_MODULE, 185 .id_table = id_table, 186 .probe = virtrng_probe, 187 .remove = virtrng_remove, 188 #ifdef CONFIG_PM_SLEEP 189 .freeze = virtrng_freeze, 190 .restore = virtrng_restore, 191 #endif 192 }; 193 194 module_virtio_driver(virtio_rng_driver); 195 MODULE_DEVICE_TABLE(virtio, id_table); 196 MODULE_DESCRIPTION("Virtio random number driver"); 197 MODULE_LICENSE("GPL"); 198