drivers/dma-buf/udmabuf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/cred.h>
   3 #include <linux/device.h>
   4 #include <linux/dma-buf.h>
   5 #include <linux/highmem.h>
   6 #include <linux/init.h>
   7 #include <linux/kernel.h>
   8 #include <linux/memfd.h>
   9 #include <linux/miscdevice.h>
  10 #include <linux/module.h>
  11 #include <linux/shmem_fs.h>
  12 #include <linux/slab.h>
  13 #include <linux/udmabuf.h>
  14
  15 static const u32    list_limit = 1024;  /* udmabuf_create_list->count limit */
  16 static const size_t size_limit_mb = 64; /* total dmabuf size, in megabytes  */
  17
  18 struct udmabuf {
  19         pgoff_t pagecount;
  20         struct page **pages;
  21         struct sg_table *sg;
  22         struct miscdevice *device;
  23 };
  24
  25 static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
  26 {
  27         struct vm_area_struct *vma = vmf->vma;
  28         struct udmabuf *ubuf = vma->vm_private_data;
  29
  30         vmf->page = ubuf->pages[vmf->pgoff];
  31         get_page(vmf->page);
  32         return 0;
  33 }
  34
  35 static const struct vm_operations_struct udmabuf_vm_ops = {
  36         .fault = udmabuf_vm_fault,
  37 };
  38
  39 static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
  40 {
  41         struct udmabuf *ubuf = buf->priv;
  42
  43         if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
  44                 return -EINVAL;
  45
  46         vma->vm_ops = &udmabuf_vm_ops;
  47         vma->vm_private_data = ubuf;
  48         return 0;
  49 }
  50
  51 static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
  52                                      enum dma_data_direction direction)
  53 {
  54         struct udmabuf *ubuf = buf->priv;
  55         struct sg_table *sg;
  56         int ret;
  57
  58         sg = kzalloc(sizeof(*sg), GFP_KERNEL);
  59         if (!sg)
  60                 return ERR_PTR(-ENOMEM);
  61         ret = sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->pagecount,
  62                                         0, ubuf->pagecount << PAGE_SHIFT,
  63                                         GFP_KERNEL);
  64         if (ret < 0)
  65                 goto err;
  66         if (!dma_map_sg(dev, sg->sgl, sg->nents, direction)) {
  67                 ret = -EINVAL;
  68                 goto err;
  69         }
  70         return sg;
  71
  72 err:
  73         sg_free_table(sg);
  74         kfree(sg);
  75         return ERR_PTR(ret);
  76 }
  77
  78 static void put_sg_table(struct device *dev, struct sg_table *sg,
  79                          enum dma_data_direction direction)
  80 {
  81         dma_unmap_sg(dev, sg->sgl, sg->nents, direction);
  82         sg_free_table(sg);
  83         kfree(sg);
  84 }
  85
  86 static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,
  87                                     enum dma_data_direction direction)
  88 {
  89         return get_sg_table(at->dev, at->dmabuf, direction);
  90 }
  91
  92 static void unmap_udmabuf(struct dma_buf_attachment *at,
  93                           struct sg_table *sg,
  94                           enum dma_data_direction direction)
  95 {
  96         return put_sg_table(at->dev, sg, direction);
  97 }
  98
  99 static void release_udmabuf(struct dma_buf *buf)
 100 {
 101         struct udmabuf *ubuf = buf->priv;
 102         struct device *dev = ubuf->device->this_device;
 103         pgoff_t pg;
 104
 105         if (ubuf->sg)
 106                 put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
 107
 108         for (pg = 0; pg < ubuf->pagecount; pg++)
 109                 put_page(ubuf->pages[pg]);
 110         kfree(ubuf->pages);
 111         kfree(ubuf);
 112 }
 113
 114 static int begin_cpu_udmabuf(struct dma_buf *buf,
 115                              enum dma_data_direction direction)
 116 {
 117         struct udmabuf *ubuf = buf->priv;
 118         struct device *dev = ubuf->device->this_device;
 119
 120         if (!ubuf->sg) {
 121                 ubuf->sg = get_sg_table(dev, buf, direction);
 122                 if (IS_ERR(ubuf->sg))
 123                         return PTR_ERR(ubuf->sg);
 124         } else {
 125                 dma_sync_sg_for_device(dev, ubuf->sg->sgl,
 126                                        ubuf->sg->nents,
 127                                        direction);
 128         }
 129
 130         return 0;
 131 }
 132
 133 static int end_cpu_udmabuf(struct dma_buf *buf,
 134                            enum dma_data_direction direction)
 135 {
 136         struct udmabuf *ubuf = buf->priv;
 137         struct device *dev = ubuf->device->this_device;
 138
 139         if (!ubuf->sg)
 140                 return -EINVAL;
 141
 142         dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents, direction);
 143         return 0;
 144 }
 145
 146 static const struct dma_buf_ops udmabuf_ops = {
 147         .cache_sgt_mapping = true,
 148         .map_dma_buf       = map_udmabuf,
 149         .unmap_dma_buf     = unmap_udmabuf,
 150         .release           = release_udmabuf,
 151         .mmap              = mmap_udmabuf,
 152         .begin_cpu_access  = begin_cpu_udmabuf,
 153         .end_cpu_access    = end_cpu_udmabuf,
 154 };
 155
 156 #define SEALS_WANTED (F_SEAL_SHRINK)
 157 #define SEALS_DENIED (F_SEAL_WRITE)
 158
 159 static long udmabuf_create(struct miscdevice *device,
 160                            struct udmabuf_create_list *head,
 161                            struct udmabuf_create_item *list)
 162 {
 163         DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 164         struct file *memfd = NULL;
 165         struct udmabuf *ubuf;
 166         struct dma_buf *buf;
 167         pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit;
 168         struct page *page;
 169         int seals, ret = -EINVAL;
 170         u32 i, flags;
 171
 172         ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
 173         if (!ubuf)
 174                 return -ENOMEM;
 175
 176         pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
 177         for (i = 0; i < head->count; i++) {
 178                 if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
 179                         goto err;
 180                 if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
 181                         goto err;
 182                 ubuf->pagecount += list[i].size >> PAGE_SHIFT;
 183                 if (ubuf->pagecount > pglimit)
 184                         goto err;
 185         }
 186         ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
 187                                     GFP_KERNEL);
 188         if (!ubuf->pages) {
 189                 ret = -ENOMEM;
 190                 goto err;
 191         }
 192
 193         pgbuf = 0;
 194         for (i = 0; i < head->count; i++) {
 195                 ret = -EBADFD;
 196                 memfd = fget(list[i].memfd);
 197                 if (!memfd)
 198                         goto err;
 199                 if (!shmem_mapping(file_inode(memfd)->i_mapping))
 200                         goto err;
 201                 seals = memfd_fcntl(memfd, F_GET_SEALS, 0);
 202                 if (seals == -EINVAL)
 203                         goto err;
 204                 ret = -EINVAL;
 205                 if ((seals & SEALS_WANTED) != SEALS_WANTED ||
 206                     (seals & SEALS_DENIED) != 0)
 207                         goto err;
 208                 pgoff = list[i].offset >> PAGE_SHIFT;
 209                 pgcnt = list[i].size   >> PAGE_SHIFT;
 210                 for (pgidx = 0; pgidx < pgcnt; pgidx++) {
 211                         page = shmem_read_mapping_page(
 212                                 file_inode(memfd)->i_mapping, pgoff + pgidx);
 213                         if (IS_ERR(page)) {
 214                                 ret = PTR_ERR(page);
 215                                 goto err;
 216                         }
 217                         ubuf->pages[pgbuf++] = page;
 218                 }
 219                 fput(memfd);
 220                 memfd = NULL;
 221         }
 222
 223         exp_info.ops  = &udmabuf_ops;
 224         exp_info.size = ubuf->pagecount << PAGE_SHIFT;
 225         exp_info.priv = ubuf;
 226         exp_info.flags = O_RDWR;
 227
 228         ubuf->device = device;
 229         buf = dma_buf_export(&exp_info);
 230         if (IS_ERR(buf)) {
 231                 ret = PTR_ERR(buf);
 232                 goto err;
 233         }
 234
 235         flags = 0;
 236         if (head->flags & UDMABUF_FLAGS_CLOEXEC)
 237                 flags |= O_CLOEXEC;
 238         return dma_buf_fd(buf, flags);
 239
 240 err:
 241         while (pgbuf > 0)
 242                 put_page(ubuf->pages[--pgbuf]);
 243         if (memfd)
 244                 fput(memfd);
 245         kfree(ubuf->pages);
 246         kfree(ubuf);
 247         return ret;
 248 }
 249
 250 static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)
 251 {
 252         struct udmabuf_create create;
 253         struct udmabuf_create_list head;
 254         struct udmabuf_create_item list;
 255
 256         if (copy_from_user(&create, (void __user *)arg,
 257                            sizeof(create)))
 258                 return -EFAULT;
 259
 260         head.flags  = create.flags;
 261         head.count  = 1;
 262         list.memfd  = create.memfd;
 263         list.offset = create.offset;
 264         list.size   = create.size;
 265
 266         return udmabuf_create(filp->private_data, &head, &list);
 267 }
 268
 269 static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)
 270 {
 271         struct udmabuf_create_list head;
 272         struct udmabuf_create_item *list;
 273         int ret = -EINVAL;
 274         u32 lsize;
 275
 276         if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
 277                 return -EFAULT;
 278         if (head.count > list_limit)
 279                 return -EINVAL;
 280         lsize = sizeof(struct udmabuf_create_item) * head.count;
 281         list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
 282         if (IS_ERR(list))
 283                 return PTR_ERR(list);
 284
 285         ret = udmabuf_create(filp->private_data, &head, list);
 286         kfree(list);
 287         return ret;
 288 }
 289
 290 static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
 291                           unsigned long arg)
 292 {
 293         long ret;
 294
 295         switch (ioctl) {
 296         case UDMABUF_CREATE:
 297                 ret = udmabuf_ioctl_create(filp, arg);
 298                 break;
 299         case UDMABUF_CREATE_LIST:
 300                 ret = udmabuf_ioctl_create_list(filp, arg);
 301                 break;
 302         default:
 303                 ret = -ENOTTY;
 304                 break;
 305         }
 306         return ret;
 307 }
 308
 309 static const struct file_operations udmabuf_fops = {
 310         .owner          = THIS_MODULE,
 311         .unlocked_ioctl = udmabuf_ioctl,
 312 };
 313
 314 static struct miscdevice udmabuf_misc = {
 315         .minor          = MISC_DYNAMIC_MINOR,
 316         .name           = "udmabuf",
 317         .fops           = &udmabuf_fops,
 318 };
 319
 320 static int __init udmabuf_dev_init(void)
 321 {
 322         return misc_register(&udmabuf_misc);
 323 }
 324
 325 static void __exit udmabuf_dev_exit(void)
 326 {
 327         misc_deregister(&udmabuf_misc);
 328 }
 329
 330 module_init(udmabuf_dev_init)
 331 module_exit(udmabuf_dev_exit)
 332
 333 MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");
 334 MODULE_LICENSE("GPL v2");