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