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>
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 */
22 struct miscdevice *device;
25 static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
27 struct vm_area_struct *vma = vmf->vma;
28 struct udmabuf *ubuf = vma->vm_private_data;
30 vmf->page = ubuf->pages[vmf->pgoff];
35 static const struct vm_operations_struct udmabuf_vm_ops = {
36 .fault = udmabuf_vm_fault,
39 static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
41 struct udmabuf *ubuf = buf->priv;
43 if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
46 vma->vm_ops = &udmabuf_vm_ops;
47 vma->vm_private_data = ubuf;
51 static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
52 enum dma_data_direction direction)
54 struct udmabuf *ubuf = buf->priv;
58 sg = kzalloc(sizeof(*sg), GFP_KERNEL);
60 return ERR_PTR(-ENOMEM);
61 ret = sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->pagecount,
62 0, ubuf->pagecount << PAGE_SHIFT,
66 if (!dma_map_sg(dev, sg->sgl, sg->nents, direction)) {
78 static void put_sg_table(struct device *dev, struct sg_table *sg,
79 enum dma_data_direction direction)
81 dma_unmap_sg(dev, sg->sgl, sg->nents, direction);
86 static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,
87 enum dma_data_direction direction)
89 return get_sg_table(at->dev, at->dmabuf, direction);
92 static void unmap_udmabuf(struct dma_buf_attachment *at,
94 enum dma_data_direction direction)
96 return put_sg_table(at->dev, sg, direction);
99 static void release_udmabuf(struct dma_buf *buf)
101 struct udmabuf *ubuf = buf->priv;
102 struct device *dev = ubuf->device->this_device;
106 put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
108 for (pg = 0; pg < ubuf->pagecount; pg++)
109 put_page(ubuf->pages[pg]);
114 static int begin_cpu_udmabuf(struct dma_buf *buf,
115 enum dma_data_direction direction)
117 struct udmabuf *ubuf = buf->priv;
118 struct device *dev = ubuf->device->this_device;
121 ubuf->sg = get_sg_table(dev, buf, direction);
122 if (IS_ERR(ubuf->sg))
123 return PTR_ERR(ubuf->sg);
125 dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents,
132 static int end_cpu_udmabuf(struct dma_buf *buf,
133 enum dma_data_direction direction)
135 struct udmabuf *ubuf = buf->priv;
136 struct device *dev = ubuf->device->this_device;
141 dma_sync_sg_for_device(dev, ubuf->sg->sgl, ubuf->sg->nents, direction);
145 static const struct dma_buf_ops udmabuf_ops = {
146 .cache_sgt_mapping = true,
147 .map_dma_buf = map_udmabuf,
148 .unmap_dma_buf = unmap_udmabuf,
149 .release = release_udmabuf,
150 .mmap = mmap_udmabuf,
151 .begin_cpu_access = begin_cpu_udmabuf,
152 .end_cpu_access = end_cpu_udmabuf,
155 #define SEALS_WANTED (F_SEAL_SHRINK)
156 #define SEALS_DENIED (F_SEAL_WRITE)
158 static long udmabuf_create(struct miscdevice *device,
159 struct udmabuf_create_list *head,
160 struct udmabuf_create_item *list)
162 DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
163 struct file *memfd = NULL;
164 struct udmabuf *ubuf;
166 pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit;
168 int seals, ret = -EINVAL;
171 ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
175 pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
176 for (i = 0; i < head->count; i++) {
177 if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
179 if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
181 ubuf->pagecount += list[i].size >> PAGE_SHIFT;
182 if (ubuf->pagecount > pglimit)
185 ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
193 for (i = 0; i < head->count; i++) {
195 memfd = fget(list[i].memfd);
198 if (!shmem_mapping(file_inode(memfd)->i_mapping))
200 seals = memfd_fcntl(memfd, F_GET_SEALS, 0);
201 if (seals == -EINVAL)
204 if ((seals & SEALS_WANTED) != SEALS_WANTED ||
205 (seals & SEALS_DENIED) != 0)
207 pgoff = list[i].offset >> PAGE_SHIFT;
208 pgcnt = list[i].size >> PAGE_SHIFT;
209 for (pgidx = 0; pgidx < pgcnt; pgidx++) {
210 page = shmem_read_mapping_page(
211 file_inode(memfd)->i_mapping, pgoff + pgidx);
216 ubuf->pages[pgbuf++] = page;
222 exp_info.ops = &udmabuf_ops;
223 exp_info.size = ubuf->pagecount << PAGE_SHIFT;
224 exp_info.priv = ubuf;
225 exp_info.flags = O_RDWR;
227 ubuf->device = device;
228 buf = dma_buf_export(&exp_info);
235 if (head->flags & UDMABUF_FLAGS_CLOEXEC)
237 return dma_buf_fd(buf, flags);
241 put_page(ubuf->pages[--pgbuf]);
249 static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)
251 struct udmabuf_create create;
252 struct udmabuf_create_list head;
253 struct udmabuf_create_item list;
255 if (copy_from_user(&create, (void __user *)arg,
259 head.flags = create.flags;
261 list.memfd = create.memfd;
262 list.offset = create.offset;
263 list.size = create.size;
265 return udmabuf_create(filp->private_data, &head, &list);
268 static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)
270 struct udmabuf_create_list head;
271 struct udmabuf_create_item *list;
275 if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
277 if (head.count > list_limit)
279 lsize = sizeof(struct udmabuf_create_item) * head.count;
280 list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
282 return PTR_ERR(list);
284 ret = udmabuf_create(filp->private_data, &head, list);
289 static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
296 ret = udmabuf_ioctl_create(filp, arg);
298 case UDMABUF_CREATE_LIST:
299 ret = udmabuf_ioctl_create_list(filp, arg);
308 static const struct file_operations udmabuf_fops = {
309 .owner = THIS_MODULE,
310 .unlocked_ioctl = udmabuf_ioctl,
313 static struct miscdevice udmabuf_misc = {
314 .minor = MISC_DYNAMIC_MINOR,
316 .fops = &udmabuf_fops,
319 static int __init udmabuf_dev_init(void)
321 return misc_register(&udmabuf_misc);
324 static void __exit udmabuf_dev_exit(void)
326 misc_deregister(&udmabuf_misc);
329 module_init(udmabuf_dev_init)
330 module_exit(udmabuf_dev_exit)
332 MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");
333 MODULE_LICENSE("GPL v2");