1
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
15static const u32 list_limit = 1024;
16static const size_t size_limit_mb = 64;
17
18struct udmabuf {
19 pgoff_t pagecount;
20 struct page **pages;
21};
22
23static vm_fault_t 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
33static const struct vm_operations_struct udmabuf_vm_ops = {
34 .fault = udmabuf_vm_fault,
35};
36
37static 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
49static 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
70err:
71 sg_free_table(sg);
72 kfree(sg);
73 return ERR_PTR(ret);
74}
75
76static void unmap_udmabuf(struct dma_buf_attachment *at,
77 struct sg_table *sg,
78 enum dma_data_direction direction)
79{
80 dma_unmap_sg(at->dev, sg->sgl, sg->nents, direction);
81 sg_free_table(sg);
82 kfree(sg);
83}
84
85static void release_udmabuf(struct dma_buf *buf)
86{
87 struct udmabuf *ubuf = buf->priv;
88 pgoff_t pg;
89
90 for (pg = 0; pg < ubuf->pagecount; pg++)
91 put_page(ubuf->pages[pg]);
92 kfree(ubuf->pages);
93 kfree(ubuf);
94}
95
96static void *kmap_udmabuf(struct dma_buf *buf, unsigned long page_num)
97{
98 struct udmabuf *ubuf = buf->priv;
99 struct page *page = ubuf->pages[page_num];
100
101 return kmap(page);
102}
103
104static void kunmap_udmabuf(struct dma_buf *buf, unsigned long page_num,
105 void *vaddr)
106{
107 kunmap(vaddr);
108}
109
110static const struct dma_buf_ops udmabuf_ops = {
111 .map_dma_buf = map_udmabuf,
112 .unmap_dma_buf = unmap_udmabuf,
113 .release = release_udmabuf,
114 .map = kmap_udmabuf,
115 .unmap = kunmap_udmabuf,
116 .mmap = mmap_udmabuf,
117};
118
119#define SEALS_WANTED (F_SEAL_SHRINK)
120#define SEALS_DENIED (F_SEAL_WRITE)
121
122static long udmabuf_create(const struct udmabuf_create_list *head,
123 const struct udmabuf_create_item *list)
124{
125 DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
126 struct file *memfd = NULL;
127 struct udmabuf *ubuf;
128 struct dma_buf *buf;
129 pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit;
130 struct page *page;
131 int seals, ret = -EINVAL;
132 u32 i, flags;
133
134 ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
135 if (!ubuf)
136 return -ENOMEM;
137
138 pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
139 for (i = 0; i < head->count; i++) {
140 if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
141 goto err;
142 if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
143 goto err;
144 ubuf->pagecount += list[i].size >> PAGE_SHIFT;
145 if (ubuf->pagecount > pglimit)
146 goto err;
147 }
148 ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
149 GFP_KERNEL);
150 if (!ubuf->pages) {
151 ret = -ENOMEM;
152 goto err;
153 }
154
155 pgbuf = 0;
156 for (i = 0; i < head->count; i++) {
157 ret = -EBADFD;
158 memfd = fget(list[i].memfd);
159 if (!memfd)
160 goto err;
161 if (!shmem_mapping(file_inode(memfd)->i_mapping))
162 goto err;
163 seals = memfd_fcntl(memfd, F_GET_SEALS, 0);
164 if (seals == -EINVAL)
165 goto err;
166 ret = -EINVAL;
167 if ((seals & SEALS_WANTED) != SEALS_WANTED ||
168 (seals & SEALS_DENIED) != 0)
169 goto err;
170 pgoff = list[i].offset >> PAGE_SHIFT;
171 pgcnt = list[i].size >> PAGE_SHIFT;
172 for (pgidx = 0; pgidx < pgcnt; pgidx++) {
173 page = shmem_read_mapping_page(
174 file_inode(memfd)->i_mapping, pgoff + pgidx);
175 if (IS_ERR(page)) {
176 ret = PTR_ERR(page);
177 goto err;
178 }
179 ubuf->pages[pgbuf++] = page;
180 }
181 fput(memfd);
182 memfd = NULL;
183 }
184
185 exp_info.ops = &udmabuf_ops;
186 exp_info.size = ubuf->pagecount << PAGE_SHIFT;
187 exp_info.priv = ubuf;
188 exp_info.flags = O_RDWR;
189
190 buf = dma_buf_export(&exp_info);
191 if (IS_ERR(buf)) {
192 ret = PTR_ERR(buf);
193 goto err;
194 }
195
196 flags = 0;
197 if (head->flags & UDMABUF_FLAGS_CLOEXEC)
198 flags |= O_CLOEXEC;
199 return dma_buf_fd(buf, flags);
200
201err:
202 while (pgbuf > 0)
203 put_page(ubuf->pages[--pgbuf]);
204 if (memfd)
205 fput(memfd);
206 kfree(ubuf->pages);
207 kfree(ubuf);
208 return ret;
209}
210
211static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)
212{
213 struct udmabuf_create create;
214 struct udmabuf_create_list head;
215 struct udmabuf_create_item list;
216
217 if (copy_from_user(&create, (void __user *)arg,
218 sizeof(create)))
219 return -EFAULT;
220
221 head.flags = create.flags;
222 head.count = 1;
223 list.memfd = create.memfd;
224 list.offset = create.offset;
225 list.size = create.size;
226
227 return udmabuf_create(&head, &list);
228}
229
230static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)
231{
232 struct udmabuf_create_list head;
233 struct udmabuf_create_item *list;
234 int ret = -EINVAL;
235 u32 lsize;
236
237 if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
238 return -EFAULT;
239 if (head.count > list_limit)
240 return -EINVAL;
241 lsize = sizeof(struct udmabuf_create_item) * head.count;
242 list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
243 if (IS_ERR(list))
244 return PTR_ERR(list);
245
246 ret = udmabuf_create(&head, list);
247 kfree(list);
248 return ret;
249}
250
251static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
252 unsigned long arg)
253{
254 long ret;
255
256 switch (ioctl) {
257 case UDMABUF_CREATE:
258 ret = udmabuf_ioctl_create(filp, arg);
259 break;
260 case UDMABUF_CREATE_LIST:
261 ret = udmabuf_ioctl_create_list(filp, arg);
262 break;
263 default:
264 ret = -ENOTTY;
265 break;
266 }
267 return ret;
268}
269
270static const struct file_operations udmabuf_fops = {
271 .owner = THIS_MODULE,
272 .unlocked_ioctl = udmabuf_ioctl,
273};
274
275static struct miscdevice udmabuf_misc = {
276 .minor = MISC_DYNAMIC_MINOR,
277 .name = "udmabuf",
278 .fops = &udmabuf_fops,
279};
280
281static int __init udmabuf_dev_init(void)
282{
283 return misc_register(&udmabuf_misc);
284}
285
286static void __exit udmabuf_dev_exit(void)
287{
288 misc_deregister(&udmabuf_misc);
289}
290
291module_init(udmabuf_dev_init)
292module_exit(udmabuf_dev_exit)
293
294MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");
295MODULE_LICENSE("GPL v2");
296
