1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Framework for userspace DMA-BUF allocations
4 *
5 * Copyright (C) 2011 Google, Inc.
6 * Copyright (C) 2019 Linaro Ltd.
7 */
8
9#include <linux/cdev.h>
10#include <linux/debugfs.h>
11#include <linux/device.h>
12#include <linux/dma-buf.h>
13#include <linux/err.h>
14#include <linux/xarray.h>
15#include <linux/list.h>
16#include <linux/slab.h>
17#include <linux/nospec.h>
18#include <linux/uaccess.h>
19#include <linux/syscalls.h>
20#include <linux/dma-heap.h>
21#include <uapi/linux/dma-heap.h>
22
23#define DEVNAME "dma_heap"
24
25#define NUM_HEAP_MINORS 128
26
27/**
28 * struct dma_heap - represents a dmabuf heap in the system
29 * @name:		used for debugging/device-node name
30 * @ops:		ops struct for this heap
31 * @heap_devt		heap device node
32 * @list		list head connecting to list of heaps
33 * @heap_cdev		heap char device
34 *
35 * Represents a heap of memory from which buffers can be made.
36 */
37struct dma_heap {
38	const char *name;
39	const struct dma_heap_ops *ops;
40	void *priv;
41	dev_t heap_devt;
42	struct list_head list;
43	struct cdev heap_cdev;
44};
45
46static LIST_HEAD(heap_list);
47static DEFINE_MUTEX(heap_list_lock);
48static dev_t dma_heap_devt;
49static struct class *dma_heap_class;
50static DEFINE_XARRAY_ALLOC(dma_heap_minors);
51
52static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
53				 unsigned int fd_flags,
54				 unsigned int heap_flags)
55{
56	struct dma_buf *dmabuf;
57	int fd;
58
59	/*
60	 * Allocations from all heaps have to begin
61	 * and end on page boundaries.
62	 */
63	len = PAGE_ALIGN(len);
64	if (!len)
65		return -EINVAL;
66
67	dmabuf = heap->ops->allocate(heap, len, fd_flags, heap_flags);
68	if (IS_ERR(dmabuf))
69		return PTR_ERR(dmabuf);
70
71	fd = dma_buf_fd(dmabuf, fd_flags);
72	if (fd < 0) {
73		dma_buf_put(dmabuf);
74		/* just return, as put will call release and that will free */
75	}
76	return fd;
77}
78
79static int dma_heap_open(struct inode *inode, struct file *file)
80{
81	struct dma_heap *heap;
82
83	heap = xa_load(&dma_heap_minors, iminor(inode));
84	if (!heap) {
85		pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
86		return -ENODEV;
87	}
88
89	/* instance data as context */
90	file->private_data = heap;
91	nonseekable_open(inode, file);
92
93	return 0;
94}
95
96static long dma_heap_ioctl_allocate(struct file *file, void *data)
97{
98	struct dma_heap_allocation_data *heap_allocation = data;
99	struct dma_heap *heap = file->private_data;
100	int fd;
101
102	if (heap_allocation->fd)
103		return -EINVAL;
104
105	if (heap_allocation->fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
106		return -EINVAL;
107
108	if (heap_allocation->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
109		return -EINVAL;
110
111	fd = dma_heap_buffer_alloc(heap, heap_allocation->len,
112				   heap_allocation->fd_flags,
113				   heap_allocation->heap_flags);
114	if (fd < 0)
115		return fd;
116
117	heap_allocation->fd = fd;
118
119	return 0;
120}
121
122static unsigned int dma_heap_ioctl_cmds[] = {
123	DMA_HEAP_IOCTL_ALLOC,
124};
125
126static long dma_heap_ioctl(struct file *file, unsigned int ucmd,
127			   unsigned long arg)
128{
129	char stack_kdata[128];
130	char *kdata = stack_kdata;
131	unsigned int kcmd;
132	unsigned int in_size, out_size, drv_size, ksize;
133	int nr = _IOC_NR(ucmd);
134	int ret = 0;
135
136	if (nr >= ARRAY_SIZE(dma_heap_ioctl_cmds))
137		return -EINVAL;
138
139	nr = array_index_nospec(nr, ARRAY_SIZE(dma_heap_ioctl_cmds));
140	/* Get the kernel ioctl cmd that matches */
141	kcmd = dma_heap_ioctl_cmds[nr];
142
143	/* Figure out the delta between user cmd size and kernel cmd size */
144	drv_size = _IOC_SIZE(kcmd);
145	out_size = _IOC_SIZE(ucmd);
146	in_size = out_size;
147	if ((ucmd & kcmd & IOC_IN) == 0)
148		in_size = 0;
149	if ((ucmd & kcmd & IOC_OUT) == 0)
150		out_size = 0;
151	ksize = max(max(in_size, out_size), drv_size);
152
153	/* If necessary, allocate buffer for ioctl argument */
154	if (ksize > sizeof(stack_kdata)) {
155		kdata = kmalloc(ksize, GFP_KERNEL);
156		if (!kdata)
157			return -ENOMEM;
158	}
159
160	if (copy_from_user(kdata, (void __user *)arg, in_size) != 0) {
161		ret = -EFAULT;
162		goto err;
163	}
164
165	/* zero out any difference between the kernel/user structure size */
166	if (ksize > in_size)
167		memset(kdata + in_size, 0, ksize - in_size);
168
169	switch (kcmd) {
170	case DMA_HEAP_IOCTL_ALLOC:
171		ret = dma_heap_ioctl_allocate(file, kdata);
172		break;
173	default:
174		ret = -ENOTTY;
175		goto err;
176	}
177
178	if (copy_to_user((void __user *)arg, kdata, out_size) != 0)
179		ret = -EFAULT;
180err:
181	if (kdata != stack_kdata)
182		kfree(kdata);
183	return ret;
184}
185
186static const struct file_operations dma_heap_fops = {
187	.owner          = THIS_MODULE,
188	.open		= dma_heap_open,
189	.unlocked_ioctl = dma_heap_ioctl,
190#ifdef CONFIG_COMPAT
191	.compat_ioctl	= dma_heap_ioctl,
192#endif
193};
194
195/**
196 * dma_heap_get_drvdata() - get per-subdriver data for the heap
197 * @heap: DMA-Heap to retrieve private data for
198 *
199 * Returns:
200 * The per-subdriver data for the heap.
201 */
202void *dma_heap_get_drvdata(struct dma_heap *heap)
203{
204	return heap->priv;
205}
206
207/**
208 * dma_heap_get_name() - get heap name
209 * @heap: DMA-Heap to retrieve private data for
210 *
211 * Returns:
212 * The char* for the heap name.
213 */
214const char *dma_heap_get_name(struct dma_heap *heap)
215{
216	return heap->name;
217}
218
219struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
220{
221	struct dma_heap *heap, *h, *err_ret;
222	struct device *dev_ret;
223	unsigned int minor;
224	int ret;
225
226	if (!exp_info->name || !strcmp(exp_info->name, "")) {
227		pr_err("dma_heap: Cannot add heap without a name\n");
228		return ERR_PTR(-EINVAL);
229	}
230
231	if (!exp_info->ops || !exp_info->ops->allocate) {
232		pr_err("dma_heap: Cannot add heap with invalid ops struct\n");
233		return ERR_PTR(-EINVAL);
234	}
235
236	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
237	if (!heap)
238		return ERR_PTR(-ENOMEM);
239
240	heap->name = exp_info->name;
241	heap->ops = exp_info->ops;
242	heap->priv = exp_info->priv;
243
244	/* Find unused minor number */
245	ret = xa_alloc(&dma_heap_minors, &minor, heap,
246		       XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
247	if (ret < 0) {
248		pr_err("dma_heap: Unable to get minor number for heap\n");
249		err_ret = ERR_PTR(ret);
250		goto err0;
251	}
252
253	/* Create device */
254	heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), minor);
255
256	cdev_init(&heap->heap_cdev, &dma_heap_fops);
257	ret = cdev_add(&heap->heap_cdev, heap->heap_devt, 1);
258	if (ret < 0) {
259		pr_err("dma_heap: Unable to add char device\n");
260		err_ret = ERR_PTR(ret);
261		goto err1;
262	}
263
264	dev_ret = device_create(dma_heap_class,
265				NULL,
266				heap->heap_devt,
267				NULL,
268				heap->name);
269	if (IS_ERR(dev_ret)) {
270		pr_err("dma_heap: Unable to create device\n");
271		err_ret = ERR_CAST(dev_ret);
272		goto err2;
273	}
274
275	mutex_lock(&heap_list_lock);
276	/* check the name is unique */
277	list_for_each_entry(h, &heap_list, list) {
278		if (!strcmp(h->name, exp_info->name)) {
279			mutex_unlock(&heap_list_lock);
280			pr_err("dma_heap: Already registered heap named %s\n",
281			       exp_info->name);
282			err_ret = ERR_PTR(-EINVAL);
283			goto err3;
284		}
285	}
286
287	/* Add heap to the list */
288	list_add(&heap->list, &heap_list);
289	mutex_unlock(&heap_list_lock);
290
291	return heap;
292
293err3:
294	device_destroy(dma_heap_class, heap->heap_devt);
295err2:
296	cdev_del(&heap->heap_cdev);
297err1:
298	xa_erase(&dma_heap_minors, minor);
299err0:
300	kfree(heap);
301	return err_ret;
302}
303
304static char *dma_heap_devnode(const struct device *dev, umode_t *mode)
305{
306	return kasprintf(GFP_KERNEL, "dma_heap/%s", dev_name(dev));
307}
308
309static int dma_heap_init(void)
310{
311	int ret;
312
313	ret = alloc_chrdev_region(&dma_heap_devt, 0, NUM_HEAP_MINORS, DEVNAME);
314	if (ret)
315		return ret;
316
317	dma_heap_class = class_create(DEVNAME);
318	if (IS_ERR(dma_heap_class)) {
319		unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
320		return PTR_ERR(dma_heap_class);
321	}
322	dma_heap_class->devnode = dma_heap_devnode;
323
324	return 0;
325}
326subsys_initcall(dma_heap_init);
327