1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
4 #include <linux/err.h>
5 #include <linux/mm.h>
6 #include <linux/slab.h>
7 #include <linux/vmalloc.h>
8 #include <linux/pagemap.h>
9 #include <linux/sched.h>
10 
11 #include <media/frame_vector.h>
12 
13 /**
14  * get_vaddr_frames() - map virtual addresses to pfns
15  * @start:	starting user address
16  * @nr_frames:	number of pages / pfns from start to map
17  * @write:	the mapped address has write permission
18  * @vec:	structure which receives pages / pfns of the addresses mapped.
19  *		It should have space for at least nr_frames entries.
20  *
21  * This function maps virtual addresses from @start and fills @vec structure
22  * with page frame numbers or page pointers to corresponding pages (choice
23  * depends on the type of the vma underlying the virtual address). If @start
24  * belongs to a normal vma, the function grabs reference to each of the pages
25  * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
26  * touch page structures and the caller must make sure pfns aren't reused for
27  * anything else while he is using them.
28  *
29  * The function returns number of pages mapped which may be less than
30  * @nr_frames. In particular we stop mapping if there are more vmas of
31  * different type underlying the specified range of virtual addresses.
32  * When the function isn't able to map a single page, it returns error.
33  *
34  * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
35  * to be able to do that, but that could (racily) return non-refcounted
36  * pfns.
37  *
38  * This function takes care of grabbing mmap_lock as necessary.
39  */
40 int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
41 		     struct frame_vector *vec)
42 {
43 	int ret;
44 	unsigned int gup_flags = FOLL_LONGTERM;
45 
46 	if (nr_frames == 0)
47 		return 0;
48 
49 	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
50 		nr_frames = vec->nr_allocated;
51 
52 	start = untagged_addr(start);
53 
54 	if (write)
55 		gup_flags |= FOLL_WRITE;
56 
57 	ret = pin_user_pages_fast(start, nr_frames, gup_flags,
58 				  (struct page **)(vec->ptrs));
59 	vec->got_ref = true;
60 	vec->is_pfns = false;
61 	vec->nr_frames = ret;
62 
63 	if (likely(ret > 0))
64 		return ret;
65 
66 	vec->nr_frames = 0;
67 	return ret ? ret : -EFAULT;
68 }
69 EXPORT_SYMBOL(get_vaddr_frames);
70 
71 /**
72  * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
73  *			them
74  * @vec:	frame vector to put
75  *
76  * Drop references to pages if get_vaddr_frames() acquired them. We also
77  * invalidate the frame vector so that it is prepared for the next call into
78  * get_vaddr_frames().
79  */
80 void put_vaddr_frames(struct frame_vector *vec)
81 {
82 	struct page **pages;
83 
84 	if (!vec->got_ref)
85 		goto out;
86 	pages = frame_vector_pages(vec);
87 	/*
88 	 * frame_vector_pages() might needed to do a conversion when
89 	 * get_vaddr_frames() got pages but vec was later converted to pfns.
90 	 * But it shouldn't really fail to convert pfns back...
91 	 */
92 	if (WARN_ON(IS_ERR(pages)))
93 		goto out;
94 
95 	unpin_user_pages(pages, vec->nr_frames);
96 	vec->got_ref = false;
97 out:
98 	vec->nr_frames = 0;
99 }
100 EXPORT_SYMBOL(put_vaddr_frames);
101 
102 /**
103  * frame_vector_to_pages - convert frame vector to contain page pointers
104  * @vec:	frame vector to convert
105  *
106  * Convert @vec to contain array of page pointers.  If the conversion is
107  * successful, return 0. Otherwise return an error. Note that we do not grab
108  * page references for the page structures.
109  */
110 int frame_vector_to_pages(struct frame_vector *vec)
111 {
112 	int i;
113 	unsigned long *nums;
114 	struct page **pages;
115 
116 	if (!vec->is_pfns)
117 		return 0;
118 	nums = frame_vector_pfns(vec);
119 	for (i = 0; i < vec->nr_frames; i++)
120 		if (!pfn_valid(nums[i]))
121 			return -EINVAL;
122 	pages = (struct page **)nums;
123 	for (i = 0; i < vec->nr_frames; i++)
124 		pages[i] = pfn_to_page(nums[i]);
125 	vec->is_pfns = false;
126 	return 0;
127 }
128 EXPORT_SYMBOL(frame_vector_to_pages);
129 
130 /**
131  * frame_vector_to_pfns - convert frame vector to contain pfns
132  * @vec:	frame vector to convert
133  *
134  * Convert @vec to contain array of pfns.
135  */
136 void frame_vector_to_pfns(struct frame_vector *vec)
137 {
138 	int i;
139 	unsigned long *nums;
140 	struct page **pages;
141 
142 	if (vec->is_pfns)
143 		return;
144 	pages = (struct page **)(vec->ptrs);
145 	nums = (unsigned long *)pages;
146 	for (i = 0; i < vec->nr_frames; i++)
147 		nums[i] = page_to_pfn(pages[i]);
148 	vec->is_pfns = true;
149 }
150 EXPORT_SYMBOL(frame_vector_to_pfns);
151 
152 /**
153  * frame_vector_create() - allocate & initialize structure for pinned pfns
154  * @nr_frames:	number of pfns slots we should reserve
155  *
156  * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
157  * pfns.
158  */
159 struct frame_vector *frame_vector_create(unsigned int nr_frames)
160 {
161 	struct frame_vector *vec;
162 	int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
163 
164 	if (WARN_ON_ONCE(nr_frames == 0))
165 		return NULL;
166 	/*
167 	 * This is absurdly high. It's here just to avoid strange effects when
168 	 * arithmetics overflows.
169 	 */
170 	if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
171 		return NULL;
172 	/*
173 	 * Avoid higher order allocations, use vmalloc instead. It should
174 	 * be rare anyway.
175 	 */
176 	vec = kvmalloc(size, GFP_KERNEL);
177 	if (!vec)
178 		return NULL;
179 	vec->nr_allocated = nr_frames;
180 	vec->nr_frames = 0;
181 	return vec;
182 }
183 EXPORT_SYMBOL(frame_vector_create);
184 
185 /**
186  * frame_vector_destroy() - free memory allocated to carry frame vector
187  * @vec:	Frame vector to free
188  *
189  * Free structure allocated by frame_vector_create() to carry frames.
190  */
191 void frame_vector_destroy(struct frame_vector *vec)
192 {
193 	/* Make sure put_vaddr_frames() got called properly... */
194 	VM_BUG_ON(vec->nr_frames > 0);
195 	kvfree(vec);
196 }
197 EXPORT_SYMBOL(frame_vector_destroy);
198