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 */
40int 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}
69EXPORT_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 */
80void 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;
97out:
98	vec->nr_frames = 0;
99}
100EXPORT_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 */
110int 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}
128EXPORT_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 */
136void 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}
150EXPORT_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 */
159struct frame_vector *frame_vector_create(unsigned int nr_frames)
160{
161	struct frame_vector *vec;
162	int size = struct_size(vec, ptrs, 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}
183EXPORT_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 */
191void 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}
197EXPORT_SYMBOL(frame_vector_destroy);
198