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 /**
12 * get_vaddr_frames() - map virtual addresses to pfns
13 * @start: starting user address
14 * @nr_frames: number of pages / pfns from start to map
15 * @gup_flags: flags modifying lookup behaviour
16 * @vec: structure which receives pages / pfns of the addresses mapped.
17 * It should have space for at least nr_frames entries.
18 *
19 * This function maps virtual addresses from @start and fills @vec structure
20 * with page frame numbers or page pointers to corresponding pages (choice
21 * depends on the type of the vma underlying the virtual address). If @start
22 * belongs to a normal vma, the function grabs reference to each of the pages
23 * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
24 * touch page structures and the caller must make sure pfns aren't reused for
25 * anything else while he is using them.
26 *
27 * The function returns number of pages mapped which may be less than
28 * @nr_frames. In particular we stop mapping if there are more vmas of
29 * different type underlying the specified range of virtual addresses.
30 * When the function isn't able to map a single page, it returns error.
31 *
32 * This function takes care of grabbing mmap_sem as necessary.
33 */
34 int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
35 unsigned int gup_flags, struct frame_vector *vec)
36 {
37 struct mm_struct *mm = current->mm;
38 struct vm_area_struct *vma;
39 int ret = 0;
40 int err;
41 int locked;
42
43 if (nr_frames == 0)
44 return 0;
45
46 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
47 nr_frames = vec->nr_allocated;
48
49 down_read(&mm->mmap_sem);
50 locked = 1;
51 vma = find_vma_intersection(mm, start, start + 1);
52 if (!vma) {
53 ret = -EFAULT;
54 goto out;
55 }
56
57 /*
58 * While get_vaddr_frames() could be used for transient (kernel
59 * controlled lifetime) pinning of memory pages all current
60 * users establish long term (userspace controlled lifetime)
61 * page pinning. Treat get_vaddr_frames() like
62 * get_user_pages_longterm() and disallow it for filesystem-dax
63 * mappings.
64 */
65 if (vma_is_fsdax(vma)) {
66 ret = -EOPNOTSUPP;
67 goto out;
68 }
69
70 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
71 vec->got_ref = true;
72 vec->is_pfns = false;
73 ret = get_user_pages_locked(start, nr_frames,
74 gup_flags, (struct page **)(vec->ptrs), &locked);
75 goto out;
76 }
77
78 vec->got_ref = false;
79 vec->is_pfns = true;
80 do {
81 unsigned long *nums = frame_vector_pfns(vec);
82
83 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
84 err = follow_pfn(vma, start, &nums[ret]);
85 if (err) {
86 if (ret == 0)
87 ret = err;
88 goto out;
89 }
90 start += PAGE_SIZE;
91 ret++;
92 }
93 /*
94 * We stop if we have enough pages or if VMA doesn't completely
95 * cover the tail page.
96 */
97 if (ret >= nr_frames || start < vma->vm_end)
98 break;
99 vma = find_vma_intersection(mm, start, start + 1);
100 } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
101 out:
102 if (locked)
103 up_read(&mm->mmap_sem);
104 if (!ret)
105 ret = -EFAULT;
106 if (ret > 0)
107 vec->nr_frames = ret;
108 return ret;
109 }
110 EXPORT_SYMBOL(get_vaddr_frames);
111
112 /**
113 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
114 * them
115 * @vec: frame vector to put
116 *
117 * Drop references to pages if get_vaddr_frames() acquired them. We also
118 * invalidate the frame vector so that it is prepared for the next call into
119 * get_vaddr_frames().
120 */
121 void put_vaddr_frames(struct frame_vector *vec)
122 {
123 int i;
124 struct page **pages;
125
126 if (!vec->got_ref)
127 goto out;
128 pages = frame_vector_pages(vec);
129 /*
130 * frame_vector_pages() might needed to do a conversion when
131 * get_vaddr_frames() got pages but vec was later converted to pfns.
132 * But it shouldn't really fail to convert pfns back...
133 */
134 if (WARN_ON(IS_ERR(pages)))
135 goto out;
136 for (i = 0; i < vec->nr_frames; i++)
137 put_page(pages[i]);
138 vec->got_ref = false;
139 out:
140 vec->nr_frames = 0;
141 }
142 EXPORT_SYMBOL(put_vaddr_frames);
143
144 /**
145 * frame_vector_to_pages - convert frame vector to contain page pointers
146 * @vec: frame vector to convert
147 *
148 * Convert @vec to contain array of page pointers. If the conversion is
149 * successful, return 0. Otherwise return an error. Note that we do not grab
150 * page references for the page structures.
151 */
152 int frame_vector_to_pages(struct frame_vector *vec)
153 {
154 int i;
155 unsigned long *nums;
156 struct page **pages;
157
158 if (!vec->is_pfns)
159 return 0;
160 nums = frame_vector_pfns(vec);
161 for (i = 0; i < vec->nr_frames; i++)
162 if (!pfn_valid(nums[i]))
163 return -EINVAL;
164 pages = (struct page **)nums;
165 for (i = 0; i < vec->nr_frames; i++)
166 pages[i] = pfn_to_page(nums[i]);
167 vec->is_pfns = false;
168 return 0;
169 }
170 EXPORT_SYMBOL(frame_vector_to_pages);
171
172 /**
173 * frame_vector_to_pfns - convert frame vector to contain pfns
174 * @vec: frame vector to convert
175 *
176 * Convert @vec to contain array of pfns.
177 */
178 void frame_vector_to_pfns(struct frame_vector *vec)
179 {
180 int i;
181 unsigned long *nums;
182 struct page **pages;
183
184 if (vec->is_pfns)
185 return;
186 pages = (struct page **)(vec->ptrs);
187 nums = (unsigned long *)pages;
188 for (i = 0; i < vec->nr_frames; i++)
189 nums[i] = page_to_pfn(pages[i]);
190 vec->is_pfns = true;
191 }
192 EXPORT_SYMBOL(frame_vector_to_pfns);
193
194 /**
195 * frame_vector_create() - allocate & initialize structure for pinned pfns
196 * @nr_frames: number of pfns slots we should reserve
197 *
198 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
199 * pfns.
200 */
201 struct frame_vector *frame_vector_create(unsigned int nr_frames)
202 {
203 struct frame_vector *vec;
204 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
205
206 if (WARN_ON_ONCE(nr_frames == 0))
207 return NULL;
208 /*
209 * This is absurdly high. It's here just to avoid strange effects when
210 * arithmetics overflows.
211 */
212 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
213 return NULL;
214 /*
215 * Avoid higher order allocations, use vmalloc instead. It should
216 * be rare anyway.
217 */
218 vec = kvmalloc(size, GFP_KERNEL);
219 if (!vec)
220 return NULL;
221 vec->nr_allocated = nr_frames;
222 vec->nr_frames = 0;
223 return vec;
224 }
225 EXPORT_SYMBOL(frame_vector_create);
226
227 /**
228 * frame_vector_destroy() - free memory allocated to carry frame vector
229 * @vec: Frame vector to free
230 *
231 * Free structure allocated by frame_vector_create() to carry frames.
232 */
233 void frame_vector_destroy(struct frame_vector *vec)
234 {
235 /* Make sure put_vaddr_frames() got called properly... */
236 VM_BUG_ON(vec->nr_frames > 0);
237 kvfree(vec);
238 }
239 EXPORT_SYMBOL(frame_vector_destroy);
240
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