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 start = untagged_addr(start);
50
51 down_read(&mm->mmap_sem);
52 locked = 1;
53 vma = find_vma_intersection(mm, start, start + 1);
54 if (!vma) {
55 ret = -EFAULT;
56 goto out;
57 }
58
59 /*
60 * While get_vaddr_frames() could be used for transient (kernel
61 * controlled lifetime) pinning of memory pages all current
62 * users establish long term (userspace controlled lifetime)
63 * page pinning. Treat get_vaddr_frames() like
64 * get_user_pages_longterm() and disallow it for filesystem-dax
65 * mappings.
66 */
67 if (vma_is_fsdax(vma)) {
68 ret = -EOPNOTSUPP;
69 goto out;
70 }
71
72 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
73 vec->got_ref = true;
74 vec->is_pfns = false;
75 ret = get_user_pages_locked(start, nr_frames,
76 gup_flags, (struct page **)(vec->ptrs), &locked);
77 goto out;
78 }
79
80 vec->got_ref = false;
81 vec->is_pfns = true;
82 do {
83 unsigned long *nums = frame_vector_pfns(vec);
84
85 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
86 err = follow_pfn(vma, start, &nums[ret]);
87 if (err) {
88 if (ret == 0)
89 ret = err;
90 goto out;
91 }
92 start += PAGE_SIZE;
93 ret++;
94 }
95 /*
96 * We stop if we have enough pages or if VMA doesn't completely
97 * cover the tail page.
98 */
99 if (ret >= nr_frames || start < vma->vm_end)
100 break;
101 vma = find_vma_intersection(mm, start, start + 1);
102 } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
103 out:
104 if (locked)
105 up_read(&mm->mmap_sem);
106 if (!ret)
107 ret = -EFAULT;
108 if (ret > 0)
109 vec->nr_frames = ret;
110 return ret;
111 }
112 EXPORT_SYMBOL(get_vaddr_frames);
113
114 /**
115 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
116 * them
117 * @vec: frame vector to put
118 *
119 * Drop references to pages if get_vaddr_frames() acquired them. We also
120 * invalidate the frame vector so that it is prepared for the next call into
121 * get_vaddr_frames().
122 */
123 void put_vaddr_frames(struct frame_vector *vec)
124 {
125 int i;
126 struct page **pages;
127
128 if (!vec->got_ref)
129 goto out;
130 pages = frame_vector_pages(vec);
131 /*
132 * frame_vector_pages() might needed to do a conversion when
133 * get_vaddr_frames() got pages but vec was later converted to pfns.
134 * But it shouldn't really fail to convert pfns back...
135 */
136 if (WARN_ON(IS_ERR(pages)))
137 goto out;
138 for (i = 0; i < vec->nr_frames; i++)
139 put_page(pages[i]);
140 vec->got_ref = false;
141 out:
142 vec->nr_frames = 0;
143 }
144 EXPORT_SYMBOL(put_vaddr_frames);
145
146 /**
147 * frame_vector_to_pages - convert frame vector to contain page pointers
148 * @vec: frame vector to convert
149 *
150 * Convert @vec to contain array of page pointers. If the conversion is
151 * successful, return 0. Otherwise return an error. Note that we do not grab
152 * page references for the page structures.
153 */
154 int frame_vector_to_pages(struct frame_vector *vec)
155 {
156 int i;
157 unsigned long *nums;
158 struct page **pages;
159
160 if (!vec->is_pfns)
161 return 0;
162 nums = frame_vector_pfns(vec);
163 for (i = 0; i < vec->nr_frames; i++)
164 if (!pfn_valid(nums[i]))
165 return -EINVAL;
166 pages = (struct page **)nums;
167 for (i = 0; i < vec->nr_frames; i++)
168 pages[i] = pfn_to_page(nums[i]);
169 vec->is_pfns = false;
170 return 0;
171 }
172 EXPORT_SYMBOL(frame_vector_to_pages);
173
174 /**
175 * frame_vector_to_pfns - convert frame vector to contain pfns
176 * @vec: frame vector to convert
177 *
178 * Convert @vec to contain array of pfns.
179 */
180 void frame_vector_to_pfns(struct frame_vector *vec)
181 {
182 int i;
183 unsigned long *nums;
184 struct page **pages;
185
186 if (vec->is_pfns)
187 return;
188 pages = (struct page **)(vec->ptrs);
189 nums = (unsigned long *)pages;
190 for (i = 0; i < vec->nr_frames; i++)
191 nums[i] = page_to_pfn(pages[i]);
192 vec->is_pfns = true;
193 }
194 EXPORT_SYMBOL(frame_vector_to_pfns);
195
196 /**
197 * frame_vector_create() - allocate & initialize structure for pinned pfns
198 * @nr_frames: number of pfns slots we should reserve
199 *
200 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
201 * pfns.
202 */
203 struct frame_vector *frame_vector_create(unsigned int nr_frames)
204 {
205 struct frame_vector *vec;
206 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
207
208 if (WARN_ON_ONCE(nr_frames == 0))
209 return NULL;
210 /*
211 * This is absurdly high. It's here just to avoid strange effects when
212 * arithmetics overflows.
213 */
214 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
215 return NULL;
216 /*
217 * Avoid higher order allocations, use vmalloc instead. It should
218 * be rare anyway.
219 */
220 vec = kvmalloc(size, GFP_KERNEL);
221 if (!vec)
222 return NULL;
223 vec->nr_allocated = nr_frames;
224 vec->nr_frames = 0;
225 return vec;
226 }
227 EXPORT_SYMBOL(frame_vector_create);
228
229 /**
230 * frame_vector_destroy() - free memory allocated to carry frame vector
231 * @vec: Frame vector to free
232 *
233 * Free structure allocated by frame_vector_create() to carry frames.
234 */
235 void frame_vector_destroy(struct frame_vector *vec)
236 {
237 /* Make sure put_vaddr_frames() got called properly... */
238 VM_BUG_ON(vec->nr_frames > 0);
239 kvfree(vec);
240 }
241 EXPORT_SYMBOL(frame_vector_destroy);