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_lock as necessary.
33 */
get_vaddr_frames(unsigned long start,unsigned int nr_frames,unsigned int gup_flags,struct frame_vector * vec)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 mmap_read_lock(mm);
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 = pin_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 mmap_read_unlock(mm);
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 */
put_vaddr_frames(struct frame_vector * vec)123 void put_vaddr_frames(struct frame_vector *vec)
124 {
125 struct page **pages;
126
127 if (!vec->got_ref)
128 goto out;
129 pages = frame_vector_pages(vec);
130 /*
131 * frame_vector_pages() might needed to do a conversion when
132 * get_vaddr_frames() got pages but vec was later converted to pfns.
133 * But it shouldn't really fail to convert pfns back...
134 */
135 if (WARN_ON(IS_ERR(pages)))
136 goto out;
137
138 unpin_user_pages(pages, vec->nr_frames);
139 vec->got_ref = false;
140 out:
141 vec->nr_frames = 0;
142 }
143 EXPORT_SYMBOL(put_vaddr_frames);
144
145 /**
146 * frame_vector_to_pages - convert frame vector to contain page pointers
147 * @vec: frame vector to convert
148 *
149 * Convert @vec to contain array of page pointers. If the conversion is
150 * successful, return 0. Otherwise return an error. Note that we do not grab
151 * page references for the page structures.
152 */
frame_vector_to_pages(struct frame_vector * vec)153 int frame_vector_to_pages(struct frame_vector *vec)
154 {
155 int i;
156 unsigned long *nums;
157 struct page **pages;
158
159 if (!vec->is_pfns)
160 return 0;
161 nums = frame_vector_pfns(vec);
162 for (i = 0; i < vec->nr_frames; i++)
163 if (!pfn_valid(nums[i]))
164 return -EINVAL;
165 pages = (struct page **)nums;
166 for (i = 0; i < vec->nr_frames; i++)
167 pages[i] = pfn_to_page(nums[i]);
168 vec->is_pfns = false;
169 return 0;
170 }
171 EXPORT_SYMBOL(frame_vector_to_pages);
172
173 /**
174 * frame_vector_to_pfns - convert frame vector to contain pfns
175 * @vec: frame vector to convert
176 *
177 * Convert @vec to contain array of pfns.
178 */
frame_vector_to_pfns(struct frame_vector * vec)179 void frame_vector_to_pfns(struct frame_vector *vec)
180 {
181 int i;
182 unsigned long *nums;
183 struct page **pages;
184
185 if (vec->is_pfns)
186 return;
187 pages = (struct page **)(vec->ptrs);
188 nums = (unsigned long *)pages;
189 for (i = 0; i < vec->nr_frames; i++)
190 nums[i] = page_to_pfn(pages[i]);
191 vec->is_pfns = true;
192 }
193 EXPORT_SYMBOL(frame_vector_to_pfns);
194
195 /**
196 * frame_vector_create() - allocate & initialize structure for pinned pfns
197 * @nr_frames: number of pfns slots we should reserve
198 *
199 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
200 * pfns.
201 */
frame_vector_create(unsigned int nr_frames)202 struct frame_vector *frame_vector_create(unsigned int nr_frames)
203 {
204 struct frame_vector *vec;
205 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
206
207 if (WARN_ON_ONCE(nr_frames == 0))
208 return NULL;
209 /*
210 * This is absurdly high. It's here just to avoid strange effects when
211 * arithmetics overflows.
212 */
213 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
214 return NULL;
215 /*
216 * Avoid higher order allocations, use vmalloc instead. It should
217 * be rare anyway.
218 */
219 vec = kvmalloc(size, GFP_KERNEL);
220 if (!vec)
221 return NULL;
222 vec->nr_allocated = nr_frames;
223 vec->nr_frames = 0;
224 return vec;
225 }
226 EXPORT_SYMBOL(frame_vector_create);
227
228 /**
229 * frame_vector_destroy() - free memory allocated to carry frame vector
230 * @vec: Frame vector to free
231 *
232 * Free structure allocated by frame_vector_create() to carry frames.
233 */
frame_vector_destroy(struct frame_vector * vec)234 void frame_vector_destroy(struct frame_vector *vec)
235 {
236 /* Make sure put_vaddr_frames() got called properly... */
237 VM_BUG_ON(vec->nr_frames > 0);
238 kvfree(vec);
239 }
240 EXPORT_SYMBOL(frame_vector_destroy);
241
