Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
1#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/err.h>
4#include <linux/mm.h>
5#include <linux/slab.h>
6#include <linux/vmalloc.h>
7#include <linux/pagemap.h>
8#include <linux/sched.h>
9
10/**
11 * get_vaddr_frames() - map virtual addresses to pfns
12 * @start: starting user address
13 * @nr_frames: number of pages / pfns from start to map
14 * @gup_flags: flags modifying lookup behaviour
15 * @vec: structure which receives pages / pfns of the addresses mapped.
16 * It should have space for at least nr_frames entries.
17 *
18 * This function maps virtual addresses from @start and fills @vec structure
19 * with page frame numbers or page pointers to corresponding pages (choice
20 * depends on the type of the vma underlying the virtual address). If @start
21 * belongs to a normal vma, the function grabs reference to each of the pages
22 * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
23 * touch page structures and the caller must make sure pfns aren't reused for
24 * anything else while he is using them.
25 *
26 * The function returns number of pages mapped which may be less than
27 * @nr_frames. In particular we stop mapping if there are more vmas of
28 * different type underlying the specified range of virtual addresses.
29 * When the function isn't able to map a single page, it returns error.
30 *
31 * This function takes care of grabbing mmap_sem as necessary.
32 */
33int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
34 unsigned int gup_flags, struct frame_vector *vec)
35{
36 struct mm_struct *mm = current->mm;
37 struct vm_area_struct *vma;
38 int ret = 0;
39 int err;
40 int locked;
41
42 if (nr_frames == 0)
43 return 0;
44
45 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
46 nr_frames = vec->nr_allocated;
47
48 down_read(&mm->mmap_sem);
49 locked = 1;
50 vma = find_vma_intersection(mm, start, start + 1);
51 if (!vma) {
52 ret = -EFAULT;
53 goto out;
54 }
55 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
56 vec->got_ref = true;
57 vec->is_pfns = false;
58 ret = get_user_pages_locked(start, nr_frames,
59 gup_flags, (struct page **)(vec->ptrs), &locked);
60 goto out;
61 }
62
63 vec->got_ref = false;
64 vec->is_pfns = true;
65 do {
66 unsigned long *nums = frame_vector_pfns(vec);
67
68 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
69 err = follow_pfn(vma, start, &nums[ret]);
70 if (err) {
71 if (ret == 0)
72 ret = err;
73 goto out;
74 }
75 start += PAGE_SIZE;
76 ret++;
77 }
78 /*
79 * We stop if we have enough pages or if VMA doesn't completely
80 * cover the tail page.
81 */
82 if (ret >= nr_frames || start < vma->vm_end)
83 break;
84 vma = find_vma_intersection(mm, start, start + 1);
85 } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
86out:
87 if (locked)
88 up_read(&mm->mmap_sem);
89 if (!ret)
90 ret = -EFAULT;
91 if (ret > 0)
92 vec->nr_frames = ret;
93 return ret;
94}
95EXPORT_SYMBOL(get_vaddr_frames);
96
97/**
98 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
99 * them
100 * @vec: frame vector to put
101 *
102 * Drop references to pages if get_vaddr_frames() acquired them. We also
103 * invalidate the frame vector so that it is prepared for the next call into
104 * get_vaddr_frames().
105 */
106void put_vaddr_frames(struct frame_vector *vec)
107{
108 int i;
109 struct page **pages;
110
111 if (!vec->got_ref)
112 goto out;
113 pages = frame_vector_pages(vec);
114 /*
115 * frame_vector_pages() might needed to do a conversion when
116 * get_vaddr_frames() got pages but vec was later converted to pfns.
117 * But it shouldn't really fail to convert pfns back...
118 */
119 if (WARN_ON(IS_ERR(pages)))
120 goto out;
121 for (i = 0; i < vec->nr_frames; i++)
122 put_page(pages[i]);
123 vec->got_ref = false;
124out:
125 vec->nr_frames = 0;
126}
127EXPORT_SYMBOL(put_vaddr_frames);
128
129/**
130 * frame_vector_to_pages - convert frame vector to contain page pointers
131 * @vec: frame vector to convert
132 *
133 * Convert @vec to contain array of page pointers. If the conversion is
134 * successful, return 0. Otherwise return an error. Note that we do not grab
135 * page references for the page structures.
136 */
137int frame_vector_to_pages(struct frame_vector *vec)
138{
139 int i;
140 unsigned long *nums;
141 struct page **pages;
142
143 if (!vec->is_pfns)
144 return 0;
145 nums = frame_vector_pfns(vec);
146 for (i = 0; i < vec->nr_frames; i++)
147 if (!pfn_valid(nums[i]))
148 return -EINVAL;
149 pages = (struct page **)nums;
150 for (i = 0; i < vec->nr_frames; i++)
151 pages[i] = pfn_to_page(nums[i]);
152 vec->is_pfns = false;
153 return 0;
154}
155EXPORT_SYMBOL(frame_vector_to_pages);
156
157/**
158 * frame_vector_to_pfns - convert frame vector to contain pfns
159 * @vec: frame vector to convert
160 *
161 * Convert @vec to contain array of pfns.
162 */
163void frame_vector_to_pfns(struct frame_vector *vec)
164{
165 int i;
166 unsigned long *nums;
167 struct page **pages;
168
169 if (vec->is_pfns)
170 return;
171 pages = (struct page **)(vec->ptrs);
172 nums = (unsigned long *)pages;
173 for (i = 0; i < vec->nr_frames; i++)
174 nums[i] = page_to_pfn(pages[i]);
175 vec->is_pfns = true;
176}
177EXPORT_SYMBOL(frame_vector_to_pfns);
178
179/**
180 * frame_vector_create() - allocate & initialize structure for pinned pfns
181 * @nr_frames: number of pfns slots we should reserve
182 *
183 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
184 * pfns.
185 */
186struct frame_vector *frame_vector_create(unsigned int nr_frames)
187{
188 struct frame_vector *vec;
189 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
190
191 if (WARN_ON_ONCE(nr_frames == 0))
192 return NULL;
193 /*
194 * This is absurdly high. It's here just to avoid strange effects when
195 * arithmetics overflows.
196 */
197 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
198 return NULL;
199 /*
200 * Avoid higher order allocations, use vmalloc instead. It should
201 * be rare anyway.
202 */
203 if (size <= PAGE_SIZE)
204 vec = kmalloc(size, GFP_KERNEL);
205 else
206 vec = vmalloc(size);
207 if (!vec)
208 return NULL;
209 vec->nr_allocated = nr_frames;
210 vec->nr_frames = 0;
211 return vec;
212}
213EXPORT_SYMBOL(frame_vector_create);
214
215/**
216 * frame_vector_destroy() - free memory allocated to carry frame vector
217 * @vec: Frame vector to free
218 *
219 * Free structure allocated by frame_vector_create() to carry frames.
220 */
221void frame_vector_destroy(struct frame_vector *vec)
222{
223 /* Make sure put_vaddr_frames() got called properly... */
224 VM_BUG_ON(vec->nr_frames > 0);
225 kvfree(vec);
226}
227EXPORT_SYMBOL(frame_vector_destroy);