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 * @write: whether pages will be written to by the caller
15 * @force: whether to force write access even if user mapping is
16 * readonly. See description of the same argument of
17 get_user_pages().
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 * This function takes care of grabbing mmap_sem as necessary.
35 */
get_vaddr_frames(unsigned long start,unsigned int nr_frames,bool write,bool force,struct frame_vector * vec)36 int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
37 bool write, bool force, struct frame_vector *vec)
38 {
39 struct mm_struct *mm = current->mm;
40 struct vm_area_struct *vma;
41 int ret = 0;
42 int err;
43 int locked;
44
45 if (nr_frames == 0)
46 return 0;
47
48 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
49 nr_frames = vec->nr_allocated;
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 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
59 vec->got_ref = true;
60 vec->is_pfns = false;
61 ret = get_user_pages_locked(current, mm, start, nr_frames,
62 write, force, (struct page **)(vec->ptrs), &locked);
63 goto out;
64 }
65
66 vec->got_ref = false;
67 vec->is_pfns = true;
68 do {
69 unsigned long *nums = frame_vector_pfns(vec);
70
71 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
72 err = follow_pfn(vma, start, &nums[ret]);
73 if (err) {
74 if (ret == 0)
75 ret = err;
76 goto out;
77 }
78 start += PAGE_SIZE;
79 ret++;
80 }
81 /*
82 * We stop if we have enough pages or if VMA doesn't completely
83 * cover the tail page.
84 */
85 if (ret >= nr_frames || start < vma->vm_end)
86 break;
87 vma = find_vma_intersection(mm, start, start + 1);
88 } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
89 out:
90 if (locked)
91 up_read(&mm->mmap_sem);
92 if (!ret)
93 ret = -EFAULT;
94 if (ret > 0)
95 vec->nr_frames = ret;
96 return ret;
97 }
98 EXPORT_SYMBOL(get_vaddr_frames);
99
100 /**
101 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
102 * them
103 * @vec: frame vector to put
104 *
105 * Drop references to pages if get_vaddr_frames() acquired them. We also
106 * invalidate the frame vector so that it is prepared for the next call into
107 * get_vaddr_frames().
108 */
put_vaddr_frames(struct frame_vector * vec)109 void put_vaddr_frames(struct frame_vector *vec)
110 {
111 int i;
112 struct page **pages;
113
114 if (!vec->got_ref)
115 goto out;
116 pages = frame_vector_pages(vec);
117 /*
118 * frame_vector_pages() might needed to do a conversion when
119 * get_vaddr_frames() got pages but vec was later converted to pfns.
120 * But it shouldn't really fail to convert pfns back...
121 */
122 if (WARN_ON(IS_ERR(pages)))
123 goto out;
124 for (i = 0; i < vec->nr_frames; i++)
125 put_page(pages[i]);
126 vec->got_ref = false;
127 out:
128 vec->nr_frames = 0;
129 }
130 EXPORT_SYMBOL(put_vaddr_frames);
131
132 /**
133 * frame_vector_to_pages - convert frame vector to contain page pointers
134 * @vec: frame vector to convert
135 *
136 * Convert @vec to contain array of page pointers. If the conversion is
137 * successful, return 0. Otherwise return an error. Note that we do not grab
138 * page references for the page structures.
139 */
frame_vector_to_pages(struct frame_vector * vec)140 int frame_vector_to_pages(struct frame_vector *vec)
141 {
142 int i;
143 unsigned long *nums;
144 struct page **pages;
145
146 if (!vec->is_pfns)
147 return 0;
148 nums = frame_vector_pfns(vec);
149 for (i = 0; i < vec->nr_frames; i++)
150 if (!pfn_valid(nums[i]))
151 return -EINVAL;
152 pages = (struct page **)nums;
153 for (i = 0; i < vec->nr_frames; i++)
154 pages[i] = pfn_to_page(nums[i]);
155 vec->is_pfns = false;
156 return 0;
157 }
158 EXPORT_SYMBOL(frame_vector_to_pages);
159
160 /**
161 * frame_vector_to_pfns - convert frame vector to contain pfns
162 * @vec: frame vector to convert
163 *
164 * Convert @vec to contain array of pfns.
165 */
frame_vector_to_pfns(struct frame_vector * vec)166 void frame_vector_to_pfns(struct frame_vector *vec)
167 {
168 int i;
169 unsigned long *nums;
170 struct page **pages;
171
172 if (vec->is_pfns)
173 return;
174 pages = (struct page **)(vec->ptrs);
175 nums = (unsigned long *)pages;
176 for (i = 0; i < vec->nr_frames; i++)
177 nums[i] = page_to_pfn(pages[i]);
178 vec->is_pfns = true;
179 }
180 EXPORT_SYMBOL(frame_vector_to_pfns);
181
182 /**
183 * frame_vector_create() - allocate & initialize structure for pinned pfns
184 * @nr_frames: number of pfns slots we should reserve
185 *
186 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
187 * pfns.
188 */
frame_vector_create(unsigned int nr_frames)189 struct frame_vector *frame_vector_create(unsigned int nr_frames)
190 {
191 struct frame_vector *vec;
192 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
193
194 if (WARN_ON_ONCE(nr_frames == 0))
195 return NULL;
196 /*
197 * This is absurdly high. It's here just to avoid strange effects when
198 * arithmetics overflows.
199 */
200 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
201 return NULL;
202 /*
203 * Avoid higher order allocations, use vmalloc instead. It should
204 * be rare anyway.
205 */
206 if (size <= PAGE_SIZE)
207 vec = kmalloc(size, GFP_KERNEL);
208 else
209 vec = vmalloc(size);
210 if (!vec)
211 return NULL;
212 vec->nr_allocated = nr_frames;
213 vec->nr_frames = 0;
214 return vec;
215 }
216 EXPORT_SYMBOL(frame_vector_create);
217
218 /**
219 * frame_vector_destroy() - free memory allocated to carry frame vector
220 * @vec: Frame vector to free
221 *
222 * Free structure allocated by frame_vector_create() to carry frames.
223 */
frame_vector_destroy(struct frame_vector * vec)224 void frame_vector_destroy(struct frame_vector *vec)
225 {
226 /* Make sure put_vaddr_frames() got called properly... */
227 VM_BUG_ON(vec->nr_frames > 0);
228 kvfree(vec);
229 }
230 EXPORT_SYMBOL(frame_vector_destroy);
231