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TOMOYO Linux Cross Reference
Linux/mm/frame_vector.c

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  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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