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