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 * @gup_flags: flags modifying lookup behaviour 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_lock as necessary. 35 */ 36 int get_vaddr_frames(unsigned long start, unsigned int nr_frames, 37 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 44 if (nr_frames == 0) 45 return 0; 46 47 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated)) 48 nr_frames = vec->nr_allocated; 49 50 start = untagged_addr(start); 51 52 ret = pin_user_pages_fast(start, nr_frames, 53 FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM, 54 (struct page **)(vec->ptrs)); 55 if (ret > 0) { 56 vec->got_ref = true; 57 vec->is_pfns = false; 58 goto out_unlocked; 59 } 60 61 mmap_read_lock(mm); 62 vec->got_ref = false; 63 vec->is_pfns = true; 64 ret = 0; 65 do { 66 unsigned long *nums = frame_vector_pfns(vec); 67 68 vma = find_vma_intersection(mm, start, start + 1); 69 if (!vma) 70 break; 71 72 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) { 73 err = follow_pfn(vma, start, &nums[ret]); 74 if (err) { 75 if (ret == 0) 76 ret = err; 77 goto out; 78 } 79 start += PAGE_SIZE; 80 ret++; 81 } 82 /* Bail out if VMA doesn't completely cover the tail page. */ 83 if (start < vma->vm_end) 84 break; 85 } while (ret < nr_frames); 86 out: 87 mmap_read_unlock(mm); 88 out_unlocked: 89 if (!ret) 90 ret = -EFAULT; 91 if (ret > 0) 92 vec->nr_frames = ret; 93 return ret; 94 } 95 EXPORT_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 */ 106 void put_vaddr_frames(struct frame_vector *vec) 107 { 108 struct page **pages; 109 110 if (!vec->got_ref) 111 goto out; 112 pages = frame_vector_pages(vec); 113 /* 114 * frame_vector_pages() might needed to do a conversion when 115 * get_vaddr_frames() got pages but vec was later converted to pfns. 116 * But it shouldn't really fail to convert pfns back... 117 */ 118 if (WARN_ON(IS_ERR(pages))) 119 goto out; 120 121 unpin_user_pages(pages, vec->nr_frames); 122 vec->got_ref = false; 123 out: 124 vec->nr_frames = 0; 125 } 126 EXPORT_SYMBOL(put_vaddr_frames); 127 128 /** 129 * frame_vector_to_pages - convert frame vector to contain page pointers 130 * @vec: frame vector to convert 131 * 132 * Convert @vec to contain array of page pointers. If the conversion is 133 * successful, return 0. Otherwise return an error. Note that we do not grab 134 * page references for the page structures. 135 */ 136 int frame_vector_to_pages(struct frame_vector *vec) 137 { 138 int i; 139 unsigned long *nums; 140 struct page **pages; 141 142 if (!vec->is_pfns) 143 return 0; 144 nums = frame_vector_pfns(vec); 145 for (i = 0; i < vec->nr_frames; i++) 146 if (!pfn_valid(nums[i])) 147 return -EINVAL; 148 pages = (struct page **)nums; 149 for (i = 0; i < vec->nr_frames; i++) 150 pages[i] = pfn_to_page(nums[i]); 151 vec->is_pfns = false; 152 return 0; 153 } 154 EXPORT_SYMBOL(frame_vector_to_pages); 155 156 /** 157 * frame_vector_to_pfns - convert frame vector to contain pfns 158 * @vec: frame vector to convert 159 * 160 * Convert @vec to contain array of pfns. 161 */ 162 void frame_vector_to_pfns(struct frame_vector *vec) 163 { 164 int i; 165 unsigned long *nums; 166 struct page **pages; 167 168 if (vec->is_pfns) 169 return; 170 pages = (struct page **)(vec->ptrs); 171 nums = (unsigned long *)pages; 172 for (i = 0; i < vec->nr_frames; i++) 173 nums[i] = page_to_pfn(pages[i]); 174 vec->is_pfns = true; 175 } 176 EXPORT_SYMBOL(frame_vector_to_pfns); 177 178 /** 179 * frame_vector_create() - allocate & initialize structure for pinned pfns 180 * @nr_frames: number of pfns slots we should reserve 181 * 182 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns 183 * pfns. 184 */ 185 struct frame_vector *frame_vector_create(unsigned int nr_frames) 186 { 187 struct frame_vector *vec; 188 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames; 189 190 if (WARN_ON_ONCE(nr_frames == 0)) 191 return NULL; 192 /* 193 * This is absurdly high. It's here just to avoid strange effects when 194 * arithmetics overflows. 195 */ 196 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2)) 197 return NULL; 198 /* 199 * Avoid higher order allocations, use vmalloc instead. It should 200 * be rare anyway. 201 */ 202 vec = kvmalloc(size, GFP_KERNEL); 203 if (!vec) 204 return NULL; 205 vec->nr_allocated = nr_frames; 206 vec->nr_frames = 0; 207 return vec; 208 } 209 EXPORT_SYMBOL(frame_vector_create); 210 211 /** 212 * frame_vector_destroy() - free memory allocated to carry frame vector 213 * @vec: Frame vector to free 214 * 215 * Free structure allocated by frame_vector_create() to carry frames. 216 */ 217 void frame_vector_destroy(struct frame_vector *vec) 218 { 219 /* Make sure put_vaddr_frames() got called properly... */ 220 VM_BUG_ON(vec->nr_frames > 0); 221 kvfree(vec); 222 } 223 EXPORT_SYMBOL(frame_vector_destroy); 224