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 * @write: the mapped address has write permission 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 * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used 35 * to be able to do that, but that could (racily) return non-refcounted 36 * pfns. 37 * 38 * This function takes care of grabbing mmap_lock as necessary. 39 */ 40 int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write, 41 struct frame_vector *vec) 42 { 43 int ret; 44 unsigned int gup_flags = FOLL_LONGTERM; 45 46 if (nr_frames == 0) 47 return 0; 48 49 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated)) 50 nr_frames = vec->nr_allocated; 51 52 start = untagged_addr(start); 53 54 if (write) 55 gup_flags |= FOLL_WRITE; 56 57 ret = pin_user_pages_fast(start, nr_frames, gup_flags, 58 (struct page **)(vec->ptrs)); 59 vec->got_ref = true; 60 vec->is_pfns = false; 61 vec->nr_frames = ret; 62 63 if (likely(ret > 0)) 64 return ret; 65 66 vec->nr_frames = 0; 67 return ret ? ret : -EFAULT; 68 } 69 EXPORT_SYMBOL(get_vaddr_frames); 70 71 /** 72 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired 73 * them 74 * @vec: frame vector to put 75 * 76 * Drop references to pages if get_vaddr_frames() acquired them. We also 77 * invalidate the frame vector so that it is prepared for the next call into 78 * get_vaddr_frames(). 79 */ 80 void put_vaddr_frames(struct frame_vector *vec) 81 { 82 struct page **pages; 83 84 if (!vec->got_ref) 85 goto out; 86 pages = frame_vector_pages(vec); 87 /* 88 * frame_vector_pages() might needed to do a conversion when 89 * get_vaddr_frames() got pages but vec was later converted to pfns. 90 * But it shouldn't really fail to convert pfns back... 91 */ 92 if (WARN_ON(IS_ERR(pages))) 93 goto out; 94 95 unpin_user_pages(pages, vec->nr_frames); 96 vec->got_ref = false; 97 out: 98 vec->nr_frames = 0; 99 } 100 EXPORT_SYMBOL(put_vaddr_frames); 101 102 /** 103 * frame_vector_to_pages - convert frame vector to contain page pointers 104 * @vec: frame vector to convert 105 * 106 * Convert @vec to contain array of page pointers. If the conversion is 107 * successful, return 0. Otherwise return an error. Note that we do not grab 108 * page references for the page structures. 109 */ 110 int frame_vector_to_pages(struct frame_vector *vec) 111 { 112 int i; 113 unsigned long *nums; 114 struct page **pages; 115 116 if (!vec->is_pfns) 117 return 0; 118 nums = frame_vector_pfns(vec); 119 for (i = 0; i < vec->nr_frames; i++) 120 if (!pfn_valid(nums[i])) 121 return -EINVAL; 122 pages = (struct page **)nums; 123 for (i = 0; i < vec->nr_frames; i++) 124 pages[i] = pfn_to_page(nums[i]); 125 vec->is_pfns = false; 126 return 0; 127 } 128 EXPORT_SYMBOL(frame_vector_to_pages); 129 130 /** 131 * frame_vector_to_pfns - convert frame vector to contain pfns 132 * @vec: frame vector to convert 133 * 134 * Convert @vec to contain array of pfns. 135 */ 136 void frame_vector_to_pfns(struct frame_vector *vec) 137 { 138 int i; 139 unsigned long *nums; 140 struct page **pages; 141 142 if (vec->is_pfns) 143 return; 144 pages = (struct page **)(vec->ptrs); 145 nums = (unsigned long *)pages; 146 for (i = 0; i < vec->nr_frames; i++) 147 nums[i] = page_to_pfn(pages[i]); 148 vec->is_pfns = true; 149 } 150 EXPORT_SYMBOL(frame_vector_to_pfns); 151 152 /** 153 * frame_vector_create() - allocate & initialize structure for pinned pfns 154 * @nr_frames: number of pfns slots we should reserve 155 * 156 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns 157 * pfns. 158 */ 159 struct frame_vector *frame_vector_create(unsigned int nr_frames) 160 { 161 struct frame_vector *vec; 162 int size = struct_size(vec, ptrs, nr_frames); 163 164 if (WARN_ON_ONCE(nr_frames == 0)) 165 return NULL; 166 /* 167 * This is absurdly high. It's here just to avoid strange effects when 168 * arithmetics overflows. 169 */ 170 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2)) 171 return NULL; 172 /* 173 * Avoid higher order allocations, use vmalloc instead. It should 174 * be rare anyway. 175 */ 176 vec = kvmalloc(size, GFP_KERNEL); 177 if (!vec) 178 return NULL; 179 vec->nr_allocated = nr_frames; 180 vec->nr_frames = 0; 181 return vec; 182 } 183 EXPORT_SYMBOL(frame_vector_create); 184 185 /** 186 * frame_vector_destroy() - free memory allocated to carry frame vector 187 * @vec: Frame vector to free 188 * 189 * Free structure allocated by frame_vector_create() to carry frames. 190 */ 191 void frame_vector_destroy(struct frame_vector *vec) 192 { 193 /* Make sure put_vaddr_frames() got called properly... */ 194 VM_BUG_ON(vec->nr_frames > 0); 195 kvfree(vec); 196 } 197 EXPORT_SYMBOL(frame_vector_destroy); 198