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 * This function takes care of grabbing mmap_lock as necessary. 35 */ 36 int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write, 37 struct frame_vector *vec) 38 { 39 int ret; 40 unsigned int gup_flags = FOLL_LONGTERM; 41 42 if (nr_frames == 0) 43 return 0; 44 45 if (WARN_ON_ONCE(nr_frames > vec->nr_allocated)) 46 nr_frames = vec->nr_allocated; 47 48 start = untagged_addr(start); 49 50 if (write) 51 gup_flags |= FOLL_WRITE; 52 53 ret = pin_user_pages_fast(start, nr_frames, gup_flags, 54 (struct page **)(vec->ptrs)); 55 vec->got_ref = true; 56 vec->is_pfns = false; 57 vec->nr_frames = ret; 58 59 if (likely(ret > 0)) 60 return ret; 61 62 /* This used to (racily) return non-refcounted pfns. Let people know */ 63 WARN_ONCE(1, "get_vaddr_frames() cannot follow VM_IO mapping"); 64 vec->nr_frames = 0; 65 return ret ? ret : -EFAULT; 66 } 67 EXPORT_SYMBOL(get_vaddr_frames); 68 69 /** 70 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired 71 * them 72 * @vec: frame vector to put 73 * 74 * Drop references to pages if get_vaddr_frames() acquired them. We also 75 * invalidate the frame vector so that it is prepared for the next call into 76 * get_vaddr_frames(). 77 */ 78 void put_vaddr_frames(struct frame_vector *vec) 79 { 80 struct page **pages; 81 82 if (!vec->got_ref) 83 goto out; 84 pages = frame_vector_pages(vec); 85 /* 86 * frame_vector_pages() might needed to do a conversion when 87 * get_vaddr_frames() got pages but vec was later converted to pfns. 88 * But it shouldn't really fail to convert pfns back... 89 */ 90 if (WARN_ON(IS_ERR(pages))) 91 goto out; 92 93 unpin_user_pages(pages, vec->nr_frames); 94 vec->got_ref = false; 95 out: 96 vec->nr_frames = 0; 97 } 98 EXPORT_SYMBOL(put_vaddr_frames); 99 100 /** 101 * frame_vector_to_pages - convert frame vector to contain page pointers 102 * @vec: frame vector to convert 103 * 104 * Convert @vec to contain array of page pointers. If the conversion is 105 * successful, return 0. Otherwise return an error. Note that we do not grab 106 * page references for the page structures. 107 */ 108 int frame_vector_to_pages(struct frame_vector *vec) 109 { 110 int i; 111 unsigned long *nums; 112 struct page **pages; 113 114 if (!vec->is_pfns) 115 return 0; 116 nums = frame_vector_pfns(vec); 117 for (i = 0; i < vec->nr_frames; i++) 118 if (!pfn_valid(nums[i])) 119 return -EINVAL; 120 pages = (struct page **)nums; 121 for (i = 0; i < vec->nr_frames; i++) 122 pages[i] = pfn_to_page(nums[i]); 123 vec->is_pfns = false; 124 return 0; 125 } 126 EXPORT_SYMBOL(frame_vector_to_pages); 127 128 /** 129 * frame_vector_to_pfns - convert frame vector to contain pfns 130 * @vec: frame vector to convert 131 * 132 * Convert @vec to contain array of pfns. 133 */ 134 void frame_vector_to_pfns(struct frame_vector *vec) 135 { 136 int i; 137 unsigned long *nums; 138 struct page **pages; 139 140 if (vec->is_pfns) 141 return; 142 pages = (struct page **)(vec->ptrs); 143 nums = (unsigned long *)pages; 144 for (i = 0; i < vec->nr_frames; i++) 145 nums[i] = page_to_pfn(pages[i]); 146 vec->is_pfns = true; 147 } 148 EXPORT_SYMBOL(frame_vector_to_pfns); 149 150 /** 151 * frame_vector_create() - allocate & initialize structure for pinned pfns 152 * @nr_frames: number of pfns slots we should reserve 153 * 154 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns 155 * pfns. 156 */ 157 struct frame_vector *frame_vector_create(unsigned int nr_frames) 158 { 159 struct frame_vector *vec; 160 int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames; 161 162 if (WARN_ON_ONCE(nr_frames == 0)) 163 return NULL; 164 /* 165 * This is absurdly high. It's here just to avoid strange effects when 166 * arithmetics overflows. 167 */ 168 if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2)) 169 return NULL; 170 /* 171 * Avoid higher order allocations, use vmalloc instead. It should 172 * be rare anyway. 173 */ 174 vec = kvmalloc(size, GFP_KERNEL); 175 if (!vec) 176 return NULL; 177 vec->nr_allocated = nr_frames; 178 vec->nr_frames = 0; 179 return vec; 180 } 181 EXPORT_SYMBOL(frame_vector_create); 182 183 /** 184 * frame_vector_destroy() - free memory allocated to carry frame vector 185 * @vec: Frame vector to free 186 * 187 * Free structure allocated by frame_vector_create() to carry frames. 188 */ 189 void frame_vector_destroy(struct frame_vector *vec) 190 { 191 /* Make sure put_vaddr_frames() got called properly... */ 192 VM_BUG_ON(vec->nr_frames > 0); 193 kvfree(vec); 194 } 195 EXPORT_SYMBOL(frame_vector_destroy); 196