1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * Cryptographic scatter and gather helpers. 4 * 5 * Copyright (c) 2002 James Morris <jmorris@intercode.com.au> 6 * Copyright (c) 2002 Adam J. Richter <adam@yggdrasil.com> 7 * Copyright (c) 2004 Jean-Luc Cooke <jlcooke@certainkey.com> 8 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au> 9 */ 10 11 #ifndef _CRYPTO_SCATTERWALK_H 12 #define _CRYPTO_SCATTERWALK_H 13 14 #include <crypto/algapi.h> 15 16 #include <linux/highmem.h> 17 #include <linux/mm.h> 18 #include <linux/scatterlist.h> 19 20 static inline void scatterwalk_crypto_chain(struct scatterlist *head, 21 struct scatterlist *sg, int num) 22 { 23 if (sg) 24 sg_chain(head, num, sg); 25 else 26 sg_mark_end(head); 27 } 28 29 static inline void scatterwalk_start(struct scatter_walk *walk, 30 struct scatterlist *sg) 31 { 32 walk->sg = sg; 33 walk->offset = sg->offset; 34 } 35 36 /* 37 * This is equivalent to scatterwalk_start(walk, sg) followed by 38 * scatterwalk_skip(walk, pos). 39 */ 40 static inline void scatterwalk_start_at_pos(struct scatter_walk *walk, 41 struct scatterlist *sg, 42 unsigned int pos) 43 { 44 while (pos > sg->length) { 45 pos -= sg->length; 46 sg = sg_next(sg); 47 } 48 walk->sg = sg; 49 walk->offset = sg->offset + pos; 50 } 51 52 static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk, 53 unsigned int nbytes) 54 { 55 unsigned int len_this_sg; 56 unsigned int limit; 57 58 if (walk->offset >= walk->sg->offset + walk->sg->length) 59 scatterwalk_start(walk, sg_next(walk->sg)); 60 len_this_sg = walk->sg->offset + walk->sg->length - walk->offset; 61 62 /* 63 * HIGHMEM case: the page may have to be mapped into memory. To avoid 64 * the complexity of having to map multiple pages at once per sg entry, 65 * clamp the returned length to not cross a page boundary. 66 * 67 * !HIGHMEM case: no mapping is needed; all pages of the sg entry are 68 * already mapped contiguously in the kernel's direct map. For improved 69 * performance, allow the walker to return data segments that cross a 70 * page boundary. Do still cap the length to PAGE_SIZE, since some 71 * users rely on that to avoid disabling preemption for too long when 72 * using SIMD. It's also needed for when skcipher_walk uses a bounce 73 * page due to the data not being aligned to the algorithm's alignmask. 74 */ 75 if (IS_ENABLED(CONFIG_HIGHMEM)) 76 limit = PAGE_SIZE - offset_in_page(walk->offset); 77 else 78 limit = PAGE_SIZE; 79 80 return min3(nbytes, len_this_sg, limit); 81 } 82 83 /* 84 * Create a scatterlist that represents the remaining data in a walk. Uses 85 * chaining to reference the original scatterlist, so this uses at most two 86 * entries in @sg_out regardless of the number of entries in the original list. 87 * Assumes that sg_init_table() was already done. 88 */ 89 static inline void scatterwalk_get_sglist(struct scatter_walk *walk, 90 struct scatterlist sg_out[2]) 91 { 92 if (walk->offset >= walk->sg->offset + walk->sg->length) 93 scatterwalk_start(walk, sg_next(walk->sg)); 94 sg_set_page(sg_out, sg_page(walk->sg), 95 walk->sg->offset + walk->sg->length - walk->offset, 96 walk->offset); 97 scatterwalk_crypto_chain(sg_out, sg_next(walk->sg), 2); 98 } 99 100 static inline void scatterwalk_map(struct scatter_walk *walk) 101 { 102 struct page *base_page = sg_page(walk->sg); 103 unsigned int offset = walk->offset; 104 void *addr; 105 106 if (IS_ENABLED(CONFIG_HIGHMEM)) { 107 struct page *page; 108 109 page = nth_page(base_page, offset >> PAGE_SHIFT); 110 offset = offset_in_page(offset); 111 addr = kmap_local_page(page) + offset; 112 } else { 113 /* 114 * When !HIGHMEM we allow the walker to return segments that 115 * span a page boundary; see scatterwalk_clamp(). To make it 116 * clear that in this case we're working in the linear buffer of 117 * the whole sg entry in the kernel's direct map rather than 118 * within the mapped buffer of a single page, compute the 119 * address as an offset from the page_address() of the first 120 * page of the sg entry. Either way the result is the address 121 * in the direct map, but this makes it clearer what is really 122 * going on. 123 */ 124 addr = page_address(base_page) + offset; 125 } 126 127 walk->__addr = addr; 128 } 129 130 /** 131 * scatterwalk_next() - Get the next data buffer in a scatterlist walk 132 * @walk: the scatter_walk 133 * @total: the total number of bytes remaining, > 0 134 * 135 * A virtual address for the next segment of data from the scatterlist will 136 * be placed into @walk->addr. The caller must call scatterwalk_done_src() 137 * or scatterwalk_done_dst() when it is done using this virtual address. 138 * 139 * Returns: the next number of bytes available, <= @total 140 */ 141 static inline unsigned int scatterwalk_next(struct scatter_walk *walk, 142 unsigned int total) 143 { 144 unsigned int nbytes = scatterwalk_clamp(walk, total); 145 146 scatterwalk_map(walk); 147 return nbytes; 148 } 149 150 static inline void scatterwalk_unmap(struct scatter_walk *walk) 151 { 152 if (IS_ENABLED(CONFIG_HIGHMEM)) 153 kunmap_local(walk->__addr); 154 } 155 156 static inline void scatterwalk_advance(struct scatter_walk *walk, 157 unsigned int nbytes) 158 { 159 walk->offset += nbytes; 160 } 161 162 /** 163 * scatterwalk_done_src() - Finish one step of a walk of source scatterlist 164 * @walk: the scatter_walk 165 * @nbytes: the number of bytes processed this step, less than or equal to the 166 * number of bytes that scatterwalk_next() returned. 167 * 168 * Use this if the mapped address was not written to, i.e. it is source data. 169 */ 170 static inline void scatterwalk_done_src(struct scatter_walk *walk, 171 unsigned int nbytes) 172 { 173 scatterwalk_unmap(walk); 174 scatterwalk_advance(walk, nbytes); 175 } 176 177 /** 178 * scatterwalk_done_dst() - Finish one step of a walk of destination scatterlist 179 * @walk: the scatter_walk 180 * @nbytes: the number of bytes processed this step, less than or equal to the 181 * number of bytes that scatterwalk_next() returned. 182 * 183 * Use this if the mapped address may have been written to, i.e. it is 184 * destination data. 185 */ 186 static inline void scatterwalk_done_dst(struct scatter_walk *walk, 187 unsigned int nbytes) 188 { 189 scatterwalk_unmap(walk); 190 /* 191 * Explicitly check ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE instead of just 192 * relying on flush_dcache_page() being a no-op when not implemented, 193 * since otherwise the BUG_ON in sg_page() does not get optimized out. 194 * This also avoids having to consider whether the loop would get 195 * reliably optimized out or not. 196 */ 197 if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE) { 198 struct page *base_page; 199 unsigned int offset; 200 int start, end, i; 201 202 base_page = sg_page(walk->sg); 203 offset = walk->offset; 204 start = offset >> PAGE_SHIFT; 205 end = start + (nbytes >> PAGE_SHIFT); 206 end += (offset_in_page(offset) + offset_in_page(nbytes) + 207 PAGE_SIZE - 1) >> PAGE_SHIFT; 208 for (i = start; i < end; i++) 209 flush_dcache_page(nth_page(base_page, i)); 210 } 211 scatterwalk_advance(walk, nbytes); 212 } 213 214 void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes); 215 216 void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk, 217 unsigned int nbytes); 218 219 void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf, 220 unsigned int nbytes); 221 222 void memcpy_from_sglist(void *buf, struct scatterlist *sg, 223 unsigned int start, unsigned int nbytes); 224 225 void memcpy_to_sglist(struct scatterlist *sg, unsigned int start, 226 const void *buf, unsigned int nbytes); 227 228 void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src, 229 unsigned int nbytes); 230 231 /* In new code, please use memcpy_{from,to}_sglist() directly instead. */ 232 static inline void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg, 233 unsigned int start, 234 unsigned int nbytes, int out) 235 { 236 if (out) 237 memcpy_to_sglist(sg, start, buf, nbytes); 238 else 239 memcpy_from_sglist(buf, sg, start, nbytes); 240 } 241 242 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2], 243 struct scatterlist *src, 244 unsigned int len); 245 246 #endif /* _CRYPTO_SCATTERWALK_H */ 247