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 <linux/errno.h> 15 #include <linux/highmem.h> 16 #include <linux/mm.h> 17 #include <linux/scatterlist.h> 18 #include <linux/types.h> 19 20 struct scatter_walk { 21 /* Must be the first member, see struct skcipher_walk. */ 22 union { 23 void *const addr; 24 25 /* Private API field, do not touch. */ 26 union crypto_no_such_thing *__addr; 27 }; 28 struct scatterlist *sg; 29 unsigned int offset; 30 }; 31 32 struct skcipher_walk { 33 union { 34 /* Virtual address of the source. */ 35 struct { 36 struct { 37 const void *const addr; 38 } virt; 39 } src; 40 41 /* Private field for the API, do not use. */ 42 struct scatter_walk in; 43 }; 44 45 union { 46 /* Virtual address of the destination. */ 47 struct { 48 struct { 49 void *const addr; 50 } virt; 51 } dst; 52 53 /* Private field for the API, do not use. */ 54 struct scatter_walk out; 55 }; 56 57 unsigned int nbytes; 58 unsigned int total; 59 60 u8 *page; 61 u8 *buffer; 62 u8 *oiv; 63 void *iv; 64 65 unsigned int ivsize; 66 67 int flags; 68 unsigned int blocksize; 69 unsigned int stride; 70 unsigned int alignmask; 71 }; 72 73 static inline void scatterwalk_crypto_chain(struct scatterlist *head, 74 struct scatterlist *sg, int num) 75 { 76 if (sg) 77 sg_chain(head, num, sg); 78 else 79 sg_mark_end(head); 80 } 81 82 static inline void scatterwalk_start(struct scatter_walk *walk, 83 struct scatterlist *sg) 84 { 85 walk->sg = sg; 86 walk->offset = sg->offset; 87 } 88 89 /* 90 * This is equivalent to scatterwalk_start(walk, sg) followed by 91 * scatterwalk_skip(walk, pos). 92 */ 93 static inline void scatterwalk_start_at_pos(struct scatter_walk *walk, 94 struct scatterlist *sg, 95 unsigned int pos) 96 { 97 while (pos > sg->length) { 98 pos -= sg->length; 99 sg = sg_next(sg); 100 } 101 walk->sg = sg; 102 walk->offset = sg->offset + pos; 103 } 104 105 static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk, 106 unsigned int nbytes) 107 { 108 unsigned int len_this_sg; 109 unsigned int limit; 110 111 if (walk->offset >= walk->sg->offset + walk->sg->length) 112 scatterwalk_start(walk, sg_next(walk->sg)); 113 len_this_sg = walk->sg->offset + walk->sg->length - walk->offset; 114 115 /* 116 * HIGHMEM case: the page may have to be mapped into memory. To avoid 117 * the complexity of having to map multiple pages at once per sg entry, 118 * clamp the returned length to not cross a page boundary. 119 * 120 * !HIGHMEM case: no mapping is needed; all pages of the sg entry are 121 * already mapped contiguously in the kernel's direct map. For improved 122 * performance, allow the walker to return data segments that cross a 123 * page boundary. Do still cap the length to PAGE_SIZE, since some 124 * users rely on that to avoid disabling preemption for too long when 125 * using SIMD. It's also needed for when skcipher_walk uses a bounce 126 * page due to the data not being aligned to the algorithm's alignmask. 127 */ 128 if (IS_ENABLED(CONFIG_HIGHMEM)) 129 limit = PAGE_SIZE - offset_in_page(walk->offset); 130 else 131 limit = PAGE_SIZE; 132 133 return min3(nbytes, len_this_sg, limit); 134 } 135 136 /* 137 * Create a scatterlist that represents the remaining data in a walk. Uses 138 * chaining to reference the original scatterlist, so this uses at most two 139 * entries in @sg_out regardless of the number of entries in the original list. 140 * Assumes that sg_init_table() was already done. 141 */ 142 static inline void scatterwalk_get_sglist(struct scatter_walk *walk, 143 struct scatterlist sg_out[2]) 144 { 145 if (walk->offset >= walk->sg->offset + walk->sg->length) 146 scatterwalk_start(walk, sg_next(walk->sg)); 147 sg_set_page(sg_out, sg_page(walk->sg), 148 walk->sg->offset + walk->sg->length - walk->offset, 149 walk->offset); 150 scatterwalk_crypto_chain(sg_out, sg_next(walk->sg), 2); 151 } 152 153 static inline void scatterwalk_map(struct scatter_walk *walk) 154 { 155 struct page *base_page = sg_page(walk->sg); 156 unsigned int offset = walk->offset; 157 void *addr; 158 159 if (IS_ENABLED(CONFIG_HIGHMEM)) { 160 struct page *page; 161 162 page = nth_page(base_page, offset >> PAGE_SHIFT); 163 offset = offset_in_page(offset); 164 addr = kmap_local_page(page) + offset; 165 } else { 166 /* 167 * When !HIGHMEM we allow the walker to return segments that 168 * span a page boundary; see scatterwalk_clamp(). To make it 169 * clear that in this case we're working in the linear buffer of 170 * the whole sg entry in the kernel's direct map rather than 171 * within the mapped buffer of a single page, compute the 172 * address as an offset from the page_address() of the first 173 * page of the sg entry. Either way the result is the address 174 * in the direct map, but this makes it clearer what is really 175 * going on. 176 */ 177 addr = page_address(base_page) + offset; 178 } 179 180 walk->__addr = addr; 181 } 182 183 /** 184 * scatterwalk_next() - Get the next data buffer in a scatterlist walk 185 * @walk: the scatter_walk 186 * @total: the total number of bytes remaining, > 0 187 * 188 * A virtual address for the next segment of data from the scatterlist will 189 * be placed into @walk->addr. The caller must call scatterwalk_done_src() 190 * or scatterwalk_done_dst() when it is done using this virtual address. 191 * 192 * Returns: the next number of bytes available, <= @total 193 */ 194 static inline unsigned int scatterwalk_next(struct scatter_walk *walk, 195 unsigned int total) 196 { 197 unsigned int nbytes = scatterwalk_clamp(walk, total); 198 199 scatterwalk_map(walk); 200 return nbytes; 201 } 202 203 static inline void scatterwalk_unmap(struct scatter_walk *walk) 204 { 205 if (IS_ENABLED(CONFIG_HIGHMEM)) 206 kunmap_local(walk->__addr); 207 } 208 209 static inline void scatterwalk_advance(struct scatter_walk *walk, 210 unsigned int nbytes) 211 { 212 walk->offset += nbytes; 213 } 214 215 /** 216 * scatterwalk_done_src() - Finish one step of a walk of source scatterlist 217 * @walk: the scatter_walk 218 * @nbytes: the number of bytes processed this step, less than or equal to the 219 * number of bytes that scatterwalk_next() returned. 220 * 221 * Use this if the mapped address was not written to, i.e. it is source data. 222 */ 223 static inline void scatterwalk_done_src(struct scatter_walk *walk, 224 unsigned int nbytes) 225 { 226 scatterwalk_unmap(walk); 227 scatterwalk_advance(walk, nbytes); 228 } 229 230 /** 231 * scatterwalk_done_dst() - Finish one step of a walk of destination scatterlist 232 * @walk: the scatter_walk 233 * @nbytes: the number of bytes processed this step, less than or equal to the 234 * number of bytes that scatterwalk_next() returned. 235 * 236 * Use this if the mapped address may have been written to, i.e. it is 237 * destination data. 238 */ 239 static inline void scatterwalk_done_dst(struct scatter_walk *walk, 240 unsigned int nbytes) 241 { 242 scatterwalk_unmap(walk); 243 /* 244 * Explicitly check ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE instead of just 245 * relying on flush_dcache_page() being a no-op when not implemented, 246 * since otherwise the BUG_ON in sg_page() does not get optimized out. 247 * This also avoids having to consider whether the loop would get 248 * reliably optimized out or not. 249 */ 250 if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE) { 251 struct page *base_page; 252 unsigned int offset; 253 int start, end, i; 254 255 base_page = sg_page(walk->sg); 256 offset = walk->offset; 257 start = offset >> PAGE_SHIFT; 258 end = start + (nbytes >> PAGE_SHIFT); 259 end += (offset_in_page(offset) + offset_in_page(nbytes) + 260 PAGE_SIZE - 1) >> PAGE_SHIFT; 261 for (i = start; i < end; i++) 262 flush_dcache_page(nth_page(base_page, i)); 263 } 264 scatterwalk_advance(walk, nbytes); 265 } 266 267 void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes); 268 269 void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk, 270 unsigned int nbytes); 271 272 void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf, 273 unsigned int nbytes); 274 275 void memcpy_from_sglist(void *buf, struct scatterlist *sg, 276 unsigned int start, unsigned int nbytes); 277 278 void memcpy_to_sglist(struct scatterlist *sg, unsigned int start, 279 const void *buf, unsigned int nbytes); 280 281 void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src, 282 unsigned int nbytes); 283 284 /* In new code, please use memcpy_{from,to}_sglist() directly instead. */ 285 static inline void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg, 286 unsigned int start, 287 unsigned int nbytes, int out) 288 { 289 if (out) 290 memcpy_to_sglist(sg, start, buf, nbytes); 291 else 292 memcpy_from_sglist(buf, sg, start, nbytes); 293 } 294 295 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2], 296 struct scatterlist *src, 297 unsigned int len); 298 299 int skcipher_walk_first(struct skcipher_walk *walk, bool atomic); 300 int skcipher_walk_done(struct skcipher_walk *walk, int res); 301 302 static inline void skcipher_walk_abort(struct skcipher_walk *walk) 303 { 304 skcipher_walk_done(walk, -ECANCELED); 305 } 306 307 #endif /* _CRYPTO_SCATTERWALK_H */ 308