/* SPDX-License-Identifier: GPL-2.0-or-later */ /* * Cryptographic scatter and gather helpers. * * Copyright (c) 2002 James Morris * Copyright (c) 2002 Adam J. Richter * Copyright (c) 2004 Jean-Luc Cooke * Copyright (c) 2007 Herbert Xu */ #ifndef _CRYPTO_SCATTERWALK_H #define _CRYPTO_SCATTERWALK_H #include #include #include #include static inline void scatterwalk_crypto_chain(struct scatterlist *head, struct scatterlist *sg, int num) { if (sg) sg_chain(head, num, sg); else sg_mark_end(head); } static inline void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg) { walk->sg = sg; walk->offset = sg->offset; } /* * This is equivalent to scatterwalk_start(walk, sg) followed by * scatterwalk_skip(walk, pos). */ static inline void scatterwalk_start_at_pos(struct scatter_walk *walk, struct scatterlist *sg, unsigned int pos) { while (pos > sg->length) { pos -= sg->length; sg = sg_next(sg); } walk->sg = sg; walk->offset = sg->offset + pos; } static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk, unsigned int nbytes) { unsigned int len_this_sg; unsigned int limit; if (walk->offset >= walk->sg->offset + walk->sg->length) scatterwalk_start(walk, sg_next(walk->sg)); len_this_sg = walk->sg->offset + walk->sg->length - walk->offset; /* * HIGHMEM case: the page may have to be mapped into memory. To avoid * the complexity of having to map multiple pages at once per sg entry, * clamp the returned length to not cross a page boundary. * * !HIGHMEM case: no mapping is needed; all pages of the sg entry are * already mapped contiguously in the kernel's direct map. For improved * performance, allow the walker to return data segments that cross a * page boundary. Do still cap the length to PAGE_SIZE, since some * users rely on that to avoid disabling preemption for too long when * using SIMD. It's also needed for when skcipher_walk uses a bounce * page due to the data not being aligned to the algorithm's alignmask. */ if (IS_ENABLED(CONFIG_HIGHMEM)) limit = PAGE_SIZE - offset_in_page(walk->offset); else limit = PAGE_SIZE; return min3(nbytes, len_this_sg, limit); } /* * Create a scatterlist that represents the remaining data in a walk. Uses * chaining to reference the original scatterlist, so this uses at most two * entries in @sg_out regardless of the number of entries in the original list. * Assumes that sg_init_table() was already done. */ static inline void scatterwalk_get_sglist(struct scatter_walk *walk, struct scatterlist sg_out[2]) { if (walk->offset >= walk->sg->offset + walk->sg->length) scatterwalk_start(walk, sg_next(walk->sg)); sg_set_page(sg_out, sg_page(walk->sg), walk->sg->offset + walk->sg->length - walk->offset, walk->offset); scatterwalk_crypto_chain(sg_out, sg_next(walk->sg), 2); } static inline void scatterwalk_map(struct scatter_walk *walk) { struct page *base_page = sg_page(walk->sg); unsigned int offset = walk->offset; void *addr; if (IS_ENABLED(CONFIG_HIGHMEM)) { struct page *page; page = nth_page(base_page, offset >> PAGE_SHIFT); offset = offset_in_page(offset); addr = kmap_local_page(page) + offset; } else { /* * When !HIGHMEM we allow the walker to return segments that * span a page boundary; see scatterwalk_clamp(). To make it * clear that in this case we're working in the linear buffer of * the whole sg entry in the kernel's direct map rather than * within the mapped buffer of a single page, compute the * address as an offset from the page_address() of the first * page of the sg entry. Either way the result is the address * in the direct map, but this makes it clearer what is really * going on. */ addr = page_address(base_page) + offset; } walk->__addr = addr; } /** * scatterwalk_next() - Get the next data buffer in a scatterlist walk * @walk: the scatter_walk * @total: the total number of bytes remaining, > 0 * * A virtual address for the next segment of data from the scatterlist will * be placed into @walk->addr. The caller must call scatterwalk_done_src() * or scatterwalk_done_dst() when it is done using this virtual address. * * Returns: the next number of bytes available, <= @total */ static inline unsigned int scatterwalk_next(struct scatter_walk *walk, unsigned int total) { unsigned int nbytes = scatterwalk_clamp(walk, total); scatterwalk_map(walk); return nbytes; } static inline void scatterwalk_unmap(struct scatter_walk *walk) { if (IS_ENABLED(CONFIG_HIGHMEM)) kunmap_local(walk->__addr); } static inline void scatterwalk_advance(struct scatter_walk *walk, unsigned int nbytes) { walk->offset += nbytes; } /** * scatterwalk_done_src() - Finish one step of a walk of source scatterlist * @walk: the scatter_walk * @nbytes: the number of bytes processed this step, less than or equal to the * number of bytes that scatterwalk_next() returned. * * Use this if the mapped address was not written to, i.e. it is source data. */ static inline void scatterwalk_done_src(struct scatter_walk *walk, unsigned int nbytes) { scatterwalk_unmap(walk); scatterwalk_advance(walk, nbytes); } /** * scatterwalk_done_dst() - Finish one step of a walk of destination scatterlist * @walk: the scatter_walk * @nbytes: the number of bytes processed this step, less than or equal to the * number of bytes that scatterwalk_next() returned. * * Use this if the mapped address may have been written to, i.e. it is * destination data. */ static inline void scatterwalk_done_dst(struct scatter_walk *walk, unsigned int nbytes) { scatterwalk_unmap(walk); /* * Explicitly check ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE instead of just * relying on flush_dcache_page() being a no-op when not implemented, * since otherwise the BUG_ON in sg_page() does not get optimized out. * This also avoids having to consider whether the loop would get * reliably optimized out or not. */ if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE) { struct page *base_page; unsigned int offset; int start, end, i; base_page = sg_page(walk->sg); offset = walk->offset; start = offset >> PAGE_SHIFT; end = start + (nbytes >> PAGE_SHIFT); end += (offset_in_page(offset) + offset_in_page(nbytes) + PAGE_SIZE - 1) >> PAGE_SHIFT; for (i = start; i < end; i++) flush_dcache_page(nth_page(base_page, i)); } scatterwalk_advance(walk, nbytes); } void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes); void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk, unsigned int nbytes); void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf, unsigned int nbytes); void memcpy_from_sglist(void *buf, struct scatterlist *sg, unsigned int start, unsigned int nbytes); void memcpy_to_sglist(struct scatterlist *sg, unsigned int start, const void *buf, unsigned int nbytes); void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src, unsigned int nbytes); /* In new code, please use memcpy_{from,to}_sglist() directly instead. */ static inline void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg, unsigned int start, unsigned int nbytes, int out) { if (out) memcpy_to_sglist(sg, start, buf, nbytes); else memcpy_from_sglist(buf, sg, start, nbytes); } struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2], struct scatterlist *src, unsigned int len); #endif /* _CRYPTO_SCATTERWALK_H */