scatterwalk.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Cryptographic API.
  4 *
  5 * Cipher operations.
  6 *
  7 * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
  8 *               2002 Adam J. Richter <adam@yggdrasil.com>
  9 *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
 10 */
 11
 12#include <crypto/scatterwalk.h>
 13#include <linux/kernel.h>
 14#include <linux/mm.h>
 15#include <linux/module.h>
 16#include <linux/scatterlist.h>
 17
 18void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes)
 19{
 20	struct scatterlist *sg = walk->sg;
 21
 22	nbytes += walk->offset - sg->offset;
 23
 24	while (nbytes > sg->length) {
 25		nbytes -= sg->length;
 26		sg = sg_next(sg);
 27	}
 28	walk->sg = sg;
 29	walk->offset = sg->offset + nbytes;
 30}
 31EXPORT_SYMBOL_GPL(scatterwalk_skip);
 32
 33inline void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk,
 34				    unsigned int nbytes)
 35{
 36	do {
 37		unsigned int to_copy;
 38
 39		to_copy = scatterwalk_next(walk, nbytes);
 40		memcpy(buf, walk->addr, to_copy);
 41		scatterwalk_done_src(walk, to_copy);
 42		buf += to_copy;
 43		nbytes -= to_copy;
 44	} while (nbytes);
 45}
 46EXPORT_SYMBOL_GPL(memcpy_from_scatterwalk);
 47
 48inline void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf,
 49				  unsigned int nbytes)
 50{
 51	do {
 52		unsigned int to_copy;
 53
 54		to_copy = scatterwalk_next(walk, nbytes);
 55		memcpy(walk->addr, buf, to_copy);
 56		scatterwalk_done_dst(walk, to_copy);
 57		buf += to_copy;
 58		nbytes -= to_copy;
 59	} while (nbytes);
 60}
 61EXPORT_SYMBOL_GPL(memcpy_to_scatterwalk);
 62
 63void memcpy_from_sglist(void *buf, struct scatterlist *sg,
 64			unsigned int start, unsigned int nbytes)
 65{
 66	struct scatter_walk walk;
 67
 68	if (unlikely(nbytes == 0)) /* in case sg == NULL */
 69		return;
 70
 71	scatterwalk_start_at_pos(&walk, sg, start);
 72	memcpy_from_scatterwalk(buf, &walk, nbytes);
 73}
 74EXPORT_SYMBOL_GPL(memcpy_from_sglist);
 75
 76void memcpy_to_sglist(struct scatterlist *sg, unsigned int start,
 77		      const void *buf, unsigned int nbytes)
 78{
 79	struct scatter_walk walk;
 80
 81	if (unlikely(nbytes == 0)) /* in case sg == NULL */
 82		return;
 83
 84	scatterwalk_start_at_pos(&walk, sg, start);
 85	memcpy_to_scatterwalk(&walk, buf, nbytes);
 86}
 87EXPORT_SYMBOL_GPL(memcpy_to_sglist);
 88
 89/**
 90 * memcpy_sglist() - Copy data from one scatterlist to another
 91 * @dst: The destination scatterlist.  Can be NULL if @nbytes == 0.
 92 * @src: The source scatterlist.  Can be NULL if @nbytes == 0.
 93 * @nbytes: Number of bytes to copy
 94 *
 95 * The scatterlists can describe exactly the same memory, in which case this
 96 * function is a no-op.  No other overlaps are supported.
 97 *
 98 * Context: Any context
 99 */
100void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src,
101		   unsigned int nbytes)
102{
103	unsigned int src_offset, dst_offset;
104
105	if (unlikely(nbytes == 0)) /* in case src and/or dst is NULL */
106		return;
107
108	src_offset = src->offset;
109	dst_offset = dst->offset;
110	for (;;) {
111		/* Compute the length to copy this step. */
112		unsigned int len = min3(src->offset + src->length - src_offset,
113					dst->offset + dst->length - dst_offset,
114					nbytes);
115		struct page *src_page = sg_page(src);
116		struct page *dst_page = sg_page(dst);
117		const void *src_virt;
118		void *dst_virt;
119
120		if (IS_ENABLED(CONFIG_HIGHMEM)) {
121			/* HIGHMEM: we may have to actually map the pages. */
122			const unsigned int src_oip = offset_in_page(src_offset);
123			const unsigned int dst_oip = offset_in_page(dst_offset);
124			const unsigned int limit = PAGE_SIZE;
125
126			/* Further limit len to not cross a page boundary. */
127			len = min3(len, limit - src_oip, limit - dst_oip);
128
129			/* Compute the source and destination pages. */
130			src_page += src_offset / PAGE_SIZE;
131			dst_page += dst_offset / PAGE_SIZE;
132
133			if (src_page != dst_page) {
134				/* Copy between different pages. */
135				memcpy_page(dst_page, dst_oip,
136					    src_page, src_oip, len);
137				flush_dcache_page(dst_page);
138			} else if (src_oip != dst_oip) {
139				/* Copy between different parts of same page. */
140				dst_virt = kmap_local_page(dst_page);
141				memcpy(dst_virt + dst_oip, dst_virt + src_oip,
142				       len);
143				kunmap_local(dst_virt);
144				flush_dcache_page(dst_page);
145			} /* Else, it's the same memory.  No action needed. */
146		} else {
147			/*
148			 * !HIGHMEM: no mapping needed.  Just work in the linear
149			 * buffer of each sg entry.  Note that we can cross page
150			 * boundaries, as they are not significant in this case.
151			 */
152			src_virt = page_address(src_page) + src_offset;
153			dst_virt = page_address(dst_page) + dst_offset;
154			if (src_virt != dst_virt) {
155				memcpy(dst_virt, src_virt, len);
156				if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE)
157					__scatterwalk_flush_dcache_pages(
158						dst_page, dst_offset, len);
159			} /* Else, it's the same memory.  No action needed. */
160		}
161		nbytes -= len;
162		if (nbytes == 0) /* No more to copy? */
163			break;
164
165		/*
166		 * There's more to copy.  Advance the offsets by the length
167		 * copied this step, and advance the sg entries as needed.
168		 */
169		src_offset += len;
170		if (src_offset >= src->offset + src->length) {
171			src = sg_next(src);
172			src_offset = src->offset;
173		}
174		dst_offset += len;
175		if (dst_offset >= dst->offset + dst->length) {
176			dst = sg_next(dst);
177			dst_offset = dst->offset;
178		}
179	}
180}
181EXPORT_SYMBOL_GPL(memcpy_sglist);
182
183struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
184				     struct scatterlist *src,
185				     unsigned int len)
186{
187	for (;;) {
188		if (!len)
189			return src;
190
191		if (src->length > len)
192			break;
193
194		len -= src->length;
195		src = sg_next(src);
196	}
197
198	sg_init_table(dst, 2);
199	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
200	scatterwalk_crypto_chain(dst, sg_next(src), 2);
201
202	return dst;
203}
204EXPORT_SYMBOL_GPL(scatterwalk_ffwd);