1 files changed, 93 insertions, 0 deletions
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
new file mode 100644
index 0000000000..16f6ba896f
--- /dev/null
+++ b/crypto/scatterwalk.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API.
+ *
+ * Cipher operations.
+ *
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ *               2002 Adam J. Richter <adam@yggdrasil.com>
+ *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
+ */
+
+#include <crypto/scatterwalk.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+
+static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
+{
+	void *src = out ? buf : sgdata;
+	void *dst = out ? sgdata : buf;
+
+	memcpy(dst, src, nbytes);
+}
+
+void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
+			    size_t nbytes, int out)
+{
+	for (;;) {
+		unsigned int len_this_page = scatterwalk_pagelen(walk);
+		u8 *vaddr;
+
+		if (len_this_page > nbytes)
+			len_this_page = nbytes;
+
+		if (out != 2) {
+			vaddr = scatterwalk_map(walk);
+			memcpy_dir(buf, vaddr, len_this_page, out);
+			scatterwalk_unmap(vaddr);
+		}
+
+		scatterwalk_advance(walk, len_this_page);
+
+		if (nbytes == len_this_page)
+			break;
+
+		buf += len_this_page;
+		nbytes -= len_this_page;
+
+		scatterwalk_pagedone(walk, out & 1, 1);
+	}
+}
+EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
+
+void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
+			      unsigned int start, unsigned int nbytes, int out)
+{
+	struct scatter_walk walk;
+	struct scatterlist tmp[2];
+
+	if (!nbytes)
+		return;
+
+	sg = scatterwalk_ffwd(tmp, sg, start);
+
+	scatterwalk_start(&walk, sg);
+	scatterwalk_copychunks(buf, &walk, nbytes, out);
+	scatterwalk_done(&walk, out, 0);
+}
+EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
+
+struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
+				     struct scatterlist *src,
+				     unsigned int len)
+{
+	for (;;) {
+		if (!len)
+			return src;
+
+		if (src->length > len)
+			break;
+
+		len -= src->length;
+		src = sg_next(src);
+	}
+
+	sg_init_table(dst, 2);
+	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
+	scatterwalk_crypto_chain(dst, sg_next(src), 2);
+
+	return dst;
+}
+EXPORT_SYMBOL_GPL(scatterwalk_ffwd);