Commit e21d01a2 authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu
Browse files

crypto: scatterwalk - add new functions for skipping data 



Add scatterwalk_skip() to skip the given number of bytes in a
scatter_walk.  Previously support for skipping was provided through
scatterwalk_copychunks(..., 2) followed by scatterwalk_done(), which was
confusing and less efficient.

Also add scatterwalk_start_at_pos() which starts a scatter_walk at the
given position, equivalent to scatterwalk_start() + scatterwalk_skip().
This addresses another common need in a more streamlined way.

Later patches will convert various users to use these functions.

Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 3bd4b2c6

crypto/scatterwalk.c

+15 −0
Original line number Diff line number Diff line
@@ -15,6 +15,21 @@ 
#include <linux/module.h>

#include <linux/scatterlist.h>



void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes)

{

	struct scatterlist *sg = walk->sg;



	nbytes += walk->offset - sg->offset;



	while (nbytes > sg->length) {

		nbytes -= sg->length;

		sg = sg_next(sg);

	}

	walk->sg = sg;

	walk->offset = sg->offset + nbytes;

}

EXPORT_SYMBOL_GPL(scatterwalk_skip);



static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)

{

	void *src = out ? buf : sgdata;

include/crypto/scatterwalk.h

+18 −0
Original line number Diff line number Diff line
@@ -33,6 +33,22 @@ static inline void scatterwalk_start(struct scatter_walk *walk, 
	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_pagelen(struct scatter_walk *walk)

{

	unsigned int len = walk->sg->offset + walk->sg->length - walk->offset;
@@ -92,6 +108,8 @@ static inline void scatterwalk_done(struct scatter_walk *walk, int out, 
		scatterwalk_pagedone(walk, out, more);

}



void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes);



void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,

			    size_t nbytes, int out);