On Fri, Mar 07, 2025 at 11:36:19AM +0800, Herbert Xu wrote:
> Add memcpy_sglist which copies one SG list to another.
>
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> ---
> crypto/scatterwalk.c | 27 +++++++++++++++++++++++++++
> include/crypto/scatterwalk.h | 3 +++
> 2 files changed, 30 insertions(+)
>
> diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
> index 20a28c6d94da..8225801488d5 100644
> --- a/crypto/scatterwalk.c
> +++ b/crypto/scatterwalk.c
> @@ -86,6 +86,33 @@ void memcpy_to_sglist(struct scatterlist *sg, unsigned int start,
> }
> EXPORT_SYMBOL_GPL(memcpy_to_sglist);
>
> +void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src,
> + unsigned int nbytes)
> +{
> + struct scatter_walk swalk;
> + struct scatter_walk dwalk;
> +
> + if (unlikely(nbytes == 0)) /* in case sg == NULL */
> + return;
> +
> + scatterwalk_start(&swalk, src);
> + scatterwalk_start(&dwalk, dst);
> +
> + do {
> + unsigned int slen, dlen;
> + unsigned int len;
> +
> + slen = scatterwalk_next(&swalk, nbytes);
> + dlen = scatterwalk_next(&dwalk, nbytes);
> + len = min(slen, dlen);
> + memcpy(dwalk.addr, swalk.addr, len);
> + scatterwalk_done_dst(&dwalk, len);
> + scatterwalk_done_src(&swalk, len);
> + nbytes -= len;
> + } while (nbytes);
> +}
> +EXPORT_SYMBOL_GPL(memcpy_sglist);
Actually this new function is useless as-is, since it invokes undefined behavior
when the source and destination coincide (which can happen even when src ==
dst), and all the potential callers need to handle that case. I'm working on a
fixed version.
- Eric
