[PATCH] crypto: skcipher - Use scatterwalk (un)map interface for dst and src buffers

[PATCH] crypto: skcipher - Use scatterwalk (un)map interface for dst and src buffers

[Ard Biesheuvel]

The skcipher walk API implementation avoids scatterwalk_map() for
mapping the source and destination buffers, and invokes kmap_atomic()
directly if the buffer in question is not in low memory (which can only
happen on 32-bit architectures). This avoids some overhead on 64-bit
architectures, and most notably, permits the skcipher code to run with
preemption enabled.

Now that scatterwalk_map() has been updated to use kmap_local(), none of
this is needed, so we can simply use scatterwalk_map/unmap instead.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/skcipher.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 0ecab31cfe79bfd8..7bf4871fec8006ac 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -42,38 +42,24 @@ struct skcipher_walk_buffer {
 
 static int skcipher_walk_next(struct skcipher_walk *walk);
 
-static inline void skcipher_unmap(struct scatter_walk *walk, void *vaddr)
-{
-	if (PageHighMem(scatterwalk_page(walk)))
-		kunmap_atomic(vaddr);
-}
-
-static inline void *skcipher_map(struct scatter_walk *walk)
-{
-	struct page *page = scatterwalk_page(walk);
-
-	return (PageHighMem(page) ? kmap_atomic(page) : page_address(page)) +
-	       offset_in_page(walk->offset);
-}
-
 static inline void skcipher_map_src(struct skcipher_walk *walk)
 {
-	walk->src.virt.addr = skcipher_map(&walk->in);
+	walk->src.virt.addr = scatterwalk_map(&walk->in);
 }
 
 static inline void skcipher_map_dst(struct skcipher_walk *walk)
 {
-	walk->dst.virt.addr = skcipher_map(&walk->out);
+	walk->dst.virt.addr = scatterwalk_map(&walk->out);
 }
 
 static inline void skcipher_unmap_src(struct skcipher_walk *walk)
 {
-	skcipher_unmap(&walk->in, walk->src.virt.addr);
+	scatterwalk_unmap(walk->src.virt.addr);
 }
 
 static inline void skcipher_unmap_dst(struct skcipher_walk *walk)
 {
-	skcipher_unmap(&walk->out, walk->dst.virt.addr);
+	scatterwalk_unmap(walk->dst.virt.addr);
 }
 
 static inline gfp_t skcipher_walk_gfp(struct skcipher_walk *walk)
-- 
2.39.0

Re: [PATCH] crypto: skcipher - Use scatterwalk (un)map interface for dst and src buffers

[Herbert Xu]

On Mon, Jan 02, 2023 at 11:18:46AM +0100, Ard Biesheuvel wrote:
> The skcipher walk API implementation avoids scatterwalk_map() for
> mapping the source and destination buffers, and invokes kmap_atomic()
> directly if the buffer in question is not in low memory (which can only
> happen on 32-bit architectures). This avoids some overhead on 64-bit
> architectures, and most notably, permits the skcipher code to run with
> preemption enabled.
> 
> Now that scatterwalk_map() has been updated to use kmap_local(), none of
> this is needed, so we can simply use scatterwalk_map/unmap instead.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  crypto/skcipher.c | 22 ++++------------------
>  1 file changed, 4 insertions(+), 18 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt