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

PATCH In review Ard Biesheuvel 2 participants 2 messages Jan 2, 2023 – Jan 13, 2023 Crypto API

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Ard Biesheuvel

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PATCH 1/1 crypto: skcipher - Use scatterwalk (un)map interface for dst and src buffers

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 <[email protected]>
---
 crypto/skcipher.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)
crypto/skcipher.c +4 -18
index 0ecab31cfe79bfd8..7bf4871fec8006ac 100644
@@ -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)
Signature · 1 line
2.39.0
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#1 lore raw
Quoted 7 lines · 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.

Quoted 7 lines

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 <[email protected]>
---
 crypto/skcipher.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

Patch applied. Thanks.

Signature · 3 lines
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt