netdev - [PATCH v2 15/29] crypto: scatterwalk - add scatterwalk_get

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Message-ID: <20241230001418.74739-16-ebiggers@kernel.org>
Date: Sun, 29 Dec 2024 16:14:04 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Boris Pismenny <borisp@...dia.com>,
	Jakub Kicinski <kuba@...nel.org>,
	John Fastabend <john.fastabend@...il.com>
Subject: [PATCH v2 15/29] crypto: scatterwalk - add scatterwalk_get_sglist()

From: Eric Biggers <ebiggers@...gle.com>

Add a function that creates a scatterlist that represents the remaining
data in a walk.  This will be used to replace chain_to_walk() in
net/tls/tls_device_fallback.c so that it will no longer need to reach
into the internals of struct scatter_walk.

Cc: Boris Pismenny <borisp@...dia.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---

This patch is part of a long series touching many files, so I have
limited the Cc list on the full series.  If you want the full series and
did not receive it, please retrieve it from lore.kernel.org.

 include/crypto/scatterwalk.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 1689ecd7ddaf..f6262d05a3c7 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -67,10 +67,27 @@ static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk,
 static inline struct page *scatterwalk_page(struct scatter_walk *walk)
 {
 	return sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
 }
 
+/*
+ * Create a scatterlist that represents the remaining data in a walk.  Uses
+ * chaining to reference the original scatterlist, so this uses at most two
+ * entries in @sg_out regardless of the number of entries in the original list.
+ * Assumes that sg_init_table() was already done.
+ */
+static inline void scatterwalk_get_sglist(struct scatter_walk *walk,
+					  struct scatterlist sg_out[2])
+{
+	if (walk->offset >= walk->sg->offset + walk->sg->length)
+		scatterwalk_start(walk, sg_next(walk->sg));
+	sg_set_page(sg_out, sg_page(walk->sg),
+		    walk->sg->offset + walk->sg->length - walk->offset,
+		    walk->offset);
+	scatterwalk_crypto_chain(sg_out, sg_next(walk->sg), 2);
+}
+
 static inline void scatterwalk_unmap(void *vaddr)
 {
 	kunmap_local(vaddr);
 }
 
-- 
2.47.1