1 files changed, 182 insertions, 40 deletions
diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 32fc4473175b..94a8585f26b2 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -26,76 +26,218 @@ static inline void scatterwalk_crypto_chain(struct scatterlist *head,
 		sg_mark_end(head);
 }
 
-static inline unsigned int scatterwalk_pagelen(struct scatter_walk *walk)
+static inline void scatterwalk_start(struct scatter_walk *walk,
+				     struct scatterlist *sg)
+{
+	walk->sg = sg;
+	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)
 {
-	unsigned int len = walk->sg->offset + walk->sg->length - walk->offset;
-	unsigned int len_this_page = offset_in_page(~walk->offset) + 1;
-	return len_this_page > len ? len : len_this_page;
+	while (pos > sg->length) {
+		pos -= sg->length;
+		sg = sg_next(sg);
+	}
+	walk->sg = sg;
+	walk->offset = sg->offset + pos;
 }
 
 static inline unsigned int scatterwalk_clamp(struct scatter_walk *walk,
 					     unsigned int nbytes)
 {
-	unsigned int len_this_page = scatterwalk_pagelen(walk);
-	return nbytes > len_this_page ? len_this_page : nbytes;
+	unsigned int len_this_sg;
+	unsigned int limit;
+
+	if (walk->offset >= walk->sg->offset + walk->sg->length)
+		scatterwalk_start(walk, sg_next(walk->sg));
+	len_this_sg = walk->sg->offset + walk->sg->length - walk->offset;
+
+	/*
+	 * HIGHMEM case: the page may have to be mapped into memory.  To avoid
+	 * the complexity of having to map multiple pages at once per sg entry,
+	 * clamp the returned length to not cross a page boundary.
+	 *
+	 * !HIGHMEM case: no mapping is needed; all pages of the sg entry are
+	 * already mapped contiguously in the kernel's direct map.  For improved
+	 * performance, allow the walker to return data segments that cross a
+	 * page boundary.  Do still cap the length to PAGE_SIZE, since some
+	 * users rely on that to avoid disabling preemption for too long when
+	 * using SIMD.  It's also needed for when skcipher_walk uses a bounce
+	 * page due to the data not being aligned to the algorithm's alignmask.
+	 */
+	if (IS_ENABLED(CONFIG_HIGHMEM))
+		limit = PAGE_SIZE - offset_in_page(walk->offset);
+	else
+		limit = PAGE_SIZE;
+
+	return min3(nbytes, len_this_sg, limit);
 }
 
-static inline void scatterwalk_advance(struct scatter_walk *walk,
-				       unsigned int nbytes)
+/*
+ * 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])
 {
-	walk->offset += nbytes;
+	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 struct page *scatterwalk_page(struct scatter_walk *walk)
+static inline void scatterwalk_map(struct scatter_walk *walk)
 {
-	return sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
+	struct page *base_page = sg_page(walk->sg);
+	unsigned int offset = walk->offset;
+	void *addr;
+
+	if (IS_ENABLED(CONFIG_HIGHMEM)) {
+		struct page *page;
+
+		page = nth_page(base_page, offset >> PAGE_SHIFT);
+		offset = offset_in_page(offset);
+		addr = kmap_local_page(page) + offset;
+	} else {
+		/*
+		 * When !HIGHMEM we allow the walker to return segments that
+		 * span a page boundary; see scatterwalk_clamp().  To make it
+		 * clear that in this case we're working in the linear buffer of
+		 * the whole sg entry in the kernel's direct map rather than
+		 * within the mapped buffer of a single page, compute the
+		 * address as an offset from the page_address() of the first
+		 * page of the sg entry.  Either way the result is the address
+		 * in the direct map, but this makes it clearer what is really
+		 * going on.
+		 */
+		addr = page_address(base_page) + offset;
+	}
+
+	walk->__addr = addr;
 }
 
-static inline void scatterwalk_unmap(void *vaddr)
+/**
+ * scatterwalk_next() - Get the next data buffer in a scatterlist walk
+ * @walk: the scatter_walk
+ * @total: the total number of bytes remaining, > 0
+ *
+ * A virtual address for the next segment of data from the scatterlist will
+ * be placed into @walk->addr.  The caller must call scatterwalk_done_src()
+ * or scatterwalk_done_dst() when it is done using this virtual address.
+ *
+ * Returns: the next number of bytes available, <= @total
+ */
+static inline unsigned int scatterwalk_next(struct scatter_walk *walk,
+					    unsigned int total)
 {
-	kunmap_local(vaddr);
+	unsigned int nbytes = scatterwalk_clamp(walk, total);
+
+	scatterwalk_map(walk);
+	return nbytes;
 }
 
-static inline void scatterwalk_start(struct scatter_walk *walk,
-				     struct scatterlist *sg)
+static inline void scatterwalk_unmap(struct scatter_walk *walk)
 {
-	walk->sg = sg;
-	walk->offset = sg->offset;
+	if (IS_ENABLED(CONFIG_HIGHMEM))
+		kunmap_local(walk->__addr);
 }
 
-static inline void *scatterwalk_map(struct scatter_walk *walk)
+static inline void scatterwalk_advance(struct scatter_walk *walk,
+				       unsigned int nbytes)
 {
-	return kmap_local_page(scatterwalk_page(walk)) +
-	       offset_in_page(walk->offset);
+	walk->offset += nbytes;
 }
 
-static inline void scatterwalk_pagedone(struct scatter_walk *walk, int out,
-					unsigned int more)
+/**
+ * scatterwalk_done_src() - Finish one step of a walk of source scatterlist
+ * @walk: the scatter_walk
+ * @nbytes: the number of bytes processed this step, less than or equal to the
+ *	    number of bytes that scatterwalk_next() returned.
+ *
+ * Use this if the mapped address was not written to, i.e. it is source data.
+ */
+static inline void scatterwalk_done_src(struct scatter_walk *walk,
+					unsigned int nbytes)
 {
-	if (out) {
-		struct page *page;
-
-		page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
-		flush_dcache_page(page);
-	}
-
-	if (more && walk->offset >= walk->sg->offset + walk->sg->length)
-		scatterwalk_start(walk, sg_next(walk->sg));
+	scatterwalk_unmap(walk);
+	scatterwalk_advance(walk, nbytes);
 }
 
-static inline void scatterwalk_done(struct scatter_walk *walk, int out,
-				    int more)
+/**
+ * scatterwalk_done_dst() - Finish one step of a walk of destination scatterlist
+ * @walk: the scatter_walk
+ * @nbytes: the number of bytes processed this step, less than or equal to the
+ *	    number of bytes that scatterwalk_next() returned.
+ *
+ * Use this if the mapped address may have been written to, i.e. it is
+ * destination data.
+ */
+static inline void scatterwalk_done_dst(struct scatter_walk *walk,
+					unsigned int nbytes)
 {
-	if (!more || walk->offset >= walk->sg->offset + walk->sg->length ||
-	    !(walk->offset & (PAGE_SIZE - 1)))
-		scatterwalk_pagedone(walk, out, more);
+	scatterwalk_unmap(walk);
+	/*
+	 * Explicitly check ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE instead of just
+	 * relying on flush_dcache_page() being a no-op when not implemented,
+	 * since otherwise the BUG_ON in sg_page() does not get optimized out.
+	 * This also avoids having to consider whether the loop would get
+	 * reliably optimized out or not.
+	 */
+	if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE) {
+		struct page *base_page;
+		unsigned int offset;
+		int start, end, i;
+
+		base_page = sg_page(walk->sg);
+		offset = walk->offset;
+		start = offset >> PAGE_SHIFT;
+		end = start + (nbytes >> PAGE_SHIFT);
+		end += (offset_in_page(offset) + offset_in_page(nbytes) +
+			PAGE_SIZE - 1) >> PAGE_SHIFT;
+		for (i = start; i < end; i++)
+			flush_dcache_page(nth_page(base_page, i));
+	}
+	scatterwalk_advance(walk, nbytes);
 }
 
-void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
-			    size_t nbytes, int out);
+void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes);
+
+void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk,
+			     unsigned int nbytes);
+
+void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf,
+			   unsigned int nbytes);
 
-void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
-			      unsigned int start, unsigned int nbytes, int out);
+void memcpy_from_sglist(void *buf, struct scatterlist *sg,
+			unsigned int start, unsigned int nbytes);
+
+void memcpy_to_sglist(struct scatterlist *sg, unsigned int start,
+		      const void *buf, unsigned int nbytes);
+
+void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src,
+		   unsigned int nbytes);
+
+/* In new code, please use memcpy_{from,to}_sglist() directly instead. */
+static inline void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
+					    unsigned int start,
+					    unsigned int nbytes, int out)
+{
+	if (out)
+		memcpy_to_sglist(sg, start, buf, nbytes);
+	else
+		memcpy_from_sglist(buf, sg, start, nbytes);
+}
 
 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
 				     struct scatterlist *src,