[kdbus] Import iov_iter_init & iov_iter_kvec from Linux 4.0

These 2 functions are used by kdbus/pool.c and backporting patches that
adds desired functions (with dependencies) would introduce too many
changes for 3.10.

Change-Id: Ic617cc53c98eb18c15110605d577c1ed672c0153
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>

1 files changed, 142 insertions, 0 deletions

diff --git a/compat/include/linux/uio.h b/compat/include/linux/uio.h
new file mode 100644
index 00000000000..71880299ed4
--- /dev/null
+++ b/compat/include/linux/uio.h
@@ -0,0 +1,142 @@
+/*
+ *	Berkeley style UIO structures	-	Alan Cox 1994.
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ */
+#ifndef __LINUX_UIO_H
+#define __LINUX_UIO_H
+
+#include <linux/kernel.h>
+#include <uapi/linux/uio.h>
+
+struct page;
+
+struct kvec {
+	void *iov_base; /* and that should *never* hold a userland pointer */
+	size_t iov_len;
+};
+
+enum {
+	ITER_IOVEC = 0,
+	ITER_KVEC = 2,
+	ITER_BVEC = 4,
+};
+
+struct iov_iter {
+	int type;
+	size_t iov_offset;
+	size_t count;
+	union {
+		const struct iovec *iov;
+		const struct kvec *kvec;
+		const struct bio_vec *bvec;
+	};
+	unsigned long nr_segs;
+};
+
+/*
+ * Total number of bytes covered by an iovec.
+ *
+ * NOTE that it is not safe to use this function until all the iovec's
+ * segment lengths have been validated.  Because the individual lengths can
+ * overflow a size_t when added together.
+ */
+static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
+{
+	unsigned long seg;
+	size_t ret = 0;
+
+	for (seg = 0; seg < nr_segs; seg++)
+		ret += iov[seg].iov_len;
+	return ret;
+}
+
+static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
+{
+	return (struct iovec) {
+		.iov_base = iter->iov->iov_base + iter->iov_offset,
+		.iov_len = min(iter->count,
+			       iter->iov->iov_len - iter->iov_offset),
+	};
+}
+
+#define iov_for_each(iov, iter, start)				\
+	if (!((start).type & ITER_BVEC))			\
+	for (iter = (start);					\
+	     (iter).count &&					\
+	     ((iov = iov_iter_iovec(&(iter))), 1);		\
+	     iov_iter_advance(&(iter), (iov).iov_len))
+
+unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
+
+size_t iov_iter_copy_from_user_atomic(struct page *page,
+		struct iov_iter *i, unsigned long offset, size_t bytes);
+void iov_iter_advance(struct iov_iter *i, size_t bytes);
+int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
+size_t iov_iter_single_seg_count(const struct iov_iter *i);
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i);
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i);
+size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i);
+size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
+size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
+size_t iov_iter_zero(size_t bytes, struct iov_iter *);
+unsigned long iov_iter_alignment(const struct iov_iter *i);
+void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
+			unsigned long nr_segs, size_t count);
+void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
+			unsigned long nr_segs, size_t count);
+void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
+			unsigned long nr_segs, size_t count);
+ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
+			size_t maxsize, unsigned maxpages, size_t *start);
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
+			size_t maxsize, size_t *start);
+int iov_iter_npages(const struct iov_iter *i, int maxpages);
+
+const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
+
+static inline size_t iov_iter_count(struct iov_iter *i)
+{
+	return i->count;
+}
+
+static inline bool iter_is_iovec(struct iov_iter *i)
+{
+	return !(i->type & (ITER_BVEC | ITER_KVEC));
+}
+
+/*
+ * Cap the iov_iter by given limit; note that the second argument is
+ * *not* the new size - it's upper limit for such.  Passing it a value
+ * greater than the amount of data in iov_iter is fine - it'll just do
+ * nothing in that case.
+ */
+static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
+{
+	/*
+	 * count doesn't have to fit in size_t - comparison extends both
+	 * operands to u64 here and any value that would be truncated by
+	 * conversion in assignement is by definition greater than all
+	 * values of size_t, including old i->count.
+	 */
+	if (i->count > count)
+		i->count = count;
+}
+
+/*
+ * reexpand a previously truncated iterator; count must be no more than how much
+ * we had shrunk it.
+ */
+static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
+{
+	i->count = count;
+}
+size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
+size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
+
+#endif