ANDROID: dm: Add android verity target

This device-mapper target is virtually a VERITY target. This
target is setup by reading the metadata contents piggybacked
to the actual data blocks in the block device. The signature
of the metadata contents are verified against the key included
in the system keyring. Upon success, the underlying verity
target is setup.

BUG: 27175947

Change-Id: I7e99644a0960ac8279f02c0158ed20999510ea97
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 0aba34a..1036270 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -551,7 +551,7 @@
  * Bio map function. It allocates dm_verity_io structure and bio vector and
  * fills them. Then it issues prefetches and the I/O.
  */
-static int verity_map(struct dm_target *ti, struct bio *bio)
+int verity_map(struct dm_target *ti, struct bio *bio)
 {
 	struct dm_verity *v = ti->private;
 	struct dm_verity_io *io;
@@ -596,7 +596,7 @@
 /*
  * Status: V (valid) or C (corruption found)
  */
-static void verity_status(struct dm_target *ti, status_type_t type,
+void verity_status(struct dm_target *ti, status_type_t type,
 			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct dm_verity *v = ti->private;
@@ -669,7 +669,7 @@
 	return 0;
 }
 
-static int verity_iterate_devices(struct dm_target *ti,
+int verity_iterate_devices(struct dm_target *ti,
 				  iterate_devices_callout_fn fn, void *data)
 {
 	struct dm_verity *v = ti->private;
@@ -677,7 +677,7 @@
 	return fn(ti, v->data_dev, v->data_start, ti->len, data);
 }
 
-static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
+void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
 {
 	struct dm_verity *v = ti->private;
 
@@ -690,7 +690,7 @@
 	blk_limits_io_min(limits, limits->logical_block_size);
 }
 
-static void verity_dtr(struct dm_target *ti)
+void verity_dtr(struct dm_target *ti)
 {
 	struct dm_verity *v = ti->private;
 
@@ -817,7 +817,7 @@
  *	<digest>
  *	<salt>		Hex string or "-" if no salt.
  */
-static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
+int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 {
 	struct dm_verity *v;
 	struct dm_arg_set as;