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[dm-devel] [PATCH] dm: verity support data device offset (Linux 3.4.7)



From: Wesley Miaw <wmiaw netflix com>

Add data device start block index to dm-verity target parameters to support
verity targets where the data does not begin at sector 0 of the block device.
Also fix the hash block index computation so it takes into account data offsets.

Signed-off-by: Wesley Miaw <wmiaw netflix com>
---
 Documentation/device-mapper/verity.txt |    8 ++++-
 drivers/md/dm-verity.c                 |   32 +++++++++++++++--------
 2 files changed, 27 insertions(+), 13 deletions(-)
--- a/drivers/md/dm-verity.c	2012-08-07 16:03:03.778759000 -0700
+++ b/drivers/md/dm-verity.c	2012-08-07 17:32:02.130176956 -0700
@@ -491,7 +491,7 @@ static int verity_map(struct dm_target *
 	io->bio = bio;
 	io->orig_bi_end_io = bio->bi_end_io;
 	io->orig_bi_private = bio->bi_private;
-	io->block = bio->bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
+	io->block = (bio->bi_sector - v->data_start) >> (v->data_dev_block_bits - SECTOR_SHIFT);
 	io->n_blocks = bio->bi_size >> v->data_dev_block_bits;
 
 	bio->bi_end_io = verity_end_io;
@@ -641,6 +641,7 @@ static void verity_dtr(struct dm_target 
  *	<hash device>
  *	<data block size>
  *	<hash block size>
+ *	<data start block>
  *	<the number of data blocks>
  *	<hash start block>
  *	<algorithm>
@@ -671,8 +672,8 @@ static int verity_ctr(struct dm_target *
 		goto bad;
 	}
 
-	if (argc != 10) {
-		ti->error = "Invalid argument count: exactly 10 arguments required";
+	if (argc != 11) {
+		ti->error = "Invalid argument count: exactly 11 arguments required";
 		r = -EINVAL;
 		goto bad;
 	}
@@ -718,6 +719,15 @@ static int verity_ctr(struct dm_target *
 	v->hash_dev_block_bits = ffs(num) - 1;
 
 	if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
+		num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
+		(sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
+		ti->error = "Invalid data start";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->data_start = num_ll << (v->data_dev_block_bits - SECTOR_SHIFT);
+
+	if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
 	    num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
 	    (sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
 		ti->error = "Invalid data blocks";
@@ -732,7 +742,7 @@ static int verity_ctr(struct dm_target *
 		goto bad;
 	}
 
-	if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
+	if (sscanf(argv[7], "%llu%c", &num_ll, &dummy) != 1 ||
 	    num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT) !=
 	    (sector_t)num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT)) {
 		ti->error = "Invalid hash start";
@@ -741,7 +751,7 @@ static int verity_ctr(struct dm_target *
 	}
 	v->hash_start = num_ll;
 
-	v->alg_name = kstrdup(argv[7], GFP_KERNEL);
+	v->alg_name = kstrdup(argv[8], GFP_KERNEL);
 	if (!v->alg_name) {
 		ti->error = "Cannot allocate algorithm name";
 		r = -ENOMEM;
@@ -770,23 +780,23 @@ static int verity_ctr(struct dm_target *
 		r = -ENOMEM;
 		goto bad;
 	}
-	if (strlen(argv[8]) != v->digest_size * 2 ||
-	    hex2bin(v->root_digest, argv[8], v->digest_size)) {
+	if (strlen(argv[9]) != v->digest_size * 2 ||
+	    hex2bin(v->root_digest, argv[9], v->digest_size)) {
 		ti->error = "Invalid root digest";
 		r = -EINVAL;
 		goto bad;
 	}
 
-	if (strcmp(argv[9], "-")) {
-		v->salt_size = strlen(argv[9]) / 2;
+	if (strcmp(argv[10], "-")) {
+		v->salt_size = strlen(argv[10]) / 2;
 		v->salt = kmalloc(v->salt_size, GFP_KERNEL);
 		if (!v->salt) {
 			ti->error = "Cannot allocate salt";
 			r = -ENOMEM;
 			goto bad;
 		}
-		if (strlen(argv[9]) != v->salt_size * 2 ||
-		    hex2bin(v->salt, argv[9], v->salt_size)) {
+		if (strlen(argv[10]) != v->salt_size * 2 ||
+		    hex2bin(v->salt, argv[10], v->salt_size)) {
 			ti->error = "Invalid salt";
 			r = -EINVAL;
 			goto bad;
--- a/Documentation/device-mapper/verity.txt	2012-08-08 11:02:48.558883756 -0700
+++ b/Documentation/device-mapper/verity.txt	2012-08-08 11:13:01.259982498 -0700
@@ -9,7 +9,7 @@ Construction Parameters
 =======================
     <version> <dev> <hash_dev>
     <data_block_size> <hash_block_size>
-    <num_data_blocks> <hash_start_block>
+    <data_start_block> <num_data_blocks> <hash_start_block>
     <algorithm> <digest> <salt>
 
 <version>
@@ -41,6 +41,10 @@ Construction Parameters
 <hash_block_size>
     The size of a hash block in bytes.
 
+<data_start_block>
+    This is the offset, in <data_block_size>-blocks, from the start of data_dev
+    to the first block of the data.
+
 <num_data_blocks>
     The number of data blocks on the data device.  Additional blocks are
     inaccessible.  You can place hashes to the same partition as data, in this
@@ -136,7 +140,7 @@ Example
 =======
 Set up a device:
   # dmsetup create vroot --readonly --table \
-    "0 2097152 verity 1 /dev/sda1 /dev/sda2 4096 4096 262144 1 sha256 "\
+    "0 2097152 verity 1 /dev/sda1 /dev/sda2 4096 4096 0 262144 1 sha256 "\
     "4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 "\
     "1234000000000000000000000000000000000000000000000000000000000000"
 

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