fsverity: store log2(digest_size) precomputed

Add log_digestsize to struct merkle_tree_params so that it can be used
in verify.c.  Also save memory by using u8 for all the log_* fields.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-4-ebiggers@kernel.org

diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index 48b97f5..fc1c279 100644 (file)
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -42,8 +42,9 @@ struct merkle_tree_params {
        unsigned int digest_size;       /* same as hash_alg->digest_size */
        unsigned int block_size;        /* size of data and tree blocks */
        unsigned int hashes_per_block;  /* number of hashes per tree block */
-       unsigned int log_blocksize;     /* log2(block_size) */
-       unsigned int log_arity;         /* log2(hashes_per_block) */
+       u8 log_digestsize;              /* log2(digest_size) */
+       u8 log_blocksize;               /* log2(block_size) */
+       u8 log_arity;                   /* log2(hashes_per_block) */
        unsigned int num_levels;        /* number of levels in Merkle tree */
        u64 tree_size;                  /* Merkle tree size in bytes */
        unsigned long tree_pages;       /* Merkle tree size in pages */

diff --git a/fs/verity/open.c b/fs/verity/open.c
index e356eef..ca8de73 100644 (file)
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -76,7 +76,8 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
                err = -EINVAL;
                goto out_err;
        }
-       params->log_arity = params->log_blocksize - ilog2(params->digest_size);
+       params->log_digestsize = ilog2(params->digest_size);
+       params->log_arity = log_blocksize - params->log_digestsize;
        params->hashes_per_block = 1 << params->log_arity;
 
        /*

diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index 4c57a1b..d2fcb6a 100644 (file)
--- a/fs/verity/verify.c
+++ b/fs/verity/verify.c
@@ -35,7 +35,7 @@ static void hash_at_level(const struct merkle_tree_params *params,
 
        /* Offset of the wanted hash (in bytes) within the hash block */
        *hoffset = (position & ((1 << params->log_arity) - 1)) <<
-                  (params->log_blocksize - params->log_arity);
+                  params->log_digestsize;
 }
 
 static inline int cmp_hashes(const struct fsverity_info *vi,