generic: add helpers for dumping fs-verity metadata

In common/verity, add helper functions for dumping a file's fs-verity
metadata using the new FS_IOC_READ_VERITY_METADATA ioctl.

Signed-off-by: Eric Biggers <ebiggers@google.com>

common/verity

@@ -120,6 +120,27 @@ _restore_fsverity_signatures()
         fi
 }
 
+# Require userspace and kernel support for 'fsverity dump_metadata'.
+# $1 must be a file with fs-verity enabled.
+_require_fsverity_dump_metadata()
+{
+	local verity_file=$1
+	local tmpfile=$tmp.require_fsverity_dump_metadata
+
+	if _fsv_dump_merkle_tree "$verity_file" 2>"$tmpfile" >/dev/null; then
+		return
+	fi
+	if grep -q "^ERROR: unrecognized command: 'dump_metadata'$" "$tmpfile"
+	then
+		_notrun "Missing 'fsverity dump_metadata' command"
+	fi
+	if grep -q "^ERROR: FS_IOC_READ_VERITY_METADATA failed on '.*': Inappropriate ioctl for device$" "$tmpfile"
+	then
+		_notrun "Kernel doesn't support FS_IOC_READ_VERITY_METADATA"
+	fi
+	_fail "Unexpected output from 'fsverity dump_metadata': $(<"$tmpfile")"
+}
+
 _scratch_mkfs_verity()
 {
 	case $FSTYP in
@@ -157,6 +178,21 @@ _fsv_scratch_begin_subtest()
 	echo -e "\n# $msg"
 }
 
+_fsv_dump_merkle_tree()
+{
+	$FSVERITY_PROG dump_metadata merkle_tree "$@"
+}
+
+_fsv_dump_descriptor()
+{
+	$FSVERITY_PROG dump_metadata descriptor "$@"
+}
+
+_fsv_dump_signature()
+{
+	$FSVERITY_PROG dump_metadata signature "$@"
+}
+
 _fsv_enable()
 {
 	$FSVERITY_PROG enable "$@"