ima: audit log hashes

This adds an 'audit' policy action which audit logs file measurements.

Changelog v6:
 - use new action flag handling (Dmitry Kasatkin).
 - removed whitespace (Mimi)

Changelog v5:
 - use audit_log_untrustedstring.

Changelog v4:
 - cleanup digest -> hash conversion.
 - use filename rather than d_path in ima_audit_measurement.

Changelog v3:
 - Use newly exported audit_log_task_info for logging pid/ppid/uid/etc.
 - Update the ima_policy ABI documentation.

Changelog v2:
 - Use 'audit' action rather than 'measure_and_audit' to permit
 auditing in the absence of measuring..

Changelog v1:
 - Initial posting.

Signed-off-by: Peter Moody <pmoody@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index dcff822..9869466 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -17,7 +17,7 @@
 
 		rule format: action [condition ...]
 
-		action: measure | dont_measure | appraise | dont_appraise
+		action: measure | dont_measure | appraise | dont_appraise | audit
 		condition:= base | lsm
 			base:	[[func=] [mask=] [fsmagic=] [uid=] [fowner]]
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]