selftests/ftrace: Add BTF fields access testcases

Add test cases for accessing the data structure fields using BTF info.
This includes the field access from parameters and retval, and accessing
string information.

Link: https://lore.kernel.org/all/169272161265.160970.14048619786574971276.stgit@devnote2/Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/testing/selftests/ftrace/test.d/dynevent/add_remove_btfarg.tc

@@ -5,6 +5,7 @@
 
 KPROBES=
 FPROBES=
+FIELDS=
 
 if grep -qF "p[:[<group>/][<event>]] <place> [<args>]" README ; then
   KPROBES=yes
@@ -12,6 +13,9 @@ fi
 if grep -qF "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README ; then
   FPROBES=yes
 fi
+if grep -qF "<argname>[->field[->field|.field...]]" README ; then
+  FIELDS=yes
+fi
 
 if [ -z "$KPROBES" -a -z "$FPROBES" ] ; then
   exit_unsupported
@@ -21,6 +25,9 @@ echo 0 > events/enable
 echo > dynamic_events
 
 TP=kfree
+TP2=kmem_cache_alloc
+TP3=getname_flags
+TP4=sched_wakeup
 
 if [ "$FPROBES" ] ; then
 echo "f:fpevent $TP object" >> dynamic_events
@@ -33,6 +40,7 @@ echo > dynamic_events
 
 echo "f:fpevent $TP "'$arg1' >> dynamic_events
 grep -q "fpevent.*object=object" dynamic_events
+
 echo > dynamic_events
 
 echo "f:fpevent $TP "'$arg*' >> dynamic_events
@@ -45,6 +53,18 @@ fi
 
 echo > dynamic_events
 
+if [ "$FIELDS" ] ; then
+echo "t:tpevent ${TP2} obj_size=s->object_size" >> dynamic_events
+echo "f:fpevent ${TP3}%return path=\$retval->name:string" >> dynamic_events
+echo "t:tpevent2 ${TP4} p->se.group_node.next->prev" >> dynamic_events
+
+grep -q "tpevent .*obj_size=s->object_size" dynamic_events
+grep -q "fpevent.*path=\$retval->name:string" dynamic_events
+grep -q 'tpevent2 .*p->se.group_node.next->prev' dynamic_events
+
+echo > dynamic_events
+fi
+
 if [ "$KPROBES" ] ; then
 echo "p:kpevent $TP object" >> dynamic_events
 grep -q "kpevent.*object=object" dynamic_events

tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc

@@ -103,6 +103,14 @@ check_error 'f vfs_read%return ^$arg*'		# NOFENTRY_ARGS
 check_error 'f vfs_read ^hoge'			# NO_BTFARG
 check_error 'f kfree ^$arg10'			# NO_BTFARG (exceed the number of parameters)
 check_error 'f kfree%return ^$retval'		# NO_RETVAL
+
+if grep -qF "<argname>[->field[->field|.field...]]" README ; then
+check_error 'f vfs_read%return $retval->^foo'	# NO_PTR_STRCT
+check_error 'f vfs_read file->^foo'		# NO_BTF_FIELD
+check_error 'f vfs_read file^-.foo'		# BAD_HYPHEN
+check_error 'f vfs_read ^file:string'		# BAD_TYPE4STR
+fi
+
 else
 check_error 'f vfs_read ^$arg*'			# NOSUP_BTFARG
 check_error 't kfree ^$arg*'			# NOSUP_BTFARG