[PATCH v4] kselftests/damon: add support for cases where debugfs cannot be read

[Gautam]

The kernel is in lockdown mode when secureboot is enabled and hence
debugfs cannot be used. Add support for this and other general cases 
where debugfs cannot be read and communicate the same to the user before
running tests.

Signed-off-by: Gautam <gautammenghani201@xxxxxxxxx>
---
Changes in v2:
1. Modify the error message to account for general cases.
2. Change the return code so that the test is skipped.

Changes in v3:
1. Change the name of variable holding the error message.

Changes in v4:
1. Correct the mode of the source file.

 tools/testing/selftests/damon/_chk_dependency.sh | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/testing/selftests/damon/_chk_dependency.sh b/tools/testing/selftests/damon/_chk_dependency.sh
index 0189db81550b..0328ac0b5a5e 100644
--- a/tools/testing/selftests/damon/_chk_dependency.sh
+++ b/tools/testing/selftests/damon/_chk_dependency.sh
@@ -26,3 +26,13 @@ do
 		exit 1
 	fi
 done
+
+permission_error="Operation not permitted"
+for f in attrs target_ids monitor_on
+do
+	status=$( cat "$DBGFS/$f" 2>&1 )
+	if [ "${status#*$permission_error}" != "$status" ]; then
+		echo "Permission for reading $DBGFS/$f denied; maybe secureboot enabled?"
+		exit $ksft_skip
+	fi
+done
-- 
2.36.1