Merge: Updates for lkdtm selftests

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5439

Description: Updates for lkdtm selftests

JIRA: https://issues.redhat.com/browse/RHEL-52232

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=65130378

Tested: Verified Brew build test kernel RPMs and confirmed issue is resovled

Signed-off-by: Mamatha Inamdar <[email protected]>

commit 90091c3
Author: Misono Tomohiro <[email protected]>
Date:   Thu Aug 5 19:12:36 2021 +0900

    selftest/lkdtm: Skip stack-entropy test if lkdtm is not available

    Exit with return code 4 if lkdtm is not available like other tests
    in order to properly skip the test.

    Signed-off-by: Misono Tomohiro <[email protected]>
    Signed-off-by: Kees Cook <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]

Signed-off-by: Mamatha Inamdar <[email protected]>

Approved-by: Steve Best <[email protected]>
Approved-by: Tony Camuso <[email protected]>
Approved-by: Desnes Nunes <[email protected]>
Approved-by: CKI KWF Bot <[email protected]>

Merged-by: Rado Vrbovsky <[email protected]>

Author: emmil

tools/testing/selftests/lkdtm/stack-entropy.sh

@@ -4,13 +4,27 @@
 # Measure kernel stack entropy by sampling via LKDTM's REPORT_STACK test.
 set -e
 samples="${1:-1000}"
+TRIGGER=/sys/kernel/debug/provoke-crash/DIRECT
+KSELFTEST_SKIP_TEST=4
+
+# Verify we have LKDTM available in the kernel.
+if [ ! -r $TRIGGER ] ; then
+	/sbin/modprobe -q lkdtm || true
+	if [ ! -r $TRIGGER ] ; then
+		echo "Cannot find $TRIGGER (missing CONFIG_LKDTM?)"
+	else
+		echo "Cannot write $TRIGGER (need to run as root?)"
+	fi
+	# Skip this test
+	exit $KSELFTEST_SKIP_TEST
+fi
 
 # Capture dmesg continuously since it may fill up depending on sample size.
 log=$(mktemp -t stack-entropy-XXXXXX)
 dmesg --follow >"$log" & pid=$!
 report=-1
 for i in $(seq 1 $samples); do
-        echo "REPORT_STACK" >/sys/kernel/debug/provoke-crash/DIRECT
+        echo "REPORT_STACK" > $TRIGGER
 	if [ -t 1 ]; then
 		percent=$(( 100 * $i / $samples ))
 		if [ "$percent" -ne "$report" ]; then