Merge: selftests/ftrace: Use readelf to find entry point in uprobe test

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1381

# Merge Request Required Information
JIRA: https://issues.redhat.com/browse/RHEL-87219

## Summary of Changes
Use "readelf -h" to find the entrypoint of /bin/sh when adding the uprobe event, and add a check to make sure readelf is installed.

Signed-off-by: Anubhav Shelat <ashelat@redhat.com>

Approved-by: jbrnak <jbrnak@redhat.com>
Approved-by: tallison1 <tallison@redhat.com>
Approved-by: Michael Petlan <mpetlan@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

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

@@ -3,12 +3,18 @@
 # description: Generic dynamic event - add/remove/test uprobe events
 # requires: uprobe_events
 
+if ! which readelf > /dev/null 2>&1 ; then
+  echo "No readelf found. skipped."
+  exit_unresolved
+fi
+
 echo 0 > events/enable
 echo > dynamic_events
 
-echo 'cat /proc/$$/maps' | /bin/sh | \
-	grep "r-xp .*/bin/.*sh$" | \
-	awk '{printf "p:myevent %s:0x%s\n", $6,$3 }' >> uprobe_events
+REALBIN=`readlink -f /bin/sh`
+ENTRYPOINT=`readelf -h ${REALBIN} | grep Entry | sed -e 's/[^0]*//'`
+
+echo "p:myevent ${REALBIN}:${ENTRYPOINT}" >> uprobe_events
 
 grep -q myevent uprobe_events
 test -d events/uprobes/myevent