[PATCH] selftests/ftrace: refactor eprobes test to fix argument checks

[Martin Kaiser <martin@kaiser.cx>]

The add/remove eprobe test installs an eprobe for the openat syscall and
runs ls. It checks the filenames that were opened by ls against a
whitelist and a blacklist.

Commit 206b25c09080 ("tracing: eprobe: read the complete FILTER_PTR_STRING
pointer") fixed access to some string fields in eprobes. This triggers
test failures as the blacklist does not allow relative paths for the
openat parameters.

What makes this test unstable is the fact that the openat calls vary a
lot between different systems.

Refactor the test to make it more robust. "cd <directory>" will issue a
chdir syscall with the target directory as parameter. Set an eprobe on
the sys_enter_chdir event and filter for the exact directory name. Allow
(fault) as fallback.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202607151010.b68428e1-lkp@intel.com
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
---
 .../ftrace/test.d/dynevent/add_remove_eprobe.tc  | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_eprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_eprobe.tc
index c300eb020262..e2322693d0c3 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_eprobe.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_eprobe.tc
@@ -1,16 +1,16 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 # description: Generic dynamic event - add/remove eprobe events
-# requires: dynamic_events events/syscalls/sys_enter_openat "<attached-group>.<attached-event> [<args>]":README
+# requires: dynamic_events events/syscalls/sys_enter_chdir "<attached-group>.<attached-event> [<args>]":README
 
 echo 0 > events/enable
 
 clear_dynamic_events
 
 SYSTEM="syscalls"
-EVENT="sys_enter_openat"
+EVENT="sys_enter_chdir"
 FIELD="filename"
-EPROBE="eprobe_open"
+EPROBE="eprobe_chdir"
 OPTIONS="file=+0(\$filename):ustring"
 echo "e:$EPROBE $SYSTEM/$EVENT $OPTIONS" >> dynamic_events
 
@@ -18,20 +18,14 @@ grep -q "$EPROBE" dynamic_events
 test -d events/eprobes/$EPROBE
 
 echo 1 > events/eprobes/$EPROBE/enable
-ls
+cd /sys/kernel/tracing
 echo 0 > events/eprobes/$EPROBE/enable
 
-content=`grep '^ *ls-' trace | grep 'file='`
-nocontent=`grep '^ *ls-' trace | grep 'file=' | grep -v -e '"/' -e '"."' -e '(fault)' ` || true
-
+content=`grep -e 'file="/sys/kernel/tracing"\|(fault)' trace`
 if [ -z "$content" ]; then
 	exit_fail
 fi
 
-if [ ! -z "$nocontent" ]; then
-	exit_fail
-fi
-
 echo "-:$EPROBE" >> dynamic_events
 
 ! grep -q "$EPROBE" dynamic_events
-- 
2.43.7