linux-kernel - [PATCH v2] selftests/ftrace: Skip test for optimized probes on PowerPC if Secure Boot is enabled

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Message-ID: <20240813034056.74717-1-akanksha@linux.ibm.com>
Date: Tue, 13 Aug 2024 09:10:56 +0530
From: Akanksha J N <akanksha@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc: shuah@...nel.org, mathieu.desnoyers@...icios.com, mhiramat@...nel.org,
        rostedt@...dmis.org, akanksha@...ux.ibm.com
Subject: [PATCH v2] selftests/ftrace: Skip test for optimized probes on PowerPC if Secure Boot is enabled

Currently while accessing debugfs with Secure Boot enabled on PowerPC,
it is causing the kprobe_opt_types.tc test to fail. Below is the snippet
of the error:

+++ grep kernel_clone /sys/kernel/debug/kprobes/list
grep: /sys/kernel/debug/kprobes/list: Operation not permitted
++ PROBE=
+ '[' 2 -ne 0 ']'
+ kill -s 37 7595
++ SIG_RESULT=1
+ eval_result 1
+ case $1 in
+ prlog '	[\033[31mFAIL\033[0m]'
+ newline='\n'
+ '[' '	[\033[31mFAIL\033[0m]' = -n ']'
+ printf '	[\033[31mFAIL\033[0m]\n'
	[FAIL]

This is happening when secure boot is enabled, as it enables lockdown
by default. With lockdown, access to certain debug features and
filesystems like debugfs may be restricted or completely disabled.

To fix this, modify the test to check for Secure Boot status using
lsprop /proc/device-tree/ibm,secure-boot. And, skip execution of the
test on PowerPC if Secure Boot is enabled (00000002).

With this patch, test skips as unsupported:
=== Ftrace unit tests ===
[1] Register/unregister optimized probe	[UNSUPPORTED]

Signed-off-by: Akanksha J N <akanksha@...ux.ibm.com>
---
 .../selftests/ftrace/test.d/kprobe/kprobe_opt_types.tc       | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_opt_types.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_opt_types.tc
index 9f5d99328086..925e74d6acc7 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_opt_types.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_opt_types.tc
@@ -10,6 +10,11 @@ x86_64)
 arm*)
 ;;
 ppc*)
+  lsprop_output=$(lsprop /proc/device-tree/ibm,secure-boot)
+  if echo "$lsprop_output" | grep -q "00000002"; then
+    echo "Secure Boot is enabled on PowerPC."
+    exit_unsupported
+  fi
 ;;
 *)
   echo "Please implement other architecture here"
-- 
2.45.2