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

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

[Akanksha J N]

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@linux.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

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

[Masami Hiramatsu]

On Tue, 13 Aug 2024 09:10:56 +0530
Akanksha J N <akanksha@linux.ibm.com> wrote:

> 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.

Hmm, if the kprobes lockdown causes this problem, all tests which use
kprobes must not run. This seems onlu checks kprobe_opt_types.tc, but
what about other tests?

(Anyway, we don't recommend user to run tests in lockdown environment.)

Thank you,

> 
> 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@linux.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
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>