linux-kernel - Re: [PATCH v2] selftests: livepatch: test if ftrace can trace a livepatched function

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Message-ID: <b2637bad-9022-496a-9b83-0d348a6350b4@gmail.com>
Date: Thu, 6 Mar 2025 19:12:32 -0300
From: Filipe Xavier <felipeaggger@...il.com>
To: Marcos Paulo de Souza <mpdesouza@...e.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>, Jiri Kosina <jikos@...nel.org>,
 Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>,
 Joe Lawrence <joe.lawrence@...hat.com>, Shuah Khan <shuah@...nel.org>
Cc: live-patching@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Felipe Xavier <felipe_life@...e.com>
Subject: Re: [PATCH v2] selftests: livepatch: test if ftrace can trace a
 livepatched function

On 1/11/25 3:42 PM, Filipe Xavier wrote:

> This new test makes sure that ftrace can trace a
> function that was introduced by a livepatch.
>
> Signed-off-by: Filipe Xavier <felipeaggger@...il.com>
> ---
> Changes in v2:
> - functions.sh: added reset tracing on push and pop_config.
> - test-ftrace.sh: enabled tracing_on before test init.
> - nitpick: added double quotations on filenames and fixed some wording.
> - Link to v1: https://lore.kernel.org/r/20250102-ftrace-selftest-livepatch-v1-1-84880baefc1b@gmail.com
> ---
>   tools/testing/selftests/livepatch/functions.sh   | 14 ++++++++++
>   tools/testing/selftests/livepatch/test-ftrace.sh | 33 ++++++++++++++++++++++++
>   2 files changed, 47 insertions(+)
>
> diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
> index e5d06fb402335d85959bafe099087effc6ddce12..e6c13514002dae5f8d7461f90b8241ab43024ea4 100644
> --- a/tools/testing/selftests/livepatch/functions.sh
> +++ b/tools/testing/selftests/livepatch/functions.sh
> @@ -62,6 +62,9 @@ function push_config() {
>   			awk -F'[: ]' '{print "file " $1 " line " $2 " " $4}')
>   	FTRACE_ENABLED=$(sysctl --values kernel.ftrace_enabled)
>   	KPROBE_ENABLED=$(cat "$SYSFS_KPROBES_DIR/enabled")
> +	TRACING_ON=$(cat "$SYSFS_DEBUG_DIR/tracing/tracing_on")
> +	CURRENT_TRACER=$(cat "$SYSFS_DEBUG_DIR/tracing/current_tracer")
> +	FTRACE_FILTER=$(cat "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter")
>   }
>   
>   function pop_config() {
> @@ -74,6 +77,17 @@ function pop_config() {
>   	if [[ -n "$KPROBE_ENABLED" ]]; then
>   		echo "$KPROBE_ENABLED" > "$SYSFS_KPROBES_DIR/enabled"
>   	fi
> +	if [[ -n "$TRACING_ON" ]]; then
> +		echo "$TRACING_ON" > "$SYSFS_DEBUG_DIR/tracing/tracing_on"
> +	fi
> +	if [[ -n "$CURRENT_TRACER" ]]; then
> +		echo "$CURRENT_TRACER" > "$SYSFS_DEBUG_DIR/tracing/current_tracer"
> +	fi
> +	if [[ "$FTRACE_FILTER" == *"#"* ]]; then
> +		echo > "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
> +	elif [[ -n "$FTRACE_FILTER" ]]; then
> +		echo "$FTRACE_FILTER" > "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
> +	fi
>   }
>   
>   function set_dynamic_debug() {
> diff --git a/tools/testing/selftests/livepatch/test-ftrace.sh b/tools/testing/selftests/livepatch/test-ftrace.sh
> index fe14f248913acbec46fb6c0fec38a2fc84209d39..66af5d726c52e48e5177804e182b4ff31784d5ac 100755
> --- a/tools/testing/selftests/livepatch/test-ftrace.sh
> +++ b/tools/testing/selftests/livepatch/test-ftrace.sh
> @@ -61,4 +61,37 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
>   % rmmod $MOD_LIVEPATCH"
>   
>   
> +# - verify livepatch can load
> +# - check if traces have a patched function
> +# - unload livepatch and reset trace
> +
> +start_test "trace livepatched function and check that the live patch remains in effect"
> +
> +TRACE_FILE="$SYSFS_DEBUG_DIR/tracing/trace"
> +FUNCTION_NAME="livepatch_cmdline_proc_show"
> +
> +load_lp $MOD_LIVEPATCH
> +
> +echo 1 > "$SYSFS_DEBUG_DIR/tracing/tracing_on"
> +echo $FUNCTION_NAME > "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
> +echo "function" > "$SYSFS_DEBUG_DIR/tracing/current_tracer"
> +echo "" > "$TRACE_FILE"
> +
> +if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
> +	echo -e "FAIL\n\n"
> +	die "livepatch kselftest(s) failed"
> +fi
> +
> +grep -q $FUNCTION_NAME "$TRACE_FILE"
> +FOUND=$?
> +
> +disable_lp $MOD_LIVEPATCH
> +unload_lp $MOD_LIVEPATCH
> +
> +if [ "$FOUND" -eq 1 ]; then
> +	echo -e "FAIL\n\n"
> +	die "livepatch kselftest(s) failed"
> +fi
> +
> +
>   exit 0
>
> ---
> base-commit: fc033cf25e612e840e545f8d5ad2edd6ba613ed5
> change-id: 20250101-ftrace-selftest-livepatch-161fb77dbed8
>
> Best regards,

Hi Folks, sorry for the delay... thanks everyone for the feedback's.

I applied almost all the requested adjustments, except this one:

 > echo '!*:traceoff' > "$SYSFS_TRACING_DIR/set_ftrace_filter"
causes this error:  "echo: write error: no such device"

 > echo "" > "$SYSFS_TRACING_DIR/current_tracer"
causes this error:  "echo: write error: invalid argument"

I sent a new patchSet(splited) to the list.

Cheers,

Filipe Xavier