linux-kernel - Re: [PATCH] selftests/tracing: Add basic test for trace_marker

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Message-Id: <20251105084748.f34e1efec291d420a50a7b62@kernel.org>
Date: Wed, 5 Nov 2025 08:47:48 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, linux-kselftest@...r.kernel.org,
 Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Shuah Khan <skhan@...uxfoundation.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] selftests/tracing: Add basic test for trace_marker_raw
 file

On Tue, 14 Oct 2025 14:51:49 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: Steven Rostedt <rostedt@...dmis.org>
> 
> Commit 64cf7d058a00 ("tracing: Have trace_marker use per-cpu data to read
> user space") made an update that fixed both trace_marker and
> trace_marker_raw. But the small difference made to trace_marker_raw had a
> blatant bug in it that any basic testing would have uncovered.
> Unfortunately, the self tests have tests for trace_marker but nothing for
> trace_marker_raw which allowed the bug to get upstream.
> 
> Add basic selftests to test trace_marker_raw so that this doesn't happen
> again.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  .../ftrace/test.d/00basic/trace_marker_raw.tc | 107 ++++++++++++++++++
>  1 file changed, 107 insertions(+)
>  create mode 100644 tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
> new file mode 100644
> index 000000000000..7daf7292209e
> --- /dev/null
> +++ b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
> @@ -0,0 +1,107 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +# description: Basic tests on writing to trace_marker_raw
> +# requires: trace_marker_raw
> +# flags: instance
> +
> +is_little_endian() {
> +	if lscpu | grep -q 'Little Endian'; then
> +		echo 1;
> +	else
> +		echo 0;
> +	fi
> +}
> +
> +little=`is_little_endian`
> +
> +make_str() {
> +	id=$1
> +	cnt=$2
> +
> +	if [ $little -eq 1 ]; then
> +		val=`printf "\\%03o\\%03o\\%03o\\%03o" \
> +			$(($id & 0xff)) \
> +			$((($id >> 8) & 0xff)) \
> +			$((($id >> 16) & 0xff)) \
> +			$((($id >> 24) & 0xff))`
> +	else
> +		val=`printf "\\%03o\\%03o\\%03o\\%03o" \
> +			$((($id >> 24) & 0xff)) \
> +			$((($id >> 16) & 0xff)) \
> +			$((($id >> 8) & 0xff)) \
> +			$(($id & 0xff))`
> +	fi
> +
> +	data=`printf -- 'X%.0s' $(seq $cnt)`
> +
> +	printf "${val}${data}"
> +}
> +
> +write_buffer() {
> +	id=$1
> +	size=$2
> +
> +	# write the string into the raw marker
> +	make_str $id $size > trace_marker_raw
> +}
> +
> +
> +test_multiple_writes() {
> +
> +	# Write a bunch of data where the id is the count of
> +	# data to write
> +	for i in `seq 1 10` `seq 101 110` `seq 1001 1010`; do
> +		write_buffer $i $i
> +	done
> +
> +	# add a little buffer
> +	echo stop > trace_marker
> +
> +	# Check to make sure the number of entries is the id (rounded up by 4)
> +	awk '/.*: # [0-9a-f]* / {
> +			print;
> +			cnt = -1;
> +			for (i = 0; i < NF; i++) {
> +				# The counter is after the "#" marker
> +				if ( $i == "#" ) {
> +					i++;
> +					cnt = strtonum("0x" $i);
> +					num = NF - (i + 1);
> +					# The number of items is always rounded up by 4
> +					cnt2 = int((cnt + 3) / 4) * 4;
> +					if (cnt2 != num) {
> +						exit 1;
> +					}
> +					break;
> +				}
> +			}
> +		}
> +	// { if (NR > 30) { exit 0; } } ' trace_pipe;
> +}
> +
> +
> +get_buffer_data_size() {
> +	sed -ne 's/^.*data.*size:\([0-9][0-9]*\).*/\1/p' events/header_page
> +}
> +
> +test_buffer() {
> +
> +	# The id must be four bytes, test that 3 bytes fails a write
> +	if echo -n abc > ./trace_marker_raw ; then
> +		echo "Too small of write expected to fail but did not"
> +		exit_fail
> +	fi
> +
> +	size=`get_buffer_data_size`
> +	echo size = $size
> +
> +	# Now add a little more than what it can handle
> +
> +	if write_buffer 0xdeadbeef $size ; then
> +		echo "Too big of write expected to fail but did not"
> +		exit_fail
> +	fi
> +}
> +
> +test_buffer
> +test_multiple_writes
> -- 
> 2.51.0
> 


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