ringbuffer/selftest: Add basic selftest to test changing subbuf order

Add a self test that will write into the trace buffer with differ trace
sub buffer order sizes.

Link: https://lore.kernel.org/linux-trace-kernel/20231219185631.520496304@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/tools/testing/selftests/ftrace/test.d/00basic/ringbuffer_order.tc b/tools/testing/selftests/ftrace/test.d/00basic/ringbuffer_order.tc
new file mode 100644 (file)
index 0000000..ecbcc81
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/00basic/ringbuffer_order.tc
@@ -0,0 +1,95 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Change the ringbuffer sub-buffer order
+# requires: buffer_subbuf_order
+# flags: instance
+
+get_buffer_data_size() {
+       sed -ne 's/^.*data.*size:\([0-9][0-9]*\).*/\1/p' events/header_page
+}
+
+get_buffer_data_offset() {
+       sed -ne 's/^.*data.*offset:\([0-9][0-9]*\).*/\1/p' events/header_page
+}
+
+get_event_header_size() {
+       type_len=`sed -ne 's/^.*type_len.*:[^0-9]*\([0-9][0-9]*\).*/\1/p' events/header_event`
+       time_len=`sed -ne 's/^.*time_delta.*:[^0-9]*\([0-9][0-9]*\).*/\1/p' events/header_event`
+       array_len=`sed -ne 's/^.*array.*:[^0-9]*\([0-9][0-9]*\).*/\1/p' events/header_event`
+       total_bits=$((type_len+time_len+array_len))
+       total_bits=$((total_bits+7))
+       echo $((total_bits/8))
+}
+
+get_print_event_buf_offset() {
+       sed -ne 's/^.*buf.*offset:\([0-9][0-9]*\).*/\1/p' events/ftrace/print/format
+}
+
+event_header_size=`get_event_header_size`
+print_header_size=`get_print_event_buf_offset`
+
+data_offset=`get_buffer_data_offset`
+
+marker_meta=$((event_header_size+print_header_size))
+
+make_str() {
+        cnt=$1
+       printf -- 'X%.0s' $(seq $cnt)
+}
+
+write_buffer() {
+       size=$1
+
+       str=`make_str $size`
+
+       # clear the buffer
+       echo > trace
+
+       # write the string into the marker
+       echo $str > trace_marker
+
+       echo $str
+}
+
+test_buffer() {
+       orde=$1
+       page_size=$((4096<<order))
+
+       size=`get_buffer_data_size`
+
+       # the size must be greater than or equal to page_size - data_offset
+       page_size=$((page_size-data_offset))
+       if [ $size -lt $page_size ]; then
+               exit fail
+       fi
+
+       # Now add a little more the meta data overhead will overflow
+
+       str=`write_buffer $size`
+
+       # Make sure the line was broken
+       new_str=`awk ' /tracing_mark_write:/ { sub(/^.*tracing_mark_write: /,"");printf "%s", $0; exit}' trace`
+
+       if [ "$new_str" = "$str" ]; then
+               exit fail;
+       fi
+
+       # Make sure the entire line can be found
+       new_str=`awk ' /tracing_mark_write:/ { sub(/^.*tracing_mark_write: /,"");printf "%s", $0; }' trace`
+
+       if [ "$new_str" != "$str" ]; then
+               exit fail;
+       fi
+}
+
+ORIG=`cat buffer_subbuf_order`
+
+# Could test bigger orders than 3, but then creating the string
+# to write into the ring buffer takes too long
+for a in 0 1 2 3 ; do
+       echo $a > buffer_subbuf_order
+       test_buffer $a
+done
+
+echo $ORIG > buffer_subbuf_order
+