[PATCH 2/2] selftests/ftrace: Account for 8-byte aligned trace_marker_raw events

[Hui Wang <hui.wang@canonical.com>]

trace_marker_raw.tc assumes that the raw marker payload length
reported in trace_pipe is the result of int((id + 3) / 4) * 4, but
that is not true on kernels with CONFIG_HAVE_64BIT_ALIGNED_ACCESS
enabled.

With forced 8-byte alignment, the ring buffer event forces 8-byte
alignment. The event length is stored in array[0], the payload data
and id are placed in a struct raw_data_entry which is stored starting
at array[1]. In this case, the printed payload data length is 8*N+4
bytes.

To make the testcase pass in this case, add a kconfig_enabled() helper
and use it to detect CONFIG_HAVE_64BIT_ALIGNED_ACCESS so
trace_marker_raw.tc can calculate the expected length correctly.

Assisted-by: Copilot:gpt-5.5
Signed-off-by: Hui Wang <hui.wang@canonical.com>
---
 .../ftrace/test.d/00basic/trace_marker_raw.tc | 16 +++++++--
 .../testing/selftests/ftrace/test.d/functions | 33 +++++++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

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
index 8e905d4fe6dd..beda0f8627b3 100644
--- a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
+++ b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
@@ -15,6 +15,11 @@ is_little_endian() {
 }
 
 little=`is_little_endian`
+raw_data_align=4
+
+if kconfig_enabled CONFIG_HAVE_64BIT_ALIGNED_ACCESS; then
+       raw_data_align=8
+fi
 
 make_str() {
 	id=$1
@@ -60,7 +65,8 @@ test_multiple_writes() {
 	echo stop > trace_marker
 
 	# Check to make sure the number of entries is the id (rounded up by 4)
-	awk '/.*: # [0-9a-f]* / {
+	# or is (((id + 3) rounded by 8) + 4) if raw_data_align is 8
+	awk -v data_align=$raw_data_align '/.*: # [0-9a-f]* / {
 			print;
 			cnt = -1;
 			for (i = 0; i < NF; i++) {
@@ -69,8 +75,12 @@ test_multiple_writes() {
 					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;
+					# The number of items is rounded up by 4
+					# or is (8 * N + 4) if data_align is 8
+					if (data_align == 4)
+						cnt2 = int((cnt + 3) / 4) * 4;
+					else
+						cnt2 = int((cnt + 3) / 8) * 8 + 4;
 					if (cnt2 != num) {
 						exit 1;
 					}
diff --git a/tools/testing/selftests/ftrace/test.d/functions b/tools/testing/selftests/ftrace/test.d/functions
index 826141e299e5..0f778087d81b 100644
--- a/tools/testing/selftests/ftrace/test.d/functions
+++ b/tools/testing/selftests/ftrace/test.d/functions
@@ -177,6 +177,39 @@ check_awk_strtonum() { # strtonum is GNU awk extension
     awk 'BEGIN{strtonum("0x1")}'
 }
 
+# a helper to check if a kconfig is enabled or not
+# return value: 0 (if kconfig is enabled)
+#               1 (if kconfig is not enabled)
+#               2 (if the config files don't exist or are unreadable)
+kconfig_enabled() { # config-name
+    local config="$1"
+    local uname_r=`uname -r`
+    local config_file
+
+    case "$config" in
+    CONFIG_*) ;;
+    *) config="CONFIG_$config" ;;
+    esac
+
+    if [ -f /proc/config.gz ] && zgrep --version >/dev/null 2>&1; then
+        zgrep -Eq "^${config}=(y|m)$" /proc/config.gz 2>/dev/null
+        return $?
+    fi
+
+    for config_file in \
+        /boot/config-$uname_r \
+        /lib/modules/$uname_r/config \
+        /lib/modules/$uname_r/build/.config
+    do
+        if [ -f "$config_file" ]; then
+            grep -Eq "^${config}=(y|m)$" "$config_file"
+            return $?
+        fi
+    done
+
+    return 2
+}
+
 LOCALHOST=127.0.0.1
 
 yield() {
-- 
2.43.0