[PATCH v7 09/20] tracing/remotes: selftests: Add a test for the dmesg tracefs file

@@ -0,0 +1,86 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Test trace remote dmesg redirection
+# requires: remotes/test remotes/test/dmesg
+
+. $TEST_DIR/remotes/functions
+
+test_dmesg()
+{
+    if [ ! -f /sys/module/printk/parameters/time ] || [ "$(cat /sys/module/printk/parameters/time)" != "Y" ]; then
+        echo "printk timestamps are disabled - please enable CONFIG_PRINTK_TIME"
+        exit_unsupported
+    fi
+
+    echo 0 > tracing_on
+    assert_unloaded
+
+    #
+    # Test dmesg on/off when tracing is disabled
+    #
+    echo 1 > dmesg
+    test $(cat dmesg) -eq 1
+    assert_loaded
+
+    echo 0 > dmesg
+    test $(cat dmesg) -eq 0
+    assert_unloaded
+
+    #
+    # Test events are logged to dmesg
+    #
+
+    echo 1 > tracing_on
+    assert_loaded
+    echo 1 > dmesg
+    test $(cat dmesg) -eq 1
+
+    # Timestamp format is '[    XXXX.YYYY]'
+    last_ts=$(dmesg | tail -1 | sed -n 's/^\[ *\([0-9]*.[0-9]*\)\].*/\1/p')
+    if [ -z "$last_ts" ]; then
+        last_ts=0
+    fi
+
+    nr_events=128
+    for i in $(seq 1 $nr_events); do
+        echo $i > write_event
+    done
+
+    sleep 1
+    output=$(mktemp $TMPDIR/remote_test.XXXXXX)
+    dmesg | awk -v ts=$last_ts '
+    /^\[ *[0-9]+\.[0-9]+\]/ {
+        t=$0; sub(/^[[ \t]*/, "", t); sub(/].*/, "", t);
+        if (t+0 > ts+0) print $0
+    }' | grep "selftest id=" | sed 's/^[^]]*] //'> $output
+
+    check_trace 1 $nr_events $output
+
+    rm $output
+
+    #
+    # Disable dmesg and verify events were not consumed by dmesg
+    #
+    echo 0 > dmesg
+    test $(cat dmesg) -eq 0
+
+    start_id=$(($nr_events + 1))
+    end_id=$(($start_id + $nr_events))
+
+    for i in $(seq $start_id $end_id); do
+        echo $i > write_event
+    done
+
+    sleep 1
+
+    output=$(dump_trace_pipe)
+    check_trace $start_id $end_id $output
+    rm $output
+}
+
+if [ -z "$SOURCE_REMOTE_TEST" ]; then
+    set -e
+
+    setup_remote_test
+    test_dmesg
+fi

@@ -8,6 +8,7 @@ setup_remote()
 
 	cd remotes/$name/
 	echo 0 > tracing_on
+	[ -f dmesg ] && echo 0 > dmesg
 	clear_trace
 	echo 7 > buffer_size_kb
 	echo 0 > events/enable

@@ -0,0 +1,11 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Test hypervisor trace dmesg redirection
+# requires: remotes/hypervisor/write_event remotes/hypervisor/dmesg
+
+SOURCE_REMOTE_TEST=1
+. $TEST_DIR/remotes/dmesg.tc
+
+set -e
+setup_remote "hypervisor"
+test_dmesg