#!/bin/bash

# Copyright (c) 2014 Wind River Systems, Inc.
#
# SPDX-License-Identifier: Apache-2.0
#


# We've been called because someone wants to dump the kernel debug trace file to
# persistent storage.
#

# This uses the "flock" binary to ensure that exactly one copy of this script
# runs on the system at a time.  Taken from the flock man page.
# Basically it takes a nonblocking exclusive lock on the script itself.
[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -en "$0" "$0" "$@" || :


# The expected behaviour is that the caller has disabled tracing already, but we
# are expected to re-enable it after we're done copying the data.


LOGFILE=kernel_trace_log


# Disable tracing just in case the caller forgot to do it.
echo 0 > /sys/kernel/debug/tracing/tracing_on

# 
cd /var/log

if [ ! -d tracing ]
then
    # This is the first trace log, make the directory.
    mkdir tracing
else
    # Handle log rotation.  We'll keep up to 5 trace logs.
    for i in {4..0}
    do
        mv tracing/${LOGFILE}.$i tracing/${LOGFILE}.$((i+1))
    done
fi

# Copy trace file and fsync it when done.
cp /sys/kernel/debug/tracing/trace tracing/${LOGFILE}.0

# Wipe the trace file.
echo > /sys/kernel/debug/tracing/trace

# Enable tracing.
echo 1 > /sys/kernel/debug/tracing/tracing_on

# Fsync the logged trace file. This uses a custom helper app.
fsync tracing/${LOGFILE}.0

# Fsync the directory to flush metadata.
fsync tracing