#!/bin/bash
#
# reset-ftrace - reset state of ftrace, disabling all tracing.
#                Written for Linux ftrace.
#
# This may only be of use to ftrace hackers who, in the process of developing
# ftrace software, often get the subsystem into a partially active state, and
# would like a quick way to reset state. Check the end of this script for the
# actually files reset, and add more if you need.
#
# USAGE: ./reset-ftrace [-fhq]
#
# REQUIREMENTS: FTRACE CONFIG.
#
# From perf-tools: https://github.com/brendangregg/perf-tools
#
# See the reset-ftrace(8) man page (in perf-tools) for more info.
#
# COPYRIGHT: Copyright (c) 2014 Brendan Gregg.
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#
#  (http://www.gnu.org/copyleft/gpl.html)
#
# 20-Jul-2014	Brendan Gregg	Created this.

setglobal tracing = '/sys/kernel/debug/tracing'
setglobal flock = '/var/tmp/.ftrace-lock'
setglobal opt_force = '0'; setglobal opt_quiet = '0'

proc usage {
	cat << """ >&2
USAGE: reset-ftrace [-fhq]
                 -f              # force: delete ftrace lock file
                 -q              # quiet: reset, but say nothing
                 -h              # this usage message
  eg,
       reset-ftrace              # disable active ftrace session
"""
> !2
USAGE: reset-ftrace [-fhq]
                 -f              # force: delete ftrace lock file
                 -q              # quiet: reset, but say nothing
                 -h              # this usage message
  eg,
       reset-ftrace              # disable active ftrace session
END
	exit
}

proc warn {
	if ! eval @Argv {
		echo >&2 "WARNING: command failed \"$ifsjoin(Argv)> !2 "WARNING: command failed \"$@\""
	}
}

proc die {
	echo >&2 @Argv> !2 "$@"
	exit 1
}

proc vecho {
	sh-expr ' opt_quiet ' && return
	echo @Argv
}

# write to file
proc writefile {
	setglobal file = $1
	setglobal string = $2	# optional
	if [[ ! -w $file ]] {
		echo >&2 "WARNING: file $file not writable/exists. Skipping.> !2 "WARNING: file $file not writable/exists. Skipping."
		return
	}
	vecho "$file, before:"
	sh-expr ' ! opt_quiet ' && cat -n $file
	warn "echo $string > $file"
	vecho "$file, after:"
	sh-expr ' ! opt_quiet ' && cat -n $file
	vecho
}

### process options
while getopts fhq opt
{
	match $opt {
	with f	setglobal opt_force = '1' 
	with q	setglobal opt_quiet = '1' 
	with h|?	usage 
	}
}
shift $shExpr(' $OPTIND - 1 ')

### ftrace lock
if [[ -e $flock ]] {
	if sh-expr ' opt_force ' {
		warn rm $flock
	} else {
		echo -e >&2 "ERROR: ftrace lock ($flock) exists. It shows" \
		    "ftrace may be in use by PID $[cat $flock].\nDouble check" \
		    "to see if that PID is still active. If not, consider" \
		    "using -f to force a reset. Exiting.> !2 "ERROR: ftrace lock ($flock) exists. It shows" \
		    "ftrace may be in use by PID $(cat $flock).\nDouble check" \
		    "to see if that PID is still active. If not, consider" \
		    "using -f to force a reset. Exiting."
		exit 1
	}
}

### reset ftrace state
vecho "Reseting ftrace state..."
vecho
cd $tracing || die "ERROR: accessing tracing. Root user? Kernel has FTRACE?"
writefile current_tracer nop
writefile set_ftrace_filter
writefile set_graph_function
writefile set_ftrace_pid
writefile events/enable 0
writefile tracing_thresh 0
writefile kprobe_events
writefile tracing_on 1
vecho "Done."