#!/bin/bash
#
# tpoint - trace a given tracepoint. Static tracing.
#          Written using Linux ftrace.
#
# This will enable a given tracepoint, print events, then disable the tracepoint
# when the program ends. This is like a simple version of the "perf" command for
# printing live tracepoint events only. Wildcards are currently not supported.
# If this is insufficient for any reason, use the perf command instead.
#
# USAGE: ./tpoint [-hHsv] [-d secs] [-p pid] [-L tid] tracepoint [filter]
#        ./tpoint -l
#
# Run "tpoint -h" for full usage.
#
# I wrote this because I often needed a quick way to dump stack traces for a
# given tracepoint.
#
# OVERHEADS: Relative to the frequency of traced events. You might want to
# check their frequency beforehand, using perf_events. Eg:
#
#	perf stat -e block:block_rq_issue -a sleep 5
#
# To count occurrences of that tracepoint for 5 seconds.
#
# REQUIREMENTS: FTRACE and tracepoints, which you may already have on recent
# kernel versions.
#
# From perf-tools: https://github.com/brendangregg/perf-tools
#
# See the tpoint(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)
#
# 22-Jul-2014	Brendan Gregg	Created this.

### default variables
setglobal tracing = '/sys/kernel/debug/tracing'
setglobal flock = '/var/tmp/.ftrace-lock'; setglobal wroteflock = '0'
setglobal opt_duration = '0'; setglobal duration = ''; setglobal opt_pid = '0'; setglobal pid = ''; setglobal opt_tid = '0'; setglobal tid = ''
setglobal opt_filter = '0'; setglobal filter = ''; setglobal opt_view = '0'; setglobal opt_headers = '0'; setglobal opt_stack = '0'; setglobal dmesg = '2'
trap ':' INT QUIT TERM PIPE HUP	# sends execution to end tracing section

proc usage {
	cat << """ >&2
USAGE: tpoint [-hHsv] [-d secs] [-p PID] [-L TID] tracepoint [filter]
       tpoint -l
                 -d seconds      # trace duration, and use buffers
                 -p PID          # PID to match on event
                 -L TID          # thread id to match on event
                 -v              # view format file (don't trace)
                 -H              # include column headers
                 -l              # list all tracepoints
                 -s              # show kernel stack traces
                 -h              # this usage message
   eg,
       tpoint -l | grep open
                                 # find tracepoints containing "open"
       tpoint syscalls:sys_enter_open
                                 # trace open() syscall entry
       tpoint block:block_rq_issue
                                 # trace block I/O issue
       tpoint -s block:block_rq_issue
                                 # show kernel stacks

See the man page and example file for more info.
"""
> !2
USAGE: tpoint [-hHsv] [-d secs] [-p PID] [-L TID] tracepoint [filter]
       tpoint -l
                 -d seconds      # trace duration, and use buffers
                 -p PID          # PID to match on event
                 -L TID          # thread id to match on event
                 -v              # view format file (don't trace)
                 -H              # include column headers
                 -l              # list all tracepoints
                 -s              # show kernel stack traces
                 -h              # this usage message
   eg,
       tpoint -l | grep open
                                 # find tracepoints containing "open"
       tpoint syscalls:sys_enter_open
                                 # trace open() syscall entry
       tpoint block:block_rq_issue
                                 # trace block I/O issue
       tpoint -s block:block_rq_issue
                                 # show kernel stacks

See the man page and example file for more info.
END
	exit
}

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

proc end {
	# disable tracing
	echo !2 >/dev/null
	echo "Ending tracing..." !2 >/dev/null
	cd $tracing
	warn "echo 0 > $tdir/enable"
	if sh-expr ' opt_filter ' {
		warn "echo 0 > $tdir/filter"
	}
	sh-expr ' opt_stack ' && warn "echo 0 > options/stacktrace"
	warn "echo > trace"
	sh-expr ' wroteflock ' && warn "rm $flock"
}

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

proc edie {
	# die with a quiet end()
	echo >&2 @Argv> !2 "$@"
	exec >/dev/null !2 > !1
	end
	exit 1
}

### process options
while getopts d:hHlp:L:sv opt
{
	match $opt {
	with d	setglobal opt_duration = '1'; setglobal duration = $OPTARG 
	with p	setglobal opt_pid = '1'; setglobal pid = $OPTARG 
	with L	setglobal opt_tid = '1'; setglobal tid = $OPTARG 
	with H	setglobal opt_headers = '1' 
	with l	setglobal opt_list = '1' 
	with s	setglobal opt_stack = '1' 
	with v	setglobal opt_view = '1' 
	with h|?	usage 
	}
}
if sh-expr ' !opt_list ' {
	shift $shExpr(' $OPTIND - 1 ')
	sh-expr ' $# ' || usage
	setglobal tpoint = $1
	shift
	if sh-expr ' $# ' {
		setglobal opt_filter = '1'
		setglobal filter = $1
	}
}

### option logic
sh-expr ' opt_pid + opt_filter + opt_tid > 1 ' && \
	die "ERROR: use at most one of -p, -L, or filter."
sh-expr ' opt_duration && opt_view ' && die "ERROR: use either -d or -v."
if sh-expr ' opt_pid ' {
	# convert to filter
	setglobal opt_filter = '1'
	# ftrace common_pid is thread id from user's perspective
	for tid in [/proc/$pid/task/*] {
		setglobal filter = ""$filter || common_pid == $(tid##*/)""
	}
	setglobal filter = $(filter:3)  # trim leading ' || ' (four characters)
}
if sh-expr ' opt_tid ' {
	setglobal opt_filter = '1'
	setglobal filter = ""common_pid == $tid""
}
if sh-expr ' !opt_view && !opt_list ' {
	if sh-expr ' opt_duration ' {
		echo "Tracing $tpoint for $duration seconds (buffered)..."
	} else {
		echo "Tracing $tpoint. Ctrl-C to end."
	}
}

### check permissions
cd $tracing || die "ERROR: accessing tracing. Root user? Kernel has FTRACE?
    debugfs mounted? (mount -t debugfs debugfs /sys/kernel/debug)"

### do list tracepoints
if sh-expr ' opt_list ' {
	cd events
	for tp in [*/*] {
		# skip filter/enable files
		[[ -f $tp ]] && continue
		echo $(tp/\//:)
	}
	exit
}

### check tracepoints
setglobal tdir = "events/$(tpoint/:/\/)"
[[ -e $tdir ]] || die "ERROR: tracepoint $tpoint not found. Exiting"

### view
if sh-expr ' opt_view ' {
	cat $tdir/format
	exit
}

### ftrace lock
[[ -e $flock ]] && die "ERROR: ftrace may be in use by PID $[cat $flock] $flock"
echo $Pid > $flock || die "ERROR: unable to write $flock."
setglobal wroteflock = '1'

### setup and begin tracing
echo nop > current_tracer
if sh-expr ' opt_filter ' {
	if ! echo $filter > $tdir/filter {
		edie "ERROR: setting filter or -p. Exiting."
	}
}
if sh-expr ' opt_stack ' {
	if ! echo 1 > options/stacktrace {
		edie "ERROR: enabling stack traces (-s). Exiting"
	}
}
if ! echo 1 >> $tdir/enable {
	edie "ERROR: enabling tracepoint $tprobe. Exiting."
}

### print trace buffer
warn "echo > trace"
if sh-expr ' opt_duration ' {
	sleep $duration
	if sh-expr ' opt_headers ' {
		cat trace
	} else {
		grep -v '^#' trace
	}
} else {
	# trace_pipe lack headers, so fetch them from trace
	sh-expr ' opt_headers ' && cat trace
	cat trace_pipe
}

### end tracing
end