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#!/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
tracing=/sys/kernel/debug/tracing
flock=/var/tmp/.ftrace-lock; wroteflock=0
opt_duration=0; duration=; opt_pid=0; pid=; opt_tid=0; tid=
opt_filter=0; filter=; opt_view=0; opt_headers=0; opt_stack=0; dmesg=2
trap ':' INT QUIT TERM PIPE HUP # sends execution to end tracing section
function usage {
cat <<-END >&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
}
function warn {
if ! eval "$@"; then
echo >&2 "WARNING: command failed \"$@\""
fi
}
function end {
# disable tracing
echo 2>/dev/null
echo "Ending tracing..." 2>/dev/null
cd $tracing
warn "echo 0 > $tdir/enable"
if (( opt_filter )); then
warn "echo 0 > $tdir/filter"
fi
(( opt_stack )) && warn "echo 0 > options/stacktrace"
warn "echo > trace"
(( wroteflock )) && warn "rm $flock"
}
function die {
echo >&2 "$@"
exit 1
}
function edie {
# die with a quiet end()
echo >&2 "$@"
exec >/dev/null 2>&1
end
exit 1
}
### process options
while getopts d:hHlp:L:sv opt
do
case $opt in
d) opt_duration=1; duration=$OPTARG ;;
p) opt_pid=1; pid=$OPTARG ;;
L) opt_tid=1; tid=$OPTARG ;;
H) opt_headers=1 ;;
l) opt_list=1 ;;
s) opt_stack=1 ;;
v) opt_view=1 ;;
h|?) usage ;;
esac
done
if (( !opt_list )); then
shift $(( $OPTIND - 1 ))
(( $# )) || usage
tpoint=$1
shift
if (( $# )); then
opt_filter=1
filter=$1
fi
fi
### option logic
(( opt_pid + opt_filter + opt_tid > 1 )) && \
die "ERROR: use at most one of -p, -L, or filter."
(( opt_duration && opt_view )) && die "ERROR: use either -d or -v."
if (( opt_pid )); then
# convert to filter
opt_filter=1
# ftrace common_pid is thread id from user's perspective
for tid in /proc/$pid/task/*; do
filter="$filter || common_pid == ${tid##*/}"
done
filter=${filter:3} # trim leading ' || ' (four characters)
fi
if (( opt_tid )); then
opt_filter=1
filter="common_pid == $tid"
fi
if (( !opt_view && !opt_list )); then
if (( opt_duration )); then
echo "Tracing $tpoint for $duration seconds (buffered)..."
else
echo "Tracing $tpoint. Ctrl-C to end."
fi
fi
### 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 (( opt_list )); then
cd events
for tp in */*; do
# skip filter/enable files
[[ -f $tp ]] && continue
echo ${tp/\//:}
done
exit
fi
### check tracepoints
tdir=events/${tpoint/:/\/}
[[ -e $tdir ]] || die "ERROR: tracepoint $tpoint not found. Exiting"
### view
if (( opt_view )); then
cat $tdir/format
exit
fi
### ftrace lock
[[ -e $flock ]] && die "ERROR: ftrace may be in use by PID $(cat $flock) $flock"
echo $$ > $flock || die "ERROR: unable to write $flock."
wroteflock=1
### setup and begin tracing
echo nop > current_tracer
if (( opt_filter )); then
if ! echo "$filter" > $tdir/filter; then
edie "ERROR: setting filter or -p. Exiting."
fi
fi
if (( opt_stack )); then
if ! echo 1 > options/stacktrace; then
edie "ERROR: enabling stack traces (-s). Exiting"
fi
fi
if ! echo 1 >> $tdir/enable; then
edie "ERROR: enabling tracepoint $tprobe. Exiting."
fi
### print trace buffer
warn "echo > trace"
if (( opt_duration )); then
sleep $duration
if (( opt_headers )); then
cat trace
else
grep -v '^#' trace
fi
else
# trace_pipe lack headers, so fetch them from trace
(( opt_headers )) && cat trace
cat trace_pipe
fi
### end tracing
end