File: killsnoop

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#!/bin/bash
#
# killsnoop - trace kill() syscalls with signal/process details.
#             Written using Linux ftrace.
#
# This traces kill() syscalls, showing which process killed which pid and
# returns the returncode (0 for success, -1 for error).
#
# This implementation is designed to work on older kernel versions, and without
# kernel debuginfo. It works by dynamic tracing of the return value of kill()
# and associating it with the previous kill() syscall return.
# This approach is kernel version specific, and may not work on your version.
# It is a workaround, and proof of concept for ftrace, until more kernel tracing
# functionality is available.
#
# USAGE: ./killsnoop [-hst] [-d secs] [-p pid] [-n name]
#
# Run "killsnoop -h" for full usage.
#
# REQUIREMENTS: FTRACE and KPROBE CONFIG, syscalls:sys_enter_kill and
# syscalls:sys_exit_kill kernel tracepoints (you may already have these
# on recent kernels) and awk.
#
# From perf-tools: https://github.com/brendangregg/perf-tools
#
# See the killsnoop(8) man page (in perf-tools) for more info.
#
# COPYRIGHT: Copyright (c) 2014 Brendan Gregg.
# COPYRIGHT: Copyright (c) 2014 Martin Probst.
#
#  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   Templated this.
# 13-Sep-2014   Martin Probst   Created this.

### default variables
tracing=/sys/kernel/debug/tracing
flock=/var/tmp/.ftrace-lock; wroteflock=0
opt_duration=0; duration=; opt_name=0; name=; opt_pid=0; pid=; ftext=
opt_time=0; opt_fail=0; opt_file=0; file=
kevent_entry=events/syscalls/sys_enter_kill
kevent_return=events/syscalls/sys_exit_kill
trap ':' INT QUIT TERM PIPE HUP # sends execution to end tracing section

function usage {
    cat <<-END >&2
USAGE: killsnoop [-hst] [-d secs] [-p PID] [-n name] [filename]
                 -d seconds      # trace duration, and use buffers
                 -n name         # process name to match 
                 -p PID          # PID to match on kill issue
                 -t              # include time (seconds)
                 -s              # human readable signal names
                 -h              # this usage message
  eg,
       killsnoop                 # watch kill()s live (unbuffered)
       killsnoop -d 1            # trace 1 sec (buffered)
       killsnoop -p 181          # trace kill()s issued to PID 181 only

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 > $kevent_entry/enable"
    warn "echo 0 > $kevent_return/enable"
    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:hn:p:st opt
do
    case $opt in
    d)  opt_duration=1; duration=$OPTARG ;;
    n)  opt_name=1; name=$OPTARG ;;
    p)  opt_pid=1; pid=$OPTARG ;;
    t)  opt_time=1 ;;
    s)  opt_fancy=1 ;;
    h|?)    usage ;;
    esac
done
shift $(( $OPTIND - 1 ))
(( $# )) && usage

### option logic
(( opt_pid && opt_name )) && die "ERROR: use either -p or -n."
(( opt_pid )) && ftext=" issued to PID $pid"
(( opt_name )) && ftext=" issued by process name \"$name\""
if (( opt_duration )); then
    echo "Tracing kill()s$ftext for $duration seconds (buffered)..."
else
    echo "Tracing kill()s$ftext. Ctrl-C to end."
fi

### select awk
# workaround for mawk fflush()
[[ -x /usr/bin/mawk ]] && awk="mawk" && mawk -W interactive && \
[ $? -eq 0 ] && awk="mawk -W interactive"
# workaround for gawk strtonum()
[[ -x /usr/bin/gawk ]] && awk="gawk --non-decimal-data"

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

### 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 ! echo 1 > $kevent_entry/enable; then
    edie "ERROR: enabling kill() entry tracepoint Exiting."
fi
if ! echo 1 > $kevent_return/enable; then
    edie "ERROR: enabling kill() return tracepoint. Exiting."
fi
(( opt_time )) && printf "%-16s " "TIMEs"
printf "%-16.16s %-6s %-8s %-10s %4s\n" "COMM" "PID" "TPID" "SIGNAL" "RETURN"

#
# Determine output format. It may be one of the following (newest first):
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#           TASK-PID    CPU#    TIMESTAMP  FUNCTION
# To differentiate between them, the number of header fields is counted,
# and an offset set, to skip the extra column when needed.
#
offset=$($awk 'BEGIN { o = 0; }
    $1 == "#" && $2 ~ /TASK/ && NF == 6 { o = 1; }
    $2 ~ /TASK/ { print o; exit }' trace)

### print trace buffer
warn "echo > trace"
( if (( opt_duration )); then
    # wait then dump buffer
    sleep $duration
    cat trace
else
    # print buffer live
    cat trace_pipe
fi ) | $awk -v o=$offset -v opt_name=$opt_name -v name=$name \
    -v opt_duration=$opt_duration -v opt_time=$opt_time \
    -v opt_pid=$pid -v opt_fancy=$opt_fancy '
    # fancy signal names
    BEGIN {
        signals[1] = "SIGHUP"
        signals[2] = "SIGINT"
        signals[3] = "SIGQUIT"
        signals[4] = "SIGILL"
        signals[6] = "SIGABRT"
        signals[8] = "SIGFPE"
        signals[9] = "SIGKILL"
        signals[11] = "SIGSEGV"
        signals[13] = "SIGPIPE"
        signals[14] = "SIGALRM"
        signals[15] = "SIGTERM"
        signals[10] = "SIGUSR1"
        signals[12] = "SIGUSR2"
        signals[17] = "SIGCHLD"
        signals[18] = "SIGCONT"
        signals[19] = "SIGSTOP"
        signals[20] = "SIGTSTP"
        signals[21] = "SIGTTIN"
        signals[22] = "SIGTTOU"
    }

    # common fields
    $1 != "#" {
        # task name can contain dashes
        comm = pid = $1
        sub(/-[0-9][0-9]*/, "", comm)
        if (opt_name && match(comm, name) == 0)
            next
        sub(/.*-/, "", pid)
    }

    # sys_kill() entry
    $1 != "#" && $(4+o) ~ /sys_kill/ && $(5+o) !~ /->/ {
        #
        # eg: ... sys_kill(pid:...
        #
        kpid = $(5+o)
        signal = $(7+o)
        sub(/,$/, "", kpid)
        sub(/\)$/, "", signal)
        kpid = int("0x"kpid)
        signal = int("0x"signal)
        current[pid,"kpid"] = kpid
        current[pid,"signal"] = signal
    }

    # sys_kill exit
    $1 != "#" && $(5+o) ~ /->/ {
        rv = int($NF)
        killed_pid = current[pid,"kpid"]
        signal = current[pid,"signal"]

        delete current[pid,"kpid"]
        delete current[pid,"signal"]

        if(opt_pid && killed_pid != opt_pid) {
            next
        }

        if (opt_time) {
            time = $(3+o); sub(":", "", time)
            printf "%-16s ", time
        }

        if (opt_fancy) {
            if (signals[signal] != "") {
                signal = signals[signal]
            }
        }

        printf "%-16.16s %-6s %-8s %-10s %-4s\n", comm, pid, killed_pid, signal,
            rv
    }

    $0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" }
'

### end tracing
end