#!/bin/bash # # opensnoop - trace open() syscalls with file details. # Written using Linux ftrace. # # This traces open() syscalls, showing the file name and returned file # descriptor number (or -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 getname() # as a string, and associating it with the following open() 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: ./opensnoop [-htx] [-d secs] [-p pid] [-L tid] [-n name] [filename] # # Run "opensnoop -h" for full usage. # # REQUIREMENTS: FTRACE and KPROBE CONFIG, syscalls:sys_exit_open tracepoint, # getname() kernel function (you may already have these on recent kernels), # and awk. # # From perf-tools: https://github.com/brendangregg/perf-tools # # See the opensnoop(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. ### 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=; opt_tid=0; tid= ftext=; opt_time=0; opt_fail=0; opt_file=0; file= trap ':' INT QUIT TERM PIPE HUP # sends execution to end tracing section function usage { cat <<-END >&2 USAGE: opensnoop [-htx] [-d secs] [-p PID] [-L TID] [-n name] [filename] -d seconds # trace duration, and use buffers -n name # process name to match on open -p PID # PID to match on open -L TID # PID to match on open -t # include time (seconds) -x # only show failed opens -h # this usage message filename # match filename (partials, REs, ok) eg, opensnoop # watch open()s live (unbuffered) opensnoop -d 1 # trace 1 sec (buffered) opensnoop -p 181 # trace I/O issued by PID 181 only opensnoop conf # trace filenames containing "conf" opensnoop 'log$' # filenames ending in "log" See the man page and example file for more info. END exit } function warn { if ! eval "$@"; 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 > events/kprobes/getnameprobe/enable" warn "echo 0 > events/syscalls/sys_exit_open/enable" if (( opt_pid || opt_tid )); then warn "echo 0 > events/kprobes/getnameprobe/filter" warn "echo 0 > events/syscalls/sys_exit_open/filter" fi warn "echo -:getnameprobe >> kprobe_events" 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:L:tx opt do case $opt in d) opt_duration=1; duration=$OPTARG ;; n) opt_name=1; name=$OPTARG ;; p) opt_pid=1; pid=$OPTARG ;; L) opt_tid=1; tid=$OPTARG ;; t) opt_time=1 ;; x) opt_fail=1 ;; h|?) usage ;; esac done shift $(( $OPTIND - 1 )) if (( $# )); then opt_file=1 file=$1 shift fi (( $# )) && usage ### option logic (( opt_pid + opt_name + opt_tid > 1 )) && \ die "ERROR: use at most one of -p, -n, -L." (( opt_pid )) && ftext=" issued by PID $pid" (( opt_tid )) && ftext=" issued by TID $tid" (( opt_name )) && ftext=" issued by process name \"$name\"" (( opt_file )) && ftext="$ftext for filenames containing \"$file\"" if (( opt_duration )); then echo "Tracing open()s$ftext for $duration seconds (buffered)..." else echo "Tracing open()s$ftext. Ctrl-C to end." fi ### select awk (( opt_duration )) && use=mawk || use=gawk # workaround for mawk fflush() [[ -x /usr/bin/$use ]] && awk=$use || awk=awk ### 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 $flock." wroteflock=1 ### setup and begin tracing echo nop > current_tracer ver=$(uname -r) if [[ "$ver" == 2.* || "$ver" == 3.[1-6].* ]]; then # rval is char * kprobe='r:getnameprobe getname +0($retval):string' else # rval is struct filename * kprobe='r:getnameprobe getname +0(+0($retval)):string' fi if ! echo $kprobe >> kprobe_events; then edie "ERROR: adding a kprobe for getname(). Exiting." fi if (( opt_pid )); then filter= for tid in /proc/$pid/task/*; do filter="$filter || common_pid == ${tid##*/}" done filter=${filter:3} # trim leading ' || ' (four characters) if ! echo $filter > events/kprobes/getnameprobe/filter || \ ! echo $filter > events/syscalls/sys_exit_open/filter then edie "ERROR: setting -p $pid. Exiting." fi fi if (( opt_tid )); then if ! echo "common_pid == $tid" > events/kprobes/getnameprobe/filter || \ ! echo "common_pid == $tid" > events/syscalls/sys_exit_open/filter then edie "ERROR: setting -L $tid. Exiting." fi fi if ! echo 1 > events/kprobes/getnameprobe/enable; then edie "ERROR: enabling kprobe for getname(). Exiting." fi if ! echo 1 > events/syscalls/sys_exit_open/enable; then edie "ERROR: enabling open() exit tracepoint. Exiting." fi (( opt_time )) && printf "%-16s " "TIMEs" printf "%-16.16s %-6s %4s %s\n" "COMM" "PID" "FD" "FILE" # # Determine output format. It may be one of the following (newest first): # TASK-PID CPU# |||| TIMESTAMP FUNCTION # TASK-PID CPU# TIMESTAMP FUNCTION # To differentiate between them, the number of header fields is counted, # and an offset set, to skip the extra column when needed. # offset=$($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_fail=$opt_fail \ -v opt_file=$opt_file -v file=$file ' # common fields $1 != "#" { # task name can contain dashes and space split($0, line, "-") sub(/^[ \t\r\n]+/, "", line[1]) comm = line[1] if (opt_name && match(comm, name) == 0) next sub(/ .*$/, "", line[2]) pid = line[2] } # do_sys_open() $1 != "#" && $(5+o) ~ /do_sys_open/ { # # eg: ... (do_sys_open+0xc3/0x220 <- getname) arg1="file1" # filename = $NF sub(/"$/, "", filename) sub(/.*"/, "", filename) lastfile[pid] = filename } # sys_open() $1 != "#" && $(4+o) == "sys_open" { filename = lastfile[pid] delete lastfile[pid] if (opt_file && filename !~ file) next rval = $NF # matched failed as beginning with 0xfffff if (opt_fail && rval !~ /0xfffff/) next if (rval ~ /0xfffff/) rval = -1 if (opt_time) { time = $(3+o); sub(":", "", time) printf "%-16s ", time } printf "%-16.16s %-6s %4s %s\n", comm, pid, rval, filename } $0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" } ' ### end tracing end