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2be76ae Sep 4, 2017
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@brendangregg @goldshtn
executable file 271 lines (253 sloc) 7.85 KB
#!/bin/bash
#
# kprobe - trace a given kprobe definition. Kernel dynamic tracing.
# Written using Linux ftrace.
#
# This will create, trace, then destroy a given kprobe definition. See
# Documentation/trace/kprobetrace.txt in the Linux kernel source for the
# syntax of a kprobe definition, and "kprobe -h" for examples. With this tool,
# the probe alias is optional (it will become to kprobe:<funcname> if not
# specified).
#
# USAGE: ./kprobe [-FhHsv] [-d secs] [-p pid] [-L tid] kprobe_definition [filter]
#
# Run "kprobe -h" for full usage.
#
# I wrote this because I kept testing different custom kprobes at the command
# line, and wanted a way to automate the steps.
#
# WARNING: This uses dynamic tracing of kernel functions, and could cause
# kernel panics or freezes, depending on the function traced. Test in a lab
# environment, and know what you are doing, before use.
#
# REQUIREMENTS: FTRACE and KPROBE CONFIG, which you may already have on recent
# kernel versions.
#
# From perf-tools: https://github.com/brendangregg/perf-tools
#
# See the kprobe(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
debug=0; opt_force=0
trap ':' INT QUIT TERM PIPE HUP # sends execution to end tracing section
function usage {
cat <<-END >&2
USAGE: kprobe [-FhHsv] [-d secs] [-p PID] [-L TID] kprobe_definition [filter]
-F # force. trace despite warnings.
-d seconds # trace duration, and use buffers
-p PID # PID to match on events
-L TID # thread id to match on events
-v # view format file (don't trace)
-H # include column headers
-s # show kernel stack traces
-h # this usage message
Note that these examples may need modification to match your kernel
version's function names and platform's register usage.
eg,
kprobe p:do_sys_open
# trace open() entry
kprobe r:do_sys_open
# trace open() return
kprobe 'r:do_sys_open \$retval'
# trace open() return value
kprobe 'r:myopen do_sys_open \$retval'
# use a custom probe name
kprobe 'p:myopen do_sys_open mode=%cx:u16'
# trace open() file mode
kprobe 'p:myopen do_sys_open filename=+0(%si):string'
# trace open() with filename
kprobe -s 'p:myprobe tcp_retransmit_skb'
# show kernel stacks
kprobe 'p:do_sys_open file=+0(%si):string' 'file ~ "*stat"'
# opened files ending in "stat"
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 $tracing
warn "echo 0 > events/kprobes/$kname/enable"
if (( opt_filter )); then
warn "echo 0 > events/kprobes/$kname/filter"
fi
warn "echo -:$kname >> kprobe_events"
(( 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 Fd:hHp:L:sv opt
do
case $opt in
F) opt_force=1 ;;
d) opt_duration=1; duration=$OPTARG ;;
p) opt_pid=1; pid=$OPTARG ;;
L) opt_tid=1; tid=$OPTARG ;;
H) opt_headers=1 ;;
s) opt_stack=1 ;;
v) opt_view=1 ;;
h|?) usage ;;
esac
done
shift $(( $OPTIND - 1 ))
(( $# )) || usage
kprobe=$1
shift
if (( $# )); then
opt_filter=1
filter=$1
fi
### option logic
(( opt_pid + opt_filter + opt_tid > 1 )) && \
die "ERROR: use at most one of -p, -L, or filter."
(( opt_duration && opt_view )) && die "ERROR: use either -d or -v."
if (( opt_pid )); then
# convert to filter
opt_filter=1
# ftrace common_pid is thread id from user's perspective
for tid in /proc/$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 == $tid"
fi
if [[ "$kprobe" != p:* && "$kprobe" != r:* ]]; then
echo >&2 "ERROR: invalid kprobe definition (should start with p: or r:)"
usage
fi
#
# parse the following:
# r:do_sys_open
# r:my_sys_open do_sys_open
# r:do_sys_open %ax
# r:do_sys_open $retval %ax
# r:my_sys_open do_sys_open $retval %ax
# r:do_sys_open rval=$retval
# r:my_sys_open do_sys_open rval=$retval
# r:my_sys_open do_sys_open rval=$retval %ax
# ... and examples from USAGE message
#
krest=${kprobe#*:}
kname=${krest%% *}
set -- $krest
if [[ $2 == "" || $2 == *[=%\$]* ]]; then
# if probe name unspecified, default to function name
ktype=${kprobe%%:*}
kprobe="$ktype:$kname $krest"
fi
if (( debug )); then
echo "kname: $kname, kprobe: $kprobe"
fi
### check permissions
cd $tracing || die "ERROR: accessing tracing. Root user? Kernel has FTRACE?
debugfs mounted? (mount -t debugfs debugfs /sys/kernel/debug)"
## check function
set -- $kprobe
fname=$2
if (( !opt_force )) && ! grep -w $fname available_filter_functions >/dev/null \
2>&1
then
echo >&2 "ERROR: func $fname not in $PWD/available_filter_functions."
printf >&2 "Either it doesn't exist, or, it might be unsafe to kprobe. "
echo >&2 "Exiting. Use -F to override."
exit 1
fi
if (( !opt_view )); then
if (( opt_duration )); then
echo "Tracing kprobe $kname for $duration seconds (buffered)..."
else
echo "Tracing kprobe $kname. Ctrl-C to end."
fi
fi
### ftrace lock
[[ -e $flock ]] && die "ERROR: ftrace may be in use by PID $(cat $flock) $flock"
echo $$ > $flock || die "ERROR: unable to write $flock."
wroteflock=1
### setup and begin tracing
echo nop > current_tracer
if ! echo "$kprobe" >> kprobe_events; then
echo >&2 "ERROR: adding kprobe \"$kprobe\"."
if (( dmesg )); then
echo >&2 "Last $dmesg dmesg entries (might contain reason):"
dmesg | tail -$dmesg | sed 's/^/ /'
fi
edie "Exiting."
fi
if (( opt_view )); then
cat events/kprobes/$kname/format
edie ""
fi
if (( opt_filter )); then
if ! echo "$filter" > events/kprobes/$kname/filter; then
edie "ERROR: setting filter or -p. Exiting."
fi
fi
if (( opt_stack )); then
if ! echo 1 > options/stacktrace; then
edie "ERROR: enabling stack traces (-s). Exiting"
fi
fi
if ! echo 1 > events/kprobes/$kname/enable; then
edie "ERROR: enabling kprobe $kname. 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