On Mon, Jun 29, 2015 at 12:00:38PM -0300, Arnaldo Carvalho de Melo wrote:
Em Sun, Jun 28, 2015 at 05:46:51PM +0200, Benjamin King escreveu:
>Is there a trick to getting perf to probe a user-level address without
>debuginfo? Eg (on Linux 4.0):
>[...]
>I can do this using ftrace ok, eg, "p:tick_0x583 /root/tick:0x583"
>works. Thanks,
Not quite what you have asked for, but you can add the probe via ftrace and
then use it from perf. Probes from /sys/kernel/debug/tracing/uprobe_events
will show up in 'perf list' as well.
Masami,
Is this already possible?
Hi Arnaldo,
for me this works in 3.19.0. I'm using the attached script to help me add
probes to /sys/kernel/debug/tracing/uprobe_events which I can then see with
'sudo perf list' and use from the other perf subcommands. Tracing arguments is
also working fine:
--- snip ---
$ uprobe /lib/x86_64-linux-gnu/libc.so.6 malloc %di
$ sudo perf stat -e uprobes:* ls
...
Performance counter stats for 'ls':
...
218 uprobes:malloc_1
$ sudo perf record -euprobes:malloc_1 ls >/dev/null 2>&1
$ sudo perf script
ls 21084 [003] 10825.526815: uprobes:malloc_1: (7f772bfc2700)
arg1=0x238
ls 21084 [003] 10825.526917: uprobes:malloc_1: (7f772bfc2700)
arg1=0x238
ls 21084 [003] 10825.526968: uprobes:malloc_1: (7f772bfc2700)
arg1=0x78
ls 21084 [003] 10825.527089: uprobes:malloc_1: (7f772bfc2700)
arg1=0x5
ls 21084 [003] 10825.527132: uprobes:malloc_1: (7f772bfc2700)
arg1=0x78
...
--- snip ---
This is superuseful to me, so thank you all for working on perf!
I failed to manage placing proper probes in C++-Code with perf probe, so I
hacked the script together after reading Brendans ftrace article on LWN.
Cheers,
Benjamin
#!/bin/bash
usage() {
cat <<EOF
Add and remove uprobes
USAGE
$0 [options] <library or executable> <regexp for function/address>
[<additional arguments to uprobe>]
This will try to find a matching symbol in the executable and add a probe at
its entry point with the given arguments.
OPTIONS
-C Clear uprobe_events, then exit
-r Probe on return rather than function entry
-n dry-run, only show what would be done, rather than doing it. Implies -v
-v verbose, show commands
-D demangle symbol names before checking the regexp
SEE ALSO
https://www.kernel.org/doc/Documentation/trace/uprobetracer.txt
EOF
exit 1
}
fail() {
echo "$@"
exit 1
}
log() {
VERBOSITY=$1
shift
(( $VERBOSITY <= $VERBOSE )) && echo "$@"
}
CLEAR=0
DEMANGLER=cat
PROBETYPE=p:
DRYRUN=0
VERBOSE=0
[[ $# == 0 ]] && usage
while getopts "CDrnvh" flag
do
case $flag in
C ) CLEAR=1;;
D ) DEMANGLER=c++filt;;
r ) PROBETYPE=r:;;
n ) DRYRUN=1;;
v ) VERBOSE=$((VERBOSE + 1));;
* ) usage;;
esac
done
shift $(($OPTIND - 1 ))
if (( $CLEAR ))
then
echo "" | sudo tee /sys/kernel/debug/tracing/uprobe_events
exit 0
fi
(( $# < 2 )) && usage
DSO=$1
REGEXP=$2
shift 2
ADDITIONAL_ARGUMENTS="$@"
#echo $DEMANGLER
#echo $PROBETYPE
#echo $DRYRUN
#echo $VERBOSE
#echo $DSO
#echo $REGEXP
#echo $ADDITIONAL_ARGUMENTS
[[ -f "$DSO" ]] || fail "Not found: '$DSO'"
# Build string to pipe into uprobe_events
TODO=$( ( eu-readelf -S "$DSO" | sed 's/^\[ */[/'; eu-readelf -s "$DSO" |
$DEMANGLER ) |
grep -- "^\[\|$REGEXP" |
grep -v UNDEF |
awk -vADDITIONAL_ARGUMENTS="$ADDITIONAL_ARGUMENTS" \
-vPROBETYPE=$PROBETYPE \
-vDSO="$DSO" \
-vPROBENAME=$(echo "$REGEXP" | tr -cd "0-9a-zA-Z") \
'/^\[/ {
# First eu-readelf checks segments. We need the offset that
# maps adresses to file offsets
seg=$1
fileoffset[seg]=strtonum("0x"$4)-strtonum("0x"$5)
#print seg, fileoffset[seg]
}
$4 == "FUNC" {
addr = $2
seg = $7
$1 = ""; $2 = ""; $3 = ""; $4 = ""; $5 = ""; $6 = ""; $7 = ""
symbol[addr]=$0
segment[addr]=seg
}
END {
for ( addr in symbol )
{
#print segment[addr], fileoffset["["segment[addr]"]"], addr,
symbol[addr]
printf "%s%s %s:0x%x %s\n", PROBETYPE, PROBENAME"_"(++num),
DSO, strtonum("0x"addr)-fileoffset["["segment[addr]"]"], ADDITIONAL_ARGUMENTS
}
}' )
log 1 "Would do this:
echo
$TODO | sudo tee -a /sys/kernel/debug/tracing/uprobe_events"
(( $DRYRUN )) || echo "$TODO" | sudo tee -a
/sys/kernel/debug/tracing/uprobe_events
log 1 "
You now have this in uprobe_events:
$( sudo cat /sys/kernel/debug/tracing/uprobe_events )"
