Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe

Hi Oleg,

For the moment, please forget about ret-probes. Could you compile this program

#define _GNU_SOURCE
#include <unistd.h>
#include <sched.h>
#include <signal.h>

int func(int i)
{
        return i;
}

int test(void *arg)
{
        int i;
        for (i = 0;; ++i) {
                sleep(1);
                func(i);
        }
        return 0;
}

int main(void)
{
        static char stack[65536];

        clone(test, stack + sizeof(stack)/2, CLONE_VM|SIGCHLD, NULL);
        test(NULL);

        return 0;
}

and then do something like

        $ ./test &
        $ bpftrace -p $! -e 'uprobe:./test:func { printf("%d\n", pid); }'

I hope that the syntax of the 2nd command is correct...

I _think_ that it will print 2 pids too.

But "perf-record -p" works as expected.

Yes, the output from bpftrace and perf matches what you described:

$ ./tester &
[1] 158592

$ perf probe -x tester --add func
Added new event:
  probe_tester:func    (on func in /root/test/tester)

$ bpftrace -p 158592 -e 'uprobe:./tester:func { printf("time=%llu pid=%d\n", elapsed / 1000000000, pid); }'
Attaching 1 probe...
time=0 pid=158592
time=0 pid=158594
time=1 pid=158592
time=1 pid=158594
time=2 pid=158592
time=2 pid=158594
time=3 pid=158592
time=3 pid=158594

$ perf record -e probe_tester:func -p 158592 -o 158592
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.022 MB 158592 (19 samples) ]

$ perf script -i 158592
tester  158592 [006] 246475.295762: probe_tester:func: (55a6def14149)
tester  158592 [006] 246476.295828: probe_tester:func: (55a6def14149)
tester  158592 [006] 246477.295892: probe_tester:func: (55a6def14149)
tester  158592 [006] 246478.295958: probe_tester:func: (55a6def14149)
tester  158592 [006] 246479.296024: probe_tester:func: (55a6def14149)
tester  158592 [010] 246480.296202: probe_tester:func: (55a6def14149)
tester  158592 [010] 246481.296360: probe_tester:func: (55a6def14149)
[...]

Thanks,