Re: [BUGFIX PATCH perf/core ] perf-probe: Fix to show lines of sys_ functions correctly

From: Arnaldo Carvalho de Melo
Date: Wed Aug 12 2015 - 09:40:54 EST

Em Wed, Aug 12, 2015 at 10:23:55AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Aug 12, 2015 at 10:24:07AM +0900, Masami Hiramatsu escreveu:
> > "perf probe --lines sys_poll" shows only the first line of
> > sys_poll, because the SYSCALL_DEFINE macro
> > ----

> Thanks! Just try prefixing those ---- lines one space so that git-am
> works on your messages :-)

> Now to build and test, will report here the results.

Ok, now -L works:

[root@zoo ~]# perf probe -L sys_select
0 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
fd_set __user *, exp, struct timeval __user *, tvp)
3 struct timespec end_time, *to = NULL;
struct timeval tv;
int ret;

7 if (tvp) {
8 if (copy_from_user(&tv, tvp, sizeof(tv)))
9 return -EFAULT;

11 to = &end_time;
12 if (poll_select_set_timeout(to,
tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
14 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
15 return -EINVAL;

18 ret = core_sys_select(n, inp, outp, exp, to);
19 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);

21 return ret;

static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,

But then adding a probe doesn't work on sys_select, even with -L stating that I
can add a probe at that line, maybe the code you added to make -L work needs to
be shared with the other operations in 'perf probe'?

[root@zoo ~]#
[root@zoo ~]# perf probe 'get_timeval=sys_select:11 tv_sec=tv.tv_sec tv_usec=tv.tv_usec'
Probe point 'sys_select:11' not found.
Error: Failed to add events.
[root@zoo ~]#

[root@zoo ~]# perf probe -V sys_select
Available variables at sys_select
long int exp
long int inp
long int n
long int outp
long int tvp
[root@zoo ~]# perf probe -V sys_select:11
Failed to find the address of sys_select:11
Error: Failed to show vars.
[root@zoo ~]#

While this works:

[root@zoo ~]# perf probe 'vfs_getname=getname_flags:72 pathname=filename:string'
Added new event:
probe:vfs_getname (on getname_flags:72 with pathname=filename:string)

You can now use it in all perf tools, such as:

perf record -e probe:vfs_getname -aR sleep 1

- Arnaldo
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