dtrace discuss - Dec 2008 - profile:::tick-1 requires dtrace_kernel privilege?

Hi all,

A user with dtrace_proc and dtrace_user privileges can see the
profile:::tick-1 probe:

$ ppriv $$
28999:  -bash
flags = <none>
        E: basic,dtrace_proc,dtrace_user,proc_owner
        I: basic,dtrace_proc,dtrace_user,proc_owner
        P: basic,dtrace_proc,dtrace_user,proc_owner
        L: all
$ dtrace -l | grep tick-1
42071    profile                                                     tick-1
42072    profile                                                     tick-10
42073    profile                                                     tick-100
42075    profile                                                     tick-1000
42681    profile                                                     tick-1sec

However when I run D code using this probe I don''t see any output
unless I add the dtrace_kernel privilege.

Here the D code I am using (this is in a script that I run as dtrace
-s tick-1.d):

/*
 * Count off and report the number of seconds elapsed
 */
dtrace:::BEGIN
{
        i = 0;
}

profile:::tick-1
{
        i = i + 1;
        trace(i);
}

dtrace:::END
{
        trace(i);
}

This behaviour has been verified on Solaris 10 and a recent OpenSolaris box.

Is this expected behaviour?

Thanks.

Toby

Hi Toby,

<chop>
> However when I run D code using this probe I don''t see any output
> unless I add the dtrace_kernel privilege.
>
> Here the D code I am using (this is in a script that I run as dtrace
> -s tick-1.d):
>
> /*
>  * Count off and report the number of seconds elapsed
>  */
> dtrace:::BEGIN
> {
>         i = 0;
> }
>
> profile:::tick-1
> {
>         i = i + 1;
>         trace(i);
> }
>
> dtrace:::END
> {
>         trace(i);
> }
>
> This behaviour has been verified on Solaris 10 and a recent OpenSolaris
box.
>
> Is this expected behaviour?
Expected, yes, but not particularly useful. If a user only has dtrace_user
privilege then probes exported by the profile provider will only fire
for that user if a process they own is executing when the probe fires.
To test this, just execute a spinloop at the same time as enabling a
''profile-1s'' probe and it should fire every second (on an
otherwise idle
system that is).

Aside from giving out dtrace_kernel privilege, I''m not aware of
anything
you can do to get periodic timers (maybe I''m forgetting something 
though...).
This needs sorting out really but it''s probably a bunch of work.

Jon.