dtrace discuss - Jan 2009 - Can I pass a parameter to Dtrace script as a part of function name?

I want to trace function whose name has certain value, such as "read"
or
"write". But seems dtrace can''t replace the variable with the
value I passed
in.

bash-3.00$ cat d.d
#!/usr/sbin/dtrace -s

#pragma D option flowindent

syscall::**$1**:entry { self->interest = 1; }
fbt::: /self->interest/ {}
syscall::**$1**:return { self->interest = 0; }



bash-3.00$ ./d.d *read*
dtrace: failed to compile script ./d.d: line 5: invalid probe description
"*
syscall::*$1*:entry*": Undefined macro variable in probe description
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$1 is not a D variable it''s a shell var.  Have a look at the
"inline" function/operand. 
http://wikis.sun.com/display/DTrace/Type+and+Constant+Definitions

There''s loads of examples in the DTrace Toolkit that you can look at
and use as examples.   Google "dtrace inline" for more examples.
-- 
This message posted from opensolaris.org

On Sat, Jan 17, 2009 at 12:43 AM, Qihua Wu <dtrace.wu at gmail.com>
wrote:
> I want to trace function whose name has certain value, such as
"read" or
> "write". But seems dtrace can''t replace the variable
with the value I passed
> in.
>
> bash-3.00$ cat d.d
> #!/usr/sbin/dtrace -s
>
> #pragma D option flowindent
>
> syscall::*$1*:entry { self->interest = 1; }
> fbt::: /self->interest/ {}
> syscall::*$1*:return { self->interest = 0; }
>
>
>
> bash-3.00$ ./d.d read
> dtrace: failed to compile script ./d.d: line 5: invalid probe description
> "syscall::*$1*:entry": Undefined macro variable in probe
description
If you want to enable exactly one syscall for which you know the name,
you could simply match every syscall specify that in the predicate:

syscall:::entry
/ probefunc == $1 /
{
        self->interest = 1;
}

etc.

To use globbing to match syscalls (e.g., read, pread, readv, etc.), try this:

#!/bin/sh

/usr/sbin/dtrace -n ''

#pragma D option flowindent

syscall::*''$1''*:entry { self->interest = 1; }
fbt::: /self->interest/ {}
syscall::*''$1''*:return { self->interest = 0; }
''

Note the placement of the single-quotes so that $1 gets replaced by the shell.

Chad

On Sat, Jan 17, 2009 at 2:46 AM, Steve Scargall <steve.scargall at
sun.com> wrote:
> $1 is not a D variable it''s a shell var.  Have a look at the
"inline" function/operand. 
http://wikis.sun.com/display/DTrace/Type+and+Constant+Definitions
>
> There''s loads of examples in the DTrace Toolkit that you can look
at and use as examples.   Google "dtrace inline" for more examples.
Actually, $1 is a macro variable, and it''s designed to be used for
things like this.  For example, the following works (at least on build
105, I don''t have a stock Solaris 10 system handy at the moment):

#!/usr/sbin/dtrace -s

syscall::$1:entry
{
	@c[execname,probefunc] = count();
}

# ./count-syscall.d read
dtrace: script ''./count-syscall.d'' matched 1 probe
^C

  sshd                                                read
                                                 2
#


This also works:

#!/usr/sbin/dtrace -s

syscall::*$1:entry
{
        @c[execname,probefunc] = count();
}



# ./count-syscall.d read
dtrace: script ''./count-syscall.d'' matched 2 probes
^C

  sshd                                                read
                                                 2
#

But placing the ''*'' on the other side doesn''t work:

#!/usr/sbin/dtrace -s

syscall::$1*:entry
{
        @c[execname,probefunc] = count();
}


# ./count-syscall.d read
dtrace: failed to compile script ./count-syscall.d: line 3: invalid
probe description "syscall::$1*:entry": Undefined macro variable in
probe description
#

I haven''t looked into the code to figure out why this fails, nor have
I searched the bug database.  I''ll look into it, though.

Chad

On Sat, Jan 17, 2009 at 5:28 PM, Chad Mynhier <cmynhier at gmail.com>
wrote:
> For example, the following works (at least on build
> 105, I don''t have a stock Solaris 10 system handy at the moment):
>
> #!/usr/sbin/dtrace -s
>
> syscall::$1:entry
> {
>        @c[execname,probefunc] = count();
> }
>
> # ./count-syscall.d read
> dtrace: script ''./count-syscall.d'' matched 1 probe
> ^C
>
>  sshd                                                read
>                                                 2
> #
>
>
> This also works:
>
> #!/usr/sbin/dtrace -s
>
> syscall::*$1:entry
> {
>        @c[execname,probefunc] = count();
> }
>
>
>
> # ./count-syscall.d read
> dtrace: script ''./count-syscall.d'' matched 2 probes
> ^C
>
>  sshd                                                read
>                                                 2
> #
>
> But placing the ''*'' on the other side doesn''t
work:
>
> #!/usr/sbin/dtrace -s
>
> syscall::$1*:entry
> {
>        @c[execname,probefunc] = count();
> }
>
>
> # ./count-syscall.d read
> dtrace: failed to compile script ./count-syscall.d: line 3: invalid
> probe description "syscall::$1*:entry": Undefined macro variable
in
> probe description
> #
>
> I haven''t looked into the code to figure out why this fails, nor
have
> I searched the bug database.  I''ll look into it, though.
For the curious, I opened bug 6795386 ("macro arguments and globbing
in DTrace probe descriptions don''t mix") for this.  I''ve
played some
with the code, but just enough to make the above work, I didn''t do it
in a general enough fashion to cover all cases.  I''ll look into a
proper fix when I get some time.

Chad