Re: kprobe string

[David Ahern <dsahern@gmail.com>]

On 07/16/2014 06:51 PM, Brendan Gregg wrote:
> G'Day,
>
> I'm not sure where else to ask this; I don't think this functionality
> is in perf_events yet...
>
> kprobes is supposed to be able to handle string arguments, but I've
> not been able to find a single working example. I'm trying (on 3.16):
>
> # cd /sys/kernel/debug/tracing
> # echo 'r:getname getname $retval:string' > kprobe_events
> -bash: echo: write error: Invalid argument
> # echo 'p:myprobe do_sys_open %dx:string' > kprobe_events
> -bash: echo: write error: Invalid argument
>
> I'm following the syntax in Documentation/trace/kprobetrace.txt by
> Masami Hiramatsu, and it is recognizing "string". But I'm getting
> these errors:
>
> # dmesg | tail -4
> [98021.813560] string type has no corresponding fetch method.
> [98021.813564] Parse error at argument[0]. (-22)
> [98705.956199] string type has no corresponding fetch method.
> [98705.956203] Parse error at argument[0]. (-22)
>
> Anyone seen this work? I'm checking the source... Thanks in advance,

Have you seen this:
https://lkml.org/lkml/2014/6/19/698

David