linux-kernel - Re: [PATCH 09/18] tracing: Add indexing of arguments for function based events

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Date:   Fri, 9 Feb 2018 08:56:15 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        linux-rt-users@...r.kernel.org, linux-trace-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Clark Williams <williams@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        kernel-team@....com
Subject: Re: [PATCH 09/18] tracing: Add indexing of arguments for function
 based events

On Thu, Feb 08, 2018 at 10:43:43AM -0500, Steven Rostedt wrote:
> On Thu, 8 Feb 2018 19:59:24 +0900
> Namhyung Kim <namhyung@...nel.org> wrote:
> 
> > > @@ -347,6 +361,8 @@ static long long get_arg(struct func_arg *arg, unsigned long val)
> > >  	char buf[8];
> > >  	int ret;
> > >  
> > > +	val += arg->index;
> > > +
> > >  	if (!arg->indirect)
> > >  		return val;  
> > 
> > So this also works without the indirect, and just add the immediate to
> > the value.
> 
> Not sure what you are asking here. The immediate adds to the current
> value, where as the indirect will then look what's at that location.

I expected that the immediate offset is only meaningful with the
indirect (dereference) as the doc says just about it.  So I asked it
was intentional or not.

Thanks,
Namhyung