linux-kernel - Re: [RFC PATCH -tip 0/5] kprobes: Abolish jprobe APIs

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Message-ID: <20171009124807.2878df95@gandalf.local.home>
Date:   Mon, 9 Oct 2017 12:48:07 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Stafford Horne <shorne@...il.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Ian McDonald <ian.mcdonald@...di.co.nz>,
        Vlad Yasevich <vyasevich@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [RFC PATCH -tip 0/5] kprobes: Abolish jprobe APIs

On Sat, 7 Oct 2017 14:24:53 +0900
Stafford Horne <shorne@...il.com> wrote:

> Hello,
> 
> Nice read, see some comments below

Thanks.


> > To enable tracing call:
> > 
> >   register_ftrace_function(&ops);  
> 
> Maybe it would help to have a small section on 'The register function'
> below to answer?
> 
> Is it possible to make changes to the filter after calling
> register_ftrace_function()?  Or do you need to call
> register_ftrace_function() again?

OK, I'll think about this.

> 


> > This takes the same parameters as ftrace_set_filter() but will add the
> > functions it finds to not be traced. This doesn't remove them from the
> > filter itself, but keeps them from being traced. If @reset is set,
> > the filter is cleaded but the functions that match @buf will still not  
> 
> 'cleared'?

Yeah, Jon pointed out the confusion here too.

> 
> > be traced (the callback will not be called on those functions).  
> 
> This is a bit confusing, I guess it means 'the existng filter is cleared
> and the filter *will match all* functions excluding those that match @buf'.

Yep, I confused Jon with it as well. I think by the time I got to this
part of the document, I was just trying to finish it and did a bit of
rambling and less cognitive thought.

Thanks for reviewing.

-- Steve