linux-kernel - Re: [PATCH v4 01/19] [BUGFIX] tracing: probeevent: Fix to support minus offset from symbol

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Message-ID: <20180305022814.GA8824@sejong>
Date:   Mon, 5 Mar 2018 11:28:14 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-trace-users@...r.kernel.org, linux-kselftest@...r.kernel.org,
        shuah@...nel.org, kernel-team@....com
Subject: Re: [PATCH v4 01/19] [BUGFIX] tracing: probeevent: Fix to support
 minus offset from symbol

Hi Masami,

On Fri, Mar 02, 2018 at 03:32:29PM +0900, Masami Hiramatsu wrote:
> On Fri, 2 Mar 2018 13:49:51 +0900
> Namhyung Kim <namhyung@...nel.org> wrote:
> 
> > Hi Masami,
> > 
> > On Wed, Feb 28, 2018 at 12:19:53PM +0900, Masami Hiramatsu wrote:
> > > In Documentation/trace/kprobetrace.txt, it says
> > > 
> > >  @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
> > > 
> > > However, the parser doesn't parse minus offset correctly, since
> > > commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be
> > > unsigned") drops minus ("-") offset support for kprobe probe
> > > address usage.
> > > 
> > > This fixes the traceprobe_split_symbol_offset() to parse minus
> > > offset again with checking the offset range, and add a minus
> > > offset check in kprobe probe address usage.
> > 
> > It now parses a minus offset but doesn't allow it, right?
> 
> No, split_symbol_offset() is used for 2 cases
>  - kprobe-event probe point
>  - kporbe-event symbol-based argument
> 
> Former one doesn't accept a minus offset, but latter accepts it.

Ah, ok then.

Acked-by: Namhyung Kim <namhyung@...nel.org>


> 
> (Frankly to say, I guess no one care about supporting minus offset :P)

:)

Thanks,
Namhyung