linux-kernel - Re: [PATCH v2 3/5] tracing: Fix operator precedence for hist triggers expression

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Message-ID: <CAC_TJvfQCjZPS50-k2Pxo0jCcfxQ7oa1MZxQdADyjnwQ_TBzRA@mail.gmail.com>
Date:   Wed, 20 Oct 2021 08:06:26 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] tracing: Fix operator precedence for hist triggers expression

On Wed, Oct 20, 2021 at 7:28 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 19 Oct 2021 18:31:40 -0700
> Kalesh Singh <kaleshsingh@...gle.com> wrote:
>
> > +     minus_op = strrchr(str, '-');
> > +     if (minus_op) {
> > +             /* Unfortunately, the modifier ".sym-offset" can confuse things. */
> > +             if (minus_op - str >= 4 && !strncmp(minus_op - 4, ".sym-offset", 11))
> > +                     goto out;
> >
>
> I was thinking about this, and perhaps we can add this later, but we could
> just replace all ".sym-offset" with ".symXoffset" after receiving it from
> the user. Then it won't be an issue during prasing.

That's a good idea. It would clean things up a bit and avoid bailing
out if the user has a sym-offest in an expression string. I can send a
separate patch for this.

>
> -- Steve