linux-kernel - RE: [PATCH RFC 01/19] kallsyms: Simplify update_iter

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Date:   Thu, 10 May 2018 17:02:18 +0000
From:   "Hunter, Adrian" <adrian.hunter@...el.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH RFC 01/19] kallsyms: Simplify update_iter_mod()

> -----Original Message-----
> From: Jiri Olsa [mailto:jolsa@...hat.com]
> Sent: Thursday, May 10, 2018 4:02 PM
> To: Hunter, Adrian <adrian.hunter@...el.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>; Arnaldo Carvalho de Melo
> <acme@...nel.org>; Ingo Molnar <mingo@...hat.com>; Peter Zijlstra
> <peterz@...radead.org>; Andy Lutomirski <luto@...nel.org>; H. Peter
> Anvin <hpa@...or.com>; Andi Kleen <ak@...ux.intel.com>; Alexander
> Shishkin <alexander.shishkin@...ux.intel.com>; Dave Hansen
> <dave.hansen@...ux.intel.com>; Joerg Roedel <joro@...tes.org>; linux-
> kernel@...r.kernel.org; x86@...nel.org
> Subject: Re: [PATCH RFC 01/19] kallsyms: Simplify update_iter_mod()
> 
> On Wed, May 09, 2018 at 02:43:30PM +0300, Adrian Hunter wrote:
> > Simplify logic in update_iter_mod().
> >
> > Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> > ---
> >  kernel/kallsyms.c | 20 ++++++--------------
> >  1 file changed, 6 insertions(+), 14 deletions(-)
> >
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index
> > a23e21ada81b..eda4b0222dab 100644
> > --- a/kernel/kallsyms.c
> > +++ b/kernel/kallsyms.c
> > @@ -510,23 +510,15 @@ static int update_iter_mod(struct kallsym_iter
> > *iter, loff_t pos)  {
> >  	iter->pos = pos;
> >
> > -	if (iter->pos_ftrace_mod_end > 0 &&
> > -	    iter->pos_ftrace_mod_end < iter->pos)
> > -		return get_ksymbol_bpf(iter);
> > -
> > -	if (iter->pos_mod_end > 0 &&
> > -	    iter->pos_mod_end < iter->pos) {
> > -		if (!get_ksymbol_ftrace_mod(iter))
> > -			return get_ksymbol_bpf(iter);
> > +	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
> > +	    get_ksymbol_mod(iter))
> >  		return 1;
> 
> hum, should that be iter-> pos_mod_end >= pos ?

But module_get_kallsym() returned -1 when pos_mod_end was set to pos.

> 
> 
> > -	}
> >
> > -	if (!get_ksymbol_mod(iter)) {
> > -		if (!get_ksymbol_ftrace_mod(iter))
> > -			return get_ksymbol_bpf(iter);
> > -	}
> > +	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end >
> pos) &&
> > +	    get_ksymbol_ftrace_mod(iter))
> 
> same here? iter->pos_ftrace_mod_end >= pos
> 
> jirka
> 
> > +		return 1;
> >
> > -	return 1;
> > +	return get_ksymbol_bpf(iter);
> >  }
> >
> >  /* Returns false if pos at or past end of file. */
> > --
> > 1.9.1
> >