linux-kernel - RE: [patch] samples/bpf: silence shift wrapping warning

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB026DD27@AcuExch.aculab.com>
Date:   Wed, 25 Jan 2017 11:08:51 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Alexei Starovoitov' <alexei.starovoitov@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
CC:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Thomas Graf <tgraf@...g.ch>,
        Alexei Starovoitov <ast@...nel.org>,
        Joe Stringer <joe@....org>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [patch] samples/bpf: silence shift wrapping warning

From: Alexei Starovoitov
> Sent: 22 January 2017 22:51
> On Sat, Jan 21, 2017 at 07:51:43AM +0300, Dan Carpenter wrote:
> > max_key is a value in the 0-63 range, so on 32 bit systems the shift
> > could wrap.
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> Looks fine. I think 'net-next' is ok.
> 
> Acked-by: Alexei Starovoitov <ast@...nel.org>
> 
> > diff --git a/samples/bpf/lwt_len_hist_user.c b/samples/bpf/lwt_len_hist_user.c
> > index ec8f3bb..bd06eef 100644
> > --- a/samples/bpf/lwt_len_hist_user.c
> > +++ b/samples/bpf/lwt_len_hist_user.c
> > @@ -68,7 +68,7 @@ int main(int argc, char **argv)
> >  	for (i = 1; i <= max_key + 1; i++) {
> >  		stars(starstr, data[i - 1], max_value, MAX_STARS);
> >  		printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
> > -		       (1l << i) >> 1, (1l << i) - 1, data[i - 1],
> > +		       (1ULL << i) >> 1, (1ULL << i) - 1, data[i - 1],
> >  		       MAX_STARS, starstr);
> >  	}

The format effectors are wrong on 32bit systems.

	David