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From: Masami Hiramatsu <masami.hiramatsu@gmail.com>
To: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Perf Users <linux-perf-users@vger.kernel.org>,
	kernel-team@lge.com
Subject: Re: perf probe and bitfields
Date: Sat, 27 Jan 2018 14:04:59 +0900	[thread overview]
Message-ID: <20180127140459.8e54eefcf9d74609cbcaa739@gmail.com> (raw)
In-Reply-To: <b506165b-22bf-db70-0ef5-30c4ee4e2295@gmail.com>

On Fri, 26 Jan 2018 09:28:49 -0700
David Ahern <dsahern@gmail.com> wrote:

> On 1/25/18 11:56 PM, Namhyung Kim wrote:
> > Hi David,
> > 
> > On Fri, Jan 19, 2018 at 08:43:50AM -0800, David Ahern wrote:
> >> Hi Arnaldo / Masami:
> >>
> >> Are there known issues / limitations with perf probe and bitfields?
> >>
> >> Here's an example: pkt_type is a bitfield in sk_buff. When I put a probe
> >> in arp_rcv to examine the pkt_type value:
> >>
> >> $ perf probe 'arp_rcv ptype=skb->pkt_type dev=dev->name:string'
> > 
> > Bitfield type takes 3 parameters according to the Doc/perf-probe.txt.
> > Maybe it's like 'ptype=skb->pkt_type:b3@0/8' ?
> 
> missed that. Thanks, Namyhung.



Hmm, if you have debuginfo, it must be automatically translated.
E.g.

$ sudo perf probe -D "arp_rcv ptype=skb->pkt_type dev=dev->name:string"
p:probe/arp_rcv _text+8135904 ptype=+144(%di):b3@5/8 dev=+0(%si):string

So as you can see the ptype automatically has ":b3@5/8" types.

Thanks,

-- 
Masami Hiramatsu

  reply	other threads:[~2018-01-27  5:05 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-19 16:43 perf probe and bitfields David Ahern
2018-01-26  6:56 ` Namhyung Kim
2018-01-26 16:28   ` David Ahern
2018-01-27  5:04     ` Masami Hiramatsu [this message]
2018-01-30 16:53       ` David Ahern

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