netdev - Re: [PATCH v3 linux-trace 4/8] samples: bpf: simple tracing example in C

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Message-ID: <20150210072701.547a5385@grimm.local.home>
Date:	Tue, 10 Feb 2015 07:27:01 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v3 linux-trace 4/8] samples: bpf: simple tracing example
 in C

On Mon, 9 Feb 2015 21:47:42 -0800
Alexei Starovoitov <ast@...mgrid.com> wrote:

> On Mon, Feb 9, 2015 at 9:45 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
> > I thought we already stated that.
> > Here is the quote from perf_event.h:
> >          *      # The RAW record below is opaque data wrt the ABI
> >          *      #
> >          *      # That is, the ABI doesn't make any promises wrt to
> >          *      # the stability of its content, it may vary depending
> >          *      # on event, hardware, kernel version and phase of
> >          *      # the moon.
> >          *      #
> >          *      # In other words, PERF_SAMPLE_RAW contents are not an ABI.
> >
> > and this example is reading PERF_SAMPLE_RAW events and
> > uses locally defined structs to print them for simplicity.
> 
> to underline my point once more:
> addition of bpf doesn't change at all what PERF_SAMPLE_RAW already
> delivers to user space.
> so no new ABIs anywhere.

Again, it we give an example of how to hard code the data, definitely
expect this to show up in user space. Users are going to look at this
code to learn how to use eBPF. I really want it to do it the correct
way instead of the 'easy' way. Because whatever way we have it here,
will be the way we will see it out in the wild.

-- Steve
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