From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753573AbbCSPiH (ORCPT <rfc822;w@1wt.eu>);
	Thu, 19 Mar 2015 11:38:07 -0400
Received: from mail-ig0-f177.google.com ([209.85.213.177]:35032 "EHLO
	mail-ig0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751332AbbCSPiE (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 19 Mar 2015 11:38:04 -0400
Message-ID: <550AED5D.3010700@plumgrid.com>
Date: Thu, 19 Mar 2015 08:38:05 -0700
From: Alexei Starovoitov <ast@plumgrid.com>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
MIME-Version: 1.0
To: Steven Rostedt <rostedt@goodmis.org>
CC: Ingo Molnar <mingo@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Jiri Olsa <jolsa@redhat.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        "David S. Miller" <davem@davemloft.net>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-api@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 tip 3/8] tracing: allow BPF programs to call bpf_ktime_get_ns()
References: <1426542584-9406-1-git-send-email-ast@plumgrid.com>	<1426542584-9406-4-git-send-email-ast@plumgrid.com> <20150319111124.38f53061@gandalf.local.home>
In-Reply-To: <20150319111124.38f53061@gandalf.local.home>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 3/19/15 8:11 AM, Steven Rostedt wrote:
> On Mon, 16 Mar 2015 14:49:39 -0700
> Alexei Starovoitov <ast@plumgrid.com> wrote:
>
>> bpf_ktime_get_ns() is used by programs to compue time delta between events
>
>   "compute"

ok :)

>> +	[BPF_FUNC_ktime_get_ns] = {
>> +		.func = bpf_ktime_get_ns,
>> +		.gpl_only = true,
>> +		.ret_type = RET_INTEGER,
>
> Hmm, a nanosecond value returned as integer? Is there a way to make
> this a 64 bit return type, or is RET_INTEGER default to 64 bits in BPF
> functions?

RET_INTEGER doesn't mean C 'int' width. It means non-pointer and
non-void value. The return value is always promoted to full
register width which is 64-bit.