linux-kernel - Re: [PATCH 28/31] perf probe: Init symbol as kprobe

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Date:	Tue, 1 Sep 2015 17:11:59 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Wang Nan <wangnan0@...wei.com>, mingo@...nel.org, ast@...mgrid.com,
	linux-kernel@...r.kernel.org, lizefan@...wei.com, pi3orama@....com,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	David Ahern <dsahern@...il.com>, He Kuang <hekuang@...wei.com>,
	Jiri Olsa <jolsa@...nel.org>, Kaixu Xia <xiakaixu@...wei.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 28/31] perf probe: Init symbol as kprobe

Em Sat, Aug 29, 2015 at 04:22:02AM +0000, Wang Nan escreveu:
> Before this patch, add_perf_probe_events() init symbol maps only for
> uprobe if the first 'struct perf_probe_event' passed to it is a uprobe
> event. This is a trick because 'perf probe''s command line syntax
> constrains the first elements of the probe_event arrays must be kprobes
> if there is one kprobe there.
> 
> However, with the incoming BPF uprobe support, that constrain is not
> hold since 'perf record' will also probe on k/u probes through BPF
> object, and is possible to pass an array with kprobe but the first
> element is uprobe.
> 
> This patch init symbol maps for kprobes even if all of events are
> uprobes, because the extra cost should be small enough.

Masami, are you Ok with this one?

- Arnaldo
 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: David Ahern <dsahern@...il.com>
> Cc: He Kuang <hekuang@...wei.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kaixu Xia <xiakaixu@...wei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Link: http://lkml.kernel.org/n/1436445342-1402-39-git-send-email-wangnan0@huawei.com
> ---
>  tools/perf/util/probe-event.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index e720913..b94a8d7 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2789,7 +2789,7 @@ int add_perf_probe_events(struct perf_probe_event *pevs, int npevs,
>  {
>  	int i, ret;
>  
> -	ret = init_symbol_maps(pevs->uprobes);
> +	ret = init_symbol_maps(false);
>  	if (ret < 0)
>  		return ret;
>  
> -- 
> 2.1.0
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