linux-kernel - Re: [RFC PATCH 1/3] perf probe: Init symbol as kprobe if any pev is kprobe

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Message-ID: <558E50C2.2030807@hitachi.com>
Date:	Sat, 27 Jun 2015 16:29:06 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Wang Nan <wangnan0@...wei.com>, acme@...nel.org, ast@...mgrid.com,
	brendan.d.gregg@...il.com, daniel@...earbox.net,
	namhyung@...nel.org, paulus@...ba.org, a.p.zijlstra@...llo.nl,
	mingo@...hat.com, jolsa@...nel.org, dsahern@...il.com
CC:	linux-kernel@...r.kernel.org, lizefan@...wei.com,
	hekuang@...wei.com, xiakaixu@...wei.com, pi3orama@....com
Subject: Re: [RFC PATCH 1/3] perf probe: Init symbol as kprobe if any pev
 is kprobe

On 2015/06/25 19:37, Wang Nan wrote:
> Before this patch, add_perf_probe_events() init symbol maps only for
> uprobe if the first pev passed to it is a uprobe event. However, with
> the incoming BPF uprobe support, now it will be possible to pass an
> array with combined kprobe and uprobe events to add_perf_probe_events().

This description is not correct. Actually, add_perf_probe_events already
supports mix of uprobes and kprobes. However, from the command line syntax
constrains the first elements of the probe_event arrays must be kprobes.
So, if the array starts with uprobes, no kprobes should be there.

> 
> This patch check all pevs instead of the first one, and init kernel
> symbol if any events is not uprobe.

Anyway, I prefer to call init_symbol_maps() with "false" :)

Thank you,

> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> ---
>  tools/perf/util/probe-event.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index b386d2f..a2b3026 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2802,8 +2802,21 @@ int cleanup_perf_probe_event(struct perf_probe_event *pev)
>  int add_perf_probe_events(struct perf_probe_event *pevs, int npevs, bool cleanup)
>  {
>  	int i, ret;
> +	bool user_only = true;
>  
> -	ret = init_symbol_maps(pevs->uprobes);
> +	/* If any pev is kprobe, init kernel symbols. */
> +	for (i = 0; i < npevs; i++) {
> +		if (!pevs[i].uprobes) {
> +			user_only = false;
> +			break;
> +		}
> +	}
> +
> +	/*
> +	 * Compiler can drop user_only:
> +	 *  ret = init_symbol_maps(i >= npevs);
> +	 */
> +	ret = init_symbol_maps(user_only);
>  	if (ret < 0)
>  		return ret;
>  
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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