linux-kernel - Re: [PATCH V3 03/13] kprobes: Add symbols for kprobe insn pages

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Date:   Fri, 28 Feb 2020 23:36:00 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 03/13] kprobes: Add symbols for kprobe insn pages

Hi Adrian,

On Fri, 28 Feb 2020 15:51:15 +0200
Adrian Hunter <adrian.hunter@...el.com> wrote:

> Symbols are needed for tools to describe instruction addresses. Pages
> allocated for kprobe's purposes need symbols to be created for them.
> Add such symbols to be visible via /proc/kallsyms.

I like this idea :)

> 
> Note: kprobe insn pages are not used if ftrace is configured. To see the
> effect of this patch, the kernel must be configured with:
> 
> 	# CONFIG_FUNCTION_TRACER is not set
> 	CONFIG_KPROBES=y
> 
> and for optimised kprobes:
> 
> 	CONFIG_OPTPROBES=y
> 
> Example on x86:
> 
> 	# perf probe __schedule
> 	Added new event:
> 	  probe:__schedule     (on __schedule)
> 	# cat /proc/kallsyms | grep '\[kprobe\]'
> 	ffffffffc0035000 t kprobe_insn_page     [kprobe]
> 	ffffffffc0054000 t kprobe_optinsn_page  [kprobe]

Could you make the module name as [kprobes] ?
BTW, it seems to pretend to be a module, but is there no concern of
confusing users? Shouldn't it be [*kprobes] so that it is non-exist
module name?

Thank you,



-- 
Masami Hiramatsu <mhiramat@...nel.org>