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

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Date:   Fri, 28 Feb 2020 18:20:04 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        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>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 03/13] kprobes: Add symbols for kprobe insn pages

On Fri, Feb 28, 2020 at 11:36:00PM +0900, Masami Hiramatsu wrote:
> 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?

note we already have bpf symbols as [bpf] module

jirka