From: Adrian Hunter <adrian.hunter@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>, "H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Leo Yan <leo.yan@linaro.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V4 03/13] kprobes: Add symbols for kprobe insn pages
Date: Tue, 24 Mar 2020 14:54:05 +0200 [thread overview]
Message-ID: <f79e6ff3-5459-64c9-385a-68ab10b1c33c@intel.com> (raw)
In-Reply-To: <20200324123108.GO20696@hirez.programming.kicks-ass.net>
On 24/03/20 2:31 pm, Peter Zijlstra wrote:
> On Wed, Mar 04, 2020 at 11:06:23AM +0200, Adrian Hunter 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.
>>
>> 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 '\[__builtin__kprobes\]'
>> ffffffffc00d4000 t kprobe_insn_page [__builtin__kprobes]
>> ffffffffc00d6000 t kprobe_optinsn_page [__builtin__kprobes]
>>
>
> I'm confused; why are you iterating pages and not slots? A 'page' is not
> a symbol, they contain text, sometimes.
A symbol for each slot is not necessary, and it doesn't look like the slots
can be walked without taking a mutex, which is a problem for kallsyms.
>
> If you iterate slots you can even get them a proper name; something
> like:
>
> optinsn-sym+xxx [__builtin__kprobes]
>
> insn-sym+xxx [__builtin__kprobes]
>
Addresses resolve to the previous symbol plus an offset, so it seems to me
that the only difference in what you are proposing is the symbol name, which
can be changed if you like.
next prev parent reply other threads:[~2020-03-24 12:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 9:06 [PATCH V4 00/13] perf/x86: Add perf text poke events Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 01/13] perf: Add perf text poke event Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 02/13] perf/x86: Add support for perf text poke event for text_poke_bp_batch() callers Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 03/13] kprobes: Add symbols for kprobe insn pages Adrian Hunter
2020-03-05 5:58 ` Masami Hiramatsu
2020-03-05 6:10 ` Alexei Starovoitov
2020-03-05 9:04 ` Masami Hiramatsu
2020-03-24 12:31 ` Peter Zijlstra
2020-03-24 12:54 ` Adrian Hunter [this message]
2020-03-04 9:06 ` [PATCH V4 04/13] kprobes: Add perf ksymbol events " Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 05/13] perf/x86: Add perf text poke events for kprobes Adrian Hunter
2020-03-24 12:21 ` Peter Zijlstra
2020-03-26 1:58 ` Masami Hiramatsu
2020-03-26 7:42 ` Adrian Hunter
2020-03-27 8:36 ` [PATCH V5 " Adrian Hunter
2020-03-31 23:44 ` Masami Hiramatsu
2020-04-01 10:13 ` Peter Zijlstra
2020-03-04 9:06 ` [PATCH V4 06/13] ftrace: Add symbols for ftrace trampolines Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 07/13] ftrace: Add perf ksymbol events " Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 08/13] ftrace: Add perf text poke " Adrian Hunter
2020-04-01 10:09 ` Peter Zijlstra
2020-04-01 10:42 ` Adrian Hunter
2020-04-01 11:14 ` Peter Zijlstra
2020-03-04 9:06 ` [PATCH V4 09/13] perf kcore_copy: Fix module map when there are no modules loaded Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 10/13] perf evlist: Disable 'immediate' events last Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 11/13] perf tools: Add support for PERF_RECORD_TEXT_POKE Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 12/13] perf tools: Add support for PERF_RECORD_KSYMBOL_TYPE_OOL Adrian Hunter
2020-03-04 9:06 ` [PATCH V4 13/13] perf intel-pt: Add support for text poke events Adrian Hunter
2020-03-16 7:07 ` [PATCH V4 00/13] perf/x86: Add perf " Adrian Hunter
2020-03-24 9:29 ` Adrian Hunter
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