From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Tom Zanussi <tom.zanussi@linux.intel.com>,
linux-rt-users@vger.kernel.org,
linux-trace-users@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Clark Williams <williams@redhat.com>,
Jiri Olsa <jolsa@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Namhyung Kim <namhyung@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [PATCH 00/18] [ANNOUNCE] Dynamically created function based events
Date: Sat, 3 Feb 2018 10:27:59 -0500 [thread overview]
Message-ID: <20180203102759.56d03ada@gandalf.local.home> (raw)
In-Reply-To: <20180203223817.0c8cc485d8163ad84039cf02@kernel.org>
On Sat, 3 Feb 2018 22:38:17 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> This seems very similar feature of what kprobe-based event does.
It is similar, but not the same as kprobes. It only focuses on
functions and their arguments, and should not require any disassembling
(no knowledge of regs required). Any need to see anything within the
function will still require kprobe based help.
>
> Earlier version of kprobe-based event supported Nth argument, but I decided
> to drop it because we can not ensure the "function signature" from kernel
> binary. It has been passed to "perf probe", so that we can define line-level
> granularity.
Sure, and if we get a wrong function, which can happen, the code is set
up not to break anything. You only get garbage output.
>
> Of course if it is easy to support "argN" again as it does if the arch's
> calling convention is clearly stated. (and now kprobe is based on ftrace
> if it is on the entry of functions)
>
> So my question is, what is the difference of those from the user perspective?
> Only event syntax is a problem?
> I'm very confusing...
Again, this is not a kprobe replacement. It is somewhat of a syntax
issue. I want this to be very simple and not need a disassembler. For
indexing of structures one may use gdb, but that's about it. You could
get the same info from counting what's in a structure itself.
I based some of the code from kprobes too. But I wanted this to be
simpler, and as such, not as powerful as kprobes. More of a "poor mans"
kprobe ;-) Where you are limited to functions and their arguments. If
you need more power, switch to kprobes. In other words, its just an
added stepping stone.
Also, this should work without kprobe support, only ftrace, and function
args from the arch.
-- Steve
next prev parent reply other threads:[~2018-02-03 15:27 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-02 23:04 [PATCH 00/18] [ANNOUNCE] Dynamically created function based events Steven Rostedt
2018-02-02 23:04 ` [PATCH 01/18] tracing: Add " Steven Rostedt
2018-02-05 8:24 ` Jiri Olsa
2018-02-05 15:00 ` Steven Rostedt
2018-02-07 3:09 ` Steven Rostedt
2018-02-07 12:06 ` Jiri Olsa
2018-02-02 23:05 ` [PATCH 02/18] tracing: Add documentation for " Steven Rostedt
2018-02-02 23:05 ` [PATCH 03/18] tracing: Add simple arguments to " Steven Rostedt
2018-02-08 10:18 ` Namhyung Kim
2018-02-08 15:37 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 04/18] tracing/x86: Add arch_get_func_args() function Steven Rostedt
2018-02-05 16:33 ` Masami Hiramatsu
2018-02-05 17:06 ` Steven Rostedt
2018-02-08 5:28 ` Namhyung Kim
2018-02-08 15:29 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 05/18] tracing: Add hex print for dynamic ftrace based events Steven Rostedt
2018-02-02 23:05 ` [PATCH 06/18] tracing: Add indirect offset to args of " Steven Rostedt
2018-02-02 23:05 ` [PATCH 07/18] tracing: Add dereferencing multiple fields per arg Steven Rostedt
2018-02-02 23:05 ` [PATCH 08/18] tracing: Add "unsigned" to function based events Steven Rostedt
2018-02-02 23:05 ` [PATCH 09/18] tracing: Add indexing of arguments for " Steven Rostedt
2018-02-08 10:59 ` Namhyung Kim
2018-02-08 15:43 ` Steven Rostedt
2018-02-08 23:56 ` Namhyung Kim
2018-02-09 0:19 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 10/18] tracing: Make func_type enums for easier comparing of arg types Steven Rostedt
2018-02-02 23:05 ` [PATCH 11/18] tracing: Add symbol type to function based events Steven Rostedt
2018-02-08 11:03 ` Namhyung Kim
2018-02-08 15:48 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 12/18] tracing: Add accessing direct address from " Steven Rostedt
2018-02-09 0:34 ` Namhyung Kim
2018-02-09 1:10 ` Steven Rostedt
2018-02-09 22:07 ` Steven Rostedt
2018-02-12 2:06 ` Namhyung Kim
2018-02-12 15:47 ` Masami Hiramatsu
2018-02-12 16:47 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 13/18] tracing: Add array type to " Steven Rostedt
2018-02-03 13:56 ` Masami Hiramatsu
2018-02-03 15:29 ` Steven Rostedt
2018-02-04 3:50 ` Masami Hiramatsu
2018-02-09 1:17 ` Namhyung Kim
2018-02-09 1:54 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 14/18] tracing: Have char arrays be strings for " Steven Rostedt
2018-02-02 23:05 ` [PATCH 15/18] tracing: Add string type for dynamic strings in " Steven Rostedt
2018-02-09 3:15 ` Namhyung Kim
2018-02-09 3:31 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 16/18] tracing: Add NULL to skip args for " Steven Rostedt
2018-02-02 23:05 ` [PATCH 17/18] tracing: Add indirect to indirect access " Steven Rostedt
2018-02-09 5:13 ` Namhyung Kim
2018-02-09 15:47 ` Steven Rostedt
2018-02-09 17:18 ` Steven Rostedt
2018-02-12 2:15 ` Namhyung Kim
2018-02-12 17:23 ` Steven Rostedt
2018-02-13 9:27 ` Namhyung Kim
2018-02-13 15:28 ` Steven Rostedt
2018-02-02 23:05 ` [PATCH 18/18] tracing/perf: Allow perf to use " Steven Rostedt
2018-02-03 13:38 ` [PATCH 00/18] [ANNOUNCE] Dynamically created " Masami Hiramatsu
2018-02-03 15:27 ` Steven Rostedt [this message]
2018-02-04 3:57 ` Masami Hiramatsu
2018-02-03 17:04 ` Mathieu Desnoyers
2018-02-03 19:02 ` Steven Rostedt
2018-02-03 20:52 ` Alexei Starovoitov
2018-02-03 21:08 ` Steven Rostedt
2018-02-03 21:30 ` Alexei Starovoitov
2018-02-04 2:37 ` Namhyung Kim
2018-02-04 15:50 ` Mathieu Desnoyers
2018-02-03 21:17 ` Steven Rostedt
2018-02-03 21:38 ` Alexei Starovoitov
2018-02-04 2:25 ` Namhyung Kim
2018-02-05 15:02 ` Steven Rostedt
2018-02-05 13:53 ` Juri Lelli
2018-02-05 15:07 ` Steven Rostedt
2018-02-03 21:43 ` Linus Torvalds
2018-02-04 15:30 ` Mathieu Desnoyers
2018-02-04 15:47 ` Steven Rostedt
2018-02-04 19:39 ` Linus Torvalds
2018-02-05 10:09 ` Peter Zijlstra
2018-02-05 15:10 ` Steven Rostedt
2018-02-05 15:14 ` Masami Hiramatsu
2018-02-03 18:52 ` Steven Rostedt
2018-02-05 10:23 ` Juri Lelli
2018-02-05 10:49 ` Daniel Bristot de Oliveira
2018-02-05 15:11 ` Steven Rostedt
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