linux-kernel - Re: [PATCHv10 2.6.35-rc6-tip 8/14] trace: Extract out common code for kprobes/uprobes traceevents.

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Date:	Tue, 27 Jul 2010 22:22:53 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Mark Wielaard <mjw@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Naren A Devaiah <naren.devaiah@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	2nddept-manager@....hitachi.co.jp
Subject: Re: [PATCHv10 2.6.35-rc6-tip 8/14]  trace: Extract out common code
 for kprobes/uprobes traceevents.

Hi Srikar,

Srikar Dronamraju wrote:
> Move common parts of trace_kprobe.c and trace_uprobe.c
> Adjust kernel/trace/trace_kprobe.c after moving common code to
> kernel/trace/trace_probe.h and kernel/trace/trace_probe.c.
> 
> TODO: Merge both events to a single probe event.
> 
> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
[...]
> +/* Recursive argument parser */
> +static int parse_probe_arg(char *arg, const struct fetch_type *t,
> +		     struct fetch_param *f, int is_return, bool is_kprobe)

If you use "bool" for "is_kprobe", change "is_return" type too.

And, maybe you missed that the fetch function supports "string" type now,
which needs a bit different manner for storing fetched value. You can find
store_trace_args() function in trace_kprobe.c.

BTW, current fetch functions doesn't support fetching "paged-out" user-variables
because kprobe can't sleep inside its handler.
However, user-space memory can be paged out, and I assume that uprobes allows
its handler to I/O (and yield). If so, it can wait for accessing paged-out
variable, can't it?

Thank you,

-- 
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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