linux-kernel - Re: [PATCH tracing/kprobes v2 2/5] tracing/kprobes: Avoid field name confliction

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Date:	Mon, 05 Oct 2009 20:16:58 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	"Frank Ch. Eigler" <fche@...hat.com>
Subject: Re: [PATCH tracing/kprobes v2 2/5] tracing/kprobes: Avoid field
 name confliction

On Fri, 2009-10-02 at 17:48 -0400, Masami Hiramatsu wrote:
> Check whether the argument name is conflict with other field names.
> 
> Changes in v2:
>  - Add common_lock_depth to reserved name list.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Mike Galbraith <efault@....de>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> Cc: Jim Keniston <jkenisto@...ibm.com>
> Cc: Frank Ch. Eigler <fche@...hat.com>
> ---
> 
>  kernel/trace/trace_kprobe.c |   65 +++++++++++++++++++++++++++++++++++--------
>  1 files changed, 53 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index f63ead0..eb1fa0f 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -38,6 +38,25 @@
>  #define MAX_EVENT_NAME_LEN 64
>  #define KPROBE_EVENT_SYSTEM "kprobes"
>  
> +/* Reserved field names */
> +#define FIELD_STRING_IP "ip"
> +#define FIELD_STRING_NARGS "nargs"
> +#define FIELD_STRING_RETIP "ret_ip"
> +#define FIELD_STRING_FUNC "func"
> +
> +const char *reserved_field_names[] = {
> +	"common_type",
> +	"common_flags",
> +	"common_preempt_count",
> +	"common_pid",
> +	"common_tgid",
> +	"common_lock_depth",
> +	FIELD_STRING_IP,
> +	FIELD_STRING_NARGS,
> +	FIELD_STRING_RETIP,
> +	FIELD_STRING_FUNC,
> +};
> +
>  /* currently, trace_kprobe only supports X86. */
>  
>  struct fetch_func {
> @@ -551,6 +570,20 @@ static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
>  	return ret;
>  }
>  
> +/* Return 1 if name is reserved or already used by another argument */
> +static int conflict_field_name(const char *name,
> +			       struct probe_arg *args, int narg)
> +{
> +	int i;
> +	for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
> +		if (!strcmp(reserved_field_names[i], name))
> +			return 1;
> +	for (i = 0; i < narg; i++)
> +		if (!strcmp(args[i].name, name))
> +			return 1;

Just a coding preference, but still, I've seen too many mistakes (made
them myself too).

	if (strcmp(args[i].name, name) == 0)

Looks better as a match then

	if (!strcmp(args[i].name, name))

That stands out to me as a miss match. But this is still just a
preference and not something to make me argue the patch.

-- Steve


> +	return 0;
> +}
> +


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