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

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Date:	Mon, 05 Oct 2009 21:07:20 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	rostedt@...dmis.org
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



Steven Rostedt wrote:
> 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.

Agreed, !strcmp() pattern would better be warned by checkpatch.pl :-)
I'll fix that.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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