linux-kernel - Re: [PATCH 2/4] perf_event: fix getting point

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Message-ID: <20091215135855.GA5833@nowhere>
Date:	Tue, 15 Dec 2009 14:58:58 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] perf_event: fix getting point

On Tue, Dec 15, 2009 at 07:20:26PM +0800, Xiao Guangrong wrote:
> The point that got by raw_field_ptr() is point to @data offset not
> tracepoint saved.
> 
> Introduce raw_field_arry() to get arry data is tracepoint save
> arry to it.


Could you please rename it into raw_field_array()?
I feel like...a kind of loss there :)



> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  tools/perf/builtin-sched.c          |    3 +--
>  tools/perf/util/trace-event-parse.c |   25 ++++++++++++++++++++++---
>  tools/perf/util/trace-event.h       |    3 +++
>  3 files changed, 26 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index d67f274..8df982e 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -630,8 +630,7 @@ static void test_calibrations(void)
>  
>  #define FILL_ARRAY(ptr, array, event, data)			\
>  do {								\
> -	void *__array = raw_field_ptr(event, #array, data);	\
> -	memcpy(ptr.array, __array, sizeof(ptr.array));	\
> +	raw_field_arry(event, #array, data, ptr.array, sizeof(ptr.array));\
>  } while(0)
>  
>  #define FILL_COMMON_FIELDS(ptr, event, data)			\
> diff --git a/tools/perf/util/trace-event-parse.c b/tools/perf/util/trace-event-parse.c
> index c5c32be..b0ee64f 100644
> --- a/tools/perf/util/trace-event-parse.c
> +++ b/tools/perf/util/trace-event-parse.c
> @@ -840,7 +840,7 @@ static int event_read_fields(struct event *event, struct format_field **fields)
>  			field->flags |= FIELD_IS_ARRAY;
>  
>  			type = read_token(&token);
> -		        while (strcmp(token, "]") != 0) {
> +			while (strcmp(token, "]") != 0) {
>  				if (last_type == EVENT_ITEM &&
>  				    type == EVENT_ITEM)
>  					len = 2;
> @@ -1919,13 +1919,32 @@ raw_field_value(struct event *event, const char *name, void *data)
>  
>  void *raw_field_ptr(struct event *event, const char *name, void *data)
>  {
> +	void *ptr;
> +	unsigned long long value;
> +
> +	value = raw_field_value(event, name, data);
> +
> +	if (!value)
> +		return NULL;
> +
> +	memcpy(&ptr, &value, sizeof(ptr));



Could you perhaps just do

ptr = (void *)value; ?

This memcpy suggest we are dereferencing some field while
actually just copy a pointer.

Thanks!

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