linux-kernel - Re: [PATCH 02/16] perf symbol: remove unused 'end' arg in kallsyms parse cb

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Date:	Fri, 10 Aug 2012 11:39:27 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Cody P Schafer <cody@...ux.vnet.ibm.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Matt Hellsley <matthltc@...ibm.com>,
	David Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [PATCH 02/16] perf symbol: remove unused 'end' arg in kallsyms parse cb

Hi, Cody

On Thu,  9 Aug 2012 15:18:27 -0700, Cody P. Schafer wrote:
> kallsyms__parse() takes a callback that is called on every discovered
> symbol. As /proc/kallsyms does not supply symbol sizes, the callback was
> simply called with end=start, faking the symbol size to 1.
>
> All of the callbacks (there are 2) used in calls to kallsyms__parse()
> are _only_ used as callbacks for kallsyms__parse().
>
> Given that kallsyms__parse() lacks real information about what
> end/length should be, don't make up a length in kallsyms__parse().
> Instead have the callbacks handle guessing the length.
>
> Also relocate a comment regarding symbol creation to the callback which
> does symbol creation (kallsyms__parse() is not in general used to create
> symbols).
>
> Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
> ---
>  tools/perf/util/event.c  |  2 +-
>  tools/perf/util/symbol.c | 21 ++++++++++-----------
>  tools/perf/util/symbol.h |  2 +-
>  3 files changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 2a6f33c..3a0f1a5 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -412,7 +412,7 @@ struct process_symbol_args {
>  };
>  
>  static int find_symbol_cb(void *arg, const char *name, char type,
> -			  u64 start, u64 end __used)
> +			  u64 start)
>  {
>  	struct process_symbol_args *args = arg;
>  
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index df4736d..b2f7597 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -574,7 +574,7 @@ size_t dso__fprintf(struct dso *dso, enum map_type type, FILE *fp)
>  
>  int kallsyms__parse(const char *filename, void *arg,
>  		    int (*process_symbol)(void *arg, const char *name,
> -					  char type, u64 start, u64 end))
> +					  char type, u64 start))
>  {
>  	char *line = NULL;
>  	size_t n;
> @@ -614,13 +614,8 @@ int kallsyms__parse(const char *filename, void *arg,
>  			break;
>  		}
>  
> -		/*
> -		 * module symbols are not sorted so we add all
> -		 * symbols, setting length to 1, and rely on
> -		 * symbols__fixup_end() to fix it up.
> -		 */
>  		err = process_symbol(arg, symbol_name,
> -				     symbol_type, start, start);
> +				     symbol_type, start);
>  		if (err)
>  			break;
>  	}
> @@ -647,7 +642,7 @@ static u8 kallsyms2elf_type(char type)
>  }
>  
>  static int map__process_kallsym_symbol(void *arg, const char *name,
> -				       char type, u64 start, u64 end)
> +				       char type, u64 start)
>  {
>  	struct symbol *sym;
>  	struct process_kallsyms_args *a = arg;
> @@ -656,8 +651,12 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
>  	if (!symbol_type__is_a(type, a->map->type))
>  		return 0;
>  
> -	sym = symbol__new(start, end - start + 1,
> -			  kallsyms2elf_type(type), name);
> +	/*
> +	 * module symbols are not sorted so we add all
> +	 * symbols, setting length to 1, and rely on
> +	 * symbols__fixup_end() to fix it up.
> +	 */
> +	sym = symbol__new(start, 1, kallsyms2elf_type(type), name);

I guess that length of 1 effectively same as zero length in this case
since we end up calling symbols__fixup_end. The 'end - start + 1' part
looks like a leftover from previous change and not needed anymore -
KSYM_NAME_LEN check too, IMHO - so I suggest using 0 length to make it
clear.

And it seems you need to rebase the series onto Arnaldo's current
perf/core branch which separates out ELF bits to symbol-elf.c.

Thanks,
Namhyung


>  	if (sym == NULL)
>  		return -ENOMEM;
>  	/*
> @@ -2528,7 +2527,7 @@ struct process_args {
>  };
>  
>  static int symbol__in_kernel(void *arg, const char *name,
> -			     char type __used, u64 start, u64 end __used)
> +			     char type __used, u64 start)
>  {
>  	struct process_args *args = arg;
>  
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 1fe733a..c8ec1d7 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -297,7 +297,7 @@ bool __dsos__read_build_ids(struct list_head *head, bool with_hits);
>  int build_id__sprintf(const u8 *build_id, int len, char *bf);
>  int kallsyms__parse(const char *filename, void *arg,
>  		    int (*process_symbol)(void *arg, const char *name,
> -					  char type, u64 start, u64 end));
> +					  char type, u64 start));
>  
>  void machine__destroy_kernel_maps(struct machine *machine);
>  int __machine__create_kernel_maps(struct machine *machine, struct dso *kernel);
--
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