linux-kernel - Re: [PATCH] perf probe: convert_name_to_addr() allocated the wrong size buffers for names

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Date:	Thu, 18 Oct 2012 12:10:53 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Hyeoncheol Lee <hyc.lee@...il.com>, acme@...stprotocols.net,
	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH] perf probe: convert_name_to_addr() allocated the wrong
 size buffers for names

(2012/10/18 10:20), Namhyung Kim wrote:
> Hi,
> 
> On Wed, 17 Oct 2012 20:06:54 +0900, Masami Hiramatsu wrote:
>> (2012/10/17 17:28), Hyeoncheol Lee wrote:
>>> The function allocated wrong size buffers for names
>>>
>>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>>> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>>> Signed-off-by: Hyeoncheol Lee <hyc.lee@...il.com>
>>> ---
>>>  tools/perf/util/probe-event.c |   11 +++++++----
>>>  1 file changed, 7 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>>> index 49a256e..5cd7c42 100644
>>> --- a/tools/perf/util/probe-event.c
>>> +++ b/tools/perf/util/probe-event.c
>>> @@ -2273,6 +2273,8 @@ int show_available_funcs(const char *target, struct strfilter *_filter,
>>>  	return available_user_funcs(target);
>>>  }
>>>  
>>
>> Please add a comment like below on the code.
>>
>> /*
>>  * sizeof(type) * 2 returns the maximum length of hexadecimal number
>>  * of type, because each half byte is encoding in one hex character.
>>  * Another 3 bytes are for "0x" and null character.
>>  */
>>
>> Others are OK for me :)
>>
>> Thanks!
>>
>>> +#define MAX_ADDRNAME_LEN  (3 + sizeof(unsigned long long) * 2)
>>> +
>>>  /*
>>>   * uprobe_events only accepts address:
>>>   * Convert function and any offset to address
>>> @@ -2332,7 +2334,7 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>>>  	if (!pev->group) {
>>>  		char *ptr1, *ptr2, *exec_copy;
>>>  
>>> -		pev->group = zalloc(sizeof(char *) * 64);
>>> +		pev->group = zalloc(sizeof(char) * 64);
> 
> I guess we don't need this 'sizeof(char)' part?

Indeed, we don't need it from the viewpoint of C.
However I'd like to keep that, because it gives us a hint that
this buffer is used for string.

Thank you,

> 
> 
>>>  		exec_copy = strdup(exec);
>>>  		if (!exec_copy) {
>>>  			ret = -ENOMEM;
>>> @@ -2352,14 +2354,15 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>>>  		free(exec_copy);
>>>  	}
>>>  	free(pp->function);
>>> -	pp->function = zalloc(sizeof(char *) * MAX_PROBE_ARGS);
>>> +	pp->function = zalloc(sizeof(char) * MAX_ADDRNAME_LEN);
> 
> Ditto.
> 
> Thanks,
> Namhyung
> 
> 
>>>  	if (!pp->function) {
>>>  		ret = -ENOMEM;
>>>  		pr_warning("Failed to allocate memory by zalloc.\n");
>>>  		goto out;
>>>  	}
>>> -	e_snprintf(pp->function, MAX_PROBE_ARGS, "0x%llx", vaddr);
>>> -	ret = 0;
>>> +	ret = e_snprintf(pp->function, MAX_ADDRNAME_LEN, "0x%llx", vaddr);
>>> +	if (ret > 0)
>>> +		ret = 0;
>>>  
>>>  out:
>>>  	if (map) {
>>>


-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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