linux-kernel - Re: How can I check creator of probe point?

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Date:	Thu, 16 Oct 2014 15:45:16 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: How can I check creator of probe point?

I'm going to try them.
Thanks a lot.


2014-10-16 ПРШФ 3:00, Masami Hiramatsu ОД Бл:
> Hello Gioh,
> 
> If you can use ftrace and perftool, you can also put probes on
> caller site. perf-probe will give you source-code level probes.
> Or, just trace kmalloc event with ftrace stacktrace option, which
> gives you caller information so that you can filter your driver
> by postprocessing.
> 
> Thank you,
> 
> (2014/10/14 11:16), Gioh Kim wrote:
>>
>> Hi,
>>
>> I am trying to find a way to make statistics for memory allocation of my device driver.
>> I want to know how much memory it allocates and how many times it calls kmalloc().
>>
>> So I am considering to use kprobe but I think it doesn't provide a way to identify who makes the probe point.
>> Can I distinguish kmalloc() calling only from my driver?
>>
>> For example I think it could be like this:
>>
>> diff --git a/samples/kprobes/kretprobe_example.c b/samples/kprobes/kretprobe_example.c
>> index 1041b67..5322e0a 100644
>> --- a/samples/kprobes/kretprobe_example.c
>> +++ b/samples/kprobes/kretprobe_example.c
>> @@ -32,6 +32,7 @@ MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
>>
>>   /* per-instance private data */
>>   struct my_data {
>> +       unsigned long signature;
>>          ktime_t entry_stamp;
>>   };
>>
>> @@ -43,8 +44,10 @@ static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
>>          if (!current->mm)
>>                  return 1;       /* Skip kernel threads */
>>
>> -       data = (struct my_data *)ri->data;
>> -       data->entry_stamp = ktime_get();
>> +       if (signature == 0xabcdabcd) {
>> +               data = (struct my_data *)ri->data;
>> +               data->entry_stamp = ktime_get();
>> +       }
>>          return 0;
>>   }
>>
>> @@ -60,10 +63,12 @@ static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
>>          s64 delta;
>>          ktime_t now;
>>
>> -       now = ktime_get();
>> -       delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
>> -       printk(KERN_INFO "%s returned %d and took %lld ns to execute\n",
>> -                       func_name, retval, (long long)delta);
>> +       if (signature == 0xabcdabcd) {
>> +               now = ktime_get();
>> +               delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
>> +               printk(KERN_INFO "%s returned %d and took %lld ns to execute\n",
>> +                      func_name, retval, (long long)delta);
>> +       }
>>          return 0;
>>   }
>>
>>
> 
> 
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