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SubjectRe: How can I check creator of probe point?
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;
> }
>
>


--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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