On 2015/06/13 4:27, Arnaldo Carvalho de Melo wrote:
> Hi Masami,
>
> I tried somethig with perf probe today, namely to ask for a
> variable that is a struct perf_event_attr to be collected after
> the perf_event_open syscall copies it from userspace, and got this
> message:
>
> [root@zoo ~]# perf probe SYSC_perf_event_open:23 args
> Failed to find 'args' in this function.
> Error: Failed to add events.
> [root@zoo ~]#
BTW, would you sure that the args exists at the given place?
I couldn't find it in kernel/events/core.c.
And also, could you make sure to run below command to clarify
the existed variables and its valid ranges?
# perf probe -V --range SYSC_perf_event_open
For example, I got below outouts.
# perf probe -V SYSC_perf_event_open:23
Available variables at SYSC_perf_event_open:23
@<SYSC_perf_event_open+502>
int cpu
int group_fd
long unsigned int flags
pid_t pid
struct perf_event_attr attr
# perf probe SYSC_perf_event_open:23 attr
perf_event_attr exceeds max-bitwidth. Cut down to 64 bits.
Added new event:
probe:SYSC_perf_event_open (on SYSC_perf_event_open:23 with attr)
You can now use it in all perf tools, such as:
perf record -e probe:SYSC_perf_event_open -aR sleep 1
Of course, this is still not enough, I must fix this as you suggested.
>
> Ok, I guess it should be instead:
>
> [root@zoo ~]# perf probe SYSC_perf_event_open:23 args
> The 'args' variable is a struct, this is not supported yet.
> Error: Failed to add events.
> [root@zoo ~]#
>
> :-)
>
--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu...@hitachi.com
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