Re: [PATCH v4 1/6] perf: Introduce ioctl to communicate driver configuration to kernel

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Nov 28, 2018 at 03:01:13PM -0700, Mathieu Poirier wrote:
> Adding a new IOCTL command to communicate PMU specific configuration to
> PMU kernel drivers.  This can be anything a PMU might need for
> configuration that doesn't fit in the perf_event_attr structure, such
> as the CoreSight sink to use for a session.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>  include/uapi/linux/perf_event.h       | 1 +
>  tools/include/uapi/linux/perf_event.h | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 9de8780ac8d9..bb558caeb33b 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -462,6 +462,7 @@ struct perf_event_query_bpf {
>  #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
>  #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
>  #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
> +#define PERF_EVENT_IOC_SET_DRV_CONFIG		_IOW('$', 12, char *)


A generic "char *" that the kernel is then going to parse?  Can you make
any more flexible of a new syscall to the kernel that allows anyone to
do anything with this?  :)

Please make this a lot more specific, this is way to generic, sorry.

greg k-h