PERF_EVENT_IOC_SET_FILTER has different values based on bitness

[David Ahern]

32-bit perf binaries are not able to set filters on 64-bit kernels.

   $ perf record -e  net:netif_receive_skb --filter 'name == "eth1"
   Error: failed to set filter with 25 (Inappropriate ioctl for device)

The reason is that the definition of PERF_EVENT_IOC_SET_FILTER contains 
a pointer:

#define PERF_EVENT_IOC_SET_FILTER       _IOW('$', 6, char *)

the size of which of course differs for 32-bit and 64-bit. This has been 
there since the original commit (6fb2915df7f07) back in 2009.

Thoughts on how to fix this? Changing the definition of SET_FILTER 
breaks existing setups so that rules it out. What about something like this:

#define PERF_EVENT_IOC_SET_FILTER_32       _IOW('$', 6, u32)

and then

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 963bf139e2b2..c805132ac1cf 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3714,6 +3714,7 @@ static long perf_ioctl(struct file *file, unsigned 
int cmd, unsigned long arg)
    }

    case PERF_EVENT_IOC_SET_FILTER:
+   case PERF_EVENT_IOC_SET_FILTER_32:
        return perf_event_set_filter(event, (void __user *)arg);

    default:

David
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