[RFC 2/2] perf/core: change errno for sampling event not supported in hardware

[Vineet Gupta]

This allows userspace to identify this case specifically from the
catch all error msg it prints currently.

This is an ABI change

Before
-------
| # perf record ls
| Error:
| The sys_perf_event_open() syscall returned with 524 (Unknown error 524)
| for event (cycles:ppp).
| /bin/dmesg may provide additional information.
| No CONFIG_PERF_EVENTS=y kernel support configured?

Now
-------
| # perf record ls
| Error:
| PMU Hardware doesn't support sampling/overflow-interrupts.

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4e2ebf6f2f1f..41c5c7122987 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8435,7 +8435,7 @@ SYSCALL_DEFINE5(perf_event_open,
 
 	if (is_sampling_event(event)) {
 		if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
-			err = -ENOTSUPP;
+			err = -EOPNOTSUPP;
 			goto err_alloc;
 		}
 	}
-- 
2.5.0