perf_counter: x86: Allow unpriviliged use of NMIs

Apply sysctl_perf_counter_priv to NMIs. Also, fail the counter
creation instead of silently down-grading to regular interrupts.

[ Impact: allow wider perf-counter usage ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 88ae8cebf3c..c19e927b697 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -280,8 +280,11 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
          * If privileged enough, allow NMI events:
          */
         hwc->nmi = 0;
-        if (capable(CAP_SYS_ADMIN) && hw_event->nmi)
+        if (hw_event->nmi) {
+                if (sysctl_perf_counter_priv && !capable(CAP_SYS_ADMIN))
+                        return -EACCES;
                 hwc->nmi = 1;
+        }
 
         hwc->irq_period = hw_event->irq_period;
         if ((s64)hwc->irq_period <= 0 || hwc->irq_period > x86_pmu.max_period)