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>

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 88ae8ce..c19e927 100644 (file)
--- 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)