perf_counter: sysctl for system wide perf counters

Impact: add sysctl for paranoid/relaxed perfcounters policy

Allow the use of system wide perf counters to everybody, but provide
a sysctl to disable it for the paranoid security minded.

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: <20090409085524.514046352@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 76376ecb23b5..7efb7ebaaae0 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -42,6 +42,8 @@ static atomic_t nr_mmap_tracking __read_mostly;
 static atomic_t nr_munmap_tracking __read_mostly;
 static atomic_t nr_comm_tracking __read_mostly;
 
+int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
+
 /*
  * Mutex for (sysadmin-configurable) counter reservations:
  */
@@ -1132,7 +1134,7 @@ static struct perf_counter_context *find_get_context(pid_t pid, int cpu)
          */
         if (cpu != -1) {
                 /* Must be root to operate on a CPU counter: */
-                if (!capable(CAP_SYS_ADMIN))
+                if (sysctl_perf_counter_priv && !capable(CAP_SYS_ADMIN))
                         return ERR_PTR(-EACCES);
 
                 if (cpu < 0 || cpu > num_possible_cpus())