perfcounters: provide expansion room in the ABI
Impact: ABI change
This expands several fields in the perf_counter_hw_event struct and adds
a "flags" argument to the perf_counter_open system call, in order that
features can be added in future without ABI changes.
In particular the record_type field is expanded to 64 bits, and the
space for flag bits has been expanded from 32 to 64 bits.
This also adds some new fields:
* read_format (64 bits) is intended to provide a way to specify what
userspace wants to get back when it does a read() on a simple
(non-interrupting) counter;
* exclude_idle (1 bit) provides a way for userspace to ask that events
that occur when the cpu is idle be excluded;
* extra_config_len will provide a way for userspace to supply an
arbitrary amount of extra machine-specific PMU configuration data
immediately following the perf_counter_hw_event struct, to allow
sophisticated users to program things such as instruction matching
CAMs and address range registers;
* __reserved_3 and __reserved_4 provide space for future expansion.
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 16b14ba..b2e8389 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1683,16 +1683,16 @@
}
/**
- * sys_perf_task_open - open a performance counter, associate it to a task/cpu
+ * sys_perf_counter_open - open a performance counter, associate it to a task/cpu
*
* @hw_event_uptr: event type attributes for monitoring/sampling
* @pid: target pid
* @cpu: target cpu
* @group_fd: group leader counter fd
*/
-SYSCALL_DEFINE4(perf_counter_open,
+SYSCALL_DEFINE5(perf_counter_open,
const struct perf_counter_hw_event __user *, hw_event_uptr,
- pid_t, pid, int, cpu, int, group_fd)
+ pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
{
struct perf_counter *counter, *group_leader;
struct perf_counter_hw_event hw_event;
@@ -1703,6 +1703,10 @@
int fput_needed2 = 0;
int ret;
+ /* for future expandability... */
+ if (flags)
+ return -EINVAL;
+
if (copy_from_user(&hw_event, hw_event_uptr, sizeof(hw_event)) != 0)
return -EFAULT;