perf/x86: Support CPU specific sysfs events

Add a way for the CPU initialization code to register additional
events, and merge them into the events attribute directory. Used
in the next patch.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: jolsa@redhat.com
Cc: namhyung.kim@lge.com
Link: http://lkml.kernel.org/r/1359040242-8269-2-git-send-email-eranian@google.com
[ small cleanups ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[ merge_attr returns a **, not just * ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

arch/x86/kernel/cpu/perf_event.c

@@ -1330,6 +1330,32 @@ static void __init filter_events(struct attribute **attrs)
 	}
 }
 
+/* Merge two pointer arrays */
+static __init struct attribute **merge_attr(struct attribute **a, struct attribute **b)
+{
+	struct attribute **new;
+	int j, i;
+
+	for (j = 0; a[j]; j++)
+		;
+	for (i = 0; b[i]; i++)
+		j++;
+	j++;
+
+	new = kmalloc(sizeof(struct attribute *) * j, GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	j = 0;
+	for (i = 0; a[i]; i++)
+		new[j++] = a[i];
+	for (i = 0; b[i]; i++)
+		new[j++] = b[i];
+	new[j] = NULL;
+
+	return new;
+}
+
 static ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr,
 			  char *page)
 {
@@ -1469,6 +1495,14 @@ static int __init init_hw_perf_events(void)
 	else
 		filter_events(x86_pmu_events_group.attrs);
 
+	if (x86_pmu.cpu_events) {
+		struct attribute **tmp;
+
+		tmp = merge_attr(x86_pmu_events_group.attrs, x86_pmu.cpu_events);
+		if (!WARN_ON(!tmp))
+			x86_pmu_events_group.attrs = tmp;
+	}
+
 	pr_info("... version:                %d\n",     x86_pmu.version);
 	pr_info("... bit width:              %d\n",     x86_pmu.cntval_bits);
 	pr_info("... generic registers:      %d\n",     x86_pmu.num_counters);

arch/x86/kernel/cpu/perf_event.h

@@ -357,6 +357,7 @@ struct x86_pmu {
 	struct attribute **format_attrs;
 
 	ssize_t		(*events_sysfs_show)(char *page, u64 config);
+	struct attribute **cpu_events;
 
 	/*
 	 * CPU Hotplug hooks