[PATCH 1/2] perf: Add persistent events

[Borislav Petkov <bp@amd64.org>]

From: Borislav Petkov <bp@alien8.de>

Register and enable events marked as persistent right after perf events
has initialized.

Not-yet-signed-off-by: Borislav Petkov <bp@alien8.de>
---
 include/linux/ftrace_event.h |   10 +++++++
 include/linux/perf_event.h   |    1 +
 kernel/perf_event.c          |   59 +++++++++++++++++++++++++++++++++++++----
 kernel/trace/trace.h         |    1 -
 4 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index c0f4b36..b40d637 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -13,6 +13,8 @@ struct dentry;
 
 DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
 
+extern struct list_head ftrace_events;
+
 struct trace_print_flags {
 	unsigned long		mask;
 	const char		*name;
@@ -134,6 +136,7 @@ struct ftrace_event_call {
 	int			perf_refcount;
 	int			(*perf_event_enable)(struct ftrace_event_call *);
 	void			(*perf_event_disable)(struct ftrace_event_call *);
+	unsigned int		type;
 };
 
 #define PERF_MAX_TRACE_SIZE	2048
@@ -155,6 +158,13 @@ enum {
 	FILTER_PTR_STRING,
 };
 
+enum event_type_t {
+	EVENT_FLEXIBLE = 0x1,
+	EVENT_PINNED = 0x2,
+	EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
+	EVENT_PERSISTENT = 0x3,
+};
+
 extern int trace_event_raw_init(struct ftrace_event_call *call);
 extern int trace_define_field(struct ftrace_event_call *call, const char *type,
 			      const char *name, int offset, int size,
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index c8e3754..aa62c97 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -579,6 +579,7 @@ struct perf_event {
 	struct list_head		group_entry;
 	struct list_head		event_entry;
 	struct list_head		sibling_list;
+	struct list_head		pevent_entry;
 	int				nr_siblings;
 	int				group_flags;
 	struct perf_event		*group_leader;
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3d1552d..84f2f36 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -72,6 +72,11 @@ static atomic64_t perf_event_id;
 static DEFINE_SPINLOCK(perf_resource_lock);
 
 /*
+ * persistent events which are always on
+ */
+DEFINE_PER_CPU(struct list_head, persistent_events);
+
+/*
  * Architecture provided APIs - weak aliases:
  */
 extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event)
@@ -1017,12 +1022,6 @@ static int perf_event_refresh(struct perf_event *event, int refresh)
 	return 0;
 }
 
-enum event_type_t {
-	EVENT_FLEXIBLE = 0x1,
-	EVENT_PINNED = 0x2,
-	EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
-};
-
 static void ctx_sched_out(struct perf_event_context *ctx,
 			  struct perf_cpu_context *cpuctx,
 			  enum event_type_t event_type)
@@ -5385,6 +5384,8 @@ static void __init perf_event_init_all_cpus(void)
 	for_each_possible_cpu(cpu) {
 		cpuctx = &per_cpu(perf_cpu_context, cpu);
 		__perf_event_init_context(&cpuctx->ctx, NULL);
+
+		INIT_LIST_HEAD(&per_cpu(persistent_events, cpu));
 	}
 }
 
@@ -5405,12 +5406,16 @@ static void __perf_event_exit_cpu(void *info)
 	struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
 	struct perf_event_context *ctx = &cpuctx->ctx;
 	struct perf_event *event, *tmp;
+	struct list_head *pers_events_list = &__get_cpu_var(persistent_events);
 
 	list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
 		__perf_event_remove_from_context(event);
 	list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
 		__perf_event_remove_from_context(event);
+	list_for_each_entry_safe(event, tmp, pers_events_list, pevent_entry)
+		__perf_event_remove_from_context(event);
 }
+
 static void perf_event_exit_cpu(int cpu)
 {
 	struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
@@ -5456,6 +5461,46 @@ static struct notifier_block __cpuinitdata perf_cpu_nb = {
 	.priority		= 20,
 };
 
+static void __init perf_init_persistent_events(void)
+{
+
+	struct ftrace_event_call *call;
+	struct perf_event_attr attr;
+	struct perf_event *event;
+	int cpu;
+
+	list_for_each_entry(call, &ftrace_events, list) {
+
+		if (call->type != EVENT_PERSISTENT)
+			continue;
+
+		attr.type	= PERF_TYPE_TRACEPOINT,
+		attr.config	= call->id,
+		attr.size	= sizeof(attr),
+
+		get_online_cpus();
+
+		for_each_online_cpu(cpu) {
+			struct list_head *list;
+
+			event = perf_event_create_kernel_counter(&attr, cpu, -1, NULL);
+			if (IS_ERR(event)) {
+				printk(KERN_ERR "Error initializing persistent "
+						"event %s on cpu %d\n",
+						call->name, cpu);
+				break;
+			}
+
+			list = &per_cpu(persistent_events, cpu);
+			list_add(&event->pevent_entry, list);
+
+			perf_event_enable(event);
+
+		}
+		put_online_cpus();
+	}
+}
+
 void __init perf_event_init(void)
 {
 	perf_event_init_all_cpus();
@@ -5464,6 +5509,8 @@ void __init perf_event_init(void)
 	perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_ONLINE,
 			(void *)(long)smp_processor_id());
 	register_cpu_notifier(&perf_cpu_nb);
+
+	perf_init_persistent_events();
 }
 
 static ssize_t perf_show_reserve_percpu(struct sysdev_class *class,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 2825ef2..95f5611 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -786,7 +786,6 @@ filter_check_discard(struct ftrace_event_call *call, void *rec,
 }
 
 extern struct mutex event_mutex;
-extern struct list_head ftrace_events;
 
 extern const char *__start___trace_bprintk_fmt[];
 extern const char *__stop___trace_bprintk_fmt[];
-- 
1.7.1