perf: add the necessary core perf APIs when accessing events counters in eBPF programs
This patch add three core perf APIs:
- perf_event_attrs(): export the struct perf_event_attr from struct
perf_event;
- perf_event_get(): get the struct perf_event from the given fd;
- perf_event_read_local(): read the events counters active on the
current CPU;
These APIs are needed when accessing events counters in eBPF programs.
The API perf_event_read_local() comes from Peter and I add the
corresponding SOB.
Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2027809..092a0e8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -641,6 +641,8 @@
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
extern void perf_event_delayed_put(struct task_struct *task);
+extern struct perf_event *perf_event_get(unsigned int fd);
+extern const struct perf_event_attr *perf_event_attrs(struct perf_event *event);
extern void perf_event_print_debug(void);
extern void perf_pmu_disable(struct pmu *pmu);
extern void perf_pmu_enable(struct pmu *pmu);
@@ -659,6 +661,7 @@
void *context);
extern void perf_pmu_migrate_context(struct pmu *pmu,
int src_cpu, int dst_cpu);
+extern u64 perf_event_read_local(struct perf_event *event);
extern u64 perf_event_read_value(struct perf_event *event,
u64 *enabled, u64 *running);
@@ -979,6 +982,12 @@
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }
static inline void perf_event_delayed_put(struct task_struct *task) { }
+static inline struct perf_event *perf_event_get(unsigned int fd) { return ERR_PTR(-EINVAL); }
+static inline const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
+{
+ return ERR_PTR(-EINVAL);
+}
+static inline u64 perf_event_read_local(struct perf_event *event) { return -EINVAL; }
static inline void perf_event_print_debug(void) { }
static inline int perf_event_task_disable(void) { return -EINVAL; }
static inline int perf_event_task_enable(void) { return -EINVAL; }
@@ -1011,6 +1020,7 @@
static inline void perf_event_disable(struct perf_event *event) { }
static inline int __perf_event_disable(void *info) { return -1; }
static inline void perf_event_task_tick(void) { }
+static inline int perf_event_release_kernel(struct perf_event *event) { return 0; }
#endif
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d3dae34..e2c6a88 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3212,6 +3212,59 @@
return __perf_event_count(event);
}
+/*
+ * NMI-safe method to read a local event, that is an event that
+ * is:
+ * - either for the current task, or for this CPU
+ * - does not have inherit set, for inherited task events
+ * will not be local and we cannot read them atomically
+ * - must not have a pmu::count method
+ */
+u64 perf_event_read_local(struct perf_event *event)
+{
+ unsigned long flags;
+ u64 val;
+
+ /*
+ * Disabling interrupts avoids all counter scheduling (context
+ * switches, timer based rotation and IPIs).
+ */
+ local_irq_save(flags);
+
+ /* If this is a per-task event, it must be for current */
+ WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
+ event->hw.target != current);
+
+ /* If this is a per-CPU event, it must be for this CPU */
+ WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
+ event->cpu != smp_processor_id());
+
+ /*
+ * It must not be an event with inherit set, we cannot read
+ * all child counters from atomic context.
+ */
+ WARN_ON_ONCE(event->attr.inherit);
+
+ /*
+ * It must not have a pmu::count method, those are not
+ * NMI safe.
+ */
+ WARN_ON_ONCE(event->pmu->count);
+
+ /*
+ * If the event is currently on this CPU, its either a per-task event,
+ * or local to this CPU. Furthermore it means its ACTIVE (otherwise
+ * oncpu == -1).
+ */
+ if (event->oncpu == smp_processor_id())
+ event->pmu->read(event);
+
+ val = local64_read(&event->count);
+ local_irq_restore(flags);
+
+ return val;
+}
+
static u64 perf_event_read(struct perf_event *event)
{
/*
@@ -8574,6 +8627,31 @@
WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
}
+struct perf_event *perf_event_get(unsigned int fd)
+{
+ int err;
+ struct fd f;
+ struct perf_event *event;
+
+ err = perf_fget_light(fd, &f);
+ if (err)
+ return ERR_PTR(err);
+
+ event = f.file->private_data;
+ atomic_long_inc(&event->refcount);
+ fdput(f);
+
+ return event;
+}
+
+const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
+{
+ if (!event)
+ return ERR_PTR(-EINVAL);
+
+ return &event->attr;
+}
+
/*
* inherit a event from parent task to child task:
*/