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[PATCH v2 4/5] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter

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According to the perf_event_map_fd and key, the function
bpf_perf_event_read() can convert the corresponding map
value to the pointer to struct perf_event and return the
Hardware PMU counter value.

The key can't be passed to bpf_perf_event_read() directly
because the function argument constraint is lacked.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
---
 include/linux/bpf.h        |  1 +
 include/linux/perf_event.h |  3 ++-
 include/uapi/linux/bpf.h   |  2 ++
 kernel/bpf/helpers.c       | 42 ++++++++++++++++++++++++++++++++++++++++++
 kernel/events/core.c       |  4 ++--
 kernel/trace/bpf_trace.c   |  2 ++
 6 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 257149c..0fbff67 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -197,5 +197,6 @@ extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
 extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
 extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
 extern const struct bpf_func_proto bpf_get_current_comm_proto;
+extern const struct bpf_func_proto bpf_perf_event_read_proto;
 
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2ea4067..899abcb 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -662,7 +662,8 @@ extern void perf_pmu_migrate_context(struct pmu *pmu,
 				int src_cpu, int dst_cpu);
 extern u64 perf_event_read_value(struct perf_event *event,
 				 u64 *enabled, u64 *running);
-
+extern void __perf_event_read(void *info);
+extern u64 perf_event_count(struct perf_event *event);
 
 struct perf_sample_data {
 	/*
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 69a1f6b..e3bb181 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -250,6 +250,8 @@ enum bpf_func_id {
 	 * Return: 0 on success
 	 */
 	BPF_FUNC_get_current_comm,
+
+	BPF_FUNC_perf_event_read,	/* u64 bpf_perf_event_read(&map, &key) */
 	__BPF_FUNC_MAX_ID,
 };
 
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1447ec0..aef2640 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -16,6 +16,7 @@
 #include <linux/ktime.h>
 #include <linux/sched.h>
 #include <linux/uidgid.h>
+#include <linux/perf_event.h>
 
 /* If kernel subsystem is allowing eBPF programs to call this function,
  * inside its own verifier_ops->get_func_proto() callback it should return
@@ -182,3 +183,44 @@ const struct bpf_func_proto bpf_get_current_comm_proto = {
 	.arg1_type	= ARG_PTR_TO_STACK,
 	.arg2_type	= ARG_CONST_STACK_SIZE,
 };
+
+static u64 bpf_perf_event_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
+	void *key = (void *) (unsigned long) r2;
+	struct perf_event *event;
+	void *ptr;
+
+	if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
+		return -EINVAL;
+
+	rcu_read_lock();
+	ptr = map->ops->map_lookup_elem(map, key);
+	rcu_read_unlock();
+	if (!ptr || !(*(unsigned long *)ptr))
+		return -EBADF;
+
+	event = (struct perf_event *)(*(unsigned long *)ptr);
+
+	if (event->state != PERF_EVENT_STATE_ACTIVE)
+		return -ENOENT;
+
+	if (event->oncpu != raw_smp_processor_id() &&
+	    event->ctx->task != current)
+		return -EINVAL;
+
+	if (event->attr.inherit)
+		return -EINVAL;
+
+	__perf_event_read(event);
+
+	return perf_event_count(event);
+}
+
+const struct bpf_func_proto bpf_perf_event_read_proto = {
+	.func		= bpf_perf_event_read,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_MAP_KEY,
+};
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 14a9924..b4bde27 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3177,7 +3177,7 @@ void perf_event_exec(void)
 /*
  * Cross CPU call to read the hardware event
  */
-static void __perf_event_read(void *info)
+void __perf_event_read(void *info)
 {
 	struct perf_event *event = info;
 	struct perf_event_context *ctx = event->ctx;
@@ -3204,7 +3204,7 @@ static void __perf_event_read(void *info)
 	raw_spin_unlock(&ctx->lock);
 }
 
-static inline u64 perf_event_count(struct perf_event *event)
+u64 perf_event_count(struct perf_event *event)
 {
 	if (event->pmu->count)
 		return event->pmu->count(event);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 88a041a..9cf094f 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -183,6 +183,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 		return bpf_get_trace_printk_proto();
 	case BPF_FUNC_get_smp_processor_id:
 		return &bpf_get_smp_processor_id_proto;
+	case BPF_FUNC_perf_event_read:
+		return &bpf_perf_event_read_proto;
 	default:
 		return NULL;
 	}
-- 
1.8.3.4

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[PATCH v2 4/5] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter Kaixu Xia <xiakaixu@huawei.com> - 2015-07-22 10:20 +0200

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