linux-kernel - [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter

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Date:	Fri, 17 Jul 2015 18:43:35 +0800
From:	kaixu xia <xiakaixu@...wei.com>
To:	<ast@...mgrid.com>, <davem@...emloft.net>, <acme@...nel.org>,
	<mingo@...hat.com>, <a.p.zijlstra@...llo.nl>,
	<masami.hiramatsu.pt@...achi.com>, <jolsa@...nel.org>
CC:	<xiakaixu@...wei.com>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	<hekuang@...wei.com>
Subject: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter

The function bpf_read_pmu() can get the specific map key, convert
the corresponding map value to the pointer to struct perf_event and
return the Hardware PMU counter value.

Signed-off-by: kaixu xia <xiakaixu@...wei.com>
---
 include/linux/bpf.h      |    2 ++
 include/uapi/linux/bpf.h |    2 ++
 kernel/bpf/helpers.c     |   27 +++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c |    2 ++
 4 files changed, 33 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 31a93fc..6efff20 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -190,6 +190,8 @@ extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
 extern const struct bpf_func_proto bpf_map_update_elem_proto;
 extern const struct bpf_func_proto bpf_map_delete_elem_proto;
 
+extern const struct bpf_func_proto bpf_read_pmu_proto;
+
 extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
 extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
 extern const struct bpf_func_proto bpf_tail_call_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 47d8516..1431ec6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -263,6 +263,8 @@ enum bpf_func_id {
 	 * Return: 0 on success
 	 */
 	BPF_FUNC_get_current_comm,
+
+	BPF_FUNC_read_pmu,	/* u64 bpf_read_pmu(&value) */
 	__BPF_FUNC_MAX_ID,
 };
 
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1447ec0..6a0ed1b 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 +183,29 @@ 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_read_pmu(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	void *value = (void *) (unsigned long) r1;
+	struct perf_event *event;
+	u64 count;
+
+	if (!value || !(*(unsigned long *)value))
+		return 0;
+
+	event = (struct perf_event *)(*(unsigned long *)value);
+
+	if (event->state == PERF_EVENT_STATE_ACTIVE)
+		event->pmu->read(event);
+
+	count = local64_read(&event->count);
+
+	return count;
+}
+
+const struct bpf_func_proto bpf_read_pmu_proto = {
+	.func = bpf_read_pmu,
+	.gpl_only = false,
+	.ret_type = RET_INTEGER,
+	.arg1_type = ARG_PTR_TO_MAP_PERF_EVENT_VALUE,
+};
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 88a041a..2343159 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_read_pmu:
+		return &bpf_read_pmu_proto;
 	default:
 		return NULL;
 	}
-- 
1.7.10.4

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