linux-kernel - [PATCH v2 1/5] bpf: Add new bpf map type to store the pointer to struct perf

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Date:	Wed, 22 Jul 2015 08:09:28 +0000
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: [PATCH v2 1/5] bpf: Add new bpf map type to store the pointer to struct perf_event

Introduce a new bpf map type 'BPF_MAP_TYPE_PERF_EVENT_ARRAY'.
This map will only store the pointer to struct perf_event.

Signed-off-by: Kaixu Xia <xiakaixu@...wei.com>
---
 include/linux/bpf.h      |  2 ++
 include/uapi/linux/bpf.h |  1 +
 kernel/bpf/arraymap.c    | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4383476..f6a2442 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -11,6 +11,8 @@
 #include <linux/workqueue.h>
 #include <linux/file.h>
 
+#define MAX_PERF_EVENT_ARRAY_ENTRY	(2*NR_CPUS)
+
 struct bpf_map;
 
 /* map is generic key/value storage optionally accesible by eBPF programs */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 29ef6f9..69a1f6b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -114,6 +114,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_HASH,
 	BPF_MAP_TYPE_ARRAY,
 	BPF_MAP_TYPE_PROG_ARRAY,
+	BPF_MAP_TYPE_PERF_EVENT_ARRAY,
 };
 
 enum bpf_prog_type {
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index cb31229..183c1f7 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -255,3 +255,43 @@ static int __init register_prog_array_map(void)
 	return 0;
 }
 late_initcall(register_prog_array_map);
+
+static struct bpf_map *perf_event_array_map_alloc(union bpf_attr *attr)
+{
+	/* only the pointer to struct perf_event can be stored in
+	 * perf_event_array map
+	 */
+	if (attr->value_size != sizeof(void *))
+		return ERR_PTR(-EINVAL);
+
+	if (attr->max_entries > MAX_PERF_EVENT_ARRAY_ENTRY)
+		return ERR_PTR(-EINVAL);
+
+	return array_map_alloc(attr);
+}
+
+static int perf_event_array_map_get_next_key(struct bpf_map *map, void *key,
+					     void *next_key)
+{
+	return -EINVAL;
+}
+
+static const struct bpf_map_ops perf_event_array_ops = {
+	.map_alloc = perf_event_array_map_alloc,
+	.map_free = array_map_free,
+	.map_get_next_key = perf_event_array_map_get_next_key,
+	.map_lookup_elem = array_map_lookup_elem,
+	.map_delete_elem = array_map_delete_elem,
+};
+
+static struct bpf_map_type_list perf_event_array_type __read_mostly = {
+	.ops = &perf_event_array_ops,
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+};
+
+static int __init register_perf_event_array_map(void)
+{
+	bpf_register_map_type(&perf_event_array_type);
+	return 0;
+}
+late_initcall(register_perf_event_array_map);
-- 
1.8.3.4

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