linux-kernel - [RFC PATCH 1/6] bpf: Add new flags that specify the value type stored in map

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Date:	Fri, 17 Jul 2015 18:43:31 +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 1/6] bpf: Add new flags that specify the value type stored in map

The pointer to struct perf_event will be stored in map. So
add new flag BPF_MAP_FLAG_PERF_EVENT that specify the value
type stored in map. The high 8-bit of attr->map_type is used
to contain the new flags.

Signed-off-by: kaixu xia <xiakaixu@...wei.com>
---
 include/linux/bpf.h      |    1 +
 include/uapi/linux/bpf.h |   14 ++++++++++++++
 kernel/bpf/syscall.c     |   13 +++++++++++--
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4383476..2634a25 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -34,6 +34,7 @@ struct bpf_map {
 	u32 max_entries;
 	const struct bpf_map_ops *ops;
 	struct work_struct work;
+	unsigned int flags;
 };
 
 struct bpf_map_type_list {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 29ef6f9..47d8516 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -131,6 +131,20 @@ enum bpf_prog_type {
 #define BPF_NOEXIST	1 /* create new element if it didn't exist */
 #define BPF_EXIST	2 /* update existing element */
 
+/* flags for BPF_MAP_CREATE command */
+enum {
+	BPF_PERF_EVENT = 0,
+	__NR_FLAG_BITS,
+};
+
+#define MAP_FLAG_BITS	__NR_FLAG_BITS
+#define MAP_FLAG_SHIFT	(32 - MAP_FLAG_BITS)
+#define MAP_FLAG_MASK	(~0U << MAP_FLAG_SHIFT)
+
+#define BPF_FLAG_PERF_EVENT_BIT	(32 - BPF_PERF_EVENT -1)
+
+#define BPF_MAP_FLAG_PERF_EVENT	(1 << BPF_FLAG_PERF_EVENT_BIT) /* create a specific map for perf_event */
+
 union bpf_attr {
 	struct { /* anonymous struct used by BPF_MAP_CREATE command */
 		__u32	map_type;	/* one of enum bpf_map_type */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a1b14d1..4c2d9e6 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -20,7 +20,7 @@
 
 static LIST_HEAD(bpf_map_types);
 
-static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
+static struct bpf_map *find_and_alloc_map(union bpf_attr *attr, unsigned int flags)
 {
 	struct bpf_map_type_list *tl;
 	struct bpf_map *map;
@@ -32,6 +32,7 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
 				return map;
 			map->ops = tl->ops;
 			map->map_type = attr->map_type;
+			map->flags = flags;
 			return map;
 		}
 	}
@@ -95,14 +96,22 @@ static const struct file_operations bpf_map_fops = {
 static int map_create(union bpf_attr *attr)
 {
 	struct bpf_map *map;
+	unsigned int flags;
 	int err;
 
 	err = CHECK_ATTR(BPF_MAP_CREATE);
 	if (err)
 		return -EINVAL;
 
+	flags = attr->map_type & MAP_FLAG_MASK;
+	attr->map_type &= ~MAP_FLAG_MASK;
+
+	/* check if the map->value_size is suitable when creating PMU map*/
+	if ((flags & BPF_MAP_FLAG_PERF_EVENT) && (attr->value_size != sizeof(void *)))
+		return -EINVAL;
+
 	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
-	map = find_and_alloc_map(attr);
+	map = find_and_alloc_map(attr, flags);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
-- 
1.7.10.4

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