[RFC PATCH v2 19/37] tools lib bpf: add bpf.c/h for common bpf operations.

[Wang Nan]

This patch introduces bpf.c and bpf.h, which hold common functions
issuing bpf syscall. The goal of these two files is to hide syscall
completly from user.  Note that bpf.c and bpf.h only deal with kernel
interface. Things like structure of 'map' section in the ELF object is
not cared by of bpf.[ch].

We first introduce bpf_create_map().

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/lib/bpf/Build |  2 +-
 tools/lib/bpf/bpf.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/bpf.h | 17 +++++++++++++++++
 3 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 tools/lib/bpf/bpf.c
 create mode 100644 tools/lib/bpf/bpf.h

diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build
index a316484..d874975 100644
--- a/tools/lib/bpf/Build
+++ b/tools/lib/bpf/Build
@@ -1 +1 @@
-libbpf-y := libbpf.o
+libbpf-y := libbpf.o bpf.o
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
new file mode 100644
index 0000000..3dbe30d
--- /dev/null
+++ b/tools/lib/bpf/bpf.c
@@ -0,0 +1,53 @@
+/*
+ * common eBPF ELF operations.
+ *
+ * Copyright (C) 2015, Wang Nan <wangnan0@xxxxxxxxxx>
+ * Copyright (C) 2015, Huawei Inc.
+ *
+ * Released under the GPL v2. (and only v2, not any later version)
+ */
+
+#include <stdlib.h>
+#include <memory.h>
+#include <unistd.h>
+#include <asm/unistd.h>
+#include <linux/bpf.h>
+#include "bpf.h"
+
+/* When building perf, unistd.h is override. __NR_bpf by ourself. */
+#if defined(__i386__)
+#ifndef __NR_bpf
+# define __NR_bpf 357
+#endif
+#endif
+
+#if defined(__x86_64__)
+#ifndef __NR_bpf
+# define __NR_bpf 321
+#endif
+#endif
+
+#if defined(__aarch64__)
+#ifndef __NR_bpf
+# define __NR_bpf 280
+#endif
+#endif
+
+static int sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr, unsigned int size)
+{
+	return syscall(__NR_bpf, cmd, attr, size);
+}
+
+int bpf_create_map(enum bpf_map_type map_type, int key_size, int value_size,
+		   int max_entries)
+{
+	union bpf_attr attr;
+	memset(&attr, '\0', sizeof(attr));
+	
+	attr.map_type = map_type;
+	attr.key_size = key_size;
+	attr.value_size = value_size;
+	attr.max_entries = max_entries;
+
+	return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+}
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
new file mode 100644
index 0000000..1e9a53b
--- /dev/null
+++ b/tools/lib/bpf/bpf.h
@@ -0,0 +1,17 @@
+/*
+ * common eBPF ELF operations.
+ *
+ * Copyright (C) 2015, Wang Nan <wangnan0@xxxxxxxxxx>
+ * Copyright (C) 2015, Huawei Inc.
+ *
+ * Released under the GPL v2. (and only v2, not any later version)
+ */
+#ifndef __LIBBPF_BPF_H
+#define __LIBBPF_BPF_H
+
+#include <linux/bpf.h>
+
+int bpf_create_map(enum bpf_map_type map_type, int key_size, int value_size,
+		   int max_entries);
+
+#endif
-- 
1.8.3.4

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