linux-kernel - [RFC PATCH v3 13/37] bpf tools: Collect map definitions from 'maps' section

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Message-ID: <1431860222-61636-14-git-send-email-wangnan0@huawei.com>
Date:	Sun, 17 May 2015 10:56:38 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <jolsa@...nel.org>,
	<dsahern@...il.com>, <ast@...mgrid.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>, <masami.hiramatsu.pt@...achi.com>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: [RFC PATCH v3 13/37] bpf tools: Collect map definitions from 'maps' section

If maps are used by eBPF programs, corresponding object file(s) should
contain a section named 'map'. Which contains map definitions. This
patch copies the data of the whole section. Map data parsing should be
acted just before map loading.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 tools/lib/bpf/libbpf.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b26f1ee..6ee5f3c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -82,6 +82,8 @@ struct bpf_object {
 	bool needs_swap;
 	char license[64];
 	u32 kern_version;
+	void *maps_buf;
+	size_t maps_buf_sz;
 
 	/*
 	 * Information when doing elf related work. Only valid if fd
@@ -244,6 +246,27 @@ static int bpf_obj_kver_init(struct bpf_object *obj,
 	return 0;
 }
 
+static int bpf_obj_maps_init(struct bpf_object *obj, void *data,
+			     size_t size)
+{
+	if (size == 0) {
+		pr_debug("%s doesn't need map definition\n",
+			 obj->path);
+		return 0;
+	}
+
+	obj->maps_buf = malloc(size);
+	if (!obj->maps_buf) {
+		pr_warning("malloc maps failed: %s\n", obj->path);
+		return -ENOMEM;
+	}
+
+	obj->maps_buf_sz = size;
+	memcpy(obj->maps_buf, data, size);
+	pr_debug("maps in %s: %ld bytes\n", obj->path, (long)size);
+	return 0;
+}
+
 static int bpf_obj_elf_collect(struct bpf_object *obj)
 {
 	Elf *elf = obj->elf.elf;
@@ -298,6 +321,9 @@ static int bpf_obj_elf_collect(struct bpf_object *obj)
 		else if (strcmp(name, "version") == 0)
 			err = bpf_obj_kver_init(obj, data->d_buf,
 						data->d_size);
+		else if (strcmp(name, "maps") == 0)
+			err = bpf_obj_maps_init(obj, data->d_buf,
+						data->d_size);
 		if (err)
 			goto out;
 	}
@@ -359,5 +385,7 @@ void bpf_close_object(struct bpf_object *obj)
 
 	if (obj->path)
 		free(obj->path);
+	if (obj->maps_buf)
+		free(obj->maps_buf);
 	free(obj);
 }
-- 
1.8.3.4

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