linux-kernel - [RFC PATCH v4 09/29] bpf tools: Collect version and license from ELF sections

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Message-ID: <1432704004-171454-10-git-send-email-wangnan0@huawei.com>
Date:	Wed, 27 May 2015 05:19:44 +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>, <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 v4 09/29] bpf tools: Collect version and license from ELF sections

Expand bpf_obj_elf_collect() to collect license and kernel version
information in eBPF object file. eBPF object file should have a section
named 'license', which contains a string. It should also have a section
named 'version', contains a u32 LINUX_VERSION_CODE.

bpf_obj_validate() is introduced to validate object file after loaded.
Currently it only check existance of 'version' section.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 tools/lib/bpf/libbpf.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 16e47a3..15525ad 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -14,6 +14,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <asm/unistd.h>
+#include <linux/kernel.h>
 #include <linux/bpf.h>
 #include <libelf.h>
 #include <gelf.h>
@@ -81,6 +82,8 @@ void libbpf_set_print(int (*warn)(const char *format, ...),
 #endif
 
 struct bpf_object {
+	char license[64];
+	u32 kern_version;
 	/*
 	 * Information when doing elf related work. Only valid if fd
 	 * is valid.
@@ -197,6 +200,32 @@ mismatch:
 	return -EINVAL;
 }
 
+static int
+bpf_object__init_license(struct bpf_object *obj,
+			 void *data, size_t size)
+{
+	memcpy(obj->license, data,
+	       min(size, sizeof(obj->license) - 1));
+	pr_debug("license of %s is %s\n", obj->path, obj->license);
+	return 0;
+}
+
+static int
+bpf_object__init_kversion(struct bpf_object *obj,
+			  void *data, size_t size)
+{
+	u32 kver;
+	if (size < sizeof(kver)) {
+		pr_warning("invalid kver section in %s\n", obj->path);
+		return -EINVAL;
+	}
+	memcpy(&kver, data, sizeof(kver));
+	obj->kern_version = kver;
+	pr_debug("kernel version of %s is %x\n", obj->path,
+		 obj->kern_version);
+	return 0;
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj)
 {
 	Elf *elf = obj->efile.elf;
@@ -243,11 +272,32 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			 name, (unsigned long)data->d_size,
 			 (int)sh.sh_link, (unsigned long)sh.sh_flags,
 			 (int)sh.sh_type);
+
+		if (strcmp(name, "license") == 0)
+			err = bpf_object__init_license(obj,
+						       data->d_buf,
+						       data->d_size);
+		else if (strcmp(name, "version") == 0)
+			err = bpf_object__init_kversion(obj,
+							data->d_buf,
+							data->d_size);
+		if (err)
+			goto out;
 	}
 out:
 	return err;
 }
 
+static int bpf_object__validate(struct bpf_object *obj)
+{
+	if (obj->kern_version == 0) {
+		pr_warning("%s doesn't provide kernel version\n",
+			   obj->path);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 struct bpf_object *bpf_object__open(const char *path)
 {
 	struct bpf_object *obj;
@@ -273,6 +323,8 @@ struct bpf_object *bpf_object__open(const char *path)
 		goto out;
 	if (bpf_object__elf_collect(obj))
 		goto out;
+	if (bpf_object__validate(obj))
+		goto out;
 
 	bpf_object__elf_finish(obj);
 	return obj;
-- 
1.8.3.4

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