[RFC PATCH 08/22] perf bpf: collect version and license from ELF.

[Wang Nan <wangnan0@huawei.com>]

Expand bpf_obj_elf_collect() to let it collect license and kernel
version information in eBPF object files. 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@huawei.com>
---
 tools/perf/util/bpf-loader.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  2 ++
 2 files changed, 49 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 9c077dd..296fb06 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -157,6 +157,32 @@ bpf_obj_swap_init(struct bpf_obj *obj)
 	}
 }
 
+static int bpf_obj_license_init(struct bpf_obj *obj,
+				void *data, size_t size)
+{
+	memcpy(obj->license, data,
+	       min(size, sizeof(obj->license) - 1));
+	pr_debug("bpf: license of %s is %s\n", obj->path, obj->license);
+	return 0;
+}
+
+static int bpf_obj_kver_init(struct bpf_obj *obj,
+			     void *data, size_t size)
+{
+	u32 kver;
+	if (size < sizeof(kver)) {
+		pr_err("bpf: invalid kver section in %s\n", obj->path);
+		return -EINVAL;
+	}
+	memcpy(&kver, data, sizeof(kver));
+	if (obj->needs_swap)
+		kver = bswap_32(kver);
+	obj->kern_version = kver;
+	pr_debug("bpf: kernel version of %s is %x\n", obj->path,
+			obj->kern_version);
+	return 0;
+}
+
 static int bpf_obj_elf_collect(struct bpf_obj *obj)
 {
 	Elf *elf = obj->elf.elf;
@@ -204,11 +230,30 @@ static int bpf_obj_elf_collect(struct bpf_obj *obj)
 				(int)sh.sh_link,
 				(unsigned long)sh.sh_flags,
 				(int)sh.sh_type);
+
+		if (strcmp(name, "license") == 0)
+			err = bpf_obj_license_init(obj, data->d_buf,
+						   data->d_size);
+		else if (strcmp(name, "version") == 0)
+			err = bpf_obj_kver_init(obj, data->d_buf,
+						data->d_size);
+		if (err)
+			goto out;
 	}
 out:
 	return err;
 }
 
+static int bpf_obj_validate(struct bpf_obj *obj)
+{
+	if (obj->kern_version == 0) {
+		pr_err("bpf: %s doesn't provide kernel version\n",
+			obj->path);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 int bpf__load(const char *path)
 {
 	struct bpf_obj *obj;
@@ -233,6 +278,8 @@ int bpf__load(const char *path)
 		goto out;
 	if ((err = bpf_obj_elf_collect(obj)))
 		goto out;
+	if ((err = bpf_obj_validate(obj)))
+		goto out;
 
 	list_add(&obj->list, &bpf_obj_list);
 	return 0;
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index c27b0ac..e1d5c42 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -23,6 +23,8 @@ struct bpf_obj {
 	struct list_head list;
 	char *path;
 	bool needs_swap;
+	char license[64];
+	u32 kern_version;
 
 	/*
 	 * Information when doing elf related work. Only valid if fd
-- 
1.8.3.4