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 existence of 'version' section.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-10-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d8d6eb5801884217dc1781bbaf65c1d228260c41..95c8d8e5c350ee8cb0ee3420146d724d12c64bc0 100644 (file)
--- 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>
@@ -78,6 +79,8 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 #endif
 
 struct bpf_object {
+       char license[64];
+       u32 kern_version;
        /*
         * Information when doing elf related work. Only valid if fd
         * is valid.
@@ -220,6 +223,33 @@ 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;
@@ -266,11 +296,32 @@ 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;
+}
+
 static struct bpf_object *
 __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
 {
@@ -291,6 +342,8 @@ __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
                goto out;
        if (bpf_object__elf_collect(obj))
                goto out;
+       if (bpf_object__validate(obj))
+               goto out;
 
        bpf_object__elf_finish(obj);
        return obj;