[RFC PATCH v7 08/37] bpf tools: Collect version and license from ELF sections

Wang Nan
2015-06-12T05:36:30Z

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@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.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 1c4da03..3bd183c 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>
@@ -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 +223,32 @@ 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;
@@ -266,11 +295,32 @@ 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 +341,8 @@ __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;
--
1.8.3.4