[RFC PATCH v3 12/37] bpf tools: Collect version and license from ELF sections

Wang Nan
2015-05-17T11:03:58Z

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>
---
tools/lib/bpf/libbpf.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1af80c3..b26f1ee 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -15,12 +15,22 @@
#include <fcntl.h>
#include <errno.h>
#include <asm/unistd.h>
+#include <byteswap.h>
#include <linux/bpf.h>
#include <libelf.h>
#include <gelf.h>

#include "libbpf.h"

+#ifdef min
+# undef min
+#endif
+#define min(x, y) ({ \
+ typeof(x) _min1 = (x); \
+ typeof(y) _min2 = (y); \
+ (void) (&_min1 == &_min2); \
+ _min1 < _min2 ? _min1 : _min2; })
+
#define __printf(a, b) __attribute__((format(printf, a, b)))

__printf(1, 2)
@@ -70,6 +80,8 @@ void libbpf_set_print(int (*warn)(const char *format, ...),
struct bpf_object {
char *path;
bool needs_swap;
+ char license[64];
+ u32 kern_version;

/*
* Information when doing elf related work. Only valid if fd
@@ -206,6 +218,32 @@ bpf_obj_swap_init(struct bpf_object *obj)
}
}

+static int bpf_obj_license_init(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_obj_kver_init(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));
+ if (obj->needs_swap)
+ kver = bswap_32(kver);
+ obj->kern_version = kver;
+ pr_debug("kernel version of %s is %x\n", obj->path,
+ obj->kern_version);
+ return 0;
+}
+
static int bpf_obj_elf_collect(struct bpf_object *obj)
{
Elf *elf = obj->elf.elf;
@@ -253,11 +291,30 @@ static int bpf_obj_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_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_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_open_object(const char *path)
{
struct bpf_object *obj;
@@ -283,6 +340,8 @@ struct bpf_object *bpf_open_object(const char *path)
goto out;
if (bpf_obj_elf_collect(obj))
goto out;
+ if (bpf_obj_validate(obj))
+ goto out;

return obj;

--
1.8.3.4