bpf tools: Iterate over ELF sections to collect information

bpf_obj_elf_collect() is introduced to iterate over each elf sections to
collection information in eBPF object files. This function will futher
enhanced to collect license, kernel version, programs, configs and map
information.

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/1435716878-189507-9-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 15b3e82..d8d6eb5 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -220,6 +220,57 @@ mismatch:
        return -EINVAL;
 }
 
+static int bpf_object__elf_collect(struct bpf_object *obj)
+{
+       Elf *elf = obj->efile.elf;
+       GElf_Ehdr *ep = &obj->efile.ehdr;
+       Elf_Scn *scn = NULL;
+       int idx = 0, err = 0;
+
+       /* Elf is corrupted/truncated, avoid calling elf_strptr. */
+       if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
+               pr_warning("failed to get e_shstrndx from %s\n",
+                          obj->path);
+               return -EINVAL;
+       }
+
+       while ((scn = elf_nextscn(elf, scn)) != NULL) {
+               char *name;
+               GElf_Shdr sh;
+               Elf_Data *data;
+
+               idx++;
+               if (gelf_getshdr(scn, &sh) != &sh) {
+                       pr_warning("failed to get section header from %s\n",
+                                  obj->path);
+                       err = -EINVAL;
+                       goto out;
+               }
+
+               name = elf_strptr(elf, ep->e_shstrndx, sh.sh_name);
+               if (!name) {
+                       pr_warning("failed to get section name from %s\n",
+                                  obj->path);
+                       err = -EINVAL;
+                       goto out;
+               }
+
+               data = elf_getdata(scn, 0);
+               if (!data) {
+                       pr_warning("failed to get section data from %s(%s)\n",
+                                  name, obj->path);
+                       err = -EINVAL;
+                       goto out;
+               }
+               pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
+                        name, (unsigned long)data->d_size,
+                        (int)sh.sh_link, (unsigned long)sh.sh_flags,
+                        (int)sh.sh_type);
+       }
+out:
+       return err;
+}
+
 static struct bpf_object *
 __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
 {
@@ -238,6 +289,8 @@ __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
                goto out;
        if (bpf_object__check_endianness(obj))
                goto out;
+       if (bpf_object__elf_collect(obj))
+               goto out;
 
        bpf_object__elf_finish(obj);
        return obj;