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>

1 files changed, 53 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 15b3e82b22f6..d8d6eb580188 100644
--- 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;