[RFC PATCH v3 11/37] bpf tools: Iterate over ELF sections to collect information

Wang Nan
2015-05-17T11:04:10Z

bpf_obj_elf_collect() is introduced to iterate over each elf sections
to collection informations 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>
---
tools/lib/bpf/libbpf.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 54 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a4910a8..1af80c3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -206,6 +206,58 @@ bpf_obj_swap_init(struct bpf_object *obj)
}
}

+static int bpf_obj_elf_collect(struct bpf_object *obj)
+{
+ Elf *elf = obj->elf.elf;
+ GElf_Ehdr *ep = &obj->elf.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;
+}
+
struct bpf_object *bpf_open_object(const char *path)
{
struct bpf_object *obj;
@@ -229,6 +281,8 @@ struct bpf_object *bpf_open_object(const char *path)
goto out;
if (bpf_obj_swap_init(obj))
goto out;
+ if (bpf_obj_elf_collect(obj))
+ goto out;

return obj;

--
1.8.3.4