[RFC PATCH v4 08/29] bpf tools: Iterate over ELF sections to collect information

From: Wang Nan
Date: Wed May 27 2015 - 01:23:44 EST


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@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index dbbea0c..16e47a3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -197,6 +197,57 @@ 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;
+}
+
struct bpf_object *bpf_object__open(const char *path)
{
struct bpf_object *obj;
@@ -220,6 +271,8 @@ struct bpf_object *bpf_object__open(const char *path)
goto out;
if (bpf_object__check_endianess(obj))
goto out;
+ if (bpf_object__elf_collect(obj))
+ goto out;

bpf_object__elf_finish(obj);
return obj;
--
1.8.3.4

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