tools/libbpf: improve the pr_debug statements to contain section numbers

While debugging a bpf ELF loading issue, I needed to correlate the
ELF section number with the failed relocation section reference.
Thus, add section numbers/index to the pr_debug.

In debug mode, also print section that were skipped.  This helped
me identify that a section (.eh_frame) was skipped, and this was
the reason the relocation section (.rel.eh_frame) could not find
that section number.

The section numbers corresponds to the readelf tools Section Headers [Nr].

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 13 insertions, 12 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index c64840365433..0c794f7fc050 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -319,8 +319,8 @@ bpf_program__init(void *data, size_t size, char *section_name, int idx,
 
         prog->section_name = strdup(section_name);
         if (!prog->section_name) {
-                pr_warning("failed to alloc name for prog under section %s\n",
-                           section_name);
+                pr_warning("failed to alloc name for prog under section(%d) %s\n",
+                           idx, section_name);
                 goto errout;
         }
 
@@ -763,29 +763,29 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 
                 idx++;
                 if (gelf_getshdr(scn, &sh) != &sh) {
-                        pr_warning("failed to get section header from %s\n",
-                                   obj->path);
+                        pr_warning("failed to get section(%d) header from %s\n",
+                                   idx, obj->path);
                         err = -LIBBPF_ERRNO__FORMAT;
                         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);
+                        pr_warning("failed to get section(%d) name from %s\n",
+                                   idx, obj->path);
                         err = -LIBBPF_ERRNO__FORMAT;
                         goto out;
                 }
 
                 data = elf_getdata(scn, 0);
                 if (!data) {
-                        pr_warning("failed to get section data from %s(%s)\n",
-                                   name, obj->path);
+                        pr_warning("failed to get section(%d) data from %s(%s)\n",
+                                   idx, name, obj->path);
                         err = -LIBBPF_ERRNO__FORMAT;
                         goto out;
                 }
-                pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
-                         name, (unsigned long)data->d_size,
+                pr_debug("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
+                         idx, name, (unsigned long)data->d_size,
                          (int)sh.sh_link, (unsigned long)sh.sh_flags,
                          (int)sh.sh_type);
 
@@ -840,6 +840,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
                                 obj->efile.reloc[n].shdr = sh;
                                 obj->efile.reloc[n].data = data;
                         }
+                } else {
+                        pr_debug("skip section(%d) %s\n", idx, name);
                 }
                 if (err)
                         goto out;
@@ -1119,8 +1121,7 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 
                 prog = bpf_object__find_prog_by_idx(obj, idx);
                 if (!prog) {
-                        pr_warning("relocation failed: no %d section\n",
-                                   idx);
+                        pr_warning("relocation failed: no section(%d)\n", idx);
                         return -LIBBPF_ERRNO__RELOC;
                 }