[bpf-next V3 PATCH 2/5] tools/libbpf: improve the pr_debug statements to contain section numbers

[Jesper Dangaard Brouer]

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 <bro...@redhat.com>
---
 tools/lib/bpf/libbpf.c |   25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 30c776375118..b4eeaa3ebff5 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -315,8 +315,8 @@ 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;
        }
 
@@ -759,29 +759,29 @@ 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);
 
@@ -836,6 +836,8 @@ 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;
@@ -1115,8 +1117,7 @@ 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;
                }