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author | Daniel Borkmann <daniel@iogearbox.net> | 2018-02-09 00:26:18 +0100 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-02-09 00:26:28 +0100 |
commit | d977ae593b2d3f9ef0df795eda93f4e6bc92b323 (patch) | |
tree | 0e3c09034cb8bc79fea586681d4de51689a23325 /tools/lib | |
parent | 69fe98edee48b4c3c7d90cb7eea1f1662202137d (diff) | |
parent | e3d91b0ca523d53158f435a3e13df7f0cb360ea2 (diff) | |
download | linux-d977ae593b2d3f9ef0df795eda93f4e6bc92b323.tar.bz2 |
Merge branch 'bpf-libbpf-relo-fix-and-tests'
Jesper Dangaard Brouer says:
====================
While playing with using libbpf for the Suricata project, we had
issues LLVM >= 4.0.1 generating ELF files that could not be loaded
with libbpf (tools/lib/bpf/).
During the troubleshooting phase, I wrote a test program and improved
the debugging output in libbpf. I turned this into a selftests
program, and it also serves as a code example for libbpf in itself.
I discovered that there are at least three ELF load issues with
libbpf. I left them as TODO comments in (tools/testing/selftests/bpf)
test_libbpf.sh. I've only fixed the load issue with eh_frames, and
other types of relo-section that does not have exec flags. We can
work on the other issues later.
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'tools/lib')
-rw-r--r-- | tools/lib/bpf/libbpf.c | 51 |
1 files changed, 39 insertions, 12 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index c64840365433..97073d649c1a 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; } @@ -742,6 +742,24 @@ bpf_object__init_maps(struct bpf_object *obj) return 0; } +static bool section_have_execinstr(struct bpf_object *obj, int idx) +{ + Elf_Scn *scn; + GElf_Shdr sh; + + scn = elf_getscn(obj->efile.elf, idx); + if (!scn) + return false; + + if (gelf_getshdr(scn, &sh) != &sh) + return false; + + if (sh.sh_flags & SHF_EXECINSTR) + return true; + + return false; +} + static int bpf_object__elf_collect(struct bpf_object *obj) { Elf *elf = obj->efile.elf; @@ -763,29 +781,29 @@ 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); @@ -825,6 +843,14 @@ static int bpf_object__elf_collect(struct bpf_object *obj) } else if (sh.sh_type == SHT_REL) { void *reloc = obj->efile.reloc; int nr_reloc = obj->efile.nr_reloc + 1; + int sec = sh.sh_info; /* points to other section */ + + /* Only do relo for section with exec instructions */ + if (!section_have_execinstr(obj, sec)) { + pr_debug("skip relo %s(%d) for section(%d)\n", + name, idx, sec); + continue; + } reloc = realloc(reloc, sizeof(*obj->efile.reloc) * nr_reloc); @@ -840,6 +866,8 @@ 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 +1147,7 @@ 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; } |