> On Jul 23, 2019, at 2:11 PM, Andrii Nakryiko <andr...@fb.com> wrote:
>
> When BPF program defines uninitialized global variable, it's put into
> a special COMMON section. Libbpf will reject such programs, but will
> provide very unhelpful message with garbage-looking section index.
>
> This patch detects special section cases and gives more explicit error
> message.
>
> Signed-off-by: Andrii Nakryiko <andr...@fb.com>
Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 794dd5064ae8..8741c39adb1c 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1760,15 +1760,22 @@ bpf_program__collect_reloc(struct bpf_program *prog,
> GElf_Shdr *shdr,
> (long long) sym.st_value, sym.st_name, name);
>
> shdr_idx = sym.st_shndx;
> + insn_idx = rel.r_offset / sizeof(struct bpf_insn);
> + pr_debug("relocation: insn_idx=%u, shdr_idx=%u\n",
> + insn_idx, shdr_idx);
> +
> + if (shdr_idx >= SHN_LORESERVE) {
> + pr_warning("relocation: not yet supported relo for
> non-static global \'%s\' variable in special section (0x%x) found in
> insns[%d].code 0x%x\n",
> + name, shdr_idx, insn_idx,
> + insns[insn_idx].code);
> + return -LIBBPF_ERRNO__RELOC;
> + }
> if (!bpf_object__relo_in_known_section(obj, shdr_idx)) {
> pr_warning("Program '%s' contains unrecognized relo
> data pointing to section %u\n",
> prog->section_name, shdr_idx);
> return -LIBBPF_ERRNO__RELOC;
> }
>
> - insn_idx = rel.r_offset / sizeof(struct bpf_insn);
> - pr_debug("relocation: insn_idx=%u\n", insn_idx);
> -
> if (insns[insn_idx].code == (BPF_JMP | BPF_CALL)) {
> if (insns[insn_idx].src_reg != BPF_PSEUDO_CALL) {
> pr_warning("incorrect bpf_call opcode\n");
> --
> 2.17.1
>
