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libbpf: provide more helpful message on uninitialized global var 

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 <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2019-07-23 14:11:33 -07:00 committed by Alexei Starovoitov
parent 3e3bb69589
commit f2a3e4e95f
1 changed files with 10 additions and 3 deletions
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13
tools/lib/bpf/libbpf.c
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@ -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");