libbpf: provide more helpful message on uninitialized global var (f2a3e4e9) · Commits · 戴 / test

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>

tools/lib/bpf/libbpf.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -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");

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