The LLVM patch https://reviews.llvm.org/D72197 makes LLVM emit function call relocations within the same section. This includes a default .text section, which contains any BPF sub-programs. This wasn't the case before and so libbpf was able to get a way with slightly simpler handling of subprogram call relocations. This patch adds support for .text section relocations. It needs to ensure correct order of relocations, so does two passes: - first, relocate .text instructions, if there are any relocations in it; - then process all the other programs and copy over patched .text instructions for all sub-program calls. Cc: Yonghong Song <yhs@xxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx> --- tools/lib/bpf/libbpf.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0c229f00a67e..c46769d558b5 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -4692,13 +4692,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, size_t new_cnt; int err; - if (prog->idx == obj->efile.text_shndx) { - pr_warn("relo in .text insn %d into off %d (insn #%d)\n", - relo->insn_idx, relo->sym_off, relo->sym_off / 8); - return -LIBBPF_ERRNO__RELOC; - } - - if (prog->main_prog_cnt == 0) { + if (prog->idx != obj->efile.text_shndx && prog->main_prog_cnt == 0) { text = bpf_object__find_prog_by_idx(obj, obj->efile.text_shndx); if (!text) { pr_warn("no .text section found yet relo into text exist\n"); @@ -4728,6 +4722,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, text->insns_cnt, text->section_name, prog->section_name); } + insn = &prog->insns[relo->insn_idx]; insn->imm += relo->sym_off / 8 + prog->main_prog_cnt - relo->insn_idx; return 0; @@ -4807,8 +4802,27 @@ bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path) return err; } } + /* ensure .text is relocated first, as it's going to be copied as-is + * later for sub-program calls + */ for (i = 0; i < obj->nr_programs; i++) { prog = &obj->programs[i]; + if (prog->idx != obj->efile.text_shndx) + continue; + + err = bpf_program__relocate(prog, obj); + if (err) { + pr_warn("failed to relocate '%s'\n", prog->section_name); + return err; + } + } + /* now relocate everything but .text, which by now is relocated + * properly, so we can copy raw sub-program instructions as is safely + */ + for (i = 0; i < obj->nr_programs; i++) { + prog = &obj->programs[i]; + if (prog->idx == obj->efile.text_shndx) + continue; err = bpf_program__relocate(prog, obj); if (err) { -- 2.17.1
