diff options
| author | Andrii Nakryiko <andriin@fb.com> | 2020-01-15 11:08:56 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-01-15 11:51:48 -0800 |
| commit | 9173cac3b64e6785dd604f5075e6035b045a0026 (patch) | |
| tree | 69fe32b9d326c5adacc059f02a5f653248407108 | |
| parent | 5640a771d7971412049d1934d2d030edfdd1c28e (diff) | |
| download | linux-9173cac3b64e6785dd604f5075e6035b045a0026.tar.bz2 | |
libbpf: Support .text sub-calls relocations
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.
v1->v2:
- break early once .text program is processed.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200115190856.2391325-1-andriin@fb.com
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 29 |
1 files changed, 22 insertions, 7 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0c229f00a67e..23868883477f 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 +4802,28 @@ 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; + } + break; + } + /* 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) { |