bpf_core_patch_insn modifies load's mem size from 8 bytes to 4 bytes. As a result, the bpf check fails, we need to skip adjust mem size to fit the verifier.
Signed-off-by: Yang Jihong yangjihong1@huawei.com --- tools/lib/bpf/libbpf.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 184ce1684dcd..e1c21b631a0b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5634,6 +5634,28 @@ static int bpf_core_resolve_relo(struct bpf_program *prog, targ_res); }
+static bool +bpf_core_patch_insn_skip(const struct btf *local_btf, const struct bpf_insn *insn, + const struct bpf_core_relo_res *res) +{ + __u8 class; + const struct btf_type *orig_t; + + class = BPF_CLASS(insn->code); + orig_t = btf_type_by_id(local_btf, res->orig_type_id); + + /* + * verifier has to see a load of a pointer as a 8-byte load, + * CO_RE should not screws up access, bpf_core_patch_insn modifies + * load's mem size from 8 bytes to 4 bytes in 32-bit arch, + * so we skip adjust mem size. + */ + if (class == BPF_LDX && btf_is_ptr(orig_t)) + return true; + + return false; +} + static int bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path) { @@ -5730,11 +5752,13 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path) goto out; }
- err = bpf_core_patch_insn(prog->name, insn, insn_idx, rec, i, &targ_res); - if (err) { - pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n", - prog->name, i, insn_idx, err); - goto out; + if (!bpf_core_patch_insn_skip(obj->btf, insn, &targ_res)) { + err = bpf_core_patch_insn(prog->name, insn, insn_idx, rec, i, &targ_res); + if (err) { + pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n", + prog->name, i, insn_idx, err); + goto out; + } } } }