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| author | Alexei Starovoitov <ast@kernel.org> | 2023-03-19 13:30:13 -0700 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2023-03-20 09:26:41 -0700 |
| commit | a506d6ce1dd184051037dc9d26c3eb187c9fe625 (patch) | |
| tree | 019291a229503abb3a262f08df214305e2212f68 /tools/lib | |
| parent | 08ff1c9f3e927ba3701c113dda70953a6f4afffa (diff) | |
| download | linux-a506d6ce1dd184051037dc9d26c3eb187c9fe625.tar.gz | |
libbpf: Fix ld_imm64 copy logic for ksym in light skeleton.
Unlike normal libbpf the light skeleton 'loader' program is doing
btf_find_by_name_kind() call at run-time to find ksym in the kernel and
populate its {btf_id, btf_obj_fd} pair in ld_imm64 insn. To avoid doing the
search multiple times for the same ksym it remembers the first patched ld_imm64
insn and copies {btf_id, btf_obj_fd} from it into subsequent ld_imm64 insn.
Fix a bug in copying logic, since it may incorrectly clear BPF_PSEUDO_BTF_ID flag.
Also replace always true if (btf_obj_fd >= 0) check with unconditional JMP_JA
to clarify the code.
Fixes: d995816b77eb ("libbpf: Avoid reload of imm for weak, unresolved, repeating ksym")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230319203014.55866-1-alexei.starovoitov@gmail.com
Diffstat (limited to 'tools/lib')
| -rw-r--r-- | tools/lib/bpf/gen_loader.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c index 23f5c46708f8..b74c82bb831e 100644 --- a/tools/lib/bpf/gen_loader.c +++ b/tools/lib/bpf/gen_loader.c @@ -804,11 +804,13 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, return; /* try to copy from existing ldimm64 insn */ if (kdesc->ref > 1) { - move_blob2blob(gen, insn + offsetof(struct bpf_insn, imm), 4, - kdesc->insn + offsetof(struct bpf_insn, imm)); move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4, kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)); - /* jump over src_reg adjustment if imm is not 0, reuse BPF_REG_0 from move_blob2blob */ + move_blob2blob(gen, insn + offsetof(struct bpf_insn, imm), 4, + kdesc->insn + offsetof(struct bpf_insn, imm)); + /* jump over src_reg adjustment if imm (btf_id) is not 0, reuse BPF_REG_0 from move_blob2blob + * If btf_id is zero, clear BPF_PSEUDO_BTF_ID flag in src_reg of ld_imm64 insn + */ emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3)); goto clear_src_reg; } @@ -831,7 +833,7 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm))); /* skip src_reg adjustment */ - emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 3)); + emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, 3)); clear_src_reg: /* clear bpf_object__relocate_data's src_reg assignment, otherwise we get a verifier failure */ reg_mask = src_reg_mask(); |