Re: [PATCH bpf-next v1 1/8] bpf: Introduce pseudo_btf_id
From: Alexei Starovoitov <hidden>
Date: 2020-08-20 21:53:34
Also in:
bpf, linux-kselftest, lkml
On Wed, Aug 19, 2020 at 03:40:23PM -0700, Hao Luo wrote:
quoted hunk ↗ jump to hunk
+ /* verify BPF_LD_IMM64 instruction */ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) {@@ -7234,6 +7296,9 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) return 0; } + if (insn->src_reg == BPF_PSEUDO_BTF_ID) + return check_pseudo_btf_id(env, insn); + map = env->used_maps[aux->map_index]; mark_reg_known_zero(env, regs, insn->dst_reg); regs[insn->dst_reg].map_ptr = map;@@ -9255,6 +9320,9 @@ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) /* valid generic load 64-bit imm */ goto next_insn; + if (insn[0].src_reg == BPF_PSEUDO_BTF_ID) + goto next_insn; +
Why did you choose to do it during main do_check() walk instead of this pre-pass ? check_ld_imm() can be called multiple times for the same insn, so it's faster and less surprising to do it during replace_map_fd_with_map_ptr(). BTF needs to be parsed first, of course. You can either move check_btf_info() before replace_map_fd_with_map_ptr() or move replace_map_fd_with_map_ptr() after check_btf_info(). The latter is probably cleaner.