On Thu, 15 Feb 2024 at 23:12, Eduard Zingerman <eddyz87@xxxxxxxxx> wrote: > > On Thu, 2024-02-01 at 04:21 +0000, Kumar Kartikeya Dwivedi wrote: > > [...] > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 942243cba9f1..aeaf97b0a749 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -2942,6 +2942,15 @@ static int check_subprogs(struct bpf_verifier_env *env) > > insn[i].src_reg == 0 && > > insn[i].imm == BPF_FUNC_tail_call) > > subprog[cur_subprog].has_tail_call = true; > > + /* Collect callee regs used in the subprog. */ > > + if (insn[i].dst_reg == BPF_REG_6 || insn[i].src_reg == BPF_REG_6) > > + subprog[cur_subprog].callee_regs_used[0] = true; > > + if (insn[i].dst_reg == BPF_REG_7 || insn[i].src_reg == BPF_REG_7) > > + subprog[cur_subprog].callee_regs_used[1] = true; > > + if (insn[i].dst_reg == BPF_REG_8 || insn[i].src_reg == BPF_REG_8) > > + subprog[cur_subprog].callee_regs_used[2] = true; > > + if (insn[i].dst_reg == BPF_REG_9 || insn[i].src_reg == BPF_REG_9) > > + subprog[cur_subprog].callee_regs_used[3] = true; > > Nit: Maybe move bpf_jit_comp.c:detect_reg_usage() to some place available to > both verifier and jit? Just to keep all related code in one place. > E.g. technically nothing prevents x86 jit to do this detection in a more > precise manner as a "fixed point" computation. > Hm, I remember I did this and then decided against it for some reason, but I can't remember now. I will make this change though, if I remember why I didn't go ahead with it, I will reply again. Also, what did you mean by the final sentence?
