On Thu, Jan 21, 2021, Borislav Petkov wrote: > On Mon, Dec 28, 2020 at 11:15:11AM -0800, Sean Christopherson wrote: > > Alternatively, could the kernel case use insn_decode_regs()? If > > vc_fetch_insn_kernel() were also modified to mirror insn_fetch_from_user(), > > the > > two code paths could be unified except for the the fetch and the PFEC. E.g. > > Personal Firearms Eligibility Check?
Ha, Page Fault Error Code. > In any case, I prefer simple, easy to follow code at a quick glance. > Stuff like... > > > > > static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt, > > unsigned char *buffer) > > { > > if (copy_from_kernel_nofault(buffer, (unsigned char *)ctxt->regs->ip, > > MAX_INSN_SIZE)) > > return 0; > > > > return MAX_INSN_SIZE; > > } > > > > static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) > > { > > char buffer[MAX_INSN_SIZE]; > > int nbytes; > > > > if (user_mode(ctxt->regs)) > > nbytes = insn_fetch_from_user(ctxt->regs, buffer); > > else > > nbytes = vc_fetch_insn_kernel(ctxt, buffer); > > > > if (!nbytes) { > > ctxt->fi.vector = X86_TRAP_PF; > > ctxt->fi.error_code = X86_PF_INSTR; > > if (user_mode(ctxt->regs)) > > ... this second repeated check here is not what I would call that. But then you're stuck maintaining two separate flows that do the same thing. > But this is my personal preference only so it's up for a vote now. Rock Paper Scissors?