Re: [PATCH v6 13/17] static_call: Add static_call_cond()

[Peter Zijlstra]

On Fri, Jul 10, 2020 at 07:08:25PM -0400, Steven Rostedt wrote:
> On Fri, 10 Jul 2020 15:38:44 +0200
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > +static void __static_call_transform(void *insn, enum insn_type type, void *func)
> >  {
> > -	const void *code = text_gen_insn(opcode, insn, func);
> > +	int size = CALL_INSN_SIZE;
> > +	const void *code;
> >  
> > -	if (WARN_ONCE(*(u8 *)insn != opcode,
> > -		      "unexpected static call insn opcode 0x%x at %pS\n",
> > -		      opcode, insn))
> 
> I would still feel better if we did some sort of sanity check before
> just writing to the text. Confirm this is a jmp, call, ret or nop?

I'll see if I can come up with something, but I'm not sure we keep
enough state to be able to reconstruct what should be there.