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

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 10 Jul 2020 15:38:44 +0200
Peter Zijlstra <peterz@infradead.org> 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?

-- Steve


> -		return;
> +	switch (type) {
> +	case CALL:
> +		code = text_gen_insn(CALL_INSN_OPCODE, insn, func);
> +		break;
> +
> +	case NOP:
> +		code = ideal_nops[NOP_ATOMIC5];
> +		break;
> +
> +	case JMP:
> +		code = text_gen_insn(JMP32_INSN_OPCODE, insn, func);
> +		break;
> +
> +	case RET:
> +		code = text_gen_insn(RET_INSN_OPCODE, insn, func);
> +		size = RET_INSN_SIZE;
> +		break;
> +	}
>  
> -	if (memcmp(insn, code, CALL_INSN_SIZE) == 0)
> +	if (memcmp(insn, code, size) == 0)
>  		return;
>  
> -	text_poke_bp(insn, code, CALL_INSN_SIZE, NULL);
> +	text_poke_bp(insn, code, size, NULL);
>  }
>