Re: [RFC][PATCH 1/3] ftrace/x86: Add dynamic allocated trampoline for ftrace_ops

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

(2014/07/04 5:07), Steven Rostedt wrote:
> +
> +void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
> +{
> +	unsigned char *new;
> +	unsigned long start_offset;
> +	unsigned long call_offset;
> +	unsigned long offset;
> +	unsigned long ip;
> +	int ret;
> +
> +	if (ops->trampoline) {
> +		/*
> +		 * The ftrace_ops caller may set up its own trampoline.
> +		 * In such a case, this code must not modify it.
> +		 */
> +		if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
> +			return;

Just a question, what happen if the ftrace_ops caller sets up a trampoline which is
not compatible to the ftrace's trampoline, and the ftrace_ops conflicts on a IP with other
ftrace_ops? I guess in that case ftrace will use the loop callback on the IP, but since
the trampoline is not compatible, the result will not be same, is that right? :)

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com