linux-kernel - Re: [PATCH ftrace/core v3 3/3] kprobes: Set IPMODIFY flag only if the probe can change regs->ip

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Message-ID: <878unrkzag.fsf@sejong.aot.lge.com>
Date:	Fri, 18 Jul 2014 14:32:07 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH ftrace/core v3 3/3] kprobes: Set IPMODIFY flag only if the probe can change regs->ip

Hi Masami,

On Tue, 15 Jul 2014 06:00:35 +0000, Masami Hiramatsu wrote:
> +static int __ftrace_add_filter_ip(struct ftrace_ops *ops, unsigned long ip,
> +				  int *ref)
> +{
> +	int ret;
> +
> +	/* Try to set given ip to filter */
> +	ret = ftrace_set_filter_ip(ops, ip, 0, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	(*ref)++;
> +	if (*ref == 1) {
> +		ret = register_ftrace_function(ops);
> +		if (ret < 0) {
> +			/* Rollback refcounter and filter */
> +			(*ref)--;
> +			ftrace_set_filter_ip(ops, ip, 1, 0);
> +		}
> +	}
> +
> +	return ret;
> +}

This function also can be changed in a similar way:

	if (*ref == 0) {
		ret = register_ftrace_function(ops);
		if (ret < 0) {
			/* Rollback filter if failed */
			ftrace_set_filter_ip(ops, ip, 1, 0);
			return ret;
		}
	}

	(*ref)++;

	return 0;


Thanks,
Namhyung

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