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

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Date:	Fri, 18 Jul 2014 16:10:29 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Namhyung Kim <namhyung@...il.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: Re: [PATCH ftrace/core v3 3/3] kprobes: Set IPMODIFY flag
 only if the probe can change regs->ip

(2014/07/18 14:32), Namhyung Kim wrote:
> 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;

Indeed :)

Thanks!


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


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