linux-kernel - Re: Re: [for-next][PATCH 1/4] ftrace/x86: Add dynamic allocated trampoline for ftrace

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Date:	Mon, 03 Nov 2014 16:50:21 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Seth Jennings <sjenning@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: Re: [for-next][PATCH 1/4] ftrace/x86: Add dynamic allocated
 trampoline for ftrace_ops

(2014/11/01 1:01), Steven Rostedt wrote:
> On Fri, 31 Oct 2014 14:19:03 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
> 
>>> +	/* Load the contents of ptr into the callback parameter */
>>> +	offset = (unsigned long)ptr;
>>> +	offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
>>> +
>>> +	op_ptr.offset = offset;
>>> +
>>> +	/* put in the new offset to the ftrace_ops */
>>> +	memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
>>
>> Would we better call flush_icache_range here?
> 
> Do we need to? We just allocated memory to execute. It shouldn't be in
> any CPU cache on the machine.

Indeed, if the trampoline buffer is not re-used (and it seems so),
we don't need to care about it.

OK, I've reviewed that :).

Thank you,

> 
> -- Steve
> 
> 
>>
>> Thank you,
>>
>>> +
>>> +	/* ALLOC_TRAMP flags lets us know we created it */
>>> +	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
>>> +
>>> +	return (unsigned long)trampoline;
>>> +}
>>
>>
> 
> --
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> 


-- 
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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