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

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Message-ID: <20141031120158.1f648f7a@gandalf.local.home>
Date:	Fri, 31 Oct 2014 12:01:58 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
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: [for-next][PATCH 1/4] ftrace/x86: Add dynamic allocated
 trampoline for ftrace_ops

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.

-- 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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