linux-kernel - Re: [PATCH] livepatch: use FTRACE_OPS_FL

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Date:	Fri, 19 Dec 2014 10:43:35 +0100
From:	Petr Mladek <pmladek@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Christoph Hellwig <hch@...radead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	live-patching@...r.kernel.org, x86@...nel.org, kpatch@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] livepatch: use FTRACE_OPS_FL_IPMODIFY

On Thu 2014-12-18 09:49:35, Josh Poimboeuf wrote:
> On Thu, Dec 18, 2014 at 08:55:21PM +0900, Masami Hiramatsu wrote:
> > (2014/12/17 2:58), Seth Jennings wrote:
> > > changes in v7:
> > > - TODO: set IPMODIFY (not a blocker to moving forward)
> > 
> > Why don't you set this?
> > IPMODIFY series are not completely applied yet, but you can already
> > use the flag. All you need is just set it :)
> 
> Yeah, I don't see any reason why we can't start using this flag now.
> How about we add this patch to the queue?
> 
> -->8--
> 
> Subject: livepatch: use FTRACE_OPS_FL_IPMODIFY
> 
> Use the FTRACE_OPS_FL_IPMODIFY flag to prevent conflicts with other
> ftrace users who also modify regs->ip.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

It makes sense. The flag is available even in 3.19.

Reviewed-by: Petr Mladek <pmladek@...e.cz>

> ---
>  kernel/livepatch/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 0004a71..bdd99975 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -640,7 +640,8 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
>  
>  	ops->private = func;
>  	ops->func = klp_ftrace_handler;
> -	ops->flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_DYNAMIC;
> +	ops->flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_DYNAMIC |
> +		     FTRACE_FL_IPMODIFY;
>  	func->fops = ops;
>  	func->state = KLP_DISABLED;
>  
> -- 
> 2.1.0
> 
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