linux-kernel - Re: [PATCH] ftrace: Remove a superfluous check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.2.02.1203291914040.10113@tycho>
Date:	Thu, 29 Mar 2012 19:17:19 +0200 (CEST)
From:	John Kacur <jkacur@...hat.com>
To:	Borislav Petkov <bp@...64.org>
cc:	John Kacur <jkacur@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: Remove a superfluous check



On Thu, 29 Mar 2012, Borislav Petkov wrote:

> On Thu, Mar 29, 2012 at 07:03:23PM +0200, John Kacur wrote:
> > If you're going to do this, then you can drop the label too.
> 
> Jahaa... thanks.
> 
> Here's an updated patch:
> 
> --
> From 135c25a609739bbdf1c33e62119517b47f0e1d07 Mon Sep 17 00:00:00 2001
> From: Borislav Petkov <borislav.petkov@....com>
> Date: Thu, 29 Mar 2012 18:41:15 +0200
> Subject: [PATCH] ftrace: Remove a superfluous check
> 
> register_ftrace_function() checks ftrace_disabled and calls
> __register_ftrace_function which does it again.
> 
> Drop the first check and add the unlikely hint to the second one. Also,
> drop the label as John correctly notices.
> 
> No functional change.
> 
> Cc: John Kacur <jkacur@...hat.com>
> Signed-off-by: Borislav Petkov <borislav.petkov@....com>
> ---
>  kernel/trace/ftrace.c |    8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 867bd1dd2dd0..0df8f8088ffe 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -311,7 +311,7 @@ static int remove_ftrace_list_ops(struct ftrace_ops **list,
>  
>  static int __register_ftrace_function(struct ftrace_ops *ops)
>  {
> -	if (ftrace_disabled)
> +	if (unlikely(ftrace_disabled))
>  		return -ENODEV;
>  
>  	if (FTRACE_WARN_ON(ops == &global_ops))
> @@ -4304,16 +4304,12 @@ int register_ftrace_function(struct ftrace_ops *ops)
>  
>  	mutex_lock(&ftrace_lock);
>  
> -	if (unlikely(ftrace_disabled))
> -		goto out_unlock;
> -
>  	ret = __register_ftrace_function(ops);
>  	if (!ret)
>  		ret = ftrace_startup(ops, 0);
>  
> -
> - out_unlock:
>  	mutex_unlock(&ftrace_lock);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(register_ftrace_function);
> -- 
> 1.7.9.3.362.g71319
> 

It looks okay to me. Technically it's not functionally equivalent though, 
because now when __register_ftrace_function is called directly, (in other 
paths), the test has an unlikely there. See what Steven says, otherwise, 
you can have my reviewed by.

Thanks

John
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/