linux-kernel - Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on func_ptr_is_kernel

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Message-ID: <20131106060737.GC24044@gmail.com>
Date:	Wed, 6 Nov 2013 07:07:37 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	x86@...nel.org, lkml <linux-kernel@...r.kernel.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on
 func_ptr_is_kernel_text


* Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> >> [...] I hope to build the list when the kernel build time if 
> >> possible... Would you have any idea to classify some annotated(but no 
> >> side-effect) functions?
> > 
> > The macro magic I can think of would need to change the syntax of the 
> > function definition - for example that is how the SYSCALL_DEFINE*() 
> > macros work.
> 
> Would you mean something like the below macro? :)
> 
> NOKPROBE_SYMBOL(int, func_ptr_is_kernel_text)(void *ptr)

I think this is rather ugly and harder to maintain. The whole _point_ of 
such annotations is to make them 'easy on the eyes', to make it easy to 
skip a 'noinline', 'noprobe' or 'notrace' tag.

Using something like NOKPROBE_SYMBOL() makes the whole construct ugly and 
attention seeking.

So until compilers get smarter (or there's some compiler trick I haven't 
noticed) lets stay with the separate section - it's not the end of the 
world, the (effective) 'noinline' aspect of noprobes changes code 
generation anyway.

Thanks,

	Ingo
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