linux-kernel - Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash

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Date:	Tue, 12 Mar 2013 09:16:28 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Timo Juhani Lindfors <timo.lindfors@....fi>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Nadia Yvette Chambers <nyc@...omorphy.com>,
	yrl.pp-manager.tt@...achi.com,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash_64() into .text.kprobe
 section


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

> Beacuse hash_64() is called from the get_kprobe() inside
> int3 handler, kernel causes int3 recursion and crashes if
> kprobes user puts a probe on it.
> 
> Usually hash_64() is inlined into caller function, but in
> some cases, it has instances by gcc's interprocedural
> constant propagation.
> 
> This patch adds __kprobes tag on the hash_64() and moves
> all those instances into .text.kprobe section so that
> kprobes can refuse probing on the instances.
> 
> I've ensured that all hash_64 instances moves to the
> address between __kprobes_text_start and __kprobes_text_end
> with this patch as below.
> 
> ffffffff8138bea0 T __kprobes_text_start
> ffffffff8138bec0 t hash_64.constprop.8
> ffffffff8138ef98 t hash_64.constprop.26
> ffffffff8138efae t hash_64
> ffffffff8138f066 t hash_64.constprop.43
> ffffffff8138f649 t hash_64.constprop.25
> ffffffff8139103a t hash_64.constprop.77
> ffffffff81391050 t hash_64.constprop.24
> ffffffff81391066 t hash_64.constprop.40
> ffffffff8139107c t hash_64.constprop.15
> ffffffff81391092 T __kprobes_text_end
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Reported-by: Timo Juhani Lindfors <timo.lindfors@....fi>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Nadia Yvette Chambers <nyc@...omorphy.com>
> Cc: Pavel Emelyanov <xemul@...allels.com>
> Cc: Jiri Kosina <jkosina@...e.cz>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> ---
>  include/linux/hash.h |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/hash.h b/include/linux/hash.h
> index 61c97ae..d83f62f 100644
> --- a/include/linux/hash.h
> +++ b/include/linux/hash.h
> @@ -15,6 +15,7 @@
>   */
>  
>  #include <asm/types.h>
> +#include <linux/kprobes.h>

I have no objections to the fix itself, but this inclusion of kprobes.h in 
hash.h is somewhat sad: kprobes.h is a 'fat' header that includes a lot of 
header files - while hash.h is a really basic type header included in 
close to a hundred .c files.

I think one solution would be for the __kprobes definition to move to a 
more basic header file - such as types.h or compiler.h (where the 
'notrace' attribute is placed too), to stop this header dependency creep.

Thanks,

	Ingo
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