linux-kernel - Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE

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Date:	Sun, 23 Nov 2008 14:27:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alexander van Heukelum <heukelum@...lshack.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Cyrill Gorcunov <gorcunov@...il.com>
Subject: Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END


* Alexander van Heukelum <heukelum@...lshack.com> wrote:

> Impact: moves some code out of .kprobes.text
> 
> KPROBE_ENTRY switches code generation to .kprobes.text, and KPROBE_END
> uses .popsection to get back to the previous section (.text, normally).
> Also replace ENDPROC by END, for consistency.
> 
> Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>

applied to tip/x86/irq, thanks Alexander!

> One more small change for today. The xen-related functions 
> xen_do_hypervisor_callback and xen_failsafe_callback are put
> in the .kprobes.text even in the current kernel: ignore_sysret
> is enclosed in KPROBE_ENTRY / ENDPROC, instead of KPROBE_ENTRY /
> KPROBE_END, but I guess the situation is harmless.

yeah. It narrows no-kprobes protection for that code, but it should 
indeed be fine (and that's the intention as well).

Note that this is a reoccuring bug type, and rather long-lived. Can 
you think of any way to get automated nesting protection of both the 
.cfi_startproc/endproc macros and kprobes start/end? A poor man's 
solution would be to grep the number of start and end methods and 
enforce that they are equal.

	Ingo
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