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

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Date:	Sun, 23 Nov 2008 16:51:34 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alexander van Heukelum <heukelum@...lshack.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END

[Ingo Molnar - Sun, Nov 23, 2008 at 02:27:52PM +0100]
| 
| * 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
| 

I think we could play with preprocessor and check if ENTRY/END matches.
Looking now.

		- Cyrill -
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