linux-kernel - Re: [patches] [PATCH for 2.6.22] [9/10] i386: Disable alternative()patching after boot with DEBUG

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Message-Id: <467931E0.76E4.0078.0@novell.com>
Date:	Wed, 20 Jun 2007 12:55:44 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	<torvalds@...l.org>, "Andi Kleen" <ak@...e.de>,
	<linux-kernel@...r.kernel.org>, <patches@...-64.org>
Subject: Re: [patches] [PATCH for 2.6.22] [9/10] i386: Disable
	alternative()patching after boot with DEBUG_RO

>>> Andi Kleen <ak@...e.de> 20.06.07 12:23 >>>
>
>Kernel text is protected now so this won't work.
>
>We'll fix it better next time.
>
>Signed-off-by: Andi Kleen <ak@...e.de>
>
>---
> arch/i386/kernel/alternative.c |    5 +++++
> 1 file changed, 5 insertions(+)
>
>Index: linux/arch/i386/kernel/alternative.c
>===================================================================
>--- linux.orig/arch/i386/kernel/alternative.c
>+++ linux/arch/i386/kernel/alternative.c
>@@ -308,6 +308,11 @@ void alternatives_smp_switch(int smp)
> 	printk("lockdep: not fixing up alternatives.\n");
> 	return;
> #endif
>+#ifdef CONFIG_DEBUG_RODATA
>+	/* To be fixed properly post 2.6.22 -- need to get writable
>+ 	   mappings of the kernel text */
>+	return;
>+#endif
> 
> 	if (noreplace_smp || smp_alt_once)
> 		return;

Why would we need this? mark_rodata_ro() already accounts for the
CONFIG_HOTPLUG_CPU case in that it doesn't write protect .text then.

Jan

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