linux-kernel - Re: [PATCH -tip v6 04/11] kprobes: Jump optimization sysctl interface

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Message-ID: <m1my27txdo.fsf@fess.ebiederm.org>
Date:	Fri, 27 Nov 2009 14:29:23 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Jim Keniston <jkenisto@...ibm.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Anders Kaseorg <andersk@...lice.com>,
	Tim Abbott <tabbott@...lice.com>,
	Andi Kleen <andi@...stfloor.org>,
	Jason Baron <jbaron@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [PATCH -tip v6 04/11] kprobes: Jump optimization sysctl interface

Masami Hiramatsu <mhiramat@...hat.com> writes:

> Add /proc/sys/debug/kprobes-optimization sysctl which enables and disables
> kprobes jump optimization on the fly for debugging.
>
> Changes in v6:
> - Update comments and coding style.
>

This will break when it hits the linux-next.  As ctl_name has been
removed in the sysctl tree.  Not setting ctl_name is equivalent
to setting ctl_name = CTL_UNNUMBERED.  It is 0 in both cases.
So you can safely drop touches of ctl_name.

Ideally you would also call register_sysctl_paths from kernel/kprobes.c
and not add to the ifdef horror that is kernel/sysctl.c but that
is probably more trouble than it is worth right now.    One way or
another there is going to be at least a minor conflict when this code 
merges with the sysctl tree.

>  #include <asm/uaccess.h>
>  #include <asm/processor.h>
> @@ -1621,6 +1622,18 @@ static struct ctl_table debug_table[] = {
>  		.proc_handler	= proc_dointvec
>  	},
>  #endif
> +#if defined(CONFIG_OPTPROBES)
> +	{
> +		.ctl_name	= CTL_UNNUMBERED,
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Please remove this line.
> +		.procname	= "kprobes-optimization",
> +		.data		= &sysctl_kprobes_optimization,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_kprobes_optimization_handler,
> +		.extra1		= &zero,
> +		.extra2		= &one,
> +	},
> +#endif
>  	{ .ctl_name = 0 }
>  };


Eric
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