linux-kernel - Re: [RFC][PATCH] Kprobes: The ON/OFF knob thru debugfs

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Message-ID: <20070408102231.GA2297@infradead.org>
Date:	Sun, 8 Apr 2007 11:22:31 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Prasanna S Panchamukhi <prasanna@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>, srinivasa@...ibm.com,
	akpm@...ux-foundation.org,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	hch@...radead.org, davem@...emloft.net, richardj_moore@...ibm.com
Subject: Re: [RFC][PATCH] Kprobes: The ON/OFF knob thru debugfs

On Wed, Apr 04, 2007 at 05:43:49PM +0530, Ananth N Mavinakayanahalli wrote:
> This patch provides a debugfs knob to turn kprobes on/off
> 
> o A new file /debug/kprobes/enabled indicates if kprobes is enabled or
>   not (default enabled)
> o Echoing 0 to this file will disarm all installed probes
> o Any new probe registration when disabled will register the probe but
>   not arm it. A message will be printed out in such a case.
> o When a value 1 is echoed to the file, all probes (including ones
>   registered in the intervening period) will be enabled
> o Unregistration will happen irrespective of whether probes are globally
>   enabled or not.
> o Update Documentation/kprobes.txt to reflect these changes. While there
>   also update the doc to make it current.

Looks good.

When I suggested a user interface to enable/disable probes was nice to
have I was more thinking about a interface to enable/disable individual
probes.  Any chance you could try to implement that aswell as see if
any code can be shared with this feature?

> -	arch_arm_kprobe(p);
> +		arch_arm_kprobe(p);
> +	} else
> +		printk("Kprobes are globally disabled. This kprobe [@ %p] "
> +			"will be enabled with all other probes\n", p->addr);

This printk seems far too verbose.  Just remove it and make sure
the debugfs interface has an indicator of whether probes are en- or
disabled.

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