linux-kernel - Re: [PATCH -mm] kprobes: kretprobe user entry-handler (updated)

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Message-ID: <20080128105702.GE12910@shadowen.org>
Date:	Mon, 28 Jan 2008 10:57:03 +0000
From:	Andy Whitcroft <apw@...dowen.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Abhishek Sagar <sagar.abhishek@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, jkenisto@...ibm.com,
	ananth@...ibm.com
Subject: Re: [PATCH -mm] kprobes: kretprobe user entry-handler (updated)

On Sun, Jan 27, 2008 at 09:32:57PM -0800, Andrew Morton wrote:
> On Sat, 26 Jan 2008 23:52:48 +0530 Abhishek Sagar <sagar.abhishek@...il.com> wrote:
> 
> > This is a repost of a patch which was reviewed earlier at:
> > http://lkml.org/lkml/2007/11/13/58 (thanks to Jim Keniston and Srinivasa for their review comments). This provides support to add an optional user defined callback to be run at function entry of a kretprobe'd function. It also modifies the kprobe smoke tests to include an entry-handler during the kretprobe sanity test.
> > 
> 
> Neither the changelog nor the newly-added documentation explain why Linux
> needs this feature.  What will it be used for??
> 
> 
> > +1.3.2 Kretprobe entry-handler
> > +
> > +Kretprobes also provides an optional user-specified handler which runs
> 
> I think "caller-specified" would be a better term here.  Generally "user"
> refers to Aunt Tillie sitting at the keyboard.
> 
> > +/* Timestamp function entry. */
> > +static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
> > +{
> > +	struct my_data *data;
> > +
> > +	if(!current->mm)
> > +		return 1; /* skip kernel threads */
> 
> gargh, what's happened to checkpatch lately?  It failed to notice the
> missing space.

This had me going for a while.  This was missed as this code is not
actually in a source file.  Its actually found in Documentation/kprobes.txt
and we do not apply source level checks to non-source file types.

Hmmm.

-apw
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