linux-kernel - Re: [patch 06/10] Text Edit Lock - kprobes architecture independent support

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Message-ID: <20070907141321.GG9735@Krystal>
Date:	Fri, 7 Sep 2007 10:13:21 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	prasanna@...ibm.com, anil.s.keshavamurthy@...el.com,
	davem@...emloft.net
Subject: Re: [patch 06/10] Text Edit Lock - kprobes architecture independent support

* Ananth N Mavinakayanahalli (ananth@...ibm.com) wrote:
> On Thu, Sep 06, 2007 at 04:01:30PM -0400, Mathieu Desnoyers wrote:
> 
> <snip>
> 
> > @@ -716,8 +720,9 @@ static int __kprobes pre_handler_kretpro
> >  				 struct kretprobe_instance, uflist);
> >  		ri->rp = rp;
> >  		ri->task = current;
> > +		kernel_text_lock();
> >  		arch_prepare_kretprobe(ri, regs);
> > -
> > +		kernel_text_unlock();
> 
> pre_handler_kretprobe() is run when the entry probe for a retprobed
> function is hit and cannot block. You can't take a mutex here.
> 
> And why do we need to take the kernel_text_lock() here anyway? All
> arch_prepare_kretprobe() does is modify the return address stored either
> on stack or a register (arch specific) to the trampoline. We don't
> change any kernel text here.
> 

Yep, good catch. Fixing.

> Ananth

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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