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Date: Tue, 19 Nov 2013 21:16:32 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <andi@firstfloor.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH] Add a text_poke syscall
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> > +	pages[1] = NULL;
> > +	npages = ((unsigned long)addr & PAGE_MASK) == 
> > +		(((unsigned long)addr + len) & PAGE_MASK) ? 1 : 2;
> 
> This is off by one, I think.  That should be addr + len - 1.

Thanks fixed.

> 
> > +	err = get_user_pages_fast((unsigned long)addr, npages, 1, pages);
> > +	if (err < 0)
> > +		return err;
> > +	err = 0;
> > +	mutex_lock(&text_mutex);
> > +	bp_target_mm = current->mm;
> > +	bp_int3_addr = (u8 *)addr + 1;
> 
> Do you need an smp_wmb here?  (Maybe there's a strong enough barrier in
> __text_poke_bp.)

__text_poke_bp already has enough barriers (although I don't
think they are really needed in any case)

-Andi