Re: [PATCH 2/3] introduce probe_slab_address()

From: Kirill Tkhai <ktkhai@parallels.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>,
	Peter Zijlstra <peterz@infradead.org>,
	<linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
	"Vladimir Davydov" <vdavydov@parallels.com>,
	Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 2/3] introduce probe_slab_address()
Date: Wed, 29 Oct 2014 08:10:32 +0300	[thread overview]
Message-ID: <1414559432.8574.15.camel@tkhai> (raw)
In-Reply-To: <20141028201221.GA2106@redhat.com>

В Вт, 28/10/2014 в 21:12 +0100, Oleg Nesterov пишет:
> On 10/28, Oleg Nesterov wrote:
> >
> > On 10/28, Kirill Tkhai wrote:
> > >
> > > Yes, probe_kernel_read() is in [1/3], but it's not the same as
> > > __probe_kernel_read() for blackfin, for example.
> > >
> > > It's defined as
> > >
> > > long __weak probe_kernel_read(void *dst, const void *src, size_t size)
> > >     __attribute__((alias("__probe_kernel_read")));
> > >
> > > But blackfin's probe_kernel_read() redefines this __weak function,
> > > isn't it? Didn't get_freepointer_safe() use to call architecture's
> > > probe_kernel_read() before?
> >
> > I _think_ that __probe_kernel_read(slab_ddr) should be fine.
> >
> > Yes, an architecture may want to reimplement probe_kernel_read() to
> > allow to safely access the special areas, or special addresses.
> >
> > But again, in this case we know that this address points to the
> > "normal" kernel memory, __copy_from_user_inatomic() should work fine.
> 
> OTOH, perhaps probe_kernel_address() should use probe_kernel_read(), not
> __probe_kernel_read(). But currently it just calls __copy_inatomic() so
> 1/3 follows this logic.

Ok, thanks for the explanation, Oleg.