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Date: Mon, 16 Mar 2015 11:08:18 +0800
From: Minfei Huang <mhuang@redhat.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@suse.de>,
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        Matt Fleming <matt.fleming@intel.com>
Subject: Re: [PATCH v4] x86, kaslr: Access the correct kaslr_enabled variable
Message-ID: <20150316030818.GA14862@dhcp-128-1.nay.redhat.com>
References: <1426405767-21100-1-git-send-email-yinghai@kernel.org>
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On 03/15/15 at 10:02am, Yinghai Lu wrote:
> On Sun, Mar 15, 2015 at 5:18 AM, Minfei Huang <mhuang@redhat.com> wrote:
> > On 03/15/15 at 12:49am, Yinghai Lu wrote:
> > It confuses me with the virtual address in function parse_kaslr_setup.
> > When we are in here(parse_kaslr_setup), we already use the virtual
> > address, instead of physical address. Is it all right?
> 
> setup_data is using physical address to have linked list.
> 
> we have setup_arch==>parse_setup_data(), that is way before
> init_mem_mapping() to have final kernel mapping setup yet.
> 
> For 64bit, we may use virtual address with help of early mapping with
> #PF handler.
> But 32bit, we don't have that.
> 
> So just use early_memmap to get virtual address to access the value.
> 

Hi, Yinghai!

Thank you for your reply.
I find that the variate kaslr_setup_data is a global variate. Always we
can use physical address to access the value.

But it is more comfortable that we use the early_memmap to access the
value.

Thanks
Minfei

> >
> > In the other words, using physical address in parse_kaslr_setup is
> > always a mistake, whatever the kaslr is on or off.
> >
> 
> The problem is: old code just use physical address as value.
> 
> Thanks
> 
> Yinghai