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Date: Mon, 16 Mar 2015 13:11:52 +0800
From: Baoquan He <bhe@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>,
        Thomas Gleixner <tglx@linutronix.de>, Jiri Kosina <jkosina@suse.cz>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
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        Matt Fleming <matt.fleming@intel.com>
Subject: Re: [PATCH v4] x86, kaslr: Access the correct kaslr_enabled variable
Message-ID: <20150316051152.GE26587@dhcp-16-105.nay.redhat.com>
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On 03/15/15 at 09:36pm, Yinghai Lu wrote:
> On Sun, Mar 15, 2015 at 8:28 PM, Baoquan He <bhe@redhat.com> wrote:
> > On 03/15/15 at 12:49am, Yinghai Lu wrote:
> > It's good to check the ret value as Boris suggested. However it could
> > fail since early_memremap self fail, e.g slot not found. In this case
> > making kaslr_enabled true may not be good.
> >
> > As Minfei talked with you kaslr_setup_data is a global variable inside
> > kernel code, it has been ident mapped. Just derefencing the physical
> > address which is virtual address too and getting the real stored value
> > may be safer. And also parse_kaslr_setup is a function specified to
> > handle kaslr, it doesn't make me uncomfortable to implement with a
> > specific knowledge which here means the setup_data is a global varialbe
> > in kernel code and no need to do early_memremap since mapping has been
> > built .
> 
> I should not put that checking in. even parse_setup_data does not check
> early_memmap return.

Yes, I think so. Otherwise it involves incorrect handling. 

Still I think no need to do early_memremap. Because kaslr_setup_data is
ident mapped, it's not like other setup_data info which is passed in
from bootloader. But I am fine too if only do early_memremap
without checking.


Thanks
Baoquan