linux-kernel - Re: [PATCH] x86, boot: Allow 64bit EFI kernel to be loaded above 4G

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Message-ID: <CAE9FiQVuT=6bDJujEK_A4CepDOq2T0bcesgiUqGh53L0aZ3xDA@mail.gmail.com>
Date:	Thu, 19 Feb 2015 19:35:19 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Baoquan He <bhe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, boot: Allow 64bit EFI kernel to be loaded above 4G

On Thu, Feb 19, 2015 at 6:13 PM, Baoquan He <bhe@...hat.com> wrote:
> On 02/18/15 at 11:47am, Yinghai Lu wrote:
>
> Kaslr need both virtual and physical address be randomized, otherwise
> it doesn't make sense. Please check what hpa said about this issue:
>
> https://lkml.org/lkml/2014/10/13/350
>

If I read correctly, it could be separated. phy one could be on bootloader
and virtual could be in kernel.

> And usually no bootloader often load kernel onto a random physical
> address. Fow now we can often see kexec/kdump did this. I believe Kees
> introduced kaslr to mainly solve security issue of normal kernel which
> is not like kexec/kdump for testing or debugging. Randomizing physical
> address makes sense for kaslr feature.

I put some grub2 patches that extend grub2 to load kernel/initrd above
4G into github tree.

https://github.com/yhlu/grub2.git

main purpose for that feature is to handle initrd that bigger than 4G.

or you can try you solution on system that have 64bit EFI support,
then you will don't need to
worry about set ident mapping even.

Thanks

Yinghai
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