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From: Kees Cook <keescook@chromium.org>
Date: Thu, 8 Dec 2016 10:31:47 -0800
Message-ID: <CAGXu5j+tUWv11ztq7Ma_z_y_jpN5a9dbO3w-FsVagxz_f5Hj8Q@mail.gmail.com>
Subject: Re: [PATCH 0/2] Determine kernel text mapping size at runtime for x86_64
To: Baoquan He <bhe@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Ingo Molnar <mingo@redhat.com>, "x86@kernel.org" <x86@kernel.org>,
        Yinghai Lu <yinghai@kernel.org>, Borislav Petkov <bp@suse.de>,
        Thomas Garnier <thgarnie@google.com>,
        Alexander Kuleshov <kuleshovmail@gmail.com>,
        Andy Lutomirski <luto@kernel.org>, Dave Anderson <anderson@redhat.com>,
        Dave Young <dyoung@redhat.com>, Xunlei Pang <xlpang@redhat.com>
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On Wed, Dec 7, 2016 at 11:56 PM, Baoquan He <bhe@redhat.com> wrote:
> Dave Anderson ever told in Crash utility he makes judgement whether it's
> a kaslr kernel by size of KERNEL_IMAGE_SIZE. As long as it's 1G, it's
> recognized as kaslr. Then the current upstream kernel has a wrong behaviour,
> it sets KERNEL_IMAGE_SIZE as 1G as long as CONFIG_RANDOMIZE_BASE is enabled,
> though people specify "nokaslr" into cmdline to disable kaslr explicitly.

I'm not sure that's the correct solution to the Crash utility -- the
kaslr-ness of a kernel should be already exposed in the dump with the
kaslr_enabled variable yes?

> So in this patchset, made changes to determine the size of kernel text mapping
> area at runtime. If "nokaslr" specified, kernel mapping size is 512M though
> CONFIG_RANDOMIZE_BASE is enabled.

This seems to make the non-KASLR case more consistent, so I'm fine
with the idea. Once the build-bots are happy with everything, consider
the series:

Acked-by: Kees Cook <keescook@chromium.org>

Thanks!

-Kees

>
> Baoquan He (2):
>   x86/64: Make kernel text mapping always take one whole page table in
>     early boot code
>   x86/KASLR/64: Determine kernel text mapping size at runtime
>
>  arch/x86/boot/compressed/kaslr.c        | 15 ++++++++++-----
>  arch/x86/include/asm/kaslr.h            |  1 +
>  arch/x86/include/asm/page_64_types.h    | 20 ++++++++++++--------
>  arch/x86/include/asm/pgtable_64_types.h |  2 +-
>  arch/x86/kernel/head64.c                | 11 ++++++-----
>  arch/x86/kernel/head_64.S               | 16 +++++++++-------
>  arch/x86/mm/dump_pagetables.c           |  3 ++-
>  arch/x86/mm/init_64.c                   |  2 +-
>  arch/x86/mm/physaddr.c                  |  6 +++---
>  9 files changed, 45 insertions(+), 31 deletions(-)
>
> --
> 2.5.5
>


-- 
Kees Cook
Nexus Security