Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual address of kernel separately

From	Baoquan He <bhe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual address of kernel separately
Date	2016-03-09 14:50 +0100
Message-ID	<raMEW-9f-3@gated-at.bofh.it> (permalink)
References	<r90M1-Y1-7@gated-at.bofh.it> <r90M3-Y1-51@gated-at.bofh.it> <radeb-1go-45@gated-at.bofh.it> <raixb-4Yw-1@gated-at.bofh.it> <rauym-4FV-13@gated-at.bofh.it>
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On 03/08/16 at 10:24am, Kees Cook wrote:
> On Mon, Mar 7, 2016 at 9:34 PM, Baoquan He <bhe@redhat.com> wrote:
> >> It seems like CONFIG_RANDOMIZE_BASE_MAX_OFFSET should have been
> >> eliminated when the on-demand page table code was added. Once that was
> >> added, there's no physical max any more. And virtual randomization
> >> should have no max at all.
> > For physically random, yes, CONFIG_RANDOMIZE_BASE_MAX_OFFSET is not
> > needed anymore. But for virtually random,
> > CONFIG_RANDOMIZE_BASE_MAX_OFFSET is still mandatory since kernel text
> > mapping and kernel module mapping share the 2G virtual address space as
> > follows. Though kaslr increase kernel text mapping from 512M to 1G, it's
> > still limited, can't exceed CONFIG_RANDOMIZE_BASE_MAX_OFFSET.
> >
> > [0xffffffff80000000, 0xffffffffffffffff]
> >
> > But now as you suggested, I would like to change
> > CONFIG_RANDOMIZE_BASE_MAX_OFFSET to another name because it's only
> > valid for virtual randomization. A more specific name is better.
> 
> Yes, right, the virtual has a 1G max, but I meant that it doesn't need
> to be a CONFIG item any more. Physical can use physical memory max as
> its max, and virtual max can now be calculated from the existing text
> mapping size.

Got it, it should be KERNEL_IMAGE_SIZE instead, right?

Thread

[PATCH v3 16/19] x86, kaslr: Randomize physical and virtual address of kernel separately Baoquan He <bhe@redhat.com> - 2016-03-04 17:30 +0100
  Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Kees Cook <keescook@chromium.org> - 2016-03-08 01:00 +0100
    Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Baoquan He <bhe@redhat.com> - 2016-03-08 06:40 +0100
      Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Kees Cook <keescook@chromium.org> - 2016-03-08 19:30 +0100
        Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Baoquan He <bhe@redhat.com> - 2016-03-09 14:50 +0100
          Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Kees Cook <keescook@chromium.org> - 2016-03-09 19:10 +0100
            Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual  address of kernel separately Baoquan He <bhe@redhat.com> - 2016-03-10 16:20 +0100

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