lkml.org 
[lkml]   [2016]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual address of kernel separately
    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?

    \
     
     \ /
      Last update: 2016-03-09 15:21    [W:3.258 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site