Messages in this thread | | | Date | Wed, 9 Mar 2016 21:40:09 +0800 | From | Baoquan He <> | Subject | Re: [PATCH v3 16/19] x86, kaslr: Randomize physical and virtual address of kernel separately |
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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?
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