Messages in this thread | | | Subject | Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack | From | "H. Peter Anvin" <> | Date | Wed, 2 Mar 2016 13:54:50 -0800 |
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On 03/02/16 13:46, Borislav Petkov wrote: > On Wed, Mar 02, 2016 at 01:35:09PM -0800, H. Peter Anvin wrote: >> You're not actually testing anything as the real issue is what happens >> with a relocating bootloader. > > Hmm, how would that relocation happen so that va - __START_KERNEL_map > doesn't give pa? > > Or do you mean something else with "relocating bootloader"? Do you know > of one which does that? >
A relocating bootloader is one that doesn't load the kernel at CONFIG_PHYSICAL_ADDRESS. The EFI stub is one example.
__START_KERNEL_map is not relocated. On x86-64 we do relocation by pointing the page tables at a different address.
So I really think we need this to be a leaq, so we take a nonstandard load address into consideration.
-hpa
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