Re: [PATCH 6/6] x86: kaslr: relocate base offset at boot

From: Yinghai Lu
Date: Mon Apr 15 2013 - 18:57:15 EST

On Mon, Apr 15, 2013 at 3:42 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Mon, Apr 15, 2013 at 3:38 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
>> so the decompressed image is not moved high?
> No, I mean the size of the relocated image is using z_extract_offset
> as the end size of the relocated memory. See select_aslr_address. It
> takes the chosen aslr offset plus the location of z_extract_offset and
> keeps reducing the offset until it's inside the physical end of
> memory.

My point is:
If you move the decompressed high, for example, before aslr uncompressed
vmlinx is on [1024g+16M, 1024g+256M).
after aslr, it is on [1024g+16M + 32M, 1024g+256M + 32M).

You will need to make sure that 32M is still RAM in e820 memmap.
also those range should not be with boot_param, command line, and initrd.
as bootloader could put boot_param, commandline and initrd in that 32M range.

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