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

[Kees Cook]

On Mon, Apr 15, 2013 at 3:38 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> On Mon, Apr 15, 2013 at 3:07 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Mon, Apr 15, 2013 at 3:00 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
>>> also do not overlap with boot_param, command_line, and initrd.
>>>
>>> and need to double check setup_header.init_size to make sure bss and
>>> etc will not
>>> fall into memory hole or reserved area in e820.
>>>
>>> also may need to setup page table for target position as bootloader may only
>>> has ident mapping only for loaded bzImage 64 areas.
>>>
>>> looks you are trying redo the work for bootloader to pick loaded phys addr.
>>
>> aslr.S's select_aslr_address uses z_extract_offset as the upper bound.
>
> 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.

-Kees

--
Kees Cook
Chrome OS Security
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