On 15.05.2018 21:10, Alexander Boettcher wrote:
I assume that a given ELF PHDR address/size does not cover VGA memory or
anything like that,
No.
so, I am not sure what exactly overwrites this region.
grub_memset() in current line 161 at some point?
No. During grub_relocator_prepare_reloc the overwrite happens, if i'm
not wrong.
An (artificial) example, imagine two ELF PHDRs, e.g.
[0x8000-0x9000) and
[0x2000000-0x2100000).
Without this patch grub calculates one relocator chunk of size 0x20f8000
(0x2100000 - 0x8000) and places it at some higher memory, e.g.
[0x3000000 - 0x30f8000). During the invocation of
Must be [0x3000000-0x50f8000)
grub_relocator_prepare_reloc the memory gets copied from
[0x3000000-0x30f8000) to [0x8000-0x2100000)
Must be [0x3000000-0x50f8000) to [0x8000-0x2100000)
Sorry.
--
Alexander Boettcher
Genode Labs
http://www.genode-labs.com - http://www.genode.org
Genode Labs GmbH - Amtsgericht Dresden - HRB 28424 - Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth
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