Re: Multiboot ELF segment handling patch

[Daniel Kiper]

On Mon, Apr 23, 2018 at 08:26:34PM +0200, Alexander Boettcher wrote:
> Hello,
>
> On 17.04.2018 21:40, Daniel Kiper wrote
> >> The overriden memory may contain device memory (vga text mode e.g.), which
> >> leads to strange boot behaviour.
> >
> > Have you been able to take a look at memory allocator/relocator code why
> > this happened?
>
> for me it looks like, that either already
> grub_relocator_alloc_chunk_addr or at latest
> grub_relocator_prepare_relocs should bail out with an error, if the
> memory range of the VGA memory (0xa0000 ++) is covered.

Exactly!

> What I don't know, respectively didn't found in the code, how and where
> this information about this VGA text memory area is excluded/reserved
> from the allocator/reallocator. Maybe you can give me a hint ?

I have skimmed through the code and I think that you should take
a look at grub-core/kern/i386/pc/init.c, grub-core/kern/mm.c and
grub-core/lib/relocator.c. At first sight it looks that
grub-core/kern/i386/pc/init.c:grub_machine_init() is the
most interesting thing.

I hope that helps. If you have further questions drop me a line.

Thank you for taking a stab at this.

Daniel