Re: [PATCH 8/8] x86/EFI: don't have an overly large image size

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Apr 01, 2021 at 11:47:35AM +0200, Jan Beulich wrote:
> While without debug info the difference is benign (so far), since we pad
> the image to 16Mb anyway, forcing the .reloc section to a 2Mb boundary
> causes subsequent .debug_* sections to go farther beyond 16Mb than
> needed. There's no reason to advance . for establishing __2M_rwdata_end,
> as all data past _end is of no interest at runtime anymore anyway.

So you just expand the load size.

> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

> ---
> This makes more explicit a possible latent problem with the ELF image:
> It ends at _end, not __2M_rwdata_end (advancing . as was done here does
> not have the effect of increasing the image size). Interestingly the
> conversion xen-syms => xen rounds up the program header specified size
> suitably, as per the comment "Do not use p_memsz: it does not include
> BSS alignment padding" in mkelf32.c. I do think this would instead want
> taking care of in the linker script. Commit 7a95e0a2c572 ("x86: properly
> calculate xen ELF end of image address") clearly only hacked an existing
> hack rather than addressing the root cause. Thoughts?

We should likely define _end after __2M_rwdata_end to account for this
padding?

Thanks, Roger.