.bss segment ends up in EFI bootloader binary

[pulkomandy]

For debugging of the EFI loader we added a static 16K buffer for storage of logs (as is done in the BIOS loader). This buffer is not initialized so it should be in the .bss section (to be cleared at program initialization). However we found out that the generated EFI file became larger according to the size of the buffer.

This likely means the BSS segments are included inside the binary, and we end up with a larger than needed loader, filled with zeros.

We should review the linker scripts and conversion to PE format to make sure the bss segment is not included in the binary, and if needed, add the startup code to allocate and clear it.

[tqh]

We probably want to compare FreeBSD and Fuchsia linker scripts. Not sure if we still use the one I derived from FreeBSD. Not assigning to me, since I am not an expert on linker script, but I can I help.

Also EFI firmware are kind of picky on file layout :(

[pulkomandy]

Untested change: ​https://review.haiku-os.org/c/haiku/+/2199

Indeed the .bss is packed together with the .data in FreeBSD, I'm not sure why. We should check that this works (no EFI machine at hand at the moment).

[tqh]

Here is what Fuchsia/Zircon does: ​https://fuchsia.googlesource.com/fuchsia/+/master/zircon/bootloader/build/efi-x86-64.lds

[tqh]

It seems you can have a .bss section. You just need to zero it as that is usually done by crt0?

​https://lists.denx.de/pipermail/u-boot/2018-October/344268.html

[pulkomandy]

Yes, that's exactly what I did in the change linked above.