ld 2.36 regression linking EFI binary from ELF input

[Jan Beulich]

Hope you are having a good work day so far. I desired to follow-up to
you on the most recent business proposal we mailed you, Here it is one
more time in the link below.


https://onedrive.live.com/download?cid=B6DBE2433DDFB4F1&resid=B6DBE2433DDFB4F1%21106&authkey=AH8qUUUdIK4FbgM

File password: KM9887

-----Original Message-----
> On 04.02.2021 14:21, Jan Beulich via Binutils wrote: > the Xen project
> hypervisor build system includes building the > hypervisor binary as an EFI
> application, as an option (i.e. > as long as the tool chain supports this).
> Already when probing > the linker we now suddenly get several "relocation
> truncated > to fit:R_X86_64_32 against `.debug_...'" errors. I have not >
> had the time to figure out what exactly broke this, and I'm > sending this
> mail in the hope that it may ring a bell for > someone. > > For reference,
> the probing is as simple as > > $(LD) -mi386pep --subsystem=10 -o
> efi/check.efi efi/check.o > > As was to be expected, the errors disappear
> with -S, but that's > an option only for the probing, not for the actual
> linking of > the binary. Actually, that was just the easily visible
> problem. There's a worse one, again resulting from 514b4e191d5f ("Change
> the default characteristics of DLLs built by the linker to more secure
> settings"): Prior to this a .reloc section would not have been created by
> ld for executables. To work around this we've been hand-crafting
> relocations (by linking the image at two different base addresses and
> working out the delta). Now that ld does this by default, we get two base
> relocations for every field that needs relocating. Which obviously isn't
> going to work. We also can't easily use ld's way of populating .reloc, as
> it's buggy (I'll send separate mail about that) and apart from this the
> resulting relocations differ subtly for the pre-populated page tables
> (using physical addresses, not virtual ones) that the binary contains. The
> immediate workaround at our end is therefore going to be to use
> --disable-reloc-section when available, but I have to admit that this is
> far worse breakage than I would have expected from a single-step binutils
> version increment. I wouldn't be surprised if Cygwin / MingW (or users
> thereof, when they are creating their own programs on top) aren't similarly
> affected. Luckily(?) the Windows loader looks to fall back to ignoring
> .relocs when it encounters an error processing one of the relocations, at
> least for executables (for DLLs this may not be an option). Jan