[PATCH] D25467: [ELF] - Alternative fix to prevent possible crash on large output.

[Ed Maste via llvm-commits]

On 17 October 2016 at 17:26, Rui Ueyama via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
>  - FreeBSD: what is the status of building the entire FreeBSD system with
> LLD? Can it build everything including the kernel?

Outstanding FreeBSD/lld issues are tracked in http://llvm.org/pr23214 .

I have booted a lld-linked FreeBSD x86-64 kernel in the past, maybe
two months or so ago, but it has since regressed. It still builds but
the kernel crashes early on, and I haven't yet bisected to find out
when this started happening. I've been testing ToT FreeBSD built with
ToT LLD, so it's possible it's a FreeBSD change that's responsible.

There are two additional issues with lld on FreeBSD x86-64:

1. Boot loaders. We used to use -omagic to produce small boot binaries
with combined .text and .data. FreeBSD has since switched to using a
linker script for the boot binaries, although it seems there's
something amiss with that change (it does not work correctly with GNU
ld either).

http://llvm.org/pr30415
https://bugs.freebsd.org/213491

The EFI loader also fails to build with lld: http://llvm.org/pr30406
I see there's a followup question from Petr Hosek in the PR that needs
a response.

2. Rescue binaries

FreeBSD's /rescue directory contains a statically-linked binary that's
built as a combination of multiple utilities, and it selects the
utility to invoke based on argv[0]. (Similar to BusyBox or toybox.)
The build uses the -dc option, currently not supported by lld. I
haven't looked at this in detail yet as it's been a lower priority.

In FreeBSD the next priority for us is linking the arm64 userland and
kernel with lld. I think the userland is in good shape although I
haven't done comprehensive testing. The kernel currently fails to link
due to http://llvm.org/pr30267. Andrew Turner applied a workaround to
the FreeBSD source, and has booted an lld-linked FreeBSD/arm64 kernel.

Bringing lld 3.9 into FreeBSD is in progress, along with the update to
Clang 3.9. It will be installed as /usr/bin/ld.lld to facilitate
-fuse-ld=lld. Once this is complete I am going to request an
experimental build (known as an exp-run in FreeBSD) of the 26,000
packages in the ports tree using lld 3.9.

> - Ports: how much mature is PowerPC port? We want to support both BE and LE
> PowerPCs. It's also interesting to work on an open-source ISA, RISC-V,
> because the patches to support the RISC-V architecture are being merged now.

We're interested in arm, i386, mips (64/32), powerpc (64/32), and
RISC-V in FreeBSD.