Date: Mon, 14 May 2018 13:50:33 -0400 From: Ed Maste <emaste@freebsd.org> To: FreeBSD Current <freebsd-current@freebsd.org>, "freebsd-toolchain@FreeBSD.org" <freebsd-toolchain@freebsd.org> Subject: HEADS-UP: Linker issues building amd64 kernels with config & make Message-ID: <CAPyFy2CyLChddhe7ONpTiJHA3HBrXJ_DXFCbkPyYNA7AxnzeUA@mail.gmail.com>
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As of r333461 the amd64 kernel makes use of ifuncs, and requires support in the linker. A safety belt added in r333470 enforces this, and will produce an explicit error if the linker does not support ifuncs. lld is the default bootstrap linker for amd64 and has ifunc support. The typical 'make buildworld' (or kernel-toolchain) followed by 'make buildkernel' process will use lld and successfully link a working kernel. The old-style kernel build (using 'config' followed by a 'make' in the kernel directory) uses the host linker (/usr/bin/ld). This still defaults to GNU ld 2.17.50, which does not support ifuncs. This can be worked around in one of two ways: 1. Install lld as the system linker (/usr/bin/ld), by adding WITH_LLD_IS_LD to /etc/src.conf and building and install world. WITH_LLD_IS_LD will become the default on amd64 in the near future - I'm just waiting on updates to the lang/ghc port and another exp-run. 2. Override LD when you build the kernel: $ LD=ld.lld make These tool chain components will undergo additional changes for the next while.
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