amd64 の FreeBSD 12.x の kernel は ifunc が必要: uyota 匠の一手

まずは、ifunc。11 系から上げる人は、buildkernel 時に、CURRENT を追っていて、11 系のシステムに上書きインストールする人は installkernel 時に見掛けると思う。私は、NFS mount 越しの installkernel 時に出てきた。

$ uname -r
11.2-RELEASE-p2
$ mount -t nfs amd64-current:/usr/src /usr/src
$ mount -t nfs amd64-current:/usr/obj /usr/obj
$ make installkernel -C /usr/src
make[2]: "/usr/src/sys/conf/kern.pre.mk" line 126: amd64 kernel requires linker ifunc support

.if (${MACHINE_CPUARCH} == "amd64" || ${MACHINE_CPUARCH} == "i386") && \
    defined(LINKER_FEATURES) && ${LINKER_FEATURES:Mifunc} == ""
.error amd64/i386 kernel requires linker ifunc support
.endif
.if ${MACHINE_CPUARCH} == "amd64"
LDFLAGS+=       -Wl,-z max-page-size=2097152 -Wl,-z common-page-size=4096 -Wl,-z -Wl,ifunc-noplt
.endif

コードを見るより、/usr/src/UPDATING を開く。

20180510:
        The amd64 kernel now requires a ld that supports ifunc to produce a
        working kernel, either lld or a newer binutils. lld is built by default
        on amd64, and the 'buildkernel' target uses it automatically. However,
        it is not the default linker, so building the kernel the traditional
        way requires LD=ld.lld on the command line (or LD=/usr/local/bin/ld for
        binutils port/package). lld will soon be default, and this requirement
        will go away.

$ make installkernel LD=ld.lld -C /usr/src