From ff8f1e8332cd60abc0bc2b189d988c5a24d4650b Mon Sep 17 00:00:00 2001
From: Ed Maste <emaste@FreeBSD.org>
Date: Thu, 10 May 2018 20:10:02 +0000
Subject: [PATCH] Error out on attempt to link amd64 kernel with old binutils
 linker

As of r333461 we require ifunc support to link a working amd64 kernel.
The default in-tree bootstrap linker is lld and it has the required
support, as does any modern out-of-tree binutils linker.  The in-tree
GNU ld is from binutils 2.17.50 and it does not have ifunc support,
so produce an error rather than a broken kernel.

Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D15378
---
 share/mk/bsd.linker.mk | 1 +
 sys/conf/kern.pre.mk   | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/share/mk/bsd.linker.mk b/share/mk/bsd.linker.mk
index d4ab69337f1..839479280cc 100644
--- a/share/mk/bsd.linker.mk
+++ b/share/mk/bsd.linker.mk
@@ -71,6 +71,7 @@ ${X_}LINKER_VERSION!=	echo "${_v:M[1-9].[0-9]*}" | \
 ${X_}LINKER_FEATURES=
 .if ${${X_}LINKER_TYPE} != "bfd" || ${${X_}LINKER_VERSION} > 21750
 ${X_}LINKER_FEATURES+=	build-id
+${X_}LINKER_FEATURES+=	ifunc
 .endif
 .if ${${X_}LINKER_TYPE} != "lld" || ${${X_}LINKER_VERSION} >= 50000
 ${X_}LINKER_FEATURES+=	filter
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 007a2355905..a51378ef769 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -121,6 +121,9 @@ LDFLAGS+=	-Wl,--build-id=sha1
 .endif
 
 .if ${MACHINE_CPUARCH} == "amd64"
+.if defined(LINKER_FEATURES) && ${LINKER_FEATURES:Mifunc} == ""
+.error amd64 kernel requires linker ifunc support
+.endif
 LDFLAGS+=	-Wl,-z max-page-size=2097152 -Wl,-z common-page-size=4096
 .endif