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From: Ian Lepore <ian@FreeBSD.org>
Date: Fri, 2 Jan 2015 03:20:14 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r276525 - head/sys/conf
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Author: ian
Date: Fri Jan  2 03:20:13 2015
New Revision: 276525
URL: https://svnweb.freebsd.org/changeset/base/276525

Log:
  Put in a workaround for bug 196407 (arm modules cause crashes & panics).
  
  When we started compiling the kernel with -march=armv7 the compiler
  started emitting new types of relocation info which are incompatible with
  the shared-lib file format used by .ko modules.  This workaround prevents
  the compiler from emitting the instruction sequences that require the
  new relocs.  This amounts to using an undocumented internal compiler
  flag, so this is just a temporary workaround while we look for a good fix.
  
  PR:		196407

Modified:
  head/sys/conf/kmod.mk

Modified: head/sys/conf/kmod.mk
==============================================================================
--- head/sys/conf/kmod.mk	Fri Jan  2 02:47:47 2015	(r276524)
+++ head/sys/conf/kmod.mk	Fri Jan  2 03:20:13 2015	(r276525)
@@ -118,6 +118,11 @@ CFLAGS+=	${DEBUG_FLAGS}
 CFLAGS+=	-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
 .endif
 
+# Temporary workaround for PR 196407, which contains the fascinating details.
+.if ${MACHINE_CPUARCH} == arm
+CFLAGS.clang+=	-mllvm -arm-use-movt=0
+.endif
+
 .if ${MACHINE_CPUARCH} == powerpc
 CFLAGS+=	-mlongcall -fno-omit-frame-pointer
 .endif