--- w/lang/mono/Makefile	
+++ w/lang/mono/Makefile	
@@ -14,7 +14,7 @@ COMMENT=	Open source implementation of .NET Development Framework
 LICENSE=	MIT
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-ONLY_FOR_ARCHS=		amd64 armv6 armv7 i386 powerpc
+ONLY_FOR_ARCHS=		amd64 armv6 armv7 aarch64 i386 powerpc
 
 BUILD_DEPENDS=	p5-XML-Parser>=0:textproc/p5-XML-Parser \
 		bash:shells/bash \
@@ -64,6 +64,15 @@ LOCALBASE?=	/usr/local
 OPTIONS_SLAVE=	MONOLITE
 .endif
 
+.include <bsd.port.pre.mk>
+
+.if ${ARCH} == "aarch64"
+EXTRA_PATCHES=	${FILESDIR}/extra-patch-aarch64-race-workaround
+PLIST_SUB+=	BOEHM="@comment "
+.else
+PLIST_SUB+=	BOEHM=""
+.endif
+
 post-extract-MONOLITE-on:
 	${MKDIR} ${WRKSRC}/mcs/class/lib/monolite-linux
 	${MV} ${WRKDIR}/monolite-linux-${MONOLITE_VERSION}-latest ${WRKSRC}/mcs/class/lib/monolite-linux/${MONOLITE_VERSION}
@@ -92,4 +101,4 @@ post-configure:
 post-install:
 	${MKDIR} ${STAGEDIR}${PREFIX}/mono
 
-.include <bsd.port.mk>
+.include <bsd.port.post.mk>
--- /dev/null	
+++ w/lang/mono/files/extra-patch-aarch64-race-workaround	
@@ -0,0 +1,24 @@ 
+Workaround for Roslyn crash: https://github.com/mono/mono/issues/7017
+
+--- mcs/build/profiles/basic.make.orig	2018-07-12 00:08:27 UTC
++++ mcs/build/profiles/basic.make
+@@ -47,7 +47,7 @@ LIBRARY_COMPILE = $(BOOT_COMPILE)
+ #
+ # Copy from rules.make because I don't know how to unset MCS_FLAGS
+ #
+-USE_MCS_FLAGS = /codepage:$(CODEPAGE) /nologo /noconfig /deterministic $(LOCAL_MCS_FLAGS) $(PLATFORM_MCS_FLAGS) $(PROFILE_MCS_FLAGS) $(MCS_FLAGS)
++USE_MCS_FLAGS = /codepage:$(CODEPAGE) /parallel- /nologo /noconfig /deterministic $(LOCAL_MCS_FLAGS) $(PLATFORM_MCS_FLAGS) $(PROFILE_MCS_FLAGS) $(MCS_FLAGS)
+
+ .PHONY: profile-check do-profile-check
+ profile-check:
+--- mcs/build/rules.make.orig	2018-07-12 00:09:18.508196000 +0000
++++ mcs/build/rules.make	2018-07-12 00:12:13.875877000 +0000
+@@ -34,7 +34,7 @@
+ endif
+ endif
+
+-USE_MCS_FLAGS = /codepage:$(CODEPAGE) /nologo /noconfig /deterministic $(LOCAL_MCS_FLAGS) $(PLATFORM_MCS_FLAGS) $(PROFILE_MCS_FLAGS) $(MCS_FLAGS)
++USE_MCS_FLAGS = /codepage:$(CODEPAGE) /parallel- /nologo /noconfig /deterministic $(LOCAL_MCS_FLAGS) $(PLATFORM_MCS_FLAGS) $(PROFILE_MCS_FLAGS) $(MCS_FLAGS)
+ USE_MBAS_FLAGS = /codepage:$(CODEPAGE) $(LOCAL_MBAS_FLAGS) $(PLATFORM_MBAS_FLAGS) $(PROFILE_MBAS_FLAGS) $(MBAS_FLAGS)
+ USE_CFLAGS = $(LOCAL_CFLAGS) $(CFLAGS) $(CPPFLAGS)
+ CSCOMPILE = $(Q_MCS) $(MCS) $(USE_MCS_FLAGS)
--- w/lang/mono/files/patch-configure.ac	
+++ w/lang/mono/files/patch-configure.ac	
@@ -1,6 +1,21 @@ 
---- configure.ac.orig	2018-04-18 10:51:42.000000000 +0300
-+++ configure.ac	2018-06-24 02:38:19.860780000 +0300
-@@ -3271,6 +3271,8 @@
+armv8-a+crypto: Obtained from: upstream https://github.com/mono/mono/commit/a81e5afce53b9dcde82376d770222123fee0aa69
+
+--- configure.ac.orig	2018-04-18 07:51:42 UTC
++++ configure.ac
+@@ -202,6 +202,12 @@ case "$host" in
+		libgc_threads=pthreads
+		use_sigposix=yes
+		has_dtrace=yes
++		case "$host" in
++		aarch64-*)
++			support_boehm=no
++			with_gc=sgen
++			;;
++		esac
+		with_sgen_default_concurrent=yes
+		;;
+	*-*-*openbsd*)
+@@ -3271,6 +3277,8 @@ case "$host" in
  			BTLS_PLATFORM=i386
  			;;
  		  openbsd*|freebsd*|kfreebsd-gnu*)
@@ -9,7 +24,7 @@ 
  		        ;;
  		esac
  		;;
-@@ -3295,6 +3297,8 @@
+@@ -3295,6 +3303,8 @@ case "$host" in
  			boehm_supported=false
  			;;
  		  openbsd*|freebsd*|kfreebsd-gnu*)
@@ -18,3 +33,11 @@ 
  			;;
  		  mingw*)
  			;;
+@@ -4398,6 +4408,7 @@ if test "x$enable_btls" = "xyes"; then
+		;;
+	aarch64)
+		btls_arch=aarch64
++		btls_cflags="-march=armv8-a+crypto"
+		;;
+	android-armv5)
+		BTLS_CMAKE_ARGS="-DANDROID_ABI=\"armeabi\" -DANDROID_NATIVE_API_LEVEL=14"
--- /dev/null	
+++ w/lang/mono/files/patch-external_boringssl_crypto_cpu-aarch64-linux.c	
@@ -0,0 +1,45 @@ 
+Obtained from: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223019
+
+--- external/boringssl/crypto/cpu-aarch64-linux.c.orig	2018-04-18 07:47:16 UTC
++++ external/boringssl/crypto/cpu-aarch64-linux.c
+@@ -16,7 +16,40 @@
+
+ #if defined(OPENSSL_AARCH64) && !defined(OPENSSL_STATIC_ARMCAP)
+
+-#include <sys/auxv.h>
++#if defined(__FreeBSD__)
++#include <sys/param.h>
++#include <sys/sysctl.h>
++#include <elf.h>
++#include <errno.h>
++#include <unistd.h>
++
++#ifndef AT_HWCAP
++#define AT_HWCAP                25
++#endif
++
++static unsigned long getauxval(unsigned long type) {
++  Elf_Auxinfo auxv[AT_COUNT];
++  size_t len = sizeof(auxv);
++  int mib[] = {
++    CTL_KERN,
++    KERN_PROC,
++    KERN_PROC_AUXV,
++    getpid(),
++  };
++
++  if (sysctl(mib, nitems(mib), auxv, &len, NULL, 0) != -1) {
++    for (size_t i = 0; i < nitems(auxv); i++)
++      if ((unsigned long)auxv[i].a_type == type)
++        return auxv[i].a_un.a_val;
++
++    errno = ENOENT;
++  }
++  return 0;
++}
++#else
++#define AT_HWCAP                16
++#define getauxval(x)            0
++#endif /* <sys/auxv.h> */
+
+ #include <openssl/arm_arch.h>
--- /dev/null	
+++ w/lang/mono/files/patch-mono_sgen_sgen-archdep.h	
@@ -0,0 +1,11 @@ 
+--- mono/sgen/sgen-archdep.h.orig	2018-07-11 23:55:34 UTC
++++ mono/sgen/sgen-archdep.h
+@@ -45,7 +45,7 @@
+
+ #elif defined(TARGET_ARM64)
+
+-#ifdef __linux__
++#if defined(__linux__) || defined(__FreeBSD__)
+ #define REDZONE_SIZE    0
+ #elif defined(__APPLE__)
+ #define REDZONE_SIZE	128
--- /dev/null	
+++ w/lang/mono/files/patch-mono_utils_mono-sigcontext.h	
@@ -0,0 +1,16 @@ 
+--- mono/utils/mono-sigcontext.h.orig	2018-07-11 23:51:16 UTC
++++ mono/utils/mono-sigcontext.h
+@@ -460,6 +460,13 @@ typedef struct ucontext {
+	#define UCONTEXT_REG_SP(ctx) (((ucontext64_t*)(ctx))->uc_mcontext64->__ss.__sp)
+	#define UCONTEXT_REG_R0(ctx) (((ucontext64_t*)(ctx))->uc_mcontext64->__ss.__x [ARMREG_R0])
+	#define UCONTEXT_GREGS(ctx) (&(((ucontext64_t*)(ctx))->uc_mcontext64->__ss.__x))
++#elif defined(__FreeBSD__)
++#include <ucontext.h>
++	/* https://lists.freebsd.org/pipermail/freebsd-arm/2017-February/015611.html */
++	#define UCONTEXT_REG_PC(ctx) (((ucontext_t*)(ctx))->uc_mcontext.mc_gpregs.gp_elr)
++	#define UCONTEXT_REG_SP(ctx) (((ucontext_t*)(ctx))->uc_mcontext.mc_gpregs.gp_sp)
++	#define UCONTEXT_REG_R0(ctx) (((ucontext_t*)(ctx))->uc_mcontext.mc_gpregs.gp_x [ARMREG_R0])
++	#define UCONTEXT_GREGS(ctx) (&(((ucontext_t*)(ctx))->uc_mcontext.mc_gpregs.gp_x))
+ #else
+ #include <ucontext.h>
+	#define UCONTEXT_REG_PC(ctx) (((ucontext_t*)(ctx))->uc_mcontext.pc)
--- w/lang/mono/pkg-plist	
+++ w/lang/mono/pkg-plist	
@@ -41,7 +41,7 @@ bin/mod
 bin/mono
 bin/mono-api-html
 bin/mono-api-info
-bin/mono-boehm
+%%BOEHM%%bin/mono-boehm
 bin/mono-cil-strip
 bin/mono-configuration-crypto
 bin/mono-find-provides
@@ -166,10 +166,10 @@ lib/libmono-profiler-log.a
 lib/libmono-profiler-log.so
 lib/libmono-profiler-log.so.0
 lib/libmono-profiler-log.so.0.0.0
-lib/libmonoboehm-2.0.a
-lib/libmonoboehm-2.0.so
-lib/libmonoboehm-2.0.so.1
-lib/libmonoboehm-2.0.so.1.0.0
+%%BOEHM%%lib/libmonoboehm-2.0.a
+%%BOEHM%%lib/libmonoboehm-2.0.so
+%%BOEHM%%lib/libmonoboehm-2.0.so.1
+%%BOEHM%%lib/libmonoboehm-2.0.so.1.0.0
 lib/libmonosgen-2.0.a
 lib/libmonosgen-2.0.so
 lib/libmonosgen-2.0.so.1
@@ -2940,38 +2940,38 @@ man/man1/xbuild.1.gz
 man/man1/xsd.1.gz
 man/man5/mdoc.5.gz
 man/man5/mono-config.5.gz
-share/libgc-mono/README
-share/libgc-mono/README.DGUX386
-share/libgc-mono/README.Mac
-share/libgc-mono/README.MacOSX
-share/libgc-mono/README.OS2
-share/libgc-mono/README.amiga
-share/libgc-mono/README.arm.cross
-share/libgc-mono/README.autoconf
-share/libgc-mono/README.changes
-share/libgc-mono/README.contributors
-share/libgc-mono/README.cords
-share/libgc-mono/README.darwin
-share/libgc-mono/README.dj
-share/libgc-mono/README.environment
-share/libgc-mono/README.ews4800
-share/libgc-mono/README.hp
-share/libgc-mono/README.linux
-share/libgc-mono/README.macros
-share/libgc-mono/README.rs6000
-share/libgc-mono/README.sgi
-share/libgc-mono/README.solaris2
-share/libgc-mono/README.uts
-share/libgc-mono/README.win32
-share/libgc-mono/barrett_diagram
-share/libgc-mono/debugging.html
-share/libgc-mono/gc.man
-share/libgc-mono/gcdescr.html
-share/libgc-mono/gcinterface.html
-share/libgc-mono/leak.html
-share/libgc-mono/scale.html
-share/libgc-mono/simple_example.html
-share/libgc-mono/tree.html
+%%BOEHM%%share/libgc-mono/README
+%%BOEHM%%share/libgc-mono/README.DGUX386
+%%BOEHM%%share/libgc-mono/README.Mac
+%%BOEHM%%share/libgc-mono/README.MacOSX
+%%BOEHM%%share/libgc-mono/README.OS2
+%%BOEHM%%share/libgc-mono/README.amiga
+%%BOEHM%%share/libgc-mono/README.arm.cross
+%%BOEHM%%share/libgc-mono/README.autoconf
+%%BOEHM%%share/libgc-mono/README.changes
+%%BOEHM%%share/libgc-mono/README.contributors
+%%BOEHM%%share/libgc-mono/README.cords
+%%BOEHM%%share/libgc-mono/README.darwin
+%%BOEHM%%share/libgc-mono/README.dj
+%%BOEHM%%share/libgc-mono/README.environment
+%%BOEHM%%share/libgc-mono/README.ews4800
+%%BOEHM%%share/libgc-mono/README.hp
+%%BOEHM%%share/libgc-mono/README.linux
+%%BOEHM%%share/libgc-mono/README.macros
+%%BOEHM%%share/libgc-mono/README.rs6000
+%%BOEHM%%share/libgc-mono/README.sgi
+%%BOEHM%%share/libgc-mono/README.solaris2
+%%BOEHM%%share/libgc-mono/README.uts
+%%BOEHM%%share/libgc-mono/README.win32
+%%BOEHM%%share/libgc-mono/barrett_diagram
+%%BOEHM%%share/libgc-mono/debugging.html
+%%BOEHM%%share/libgc-mono/gc.man
+%%BOEHM%%share/libgc-mono/gcdescr.html
+%%BOEHM%%share/libgc-mono/gcinterface.html
+%%BOEHM%%share/libgc-mono/leak.html
+%%BOEHM%%share/libgc-mono/scale.html
+%%BOEHM%%share/libgc-mono/simple_example.html
+%%BOEHM%%share/libgc-mono/tree.html
 %%NLS%%share/locale/de/LC_MESSAGES/mcs.mo
 %%NLS%%share/locale/es/LC_MESSAGES/mcs.mo
 %%NLS%%share/locale/ja/LC_MESSAGES/mcs.mo