Index: include/private/gcconfig.h
--- include/private/gcconfig.h.orig
+++ include/private/gcconfig.h
@@ -64,7 +64,8 @@
 /* Determine the machine type: */
 # if defined(__aarch64__)
 #    define AARCH64
-#    if !defined(LINUX)
+#    if !defined(LINUX) && !defined(DARWIN) && !defined(FREEBSD) \
+        && !defined(OPENBSD)
 #      define NOSYS
 #      define mach_type_known
 #    endif
@@ -82,6 +83,10 @@
 # if defined(hp9000s300)
 #    error M68K based HP machines no longer supported.
 # endif
+# if defined(OPENBSD) && defined(__aarch64__)
+#    define AARCH64
+#    define mach_type_known
+# endif
 # if defined(OPENBSD) && defined(m68k)
 #    define M68K
 #    define mach_type_known
@@ -94,6 +99,10 @@
 #    define POWERPC
 #    define mach_type_known
 # endif
+# if defined(OPENBSD) && defined(__riscv)
+#    define RISCV
+#    define mach_type_known
+# endif
 # if defined(NETBSD) && (defined(m68k) || defined(__m68k__))
 #    define M68K
 #    define mach_type_known
@@ -1334,6 +1343,19 @@
 #     define LINUX_STACKBOTTOM
 #     define DYNAMIC_LOADING
 #   endif
+#   ifdef OPENBSD
+#     define OS_TYPE "OPENBSD"
+#     ifndef GC_OPENBSD_THREADS
+#       include <sys/param.h>
+#       include <uvm/uvm_extern.h>
+#       define STACKBOTTOM ((ptr_t)USRSTACK)
+#     endif
+      extern int __data_start[];
+#     define DATASTART ((ptr_t)__data_start)
+      extern int _end[];
+#     define DATAEND ((ptr_t)(&_end))
+#     define DYNAMIC_LOADING
+#   endif
 # endif /* RISCV */
 
 # ifdef NS32K
@@ -1750,6 +1772,86 @@
 #   define DATAEND (_end)
 #   define CACHE_LINE_SIZE 256
 #   define GETPAGESIZE() 4096
+#   endif
+# endif
+
+# ifdef AARCH64
+#   define MACH_TYPE "AARCH64"
+#   ifdef __ILP32__
+#     define CPP_WORDSZ 32
+#     define ALIGNMENT 4
+#   else
+#     define CPP_WORDSZ 64
+#     define ALIGNMENT 8
+#   endif
+#   ifndef HBLKSIZE
+#     define HBLKSIZE 4096
+#   endif
+#   ifdef LINUX
+#     define OS_TYPE "LINUX"
+#     define LINUX_STACKBOTTOM
+#     define DYNAMIC_LOADING
+      extern int __data_start[];
+      extern int _end[];
+#     define DATASTART ((ptr_t)__data_start)
+#     define DATAEND ((ptr_t)(&_end))
+#   endif
+#   ifdef DARWIN
+      /* iOS */
+#     define OS_TYPE "DARWIN"
+#     define DARWIN_DONT_PARSE_STACK
+#     ifndef GC_DONT_REGISTER_MAIN_STATIC_DATA
+#       define DYNAMIC_LOADING
+#     endif
+#     define DATASTART ((ptr_t)get_etext())
+#     define DATAEND   ((ptr_t)get_end())
+#     define STACKBOTTOM ((ptr_t)0x16fdfffff)
+#     ifndef USE_MMAP
+#       define USE_MMAP
+#     endif
+#     define USE_MMAP_ANON
+#     define MPROTECT_VDB
+#     include <unistd.h>
+#     define GETPAGESIZE() (unsigned)getpagesize()
+      /* FIXME: There seems to be some issues with trylock hanging on   */
+      /* darwin. This should be looked into some more.                  */
+#     define NO_PTHREAD_TRYLOCK
+#     if TARGET_OS_IPHONE && !defined(NO_DYLD_BIND_FULLY_IMAGE)
+#       define NO_DYLD_BIND_FULLY_IMAGE
+#     endif
+#   endif
+#   ifdef FREEBSD
+#     define OS_TYPE "FREEBSD"
+#     ifndef GC_FREEBSD_THREADS
+#       define MPROTECT_VDB
+#     endif
+#     define FREEBSD_STACKBOTTOM
+#     ifdef __ELF__
+#       define DYNAMIC_LOADING
+#     endif
+      extern char etext[];
+#     define DATASTART GC_FreeBSDGetDataStart(0x1000, (ptr_t)etext)
+#     define DATASTART_USES_BSDGETDATASTART
+#   endif
+#   ifdef OPENBSD
+#     define OS_TYPE "OPENBSD"
+#     ifndef GC_OPENBSD_THREADS
+#       include <sys/param.h>
+#       include <uvm/uvm_extern.h>
+#       define STACKBOTTOM ((ptr_t)USRSTACK)
+#     endif
+      extern int __data_start[];
+#     define DATASTART ((ptr_t)__data_start)
+      extern int _end[];
+#     define DATAEND ((ptr_t)(&_end))
+#     define DYNAMIC_LOADING
+#   endif
+#   ifdef NOSYS
+      /* __data_start is usually defined in the target linker script.   */
+      extern int __data_start[];
+#     define DATASTART ((ptr_t)__data_start)
+      extern void *__stack_base__;
+#     define STACKBOTTOM ((ptr_t)__stack_base__)
 #   endif
 # endif